U.S. patent application number 13/915440 was filed with the patent office on 2014-12-11 for towed sensor array surface structure apparatus and method of use thereof.
The applicant listed for this patent is Richard E. Pearce. Invention is credited to Richard E. Pearce.
Application Number | 20140362660 13/915440 |
Document ID | / |
Family ID | 46315112 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140362660 |
Kind Code |
A1 |
Pearce; Richard E. |
December 11, 2014 |
TOWED SENSOR ARRAY SURFACE STRUCTURE APPARATUS AND METHOD OF USE
THEREOF
Abstract
A surface structure is provided for reducing drag and/or for
reducing turbulence on or proximate any element of a streamer cable
or towed sensor array. The surface structure comprises a
non-uniform surface having ridges, channels, expanding channels,
dimples, bumps, backward facing diamonds, a saw tooth pattern, or
the like integrated into, adhered to, wrapped, and/or coated onto a
surface of the streamer cable. The sharkskin like material,
coating, or surface is optionally an array of denticles or a sheet
that is also useful for fuel reduction and/or ease of guidance due
to lower resistance and noise reduction in towed sensors due to
reduction/breakup of localized zones of turbulence.
Inventors: |
Pearce; Richard E.;
(Weatherford, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pearce; Richard E. |
Weatherford |
TX |
US |
|
|
Family ID: |
46315112 |
Appl. No.: |
13/915440 |
Filed: |
June 11, 2013 |
Current U.S.
Class: |
367/15 |
Current CPC
Class: |
B06B 1/0688 20130101;
G01V 1/38 20130101; Y10T 29/42 20150115; G01V 1/201 20130101 |
Class at
Publication: |
367/15 |
International
Class: |
G01V 1/20 20060101
G01V001/20 |
Claims
1. An apparatus, comprising: a towed sensor array, said towed
sensor array comprising: a leading end; a trailing end, during use
said leading end leading said trailing end along a towing axis; and
an outer surface, said outer surface comprising an array of surface
elements, said surface elements comprising: a plurality of
channels; and a plurality of ridges.
2. The apparatus of claim 1, at least ninety percent of said ridges
predominantly aligned along the towing axis and at least ninety
percent of said channels predominantly aligned along the towing
axis.
3. The apparatus of claim 2, said plurality of ridges comprising: a
first width between two ridges of said plurality of ridges; a
second width between said two ridges, said second width greater
than fifty percent larger than said first width, said first width
directionally leading said second width along the towing axis
during use.
4. The apparatus of claim 2, wherein a majority of said plurality
of ridges further comprise at least one of: a curved leading edge;
and a curved upper edge.
5. The apparatus of claim 2, said plurality of channels comprising:
a first maximum depth of a first channel of said plurality of
channels; a second maximum depth of a second channel of said
plurality of channels, said first maximum depth at least fifty
percent deeper than said second maximum depth.
6. The apparatus of claim 2, wherein said array of surface elements
comprises a non-uniform array of surface elements.
7. The apparatus of claim 2, wherein a portion of said array of
surface elements combine to form a saw tooth shaped trailing
edge.
8. The apparatus of claim 2, wherein said array of surface elements
comprise a series of bumps, wherein said series of bumps extended
outward by at least one millimeter.
9. The apparatus of claim 2, said array of surface elements
comprising a repeating pattern.
10. The apparatus of claim 2, said array of surface elements
comprising a random pattern.
11. The apparatus of claim 2, wherein a first element of said array
of surface elements partially overlaps a second element of said
array of surface elements.
12. The apparatus of claim 2, said towed sensor array further
comprising: a hollow tube; and an elastomeric flexible syntactic
flotation material over-molded about said hollow tube, wherein said
outer surface comprises a layer affixed to an outer surface of said
elastomeric flexible syntactic flotation material.
13. The apparatus of claim 12, further comprising: a gap in
coverage of said elastomeric flexible syntactic flotation material
by said array of surface elements of at least three percent of a
surface area of said outer surface of said towed sensor array.
14. The apparatus of claim 12, wherein an outer surface of said
elastomeric flexible syntactic flotation material comprises said
plurality of channels and said plurality of ridges.
15. The apparatus of claim 1, said towed sensor array comprising
any of: a cable section; a sensor section; a connector section; and
a positioner section, said positioner section configured to control
at least depth of said sensor section, wherein said outer surface
comprises an outer surface of any of: said cable section, said
sensor section, said connector section, and said positioner
section.
16. The apparatus of claim 15, wherein said sensor section of said
towed sensor array comprises a piezoelectric sensing element,
wherein said outer surface comprises a coating of said sensor
section radially outward from said piezoelectric sensing
element.
17. The apparatus of claim 1, said array of surface elements
comprising a non-uniform surface shark-skin simulant.
18. The apparatus of claim 1, further comprising a biocide
impregnated into said outer surface of said towed sensor array.
19. A method, comprising the steps of: towing a towed sensor array
through a water body along a towing axis, said towed sensor array
comprising: a leading end; a trailing end, said leading end and
said trailing end defining the towing axis; and an outer surface,
said outer surface comprising an array of surface elements, said
array of surface elements comprising: a plurality of channels; and
a plurality of ridges; and reducing localized turbulence proximate
said outer surface of said towed sensor array using said array of
surface elements.
20. The method of claim 19, further comprising the step of:
generating a localized low pressure region proximate said outer
surface of said towed array sensor using curved outer surfaces on
said plurality of ridges by towing the towed sensor array through
the body of water.
21. The method of claim 20, further comprising the step of:
breaking apart a localized turbulence using said generated
localized low pressure region.
22. The method of claim 21, further comprising the step of:
providing an inward radial compression force on an element of said
towed sensor array using a fabric, said fabric forming said outer
surface of said towed sensor array.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is: [0002] a continuation-in-part of U.S.
patent application Ser. No. 13/295,356 filed Nov. 14, 2011; [0003]
a continuation-in-part of U.S. patent application Ser. No.
13/295,380 filed Nov. 14, 2011; [0004] a continuation-in-part of
U.S. patent application Ser. No. 13/295,402 filed Nov. 14, 2011;
and [0005] claims the benefit of U.S. provisional patent
application No. 61/427,775 filed Dec. 24, 2011, which claims the
benefit of U.S. provisional patent application No. 61/427,775 filed
Dec. 28, 2010, [0006] all of which are incorporated herein in their
entirety by this reference thereto.
TECHNICAL FIELD OF THE INVENTION
[0007] The present invention relates to a towed sensor array
streamer cable outer surface.
DESCRIPTION OF THE RELATED ART
[0008] Towed arrays of hydrophone sensors are used to map strata
beneath large bodies of water, such as gulfs, straights, and
oceans.
[0009] Patents related to the current invention are summarized
herein.
Streamer Cable
[0010] R. Pearce, "Non-Liquid Filled Streamer Cable with a Novel
Hydrophone", U.S. Pat. No. 5,883,857 (Mar. 16, 1999) describes a
streamer cable including a plurality of serially coupled active
cable sections having hydrophones located within an outer jacket
and a longitudinally and centrally located electro-mechanical
cable.
[0011] R. Pearce, "Non-Liquid Filled Streamer Cable with a Novel
Hydrophone", U.S. Pat. No. 6,108,267 (Aug. 22, 2000) describes a
towed array having a central strain member, an inner protective
jacket about the strain member, a foam material about the inner
protective jacket, and a potting material bonded to the inner
protective jacket inside an outer protective jacket.
[0012] R. Pearce, "Method and Apparatus for a Non-Oil-Filled Towed
Array with a Novel Hydrophone and Uniform Buoyancy Technique", U.S.
Pat. No. 6,498,769 B1 (Dec. 24, 2002) describes a towed array
having uniform buoyancy achieved using hollow microspheres in a
polyurethane matrix, where the percentage of hollow microspheres is
correlated with adjacent density of elements of the towed
array.
[0013] R. Pearce, "Acoustic Sensor Array", U.S. Pat. No. 6,614,723
B2 (Sep. 2, 2003) describes an acoustic sensor array having buoyant
sections formed using reaction injection molding with controlled
and varying amounts of hollow microspheres and polyurethane as a
function of position on the array.
Sensor
[0014] R. Pearce, "Acoustic Transducer", U.S. Pat. No. 5,357,486
(Oct. 18, 1994) describes a piezoelectric film strip wrapped around
a mandrel having stand off collars on each end. Variations in
hydrodynamic pressure flex the film strip in tension to generate a
voltage.
[0015] R. Pearce, "Acoustic Sensor", U.S. Pat. No. 5,361,240 (Nov.
1, 1994) describes an acoustic sensor having a hollow mandrel with
an outer surface defining a concavity and a flexible piezoelectric
film wrapped about the outer surface forming a volume between the
film and the mandrel, the volume serving as a pressure compensating
chamber.
[0016] R. Pearce, "Acoustic Sensor and Array Thereof", U.S. Pat.
No. 5,774,423 (Jun. 30, 1998) describes an acoustic sensor having
electrically coupled piezoelectric materials.
[0017] R. Pearce, "Acoustic Sensor and Array Thereof", U.S. Pat.
No. 5,982,708 (Nov. 9, 1999) describes an acoustic sensor having a
substrate with a concavity on an outer surface that is sealingly
enclosed by an active member of a piezoelectric material.
[0018] R. Pearce, "Acoustic Sensor and Array Thereof", U.S. Pat.
No. 6,108,274 (Aug. 22, 2000) describes an acoustic sensor having a
mandrel, a first substrate on an outer surface of the mandrel, a
damping layer between the first substrate and a second substrate, a
piezoelectric sensor mounted to the second substrate, and an
encapsulating material on the piezoelectric material.
[0019] R. Pearce, "Method and Apparatus for a Non-Oil-Filled Towed
Array with a Novel Hydrophone and Uniform Buoyancy Technique", U.S.
Pat. No. 6,819,631 B2 (Nov. 16, 2004) describes a towable
hydrophone having a diaphragm with a tubular shape, a thin film
piezoelectric element attached to the diaphragm, the diaphragm
having a back plane having a cylindrical shape, and at least one
longitudinal rib on the exterior of the back plane, where the back
plane and exterior rib slidingly engage the tubular diaphragm.
Problem Statement
[0020] What is needed is one or more surface structures on one or
more elements of a towed array to reduce turbulence noise observed
by sensors used in mapping objects or features under a water
body.
SUMMARY OF THE INVENTION
[0021] The invention comprises a towed array streamer cable surface
structure apparatus and method of use thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] A more complete understanding of the present invention is
derived by referring to the detailed description and claims when
considered in connection with the Figures, wherein like reference
numbers refer to similar items throughout the Figures.
[0023] FIG. 1 illustrates a towed sensor array;
[0024] FIG. 2 figuratively illustrates motion localized turbulence
about a sensor;
[0025] FIG. 3 presents an acoustic sensor using microspheres, FIG.
3A, and the acoustic sensor in cross section, FIG. 3B, where the
surface of the sensor cable reduces turbulence;
[0026] FIG. 4 represents a coating about an electrically coupled
acoustic sensor and non-acoustic sensors;
[0027] FIG. 5 illustrates multiple closely spaced sensor types on a
substrate of a towable array circumferentially enclosed in a shark
skin simulant;
[0028] FIG. 6A and FIG. 6B and FIG. 6C illustrate a surface
structure element from a top view, FIG. 6A, from a side view, FIG.
6B, and from a side view of a curved surface FIG. 6C,
respectively;
[0029] FIG. 7 illustrates a shark skin simulant having expanding
channels;
[0030] FIG. 8 illustrates overlapping surface structure
elements;
[0031] FIG. 9 illustrates an array of turbulence reduction elements
or units;
[0032] FIG. 10A and FIG. 10B represent a surface coating sheet from
a top view and from a side view, respectively; and
[0033] FIG. 11A-C respectively illustrate a stabilization/guidance
bird from a perspective, end, and side view, all coatable with the
shark skin simulant.
[0034] Elements and steps in the figures are illustrated for
simplicity and clarity and have not necessarily been rendered
according to any particular sequence. For example, steps that are
performed concurrently or in different order are illustrated in the
figures to help improve understanding of embodiments of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] The invention comprises a flow unifying and/or turbulence
reducing surface structure apparatus and method of use thereof.
[0036] In one embodiment, a surface structure is provided for
reducing drag and/or for reducing turbulence on or proximate any
element of a streamer cable or towed sensor array. For example, the
surface of any element of a streamer cable or towed sensor array
comprises a non-uniform surface having ridges, channels, expanding
channels, dimples, bumps or the like on individual partially
overlapping elements or in an extended array, where the non-uniform
surface reduces drag, compresses an element, and/or reduces
localized turbulence, which aids in fuel reduction, ease of ship
guidance, and/or noise reduction in towed sensors. For example, the
surface structure reduces turbulence noise detector by a sensor of
the towed sensor array.
[0037] In another embodiment, an acoustic sensor is provided having
a piezoelectric sensor coupled with a microsphere loaded transfer
adhesive as a compressible gas chamber, where the acoustic sensor
is optionally coated with a noise reducing coating.
[0038] In yet another embodiment, multiple sensor types are
co-positioned for use in removal of noise from turbulence, where
the multiple sensor types are optionally coated with a noise
reducing coating.
[0039] In yet still another embodiment, a piezoelectric element is
motion restricted in one or more dimensions to enhance sensitivity
and/or to select sensitivity, where the piezoelectric element is
optionally coated with a noise reducing/turbulence reduction
coating.
[0040] In one example, the system includes two piezopolymer thin
film elements configured in such a manner as to form a dedicated
acoustic sensor and a dedicated flow noise cancelling acoustic
sensor, both of which are excited by forces and in some cases
substantially similar forces manifested as dynamic pressure with
immunity to acceleration and dynamic particle motion with immunity
to dynamic pressure so as to allow for the discreet measurement of
acoustic energy and particle motion present at a single location or
in a small volume, as described infra. The acoustic sensor being
embodied in such a manner as to allow the inherent response
characteristics of thin film polyvinylidene fluoride (PVDF) to
sense both acoustics and noise produced by the turbulent boundary
layer as dynamic pressure while simultaneously sensing only the
turbulent boundary layer manifested as a response to a force,
producing a response in the non-acoustic portion of the element to
the turbulent boundary layer that is about one hundred eighty
degrees out of phase with that detected on the acoustic portion of
the element. This is accomplished in a single contiguous sensor
mechanically constrained in such a way as to allow a portion of the
element to respond to dynamic pressure and a portion of the element
to respond only to mechanical force. A simple embodiment of this
invention is presented with the sensor comprised of a single piece
of PVDF film where a single strip of acoustic sensor is surrounded
by two strips in corresponding force sensors. Complex patterns are
also available to enhance the performance of the invention
utilizing fractal pattern sampling of the turbulent boundary layer.
The completed sensors are then used to construct a seismic streamer
section necessarily of a solid construction where the sensors are
placed. Any outer element of the seismic sensor is optionally
coated with the shark skin-simulant, molded to mimic shark skin,
noise reduction surface, laminar flow enhancing surface, and/or
turbulence reduction surface. Optionally, the outer surface is a
sheet, coating, series of repeating units, and/or series of similar
shaped units. The outer surface is optionally formed as part of an
outer surface of a flotation material, such as an elastomeric
flexible syntactic flotation material.
Axes
[0041] Referring now to FIG. 1, herein an x-axis is in a horizontal
direction of towing of a sensor array. The x/y axes form a plane
parallel to a water body surface. The z-axis is aligned with
gravity. Typically, the thickness of a piezoelectric film is viewed
in terms of a z-axis, though the piezoelectric film is optionally
rolled about a mandrel, described infra.
Piezoelectric Material
[0042] Piezoelectricity is charge that accumulates in certain solid
materials in response to applied mechanical stress. A piezoelectric
material generates electricity from applied pressure.
[0043] An example of a piezoelectric material is polyvinylidene
fluoride (PVDF). Unlike ceramics, where the crystal structure of
the material creates the piezoelectric effect, in the PVDF polymer
intertwined long-chain molecules attract and repel each other when
an electric field is applied.
[0044] The polyvinylidene material is particularly useful in
aqueous environments as the acoustic impedance of PVDF is similar
to that of water. An external mechanical force applied to a film of
polyvinylidene fluoride results in a compressive or tensile force
strain. A film of PVDF develops an open circuit voltage, or
electrical charge, which is proportional to the changes in the
mechanical stress or strain. By convention, the polarization axis
is the thickness axis of the polyvinylidene material. Tensile
stress may take place along either the longitudinal axis or the
width axis.
[0045] Herein, for clarity, polyvinylidene fluoride is used as an
example of the piezoelectric material. However, any material that
generates a charge in response to pressure is optionally used.
Examples include: man-made crystals, such as gallium
orthophosphate, a quartz analogic crystal, and langasite; man-made
ceramics, such as a titanate, a niobate, a tantalate, or a
tungstate; and/or a lead-free piezoceramic.
[0046] A PVDF material is characterized in terms of a strip of PVDF
film. The PVDF film includes a width axis or x-x axis, a length
axis or y-y axis, and a thickness axis or z-z axis. The PVDF film
x-x axis is less sensitive, in terms of developed charge, to
applied forces than the length axis or the thickness axis of the
PVDF film. Hence, in the sensors described herein, the width axis
of the PVDF film is typically about parallel to the towing
direction of the sensor array to minimize noise signals resultant
from towing of the sensor array with a cable under varying strain.
As described, infra, expansion of the y-y axis of the PVDF film is
optionally restrained in a mounting step, which results in
increased thickness changes of the PVDF film resultant from applied
forces. The increased thickness change as a function of applied
force is equivalent to an increased signal-to-noise ratio.
[0047] The PVDF film is optionally cut, shaped, or wrapped about a
surface, such as a mandrel or hollow tube.
[0048] A PVDF sensor is a PVDF film coupled with at least one
charge transfer element, such as a conductive wire. In one case, a
PVDF sensor includes a PVDF film coated on both sides with a
conductive ink. In a second case, the PVDF film is coated on one
side with a conductive ink and the opposite side makes contact with
a conductive fluid, as described infra, to form a PVDF sensor.
Conditioning Electronics
[0049] Electric output from the PVDF sensor is carried along a
conductive element, such as a wire, to an electrical circuit. The
electrical circuit optionally includes: a current to voltage
converter, such as a preamplifier, an amplifier, processing
electronics, an analog-to-digital converter, and/or a data buss.
Signal from a first PVDF sensor is optionally: [0050] combined with
signal from a second PVDF sensor using the on-board electrical
circuit; and/or [0051] is post processed after communication of the
gathered signal to a processing center.
Towed Sensor Array
[0052] Still referring to FIG. 1, a system for mapping strata 100
under a floor of a water body is illustrated. In the illustrated
example, a vessel 110, such as a ship tows one or more sensor
arrays 120. A sensor array 120 includes at least a streamer cable
122 and a sensor 124.
[0053] The streamer cable 122 optionally includes: [0054] an outer
housing 126; [0055] a strain member 310, such as a central strain
member; [0056] a wire bundle configured to carry power and/or data,
the wire bundle is preferably wrapped about or within the strain
member to reduce strain from towing; [0057] a plurality of sensors
124, such as about equispaced or not equally spaced hydrophones,
non-acoustic sensors, and/or accelerometers; [0058] electronics;
[0059] a buoyancy element; [0060] a protective jacket about the
sensors, strain member, and wire bundle; and/or [0061] an outer
turbulence reduction surface.
[0062] The sensors are further described, infra.
[0063] In one use, a seismic shock wave is generated, such as with
an explosive. The shock wave partially reflects from a floor 150 of
the water body 155, and/or from a series of strata layers 152, 154
under the water body floor 150. In one case, the surface
reflections yield a vertically rising seismic wave 142 that strikes
the one or more sensors 124. In a second case, a seismic wave at
least partially reflects off of a water body surface 160 to yield a
vertically descending seismic wave 144, which strikes the one or
more sensors 124. The vertically descending seismic wave is an
interference signal, which reduces the bandwidth and associated
signal-to-noise ratio of the sensors 124.
[0064] In another use, the sensors 124 are used passively, such as
without the use of a detonated explosive.
[0065] In any case, the sensors 124 are optionally configured to
passively cancel noise, such as noise from localized
turbulence.
[0066] Still referring to FIG. 1, those skilled in the art know
that a sensor or a matrix of sensors may be used to map strata
layers, and/or to detect underwater geophysical structures.
Sensors
[0067] The sensors 124 are further described. Any of the sensors
124 described herein are optionally coated with a flexible solid
material as part of the streamer 122. Further, sensors 124 are
optionally positioned at any x-axis position of the streamer 122 to
form the sensor array 120, though equispacing of like sensor
elements 124 is preferable.
Turbulence
[0068] Referring now to FIG. 2, localized turbulence bubbles 210
are figuratively illustrated. Some turbulence bubbles 210 interact
with the outer housing 126 about a sensor 124. In same cases, the
turbulence bubbles 210 have a localized impact on a first sensor
not sensed by a second sensor. This difference in impacts allow
signal and/or noise resultant from the localized turbulence to be
removed, such as by passive removal and/or through post processing
of data from the first sensor and the second sensor. In practice,
any number of sensors are optionally used.
[0069] Still referring to FIG. 2, the outer surface 200 of any
element of the streamer cable 122 is optionally a surface designed
to reduce localized turbulence. For example, the outer surface 200
optionally contains ridges, grooves, and/or a mimicked shark skin,
which reduce localized turbulence. The outer surface 200 reduces
formation of the turbulence bubbles and/or breaks apart the
localized turbulence bubbles 210 into smaller turbulence
microelements 212 or dissipates the turbulence bubbles 210
altogether. The outer surface 200 of the streamer cable is further
described, infra.
Acoustic Sensor
[0070] Referring now to FIG. 3A and FIG. 3B, an acoustic sensor 300
is illustrated. The acoustic sensor uses a piezoelectric film,
which is described herein as a piezoelectric acoustic film 330,
which maintains the general properties of a piezoelectric material
or element.
[0071] Still referring to FIG. 3A, the acoustic sensor 300
includes: [0072] a substrate, 310; [0073] a piezoelectric motion
film 330 optionally attached to a diaphragm; and [0074] a hollow
cavity, hollow chamber, an enclosed chamber, and/or a set of
microspheres 320 between the substrate 310 and the piezoelectric
motion film 330.
[0075] Each of the acoustic sensor 300 elements are further
described herein.
Substrate
[0076] In practice, the substrate 310 is optionally a hollow tube
or a hollow mandrel. The substrate 310 is sufficiently rigid to
isolate internally radiated stresses from the embodied piezo
elements in the acoustic sensor 300 described, infra. The substrate
310 optionally includes a concave inner surface, defining an inner
wall of a tube. The tube is optionally used to contain and/or to
constrain movement of centrally placed elements, such as a strain
member of the streamer cable 122, the wire bundle configured to
carry power and/or data, a shock absorbing element, and/or the
electronics. The substrate 310 also optionally includes a convex
outer surface upon which the sensor elements are mounted. The
convex outer surface of the substrate 310 optionally contains an
outer concavity or channel 405. The channel or cavity 405 is
created either through machining or through a molding process by
which the channel 405 is presented around a circumference located
outside the rigid mandrel or substrate 310. Sensor elements are
optionally located in the outer concavity or channel 405. For
example, in one case the substrate 310 includes a pair of inner
shoulders, which function as a mechanical support for a diaphragm
and/or the piezoelectric motion film 330. The inner shoulders are
either machined or molded and are located outside and to the side
of the created channel at a depth and width sufficient to allow
attachment of the piezofilm motion sensor element 330 forming a
sealed chamber between the piezofilm and the substrate 310.
Optionally, the acoustic sensor 300 includes an outer acoustic
sensor housing. The outer acoustic sensor housing or second rigid
cylindrical mandrel is positioned over a cavity formed by the outer
shoulders thus sealing the entire acoustic sensor 300 inside. The
outer acoustic sensor housing prevents the acoustic sensor 300 from
responding to dynamic pressure. Further, the outer acoustic sensor
housing forms an outer mandrel upon which an outer passive flow
noise cancelling acoustic sensor is optionally positioned.
Preferably, the outer motion sensor housing is rigid or semi-rigid.
The outer motion sensor housing is optionally connected to the
substrate 310, such as through a pair of outer shoulders positioned
along the x-axis further from a center of the enclosed chamber 405
relative to the inner shoulders. The additional set of outer
shoulders adjacent and outside the inner shoulders optionally form
a second chamber above the first thin film piezoelectric element.
Both the inner and outer shoulders are optionally a part the
substrate 310, are removable elements affixed to the substrate 310,
are affixed to the acoustic sensor housing, and/or are part of the
acoustic sensor housing.
[0077] In one example, the piezoelectric acoustic film 330 is
mounted radially outward from the substrate 310 in a manner forming
a sealed hollow chamber or layer of microspheres 320 therebetween,
as described infra. For example, the piezoelectric polymer thin
acoustic film element 330 is constructed with a deposited single
electrode on the outer surface so as to create a continuous
electrode around the circumference of the resulting piezofilm
cylinder created when the film is attached to the shoulders
previously described and sealed where the film wrap overlaps or
meets creating a hollow and sealed chamber between the
piezoelectric acoustic film 330 and the substrate 310 within the
channel 405. For example, the piezoelectric motion film 330 is
mounted over a portion of the outer concavity or channel of the
substrate 310 or is mounted directly or indirectly to the inner
shoulders. The piezoelectric motion film 330 optionally forms one
or more layers circumferentially surrounding the substrate 310. The
hollow chamber extends to at least partially circumferentially
encompass an x-axis section of the substrate 310. In one case, the
piezoelectric film mounts directly to the substrate 310, such as by
mounting to the inner shoulders of the substrate 310. Mechanically
affixing, such as with a wrap and/or an adhesive, the piezoelectric
acoustic film 330 to the inner shoulders restricts movement of the
y-y axis of the piezoelectric film. The restricted y-y axis motion
of the piezoelectric motion film 220 and the orientation of the x-x
axis of the piezoelectric film along the x-axis or towing axis
results in enhanced changes in the z-z thickness axis of the
piezoelectric film as a response to pressure/size changes resultant
from seismic waves or a noise source, which increases the
signal-to-noise ratio of the acoustic sensor 300. The x-x axis
edges of the piezoelectric acoustic films are similarly optionally
restrained, which again increases the signal-top-noise ratio of the
acoustic sensor. In additional cases, the piezoelectric acoustic
film 330 is indirectly affixed to the substrate 310, such as
through the use of a diaphragm. In all such cases, at least a
portion of the hollow chamber is physically positioned between the
substrate 310 and the piezoelectric acoustic film 330.
[0078] Changes in thickness of the piezoelectric acoustic film 330,
which is proportional to the changes in the mechanical stress or
strain resulting from the seismic wave or noise source, is measured
using electrical connections to the piezoelectric acoustic film
330. A first electrical connection 334 is made to an outer surface
or radially outward surface of the piezoelectric acoustic film 330
using conductive material, such as a flexible conductive ink 332,
applied to the outer surface of the piezoelectric film 330. For
example, a wire is attached by suitable means to the plated outer
electrode or conductive ink 332 of the piezoelectric acoustic film
330 and passed through the outer shoulders, where the wire is
connected to signal wires of the acoustic sensor 300. A second
electrical connection 338 to at least a portion of a radially inner
surface of the piezoelectric acoustic film 330 is made, such as
with a metalized ink or conductive fluid. The open circuit voltage,
or electrical charge, of the piezoelectric acoustic film 330, which
is proportional to the changes in the mechanical stress or strain,
is measured using the electrical signal carried by the conductive
ink layers 332, 334 and the electrical leads 334, 338. For example,
the electrical lead is an electrically conductive wire or sheet
adhered to the outer diameter of the hollow chamber so as to form a
conductive surface or electrode using a stable metallic material.
In a case where wire is used, the wire is optionally wrapped a
plurality of turns around the circumference of the substrate 310 so
as to create a continuous conductive path around the circumference
passing the wire from the inside of the piezoelectric film 330 to
the outside of the hollow chamber through a hole in the inner
shoulder, which is preferably later sealed. As the external
hydrostatic pressure increases or decreases, resultant from the
seismic wave or turbulence bubble 210, contraction or expansion of
the substrate 310 and/or diaphragm to which the substrate is
optionally mounted results in corresponding contraction or
expansion of the hollow chamber, the diaphragm, the piezoelectric
acoustic film 330, and/or an array of flexible microspheres,
described infra. Changes in the piezoelectric acoustic film 330,
such as in the z-z thickness axis, are measured using the first
electrical connection 334 made to the conductive ink on one side of
the piezoelectric acoustic film 330 and the second electrical
connection 338 using the electrical lead contacting the opposite
side of the piezoelectric film 330.
Microspheres
[0079] Still referring to FIG. 3A and FIG. 3B, in this example the
acoustic sensor uses an array of flexible microspheres. In this
example, a piezoelectric acoustic film 330 is wrapped about the
mandrel 310. The piezoelectric acoustic film 330 includes
conductive material 332, 336 on the outer surface and the inner
surface, respectively. For example, a first electrical connector
334 is connected to a first flexible conductive ink circuit on the
outer surface of the piezoelectric acoustic film 330. Similarly, a
second electrical connector 338 is connected to a second flexible
conductive ink circuit on the inner surface of the piezoelectric
acoustic film 330. A set of flexible microspheres 320 are
positioned between the mandrel 310 and the inner layer 336 of the
piezoelectric acoustic film 330. The outer surface of the
piezoelectric acoustic film 330 is optionally coated or contained
within a flexible solid 340.
Shark Skin Coating
[0080] The flexible solid 340 or any outer layer of the acoustic
sensor 300 is optionally coated with or integrated into the skin
simulant outer coating 200 to reduce noise and/or drag.
[0081] Referring now to FIG. 4, the microspheres 320 are responsive
to pressure and mechanically isolate the piezoelectric acoustic
film 330. For example, if the acoustic sensor 300 is mounted on a
structure that is struck, the microspheres 320 isolate the
piezoelectric acoustic film 330 of the acoustic sensor 300 from the
transmitted energy in the structure. Similarly, the microspheres
320 isolate mechanical motion resulting from a turbulence bubble
for the piezoelectric film 330. Conversely, adjacent sensors, such
as sensor 1 and sensor 3, described infra, that do not have the
isolating microspheres respond to or sense turbulence bubbles
210.
[0082] The set of microspheres 320 is optionally a single layer of
microspheres or a thickness of microspheres 320, such as less than
about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 300, 500,
1000, 5000, or 10,000 micrometers thickness. The average diameter
of the microspheres 320 is less than about 1, 2, 5, 10, 20, 50,
100, or 1000 micrometers.
[0083] The microspheres 320 are generally flexible, are preferably
plastic, and are not to be confused with incompressible glass
spheres used for buoyancy control, such as in the outer member
445.
[0084] The microspheres 320 in the hydrophone sensor 300 are
optionally flexible and/or plastic. In the piezoelectric acoustic
sensor 300 or hydrophone, the compressible microspheres 320 are
optionally placed into and/or onto an adhesive material, such as to
form an adhesive strip or a sphere coated and/or impregnated
transfer adhesive. For example, the transfer adhesive is optionally
a flexible layer, polymer, or tape coated on preferably one side
and optionally both sides with a layer of the flexible microspheres
320. The flexible microspheres on and/or in the transfer adhesive
are wrapped about the rigid surface or mandrel, or rigid motion
sensor housing 240. Preferably, the microspheres 320 are coated
onto a surface of the transfer adhesive and the sphere coated
surface of the transfer adhesive is wrapped about the rigid
acoustic sensor mandrel 440 to form a layer of flexible
microspheres 320 on the inner surface of the piezoelectric polymer
acoustic film 330 circumferentially wrapped on the rigid substrate
or mandrel 440.
[0085] The thin film piezoelectric acoustic sensor 300 optionally
uses a flexible microsphere loaded adhesive transfer material,
which is applied to one side of the plated film along a length from
the end equal to the circumference of the outer mandrel 310.
Optionally, the microsphere loaded adhesive material, as part of
the piezoelectric acoustic sensor 300, is positioned between two
adjacent strips of non-sphere loaded adhesive forming non-acoustic
sensors, as described infra.
[0086] In practice, an acoustic pressure wave is converted to a
mechanical motion 211 at the water/flexible solid interface. The
mechanical motion is transferred to the piezoelectric acoustic film
330, where a change in shape of the piezoelectric acoustic film 330
is picked up as a corresponding electrical signal using the first
electrical connector 334 connected to the first flexible conductive
ink circuit on the outer surface of the piezoelectric acoustic film
330 and the second electrical connector 338 of the second flexible
conductive ink circuit on the inner surface of the piezoelectric
acoustic film 330. The electrical signal is amplified and
processed, as described supra, to yield information on the seafloor
structure, floor 150 of the water body, and/or on the series of
strata layers 152, 154 under the water body floor 150.
Multiple Sensors
[0087] Multiple sensors are optionally used in each sensor section
of the sensor array 120. For example, output from one or more
motion sensor is combined with output from one or more acoustic
sensor 300, output from a first motion sensor is combined with
output from a second motion sensor, output from a first acoustic
sensor is combined with output from a second acoustic sensor,
and/or output from an acoustic sensor is combined with output from
a non-acoustic sensor. The process of combining the signals
optionally occurs passively using electrical connections, in a
pre-processing stage by use of electronic circuitry, and/or occurs
in a post-processing digital signal processing process.
[0088] Referring now to FIG. 4, an example of a first multiple
sensor system 400 is illustrated. In this example, a central member
440 is encased in an outer element 445, such as a buoyancy element.
As a function of x-axis position, three sensors (S.sub.1, S.sub.2,
and S.sub.3) are figuratively illustrated. The first sensor 410 and
the third sensor 430 are each independently functioning
non-acoustic sensors using a piezoelectric film and associated
electrical connection layers applied directly to the central member
440. The second sensor 420 contains substantially the same features
as the first sensor 410 except the piezoelectric film and
associated electrical connection layers are separated from the
central member by at least one layer of hollow spheres, such as the
flexible microspheres 320, forming an acoustic sensor as described
supra. One or more of the edges and/or ends of the piezoelectric
film of the second sensor 420 are optionally constrained, as
described infra. As illustrated, the first sensor 410, second
sensor 420, and third sensor 430 are optionally electrically
connected to allow for direct subtraction of signal observed by the
non-acoustic sensors 410, 430 from signal observed by the acoustic
sensor 420. Optionally, the individual signals from each sensor are
collected and are later processed. Since the outer element dampens
mechanical motion 211 from the turbulence bubble 210, a localized
mechanical disturbance can be observed with one of the three
sensors 410, 420, 430 while not being observed by a second of the
three sensors 410, 420, 430.
[0089] Referring now to FIG. 5, an example of a second multiple
sensor system 500 is illustrated. In this example, a central tube
540, such as a rigid tube, is encased in an outer housing 550, such
as a semi-flexible housing. As a function of x-axis position, three
sensors (S.sub.4, S.sub.5, and S.sub.6) are figuratively
illustrated. The fourth sensor 510 uses a diaphragm 512 between the
central tube 540 and the piezoelectric sensor elements of the inner
and outer conductive layers on opposite sides of the piezoelectric
film. The diaphragm 512 is offset from the inner tube 440 by use of
offset elements 514, such as the inner shoulders described supra.
The fifth sensor 520 contains the same features as the fourth
sensor 510 except that one or more of the edges 522 of the
piezoelectric film are constrained, such as with an adhesive or
wrap, causing enhanced deformation along the z-z axis of the
piezoelectric film yielding an enhanced signal-to-noise ratio, as
described supra. The sixth sensor 530 also uses a piezoelectric
film between two metal layers, however, the third sensor is bonded
directly to the inner tube 540 yielding a non-acoustic sensor. The
diaphragm 512 or gap optionally contains an array of flexible
microspheres.
[0090] Still referring to FIG. 5, the fourth, fifth, and sixth
sensors 510, 520, and 530 are positioned in about the same position
on the streamer cable 122, such as within about 1, 2, 3, 5, 10, or
20 centimeters of each other. The close proximity of the three
sensors 510, 520, and 530 allows each of the three sensors 510,
520, 530 to observe the same pseudo random turbulence anomalies,
which are localized in space at a given time. By comparing output
signals from the three sensors 510, 520, 530, noise is reduced. For
example, the fourth sensor 510 and the fifth sensor 520 each
observe acoustic signal, such as from the shock wave, while the
sixth sensor 530 observes local turbulence phenomenon also observed
by the first sensor 510 and the second sensor 520. By subtracting
or mathematically removing the signal observed by the sixth sensor
530 from the signal observed by either the fourth sensor 510 or the
fifth sensor 520, the noise of the fourth sensor 510 and the fifth
sensor 520 is observed to decrease by about ten decibels. The
mathematical removal of noise from the fourth sensor 510 signal or
the fifth sensor 520 signal using the sixth sensor 530 signal is
optionally performed using on board electronics or in a post
processing step, as described supra.
Shark Skin Coating 550 550
[0091] The outer housing 550 or any outer layer of the multiple
sensors 400, 500 is optionally coated with or integrated into the
skin simulant outer coating 200 to reduce noise and/or drag.
Buoyancy
[0092] In any of the sensors 124 described herein, any of the
layers, such as an outer buoyancy element are optionally configured
with glass spheres, which function as a buoyancy element.
Generally, the glass spheres are incompressible up to about two
thousand pounds per square inch. Glass spheres are useful in
maintenance of uniform buoyancy regardless of the depth at which
the streamer 120 is towed. A preferred glass sphere has a density
of about 0.32 g/cm.sup.3; however the glass spheres optionally have
a density of less than water and/or less than about 0.9, 0.8, 0.7,
0.6, 0.5, 0.4, 0.3, or 0.2 g/cm.sup.3.
[0093] The buoyancy element, which is optionally the outer housing
126: [0094] is optionally used with any sensor 124 herein; [0095]
optionally contains non-compressible glass spheres; [0096]
optionally contains varying amounts of the glass spheres to adjust
buoyancy as a function of x-axis position and/or as a function of
streamer element size and density; and/or [0097] is optionally
coated with a noise and/or turbulence reduction coating, such as a
shark skin simulant.
Stacked Sensors
[0098] Optionally, two or more sensors, such as a motion sensor,
acoustic sensor, and/or a turbulence sensor, are stacked along the
y- and z-axes at a given point or length along the x-axis of the
streamer cable 122. Generally, the stacked sensors includes any of
the elements of the motion sensor. Similarly, the stacked sensors
includes any of the elements of the acoustic sensor 300. Still
further, generally the stacked sensor optionally includes
non-acoustic sensors similar to the non-acoustic sensors 410, 430,
and 530 described supra.
Combined Sensors
[0099] For clarity, another example of a combined sensor is
provided. While individual sensor sections are optionally placed in
different positions relative to each other, the example uses:
[0100] a sensor accelerometer positioned on a substrate; [0101] a
first non-acoustic sensor positioned radially outward from a center
of the substrate relative to the sensor accelerometer; [0102] a
second non-acoustic sensor positioned radially outward from a
center of the substrate relative to the sensor accelerometer; and
[0103] an acoustic sensor positioned both radially outward from the
center of the substrate relative to the sensor accelerometer and
about adjacent to at least one of the first and second non-acoustic
sensors.
[0104] Generally, the sensor accelerometer uses piezoelectric
motion film between a metalized ink conductor on a first z-axis
side, a second metalized ink conductor or conductive fluid in an
enclosed chamber on a second z-axis side of the piezoelectric
motion film. Any of the acoustic sensor elements described supra,
such as the inner shoulders, diaphragm, and/or the edge constraints
are optionally used.
[0105] Generally, the non-acoustic sensors are offset from the
substrate using a rigid support, such as the outer shoulders. The
non-acoustic sensors are attached without a substantial gap in
rigid layers to the convex side of the substrate, such as through
the outer shoulder and or through the rigid motion sensor housing
circumferentially encompassing the sensor accelerometer. The one or
more optional non-acoustic sensors are preferably located within
about 1, 2, 3, 4, 5, 10, 15, or 20 centimeters of a sensor
accelerometer and/or an acoustic sensor. Each of the one or more
non-acoustic sensors include a piezoelectric film between two
conductive layers, such as metalized ink layers.
[0106] Generally, an offset acoustic sensor uses any of the
elements of the acoustic sensor 300. For example, the offset
acoustic sensor includes a piezoelectric acoustic film 330 between
conductive material on both the outer surface and the inner
surface, as described supra. A set of flexible microspheres 320 or
a pressure equalizing hollow cavity are positioned between a motion
sensor housing and the inner layer 336 of the piezoelectric
acoustic film 330. The outer surface 332 of the piezoelectric
acoustic film 330 is optionally coated with a flexible solid.
[0107] Generally, the sensor accelerometer, non-acoustic sensor,
and offset acoustic sensor are optionally positioned in any spatial
position relative to each other. For example: [0108] the offset
acoustic sensor is optionally positioned radially outward from the
non-acoustic sensor; [0109] the non-acoustic sensor is optionally
at a first radial distance away from the streamer cable 122 that is
different than one or both of a second radial distance between the
streamer cable 122 and the acoustic sensor or a third radial
distance between the streamer cable and the sensor accelerometer;
and/or [0110] the sensor accelerometer, non-acoustic sensor, and
offset acoustic sensor are vertically stacked.
[0111] Stacking of at least two of the sensor accelerometer, the
non-acoustic sensor, and the offset acoustic sensor reduces the
stiff length section(s) of the sensor array 120, which aids in
durability and deployment of the sensor array 120.
[0112] A means of connecting the electrodes of the film is provided
in which wires are attached to a means by which the signal can be
passed through the outer shoulders of the assembly.
[0113] Rigid stress isolating blockers specifically designed to
allow for the inner molding and attachment of the embodied sensors
to the primary electromechanical cable are then molded to the ends
of the innermost mandrel with conductive pins insert molded to
allow for the passing of the dual sensor's respective outputs
through the outer shoulders to the adjacent sensors and ultimately
passing the signals to the core of the electromechanical cable. The
shapes at the ends of the shoulder moldings are specifically
configured to prevent the entrapment of air bubbles in the vertical
inner molding process.
[0114] Each individual sensor embodiment is then over molded
between the previously molded shoulders resident at the ends of the
individual innermost mandrels to form a smooth shape suitable for
secondary over molding with an elastomeric flexible syntactic
flotation material.
Streamer Cable
[0115] Completed sensor pairs are then arranged into a group of
sensors that forms the acoustic, motion, and/or turbulence sensor
apertures of the seismic streamer section.
[0116] The acoustic sensors 300 are typically combined electrically
in parallel by use of a twisted pair of conductors connected from
one sensor to the next with sufficient length so as to allow for
the helix of the wire around the core cable between sensors to
prevent breakage when the streamer is bent either in handling or in
winding on a reel.
[0117] The motion sensors are typically combined electrically in
parallel by use of a twisted pair of conductors connected from one
sensor to the next with sufficient length so as to allow for the
helix of the wire between sensors to prevent breakage when the
streamer is bent either in handling or in winding on a reel.
[0118] The completed inner and outer molded sensor section is then
over molded with a second form of glass spheres or glass
microspheres loaded into an incompressible elastomeric flotation
compound that creates a uniform diameter continuous flexible sensor
section.
[0119] Optional relationships between sensor 124 components are
further described: [0120] The rigid mandrel or substrate forms the
base of the sensor construction. [0121] Features molded over the
rigid substrate, such as the inner shoulders and outer shoulders
form the necessary cavities and supporting structures to place the
components of the dual sensors. [0122] The polymer film motion
sensor element resides between the inner shoulders and forms the
cavity or hollow chamber into which an optional liquid metal
electrode is placed. [0123] The motion sensor shoulders reside
beneath or adjacent to the acoustic sensor 300 shoulders. [0124]
The optional conductive material placed around the inner base of
the cavity resides in contact with the liquid metal. [0125] The
second set of shoulders provides for the mounting of a second rigid
tube, which forms a cylindrical cavity around the motion sensor
element. [0126] The second rigid tube forms the substrate for the
acoustic sensor 300 element, which resides outside the
circumference of the second rigid tube. [0127] The second
piezo-element 330 with its patterned syntactic loaded adhesive is
then wrapped around the outer rigid substrate and forms the passive
flow noise cancelling acoustic sensor 300. [0128] The electrical
wires from each respective sensor are attached together either in
parallel or series to create a group of sensors that comprise a
discreet channel within the seismic streamer 122. [0129] The group
of sensors are placed on the core cable by sliding the cable
through the inner diameter of the sensor embodiment. [0130]
Acoustic output from the acoustic sensor 300 is wired separate and
apart from acceleration output from the acceleration sensor and
both sensors are presented to an opening in the inner
electromechanical cable where they are attached to their respective
pairs of wires within the core cable. [0131] The discreet sensor
embodiments are placed in a mold that presents the individual
sensor embodiments to their desired locations within the group.
[0132] The group of sensors is then molded to the inner core cable
with the novel shoulder shape of the individual embodiments
preventing the entrapment of air bubbles during the molding
process. [0133] The cable is terminated with connectors located at
each end. Each cable length comprises a section of the cable.
[0134] Each section of the cable is then presented to the process
of over molding of the syntactic flotation material which completes
the process of construction of the dual sensor seismic section with
passive flow noise cancelling.
[0135] An example of how components work together is provided:
[0136] The first inner rigid substrate provides a rigid form that
isolates mechanical energy present in the core electromechanical
cable from both the motion sensor and the passive flow noise
cancelling acoustic sensor 300. [0137] The inner rigid substrate
provides a rigid form upon which mechanical features are molded.
The substrate is preferably a rigid filled plastic for ease of
manufacture, that form the embodiment and form for both the motion
and flow noise cancelling acoustic sensor 300 and the later molded
rigid stress isolating, bubble eliminating outer shoulders. [0138]
A piezoelectric polymer film element is constructed where a single
side of the film receives a conductive coating forming an electrode
plate and wrapped about the shoulders present at the edge of the
molded cavity that reside about the circumference of the molded
form forming a sealed cavity about the circumference and between
the outer diameter of the inner molded form and the inner diameter
of the wrapped piezoelectric element where the metalized electrode
resides on the outer diameter of the piezoelectric film. [0139] A
conductive element is wrapped a plurality of wraps about the outer
diameter of the inner molded form to create an inner electrode
conductive surface with one end presented through and outside the
sealed chamber available to attach a conductor for signal
transmission. [0140] The motion sensor 300 is enclosed in a rigid
tube, which prevents acoustic energy from contributing to the
output of the piezoelectric motion sensor. [0141] The second tube
forms the mandrel upon which the acoustic element is constructed
and isolates the acoustic sensor 300 from mechanical energy present
in the core electro mechanical cable. [0142] A second piezoelectric
polymer element 330 is constructed and plated on both sides to
create a piezoelectric element. The thin film piezoacoustic sensor
300 is created using a novel flexible microsphere loaded adhesive
transfer material, which covers a specific area on one side of the
plated film 330 along a length from the end equal to the
circumference of the outer mandrel and positioned between two
adjacent strips of non-sphere loaded transfer adhesive. Regions of
the adhesive strip that are not coated with spheres continue over
and above the remaining length of the piezo film. Beginning at the
end of the piezopolymer film that is coated with the flexible
microsphere loaded transfer adhesive, the PVDF piezopolymer thin
film 330 is wrapped around the circumference of the mandrel a
minimum of one single wrap or a plurality of wraps depending on the
length of the piezoelectric acoustic film 330. While a single wrap
minimum is specified, it is desirable to create a complex pattern
of both filled and non filled transfer adhesive to create a fractal
sampling pattern for both the acoustic sensor and the turbulent
boundary sensor. [0143] Electrical connection is made to the
piezoelectric film by crimps that puncture the piezoelectric film
and provide a conductive path to which wires are then attached to
transmit the desired signal which is a common practice in
terminating piezopolymer films.
Sensor Function
[0144] Dynamic pressure, regardless of the source, results in a
pressure differential to exist between the sealed volume of the
microspheres 320 and the outside of the sensor resulting in a
mechanical change in the piezopolymer acoustic film 330 that
mirrors the dynamic change in pressure in that area. Turbulent
boundary layer pressures present over the flexible microsphere
loaded areas also result in an output proportional to the
mechanical changes in the same manner and form as the acoustic
pressures and are considered to be "in phase". This is due to the
way in which the film deforms and the respective response by the
three axis of deformation in the PVDF film with d31, d32 and d33,
d31 and d32 being electrically in phase with d33 being electrically
out of phase by about one hundred eighty degrees. The deformation
resulting from a positive change in dynamic pressure in the areas
where the PVDF film is underlain by the compressible microspheres
320 results in the compression of the flexible microspheres 320,
thus shortening the circumference of the cylinder of wrapped PVDF
film. This shortening results in an output from the d31 axis, the
axis of highest sensitivity to change, a shortening of the d32 axis
results with it's minor contribution to the convolved output and
constrained by Poison's ratio, there is a corresponding lengthening
of the d33 axis or a thickening of the film. This action is
mechanically out of phase with the other two axis which results in
the signal output due to the change in the d33 to be in phase
electrically with both d31 and d32. The convolution of these three
outputs results in a pre-determined sensitivity to acoustic energy
controlled by the mechanical deformation.
[0145] In the areas of the PVDF film where the transfer adhesive
has no compressible microspheres, both the d31 and d32 axis of
response are now constrained, unable to contribute effectively to
dynamic pressure. The bounded condition present on d31 and d32
means that the films only available axis of response resides in the
force present on the d33 axis. It can be understood that
compression of the d33 axis results in a shortening of the d33 axis
and a corresponding output resulting from that deformation is
mechanically out of phase with the d33 axis response in those areas
where compressible microspheres reside. It has been demonstrated
that under these constrained conditions, the output from the d33
axis is some 40 dB lower than that from the d33 axis in the areas
where compressible microspheres reside and about one hundred eighty
degrees out of phase, thus subtracting from the acoustic output.
The resulting signal due to acoustic pressure is reduced
insignificantly. The pressure fields produced by the turbulent
boundary layer manifest themselves as a force in the solid
non-compressible microsphere 322 loaded flotation material which is
over molded above the sensor and electro-mechanical cable, pressing
down and into the non-sphere backed PVDF film resulting in a
compression of the d33 axis of the PVDF film producing a
corresponding output proportional to the forces present on the now
incompressible PVDF film element which is also 180 degrees out of
phase with the corresponding signal produced by the turbulent
boundary layer in the areas under which the compressible
microspheres lie, thus cancelling the signals due to turbulent
boundary layer noise.
Method of Manufacture
[0146] An example of method of manufacture is described.
[0147] To make the invention, a rigid mandrel or substrate is
fabricated to produce a desired form factor for the final
embodiment as a seismic streamer or sensor array 120. The substrate
or rigid mandrel is over molded to place the required features onto
the surface of the rigid mandrel to allow for the mounting and
isolation of the two discreet sensors, such that the two sensors
occupy the same space and are deemed co-located. The two sensors
are optionally the motion sensor and acoustic sensor 300. The
motion sensor is immune to acoustic energy by the placement of a
rigid tube that surrounds the motion sensor and prevents sound from
accessing the volume where the motion sensor resides. The rigid
tube forms the substrate or base for the acoustic sensor 300. The
acoustic sensor 300 is formed around the outer substrate with a
flexible microsphere loaded adhesive resident beneath and between
the film element and the rigid substrate. The film can be
continuous or can be comprised of discreet patterns of electrodes
deposited onto the surface of the polymer film to accomplish the
desired response characteristics.
Dual Element Sensors
[0148] A number of dual element sensors are electrically wired
either in series or in parallel to form the desired group or
aperture characteristics. Acoustic sensors are wired together
providing one signal output and the acceleration sensors are wired
together to provide a single signal output of acceleration. The
embodiment of the group or aperture is optionally a set of elements
spaced as close to one another as is mechanically practical
preserving the ability to bend the aperture around a winch or
sheave without damage while optimizing rejection of mechanical
energy propagating along the length of the cable. The wired group
is then loaded onto the core cable in the desired location by
threading the core cable through the inner diameter of the combined
sensor and electrically terminated to the core cable through a
single opening in the core cable jacket.
[0149] The group of sensors is placed in the group mold which fixes
the location of the individual sensors within the group and along
the length of the entire cable; the wires interconnecting the
individual elements within the group are wrapped in two directions
about the core cable between the discreet locations within the
group. The group is molded to the cable sealing the entrance of the
wires into the core cable jacket eliminating potential leakage
paths and centering the elements about the cable. Microsphere
loaded solid flexible elastomer flotation is then molded over the
entire cable length and over the individual groups having
previously been mounted along the entire cable length.
[0150] The location of the motion sensor is optionally either
beneath the acoustic sensor or adjacent to the acoustic sensor
residing on the same rigid substrate. This allows for a reduced
diameter of the entire embodiment as required. The spacing within
the group between the discreet elements of the group is optionally
varied depending of the desired response of the group with some
elements spaced at one interval, some at another to tailor the
response of the motion sensor to reject undesirable energy
propagating within the streamer assembly essentially tuning the
aperture to respond only to the desired vertically propagating
signal.
[0151] The dual sensor within a seismic streamer operates with two
objectives, reduction of noise due to flow and the recovery of
bandwidth in the acoustic domain that is lost as a result of the
energy that is propagating from the earth below, reflecting back
from the sea surface and air interface, inverting and propagating
down to the acoustic receivers in the streamer, thus interfering
with the desired upward propagating signals causing a loss of
signal within a bandwidth determined by the depth of tow relative
to the reflected surface. Use of both an acoustic sensor and a
motion sensor allows in post processing of the seismic data, the
use of the inherent directional characteristics of motion to be
convolved with the inherent characteristic lack of direction in
acoustic signals to remove the downward propagating energy from the
desired signals, thus recovering the lost energy and improving the
resolution of the seismic data. Unlike other descriptions of this
technique, this system provides that the motion and acoustic
response from the discreet sensors result from the same excitation
due to the co-location of the acoustic and motion sensors, allowing
for improved processing results. The noise due to flow is reduced
by placing a single continuous element where a portion of the
element is bonded to the substrate using a flexible microsphere
loaded adhesive which creates the acoustic sensing portion of the
element. The remaining surface of the element is coated with a
non-sphere filled adhesive that bonds the polymer film directly to
the surface of the rigid substrate, thus preventing its changing
length due to acoustic energy and the associated change in the
circumference of the microspheres residing beneath the film. The
portion of the film with no microspheres responds with only one
axis of deformation, that being the thickness axis, to the force
created by the turbulence present at the surface of the flotation
material which in the case of the area where the microspheres
reside is unbounded and thus responds to the pressure. The force
manifests itself out of phase with the pressure and thus the signal
generated in a contiguous piece of PVDF thin film causes the two
signals due to turbulent boundary layer flow noise to cancel, thus
mitigating the overall response to this type of undesirable
energy.
[0152] The use of these two distinct outputs from the differing
sensors allows in data processing for the recovery of lost energy
due to the reflections from above at the air water interface. In
one embodiment, the current system places both the acoustic sensor
300 and motion sensor in the same physical space thus eliminating
any differences in response due to their different location. The
system also provides for a uni-axial accelerometer that only senses
vertical and does so with no complex mechanical parts or gimbals
and resides interior to the acoustic sensor. Co-locating the
sensors results in a linear transfer function between the two
sensors and simplifies and improves post processing. The dual
output sensor utilizes acceleration so that proper phase is
maintained between the acoustic response and the acceleration
response.
[0153] In varying embodiments, the sensor 124 comprises any of:
[0154] a thin film piezopolymer acoustic sensor incorporating a
flexible microsphere loaded transfer adhesive as the compressible
gas chamber providing high sensitivity and immunity to overburden
pressure; [0155] a seismic streamer for marine seismic surveys
embodying a thin film piezopolymer acoustic sensor incorporating a
unique flexible microsphere loaded transfer adhesive as the
compressible gas chamber providing high sensitivity and immunity to
overburden pressure; [0156] a thin film piezopolymer acoustic
sensor incorporating a flexible microsphere loaded transfer
adhesive as the compressible gas chamber providing high sensitivity
and immunity to overburden pressure combined with zones of
non-microsphere loaded transfer adhesive to act as sensors of the
turbulent boundary layer whose combined output provides for passive
cancelling of noise due to turbulent boundary layer flow; [0157] a
seismic streamer for marine seismic surveys embodying a thin film
piezo polymer acoustic sensor incorporating a unique flexible
micro-sphere loaded transfer adhesive as the compressible gas
chamber providing high sensitivity and immunity to overburden
pressure combined with zones of non-microsphere loaded transfer
adhesive to act as sensors of the turbulent boundary layer whose
combined output provides for passive cancelling of noise due to
turbulent boundary layer flow; [0158] a monolithic sensor or
multiple sensors housed in a single housing, such as a rigid
housing, dual output, flow noise cancelling acoustic and liquid
metal uniaxial motion sensor embodied in a flexible elastomer, such
as a syntactic elastomer, based solid seismic streamer for marine
seismic surveys; [0159] a seismic streamer for marine seismic
surveys embodying a thin film piezo polymer acoustic sensor
incorporating a flexible microsphere loaded transfer adhesive as
the compressible gas chamber providing high sensitivity and near
immunity to overburden pressure combined with zones of
non-microsphere loaded transfer adhesive to act as sensors of the
turbulent boundary layer whose combined output provides for passive
cancelling of noise due to turbulent boundary layer flow; [0160] a
monolithic dual output, acoustic and motion sensor co-located
within a single discreet housing; [0161] a monolithic dual output,
acoustic sensor and motion sensor utilizing an acoustic sensor
employing a flexible piezopolymer film, such as a syntactic backed
piezopolymer film embodiment; [0162] a monolithic dual output,
acoustic and motion sensor utilizing a liquid metal electrode
arrangement, which uses gravity to place the fluid mass and
electrode in such a manner as to allow for sensing only vertical
motion and rejecting undesirable motion; [0163] a monolithic dual
output, acoustic and acceleration sensor utilizing a novel pressure
isolation method to prevent acoustic response in the motion sensor
response; [0164] a seismic streamer for marine seismic surveys
embodying a thin film piezo polymer acoustic sensor incorporating a
flexible microsphere loaded transfer adhesive as the compressible
gas chamber providing high sensitivity and immunity to overburden
pressure combined with zones of non-microsphere loaded transfer
adhesive to act as sensors of the turbulent boundary layer whose
combined output provides for passive cancelling of noise due to
turbulent boundary layer flow combined with a novel monolithic dual
output, acoustic and motion sensor utilizing a novel liquid metal
electrode arrangement which uses gravity to place the fluid mass
and electrode in such a manner as to allow for sensing only
vertical motion and rejecting undesirable motion; [0165] a
monolithic dual output, acoustic and motion sensor embodied within
a flexible syntactic seismic streamer in groups that are nested in
complex spacing arrangements to enhance rejection of undesirable
signals; [0166] a monolithic dual output, acoustic and motion
sensor embodied within a flexible syntactic seismic streamer
allowing for the core electro-mechanical cable to reside within the
diameter of the sensor embodiment; and [0167] an outer turbulence
reduction surface.
Shark Skin/Turbulence Reduction Surface
[0168] The surface of any element of the streamer cable 122 or
towed sensor is optionally a simulated "shark skin" surface.
Herein, the shark skin surface refers to an outer surface of any
element of the sensor array 120 or streamer cable 122 in contact
with the water body 155 during use. Herein, the clause "shark-skin"
is used, without limitation, for clarity of presentation. Shark
skin refers to any turbulence reduction/laminar flow enhancing
surface. To facilitate understanding, the shark skin surface is
herein referred to as the outer boundary layer or boundary layer
200, which is optionally and preferably a man-made surface,
coating, or layer that is formed via a mold or other technique or
is a coating, tube, or sheet for applying to a surface. For
example, the boundary layer 200 is a sheet applied to the flexible
solid 340 or outer housing 550 of the streamer cable, described
supra.
Denticle
[0169] Referring now to FIG. 6, an optional boundary layer 200
denticle 600 is illustrated. Herein, the denticle 600 is a
repeating element of the boundary layer 200 and refers to a shape
rather than a material, such as a tooth-like shape and not a
material, such as a tooth-like dentin material. For example, a
plurality of the denticles 600 are layered and/or attached to form
a larger layer, where the larger layer is used to coat a surface of
an element of the sensor array 120 and/or is integrated with an
element of the sensor array 120. The particular shape of the
denticle 600 is optionally of any shape or shapes that reduce drag
of the element of the sensor array 120, reduces turbulence
proximate one of the sensors 124, and/or increases compression
about an element of the sensor array, which leads to decreased
resistance to flow. Further, the outer perimeter shape of the
denticle 600 is not necessarily as depicted in FIG. 6, rather the
key elements of the denticle 600 and/or boundary layer 200 is
existence of one or more ridges, one or more channels, one or more
dimples or bumps, one or more raised sections, a tipped trailing
edge, a saw tooth trailing edge, and/or or turbulence reducing
surface structure that adjoins, overlaps, partially overlaps,
and/or extends as a random or repeating structure over a surface of
the boundary layer 200. The denticles are optionally configured to
create a low-pressure zone, which is also referred to as a
leading-edge vortex, as the water moves over the boundary layer
200. The leading edge vortex created by the denticles yields a low
pressure area that counters high pressure turbulence 200. In one
example, the outer surface comprises curved bumps, such as wing
shapes to induce a low pressure region countering high pressure
turbulence regions of the surrounding water body. The bumps
optionally extend outward from a nominal outer surface of an
element of the towed array by at least 0.5, 1, 2, 3, or 5
millimeters.
[0170] Still referring to FIG. 6, a first example of a denticle 600
is provided and is illustrated from a top view, FIG. 6A, and from a
side view, FIG. 6B. In this example, the water flows past the
surface of the denticle 600 along one or more ridges 610 and/or
within one or more channels 620. The ridges 610 are optionally
uniformly spaced or have differing distances or width of
intervening channels, such as a first channel width, w.sub.1, and a
second channel width, w.sub.2, where the first channel width is
greater than the second channel width by greater than 10, 20, 30,
50, 100, or 200 percent. The ridges 610 function to dampen
turbulence of water next to the denticle 200 or sheet 1000. The
channels 620 are optionally uniformly deep or have differing
depths, such as a first channel depth, d.sub.1, and a second
channel depth, d.sub.2, where the first channel depth is greater
than the second channel depth by greater than 10, 20, 30, 50, 100,
or 200 percent. Optionally, within a given denticle 600, the depths
of the channels are deeper near a longitudinal center of the
denticle and more shallow a greater radial distance from the
longitudinal center of the denticle 600.
[0171] Referring now to FIG. 7, a second example of a denticle 600
is provided. In this second example, one or more of the channels
620 increases in width to form a broadening channel 622 from a
third width, w.sub.3, to a fourth width, w.sub.4, along the length
of the channel, which reduces resistance of the flowing water layer
along the surface of the denticle or boundary layer 200, where the
fourth channel width is greater than the third channel width by
greater than 2, 5, 10, 15, 20, 25, 30, 40, or 50 percent.
[0172] Referring now to FIG. 8, a third example of the boundary
layer 200 is provided having partially overlapped structures,
surface structures of varying thickness, a ridge lining up with a
channel, no holes or gaps to the underlying outer housing 550,
and/or holes or gaps to the underlying outer housing 550 or
flexible solid 340, each of which are described herein.
Varying Thickness
[0173] Still referring to FIG. 8, a second denticle 602 contacts
the first denticle 600 or scale. In places, the second denticle 602
has a region of overlap 630 with the first denticle 600. The region
of overlap 630 creates a local zone where the thickness of the
boundary layer is increased by more than 10, 20, 30, 50, 75, or 100
percent compared to an average thickness of the boundary layer,
which creates a local structure that disrupts the localized
turbulence bubble 210. In a case where denticles are not used and
the boundary layer 200 is a sheet 1000 or corset about any element
of the sensor array 120, then the thickness of the corset or sheet
1000 optionally varies from a mean thickness by more than 10, 20,
30, 50, 75, or 100 percent.
Compression
[0174] Optionally, the outer layer or sheet of the shark-like
material provides an inward compression force on one or more parts
of the towed array, which reduced cross-sectional area of the towed
array part in the direction of towing. The reduction in
cross-sectional area in the direction of towing reduces friction,
reduces turbulence, and/or enhances fuel mileage of the towing
ship.
Gaps
[0175] Still referring to FIG. 8, the second denticle 602 contacts
the first denticle 600 or scale. In places, the second denticle 602
and the first denticle 600 have a gap 640 in coverage of an
underlying element, such as the underlying outer housing 550 or the
flexible solid 340. Preferably, the gaps 640 comprise less than
about 30, 20, 10, 5, 2, or 1 percent of any substantially covered
or coated part or element.
Ridges/Channels
[0176] Still referring to FIG. 8, the ridges 610 described supra
are further described. The ridge 610 optionally runs longitudinally
along the length of the denticle or is a partial ridge 616 or
riblet that runs only a fraction of the distance from a leading
edge to a trailing edge of a denticle 600 or sheet 1000. Generally,
the partial ridge 616 is less than about 0.25, 0.5, 0.75, 1.00, 2,
3, 4, 5, 10, 20, 40, 60, 80, or 100 millimeters long. Similarly,
the channel 622 optionally extends from the leading edge of the
denticle 600 to the trailing edge of the denticle 600 or is a
partial channel 624 that runs only a fraction of the distance from
a leading edge to a trailing edge of a denticle 600 or sheet 1000.
Generally, the partial channel 624 is less than about 0.25, 0.5,
0.75, 1.00, 2, 3, 4, 5, 10, 20, 40, 60, 80, or 100 millimeters
long. More generally, the partial ridge 616 and partial channel 624
are optionally a bump or dent, respectively. Optionally, and
preferably, a specific ridge 614 from one denticle, such as the
second denticle 602, overlaps a specific channel, such as on the
partial channel 624, which disrupts the localized turbulence bubble
210 to form the turbulence microelements 212. The ridges and/or
denticles hold water close and prevent the creation of eddies in
the boundary layer, which reduces noise and drag. Optionally, the
ridges comprise curved surfaces, such as a bump, awing shape facing
the direction of towing, and/or a wing shape in a direction
opposite that of the towing direction.
[0177] Referring now to FIG. 6C, one or more ridges optionally
includes a curved surface 612, such as a wing-shape, a leading
curved edge, a trailing curved edge, and/or a hill shape.
Array
[0178] Referring now to FIG. 9, the boundary layer 200 is
optionally a sheet 1000 and/or an array of denticles 900. In FIG.
9, an array of denticles 900 is illustrated having m rows 910 and n
columns 920, where m and n are each positive integers of at least
two. The individual denticles in the array of denticles 900 are
optionally repeating identical units, are partially rotated
relative to each other, are aligned into rows and/or columns, are
not aligned into rows and columns, have two or more shapes, have
individual shapes, and/or have gaps between individual
elements.
Sheet
[0179] Referring now to FIG. 10A and FIG. 10B, an example of a
shark-skin simulant sheet 1000 is illustrated from a top view, FIG.
10A, and from an end view, FIG. 10B, where the sheet is an example
of the boundary layer 200. The sheet 1000 optionally has
alternating sheet ridges 1010 and sheet channels 1020 of any
length. The sheet 1000 is optionally wrapped around a part, such as
any element of the towed array 120. The sheet 1000 optionally
compresses any element of the towed array 120 forming a more
streamlined underlying element, which decreases resistance. The
sheet 1000 is optionally a helical network surrounding an element
of the towed array 120, circumferentially surrounds an element of
the towed array, and/or coats or covers a surface area of an
element of the towed array. Optionally, the flotation layer or
elastomeric flexible syntactic flotation material is optionally
formed in a mold forming the shark-like surface directly into the
surface of the flotation layer without the need to apply an outer
skin layer. Optionally, the sheet 1000 is integrated into any
element of the towed array 120. In the sheet 1000, the length of
any of the sheet ridges 1010 and/or sheet channels 1020 are
optionally varied from location to location on the sheet 1000 to
resemble the partial ribs 616 and/or the partial channel 624, as
described supra.
Outer Boundary Layer
[0180] The outer boundary layer 200, which is optionally a
sharkskin simulant, yields advantages when used to coat (or is part
of) an outer layer of any element of the towed array 120. Examples
of advantages include one or more of: [0181] a hydrodynamic
advantage; [0182] a decrease in resistance to flow or towing;
[0183] a reduction in viscous drag by providing a textured surface;
[0184] a reduction in turbulence; [0185] a localized compression of
an underlying element into a more streamlined shape, which reduces
drag; and [0186] buoyancy by trapping air bubbles within the
boundary layer.
[0187] The boundary layer 200 is characterized as one or more of:
[0188] a biomimetic material; [0189] a drag reducing layer; [0190]
a hydrodynamics improved surface with decrease in drag; [0191]
resistant to bio-fouling, such as resistant to growth of barnacles,
mussels, algae, or other organisms, which can increase drag and
hence towing fuel costs, through us of an impregnated or coated
biocide; [0192] self-cleaning when towed due to local flow over the
surface of the boundary layer 200; [0193] producing tiny vortices
for drag reduction; [0194] noise reducing when being towed in
water; [0195] resistant to penetration by water; [0196] a
compression layer; and [0197] a saw tooth pattern.
[0198] The boundary layer optionally contains any of: [0199] a
biocide; [0200] diamond shaped scales; [0201] scales or denticles
that flex in and out to impede growth of organisms; [0202] a dentin
material; [0203] backward facing teeth simulants, configured to
feel smooth when running from a leading edge to a trailing edge but
rough when stroked trailing edge to leading edge, the leading edge
leading the trailing edge along the x-axis during use; [0204]
backward facing triangular projections, which causes water to
spiral away from the surface; [0205] a spandex; [0206] an
elastane-nylon; [0207] a nylon; [0208] a fabric; [0209] a
polyurethane; [0210] a water impermeable compound; and [0211] a
fabric or rigid element imitating high tech swimwear, such as
produced by Nike.RTM. (Beaverton, Oreg.), Speedo.RTM. (London, UK),
Arena.RTM. (Tolentino, Italy), or Adidas.RTM. (Herzogenaurach,
Germany).
[0212] Additionally, one or more sections of the sheet 1000 are
optionally connected using any of: [0213] an ultrasonic weld;
[0214] a tripwire or turbulator configured to keep water from
breaking over the surface and/or configured to keep water flowing
consistently along the surface of one or more sheets 1000; [0215] a
congruent height relative to an underlying part; [0216] a seam; and
[0217] a low-profile bonded seam.
Streamer Positioner/Coupler Connection
[0218] In another embodiment, a connector is used to relieve forces
resultant at and/or near a junction of a seismic streamer
positioner and a seismic streamer section.
[0219] Herein, the seismic streamer positioner is also referred to
as a depth controller. A depth controller is used to control the
depth of tow of the streamer. For example, a depth controller is
connected using a pair of collars and races connected directly to
the outside diameter of the streamer. In this example, the depth
controller is generally tube shaped with a set of fins attached to
the aft end and two standoffs where the collars attach it to the
streamer at the races, which allowed the bird to rotate around the
axis of the streamer making it always hang below the streamer.
Essentially, the depth controller controls only the vertical
position of the streamer in the water body.
[0220] Streamer arrays are often used instead of a single streamer,
which allows more accurate and precise three-dimensional maps of
underlying strata layers. To enhance performance of the towed
array, spacing between individual streamers in the array is
preferably controlled. For example, a known and/or controlled
distance between any two cables of an array of cables is preferred.
The controlled position of each cable is achieved using birds,
described infra.
[0221] Herein, the seismic streamer positioner is also referred to
as a bird, a bird positioner, and/or as a bird controller. A bird
or seismic streamer positioner is used for control and/or positive
control of one or more of: lateral position of a streamer position,
vertical control of a streamer position, roll control of a streamer
position, orientation of a streamer cable, depth of a streamer
cable, separation of two or more streamer cables in a streamer
array, and/or control of a trailing end of one or a set of
streamers. Multiple bird positioners are optionally and preferably
used for each streamer cable.
[0222] Referring now to FIGS. 11A-C, a perspective, end, and top
view, respectively, of a bird positioner 1100 relative to one or
more couplers 1230 and relative to one or more streamer sections
122 is provided. The bird positioner 1100 includes a central tube
shaped member 1110, which is optionally a hollow shaft carrying
communication lines. For clarity of presentation, the bird
positioner 1100 is illustrated with three fins; however, any number
of fins for a given bird positioner are optionally used, such as 2,
3, 4, 5, or more fins. Still referring to FIG. 11A-C, the
illustrated bird positioner has three fins at 1120 degree intervals
around the central member 1110, which is typically a dedicated
module that connects between the seismic streamer sections much the
same as the digital telemetry modules. The seismic streamer
positioner or bird positioner optionally includes: internal
inertial guidance, which allows sensor input as to which way is up,
internal compasses for determination of direction, and electro
and/or mechanical components for control of bearing and
azimuth.
[0223] The bird positioner is optionally: [0224] constructed of
titanium for tensile strength and corrosion resistance; [0225]
includes replaceable attached wings to the central tubular member
to allow winding on a streamer drum; [0226] contains wireless
and/or wired communication elements for long range streamer
communication; and/or [0227] contains wireless power transfer
between the wing 1120 and the body 1110.
[0228] An example of a bird positioner is the eBird.RTM. (Kongsberg
Maritime, Kongsberg, Norway).
[0229] A connector 1230, described supra, for connecting a terminal
end of a first streamer section and a leading end of a second
streamer section is optionally used to connect a streamer section
122 to a streamer positioner 1100. Any of the above described
elements of the stress relief module 232 are optionally used in a
streamer positioner connector. Further, the orientation along the
x-axis of any of the above described connector 1230 elements are
optionally reversed to face up a length of the streamer cable 122
as opposed to the above described elements facing down the length
of the streamer cable 122.
[0230] For example, any of the above described connectors are used:
(1) to connect at a first end to a streamer cable 122 and at a
second end to the streamer positioner 1100 or (2) to connect at the
first end to a streamer positioner 1100 and at the second end to a
streamer cable 122 section. Similarly, the connector is optionally
used at the tail end of a series of streamer sections to connect to
a trailing streamer positioner.
[0231] Still referring to FIGS. 11 A-C, any of the bird positioner
1100, bird body 1110, wing or fin 1120, and/or connector 1230 are
positions where drag on the cable exists and places where local
turbulence is preferably reduced. To reduce the drag and/or
turbulence on the streamer cable 122, any of the outer boundary
layer 200 coating, sheet 1000, shark skin scale 600, array of
scales 900, and an artificial turbulence reduction layer are
optionally used to coat any of the bird positioner 1100, bird body
1110, wing or fin 1120, connector 1230, and/or streamer cable 122
element.
[0232] Still yet another embodiment includes any combination and/or
permutation of any of the sensor elements described herein.
[0233] The particular implementations shown and described are
illustrative of the invention and its best mode and are not
intended to otherwise limit the scope of the present invention in
any way. Indeed, for the sake of brevity, conventional
manufacturing, connection, preparation, and other functional
aspects of the system may not be described in detail. Furthermore,
the connecting lines shown in the various figures are intended to
represent exemplary functional relationships and/or physical
couplings between the various elements. Many alternative or
additional functional relationships or physical connections may be
present in a practical system.
[0234] In the foregoing description, the invention has been
described with reference to specific exemplary embodiments;
however, it will be appreciated that various modifications and
changes may be made without departing from the scope of the present
invention as set forth herein. The description and figures are to
be regarded in an illustrative manner, rather than a restrictive
one and all such modifications are intended to be included within
the scope of the present invention. Accordingly, the scope of the
invention should be determined by the generic embodiments described
herein and their legal equivalents rather than by merely the
specific examples described above. For example, the steps recited
in any method or process embodiment may be executed in any order
and are not limited to the explicit order presented in the specific
examples. Additionally, the components and/or elements recited in
any apparatus embodiment may be assembled or otherwise
operationally configured in a variety of permutations to produce
substantially the same result as the present invention and are
accordingly not limited to the specific configuration recited in
the specific examples.
[0235] Benefits, other advantages and solutions to problems have
been described above with regard to particular embodiments;
however, any benefit, advantage, solution to problems or any
element that may cause any particular benefit, advantage or
solution to occur or to become more pronounced are not to be
construed as critical, required or essential features or
components.
[0236] As used herein, the terms "comprises", "comprising", or any
variation thereof, are intended to reference a non-exclusive
inclusion, such that a process, method, article, composition or
apparatus that comprises a list of elements does not include only
those elements recited, but may also include other elements not
expressly listed or inherent to such process, method, article,
composition or apparatus. Other combinations and/or modifications
of the above-described structures, arrangements, applications,
proportions, elements, materials or components used in the practice
of the present invention, in addition to those not specifically
recited, may be varied or otherwise particularly adapted to
specific environments, manufacturing specifications, design
parameters or other operating requirements without departing from
the general principles of the same.
[0237] Although the invention has been described herein with
reference to certain preferred embodiments, one skilled in the art
will readily appreciate that other applications may be substituted
for those set forth herein without departing from the spirit and
scope of the present invention. Accordingly, the invention should
only be limited by the Claims included below.
* * * * *