Apparatus and method for measuring shape of underwater tow cables
Example embodiments provide a cable measuring apparatus and method comprising a cable and a fairing system. The cable may be configured to be connected at opposite ends in a marine environment, wherein one connection provides a stabilizing force in order to allow the cable to form a catenary in response to the stabilizing force interacting with currents in the marine environment. The fairing system may be connected to the cable about its length, the fairing system comprising a plurality of fairing units, at least one of the plurality of fairing units being an instrumented replacement fairing unit. The instrumented replacement fairing unit may be configured to record measurements of at least the catenary when subjected to the stabilizing force.
1 . A cable measuring apparatus comprising:
a cable configured to be connected at opposite ends in a marine environment, wherein one connection provides a force amount in order to allow the cable to form a catenary in response to the stabilizing force interacting with currents in the marine environment; and
a fairing system connected to the cable about its length, the fairing system comprising a plurality of fairing units, at least one of the plurality of fairing units being an instrumented replacement fairing unit,
wherein the instrumented replacement fairing unit is configured to record measurements of at least the catenary when subjected to the force amount.
2 . The cable measuring apparatus of claim 1 , wherein the cable is configured to be connected at one end to a vehicle and at another end to a towed element,
wherein the force amount is provided by the vehicle moving at a towing velocity in order to tow the towed element, wherein the cable forms a catenary in response to the towing velocity.
3 . The cable measuring apparatus of claim 1 , the instrumented replacement fairing unit comprising:
a sensor configured to record the measurements of at least the catenary when subjected to the force amount;
a sensor holder configured to removably house the sensor; and
a clamp configured to fix the sensor in the sensor holder.
4 . The cable measuring apparatus of claim 3 , wherein the recorded measurements include at least one of an angle of the cable, a depth of the fairing system, and a position of at least one fairing unit.
5 . The cable measuring apparatus of claim 3 , wherein the sensor is configured to be secured in the sensor holder prior to the deployment of the towed element, and is further configured to be removed from the sensor holder after operation of the towed element.
6 . The cable measuring apparatus of claim 3 , wherein the sensor is configured to allow the recorded measurements to be captured by an external device and uploaded to a computer.
7 . The cable measuring apparatus of claim 6 , wherein the recorded measurements are captured by at least one of physically removing the sensor from the instrumented replacement fairing unit, and using a near-proximity sensing element without physical removal of the sensor from the instrumented replacement fairing unit.
8 . The cable measuring apparatus of claim 3 , the instrumented replacement fairing unit further comprising:
a cable interface removably connected to the sensor holder and configured to be mounted on a fairing system via a connecting element with at least one fairing tab; and
a fairing leading edge connected to the fairing tabs and wrapping around the cable, wherein the fairing leading edge is situated along the length of the cable in order to maintain the fairing system in place,
wherein the instrumented replacement fairing unit has the same profile as one of the plurality of fairing units.
9 . The cable measuring apparatus of claim 8 , wherein the connecting element removably connecting the cable interface comprises plastic hex-head barrel nuts.
10 . The cable measuring apparatus of claim 8 , wherein the sensor holder is connected to an aft surface of the cable interface by screws secured through at least one fixed receptacles.
11 . The cable measuring apparatus of claim 10 , wherein the at least one fixed receptacles are hex nuts adhered by epoxy.
12 . The cable measuring apparatus of claim 10 , wherein the at least one fixed receptacles are hex nuts situated within anti-rotation guide channels.
13 . The cable measuring apparatus of claim 1 , further comprising:
a modified instrumented replacement fairing unit configured to explode in lieu of recording measurements, the modified instrumented replacement fairing unit comprising an explosive charge configured to be detonated remotely and sever the cable.
14 . The cable measuring apparatus of claim 1 , wherein the cable is configured to be connected at an anchoring element and at another end to a buoyant element,
wherein the buoyant element provides a positive buoyancy on the fairing system, and
wherein the stabilizing force is provided by the anchoring element interacting with an ambient current, wherein the cable forms a catenary in response to the ambient current.
15 . The cable measuring apparatus of claim 1 , wherein the cable is configured to be connected at one end to a vehicle, wherein the vehicle is one of an aircraft and a vessel.
16 . A method for measuring a shape of a tow cable comprising:
calibrating at least one sensor, including setup of a timestamp and sampling frequency, prior to deployment of a fairing system;
placing each of the at least one sensor on corresponding sensor holder and fastening in place with a clamp;
mounting the sensor holder on a cable interface of an instrumented replacement fairing unit in the fairing system;
deploying the fairing system alongside a tow cable and a towed element into a marine environment;
sensing and recording data by the at least one sensor during deployment;
recovering the fairing system alongside at least the tow cable;
capturing of the recorded data from each sensor; and
uploading the recorded data into a computing device in order to calculate at least a tow cable catenary.
17 . The method for measuring a shape of a tow cable in claim 16 , wherein the capturing step comprises at least one of physically removing the at least one sensor from the instrumented replacement fairing unit, and using a near-proximity sensing element without physical removal of the at least one sensor from the instrumented replacement fairing unit.