Validation of a finite element model for slack ROV tethers

A three-dimensional lumped mass model was previously (Buckham et al., 1999) developed for use in simulating the dynamics of underwater remotely operated vehicles (ROVs). This paper presents the experimental validation of that model. In this experiment, the top end of a 4.12 m length of ROV tether was manipulated in a controlled aquatic environment, and video footage of the motion of the submerged tether was recorded. Simultaneously, the motion of the top end of the tether was recorded using a Litek Vscope 110/pro position sensing device. That motion data was then used to drive the numerical lumped mass model of the tether. The resulting tether motion was fed to an animation package, and the animation was compared to the video footage. Comparison of the experimental and simulated results showed only very minor differences between the real and simulated tether motions. An overestimation of the tether's bending stiffness is likely the reason for these differences. Analysis of the simulation results demonstrated that the bending forces generated in the tether maneuver approached the magnitude of the tension in the tether, and thus the inclusion of the bending effects is warranted.

[1]  Meyer Nahon,et al.  Simulation and active control of towed undersea vehicles , 1997, Oceans '97. MTS/IEEE Conference Proceedings.

[2]  M J Sterndorff,et al.  Numerical and experimental analysis of a retrievable offshore loading facility , 1995 .

[3]  C. M. Ablow,et al.  Numerical simulation of undersea cable dynamics , 1983 .

[4]  Timothy W. McLain,et al.  Experimental Measurement of ROV Tether Tension , 1992 .

[5]  Meyer Nahon,et al.  Mathematical modeling and simulation of a moored buoy system , 1996, OCEANS 96 MTS/IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century.

[6]  Hae-Hoon Park,et al.  A tension measurement method of a towing cable or a buoy cable , 1993 .

[7]  Christopher T. Howell,et al.  Simulating The Dynamics Of Underwater Vehicles With Low-Tension Tethers , 1993 .

[8]  Edwin Kreuzer,et al.  On the Mathematical Modeling of ROV'S , 1991 .

[9]  Christopher T. Howell,et al.  NUMERICAL ANALYSIS OF 2-D NONLINEAR CABLE EQUATIONS WITH APPLICATIONS TO LOW-TENSION PROBLEMS , 1991 .

[10]  J J Burgess.  EQUATIONS OF MOTION OF A SUBMERGED CABLE WITH BENDING STIFFNESS , 1992 .

[11]  J. J. Burgess,et al.  Bending Stiffness In A Simulation Of Undersea Cable Deployment , 1993 .

[12]  Minoo H. Patel,et al.  TRANSIENT BEHAVIOUR OF TOWED MARINE CABLES IN TWO DIMENSIONS , 1995 .

[13]  Bradley J. Buckham,et al.  Dynamics simulation of low tension tethers , 1999, Oceans '99. MTS/IEEE. Riding the Crest into the 21st Century. Conference and Exhibition. Conference Proceedings (IEEE Cat. No.99CH37008).

[14]  D. A. Chapman.  Effects of ship motion on a neutrally-stable towed fish , 1982 .

[15]  Yang Sun,et al.  Dynamics of ocean cables with local low-tension regions , 1998 .