Hydrodynamic Analysis of a Tethered Underwater Robot System

In this paper a three-dimensional mathematical model to simulate the hydrodynamic behavior of a tethered underwater robot system is proposed. The fluid motion around the robot is governed by mass and momentum conservation equations (Navier-Stokes equations). These highly nonlinear differential equations are solved numerically with the CFD code Fluent. From the numerical solution we obtain the hydrodynamic forces on the robot which are linked to the different relative fluid velocities and different incident angles to the robot. With such a method the hydrodynamic loading on the robot can be predicted as a whole. In the model the governing equation of umbilical cable linked to the robot is based on the Ablow and Schechter (1983) method. The boundary conditions for the robot system are presented. The sixdegrees-of-freedom equations of motion for submarine simulations are adopted to estimate the hydrodynamic performance of the underwater robot, and the dynamic effect of the active control thrusters to the robot is also incorporated into the model. The hydrodynamic behavior of underwater robot under different control manipulation introduced by control thrusters is observed numerically based on the established mathematical model in this paper.