Establishment of equations of motion of a ROV using CFD technique

In order to analyze the dynamic performance of a Remotely Operated Vehicle (ROV) during mission like ship hull inspection, it is necessary to establish the 6 degree-of-freedom equations of motion considering well modeled hydrodynamic force acting on a ROV. Typically, the hydrodynamic force is the model by polynomial functions and those coefficients are obtained by captive model tests or empirical formula. Recently, Computational Fluid Dynamic (CFD) approach are common to analyze hydrodynamic force acting on a maneuvering underwater vehicle. This paper presents a numerical simulation of the ROV utilizing CFD code ANSYS FLUENT to estimate hydrodynamic coefficients of the ROV. The simulations were performed for the motions of the ROV in straight running, static drift, and steady turning conditions, then hydrodynamic forces and moments are calculated. After calculating hydrodynamic force, the velocity-dependent coefficients such as drag, lift, and moment coefficients representing the sensitivity of hydrodynamic force due to motion variables are determined through time averaging. These coefficients are used for determining a mathematical model of the ROV's motion.