The environment where an underwater vehicle is applied is various and the environment involves near the free surface and waves. Some numerical method is promising to estimate the performance of it. Hence, we have developed CFD-based motion simulator for the underwater vehicle. However, this motion simulator can't consider the effect of free surface and waves. Therefore, the expansion of this motion simulator was started in order to consider the effect of them. As the basic research, we assumed a rectangular column as a submerged body of concrete underwater vehicle and simulated the motion of the submerged body in waves.
Until now, we have developed an underwater vehicle that intends to inspect offshore and/or coastal underwater structures. The underwater vehicle to inspect offshore and/or coastal underwater structure must have high maneuverability in the water current and/or waves. We had already developed a prototype underwater vehicle for that aim using two-pairs of mechanical pectoral fin device that showed high maneuverability in water currents and/or waves. (Kato, et. al.2004, 2005) To put this underwater vehicle practical use, we must determine of the desired levels of guidance and control law for the underwater vehicle efficiently. Therefore, to be the aid of the determination of guidance and control law, we began working on a project for developing a CFDbased motion simulator for this underwater vehicle (Suzuki et. al 2007). However, this motion simulator can't consider the effect of free surface including waves and the water currents. We intend to apply this simulator to predict the motion of the underwater vehicle in the water currents and/or waves. This study was carried out as basic research for adding the effect of free surface including waves to this numerical motion simulator. Generally, the effect of the waves for submerged body is handled by the potential theory. Because of above-mentioned reason, we decide to use CFD approach.
