Abstract
Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid. The computing code for the analysis of the motions is developed with unstructured grid.
After the developed code is validated with the problem of oscillation of a plane below a viscous fluid, it is applied to two cases. The first is the analysis of the contractive and dilative motion of surface in shallow water whose corresponding experiments have been carried out by Ninomiya and Mizutani. The computed results are compared with the experimental ones. It is found that a propulsive force can be obtained in shallow water by pressure force which can be derived by contractive and dilative motion of surface.
The second one is the analysis of the contractive and dilative motion of body. The computations are carried out both in unbounded fluid and in narrow channel. It is found that the trochoidal motion of the moving surface of body produce propulsive force in unbounded fluid by frictional force rather than pressure force. As the Reynolds number becomes smaller, more propulsive force can be obtained by the frictional force with the trochoidal motion of surface. This tendency is almost the same as in narrow channel.
By the present simulation, it can be made clear that propulsive force can be obtained in highly viscous fluid by the trochoidal motion of surface, which is expected to be applied to the propulsor of a micro-hydro machine.
