Shinichi Asao

Free Surface Flow Simulation of Fish Turning Motion.

In this paper, the influence of depth from the free surface of the fish and turning motion will be clarified by numerical simulation. We used Moving-Grid Finite volume method and Moving Computational Domain Method with free surface height function for numerical simulation schemes. Numerical analysis is performed by changing the radius at a certain depth, and the influence of the difference in radius is clarified. Next, analyze the fish that changes its depth and performs rotational motion at the same rotation radius, and clarify the influence of the difference in depth. In any cases, the drag coefficient was a positive value, the side force coefficient was a negative value and the lift coefficient was a smaller value than drag. Analysis was performed with the radius of rotation changed at a certain depth. The depth was changed and the rotational motion at the same rotation radius was analyzed. As a result, it was found the following. The smaller radius of rotation, the greater the lift and side force coefficients. The deeper the fish from free surface, the greater the lift coefficient. It is possible to clarify the influence of depth and radius of rotation from the free surface of submerged fish that is in turning motion on the flow.

Numerical Simulation of Rotation of Intermeshing Rotors using Added and Eliminated Mesh Method

Abstract To compute flows around objects with complicated motion like the intermeshing rotors, the unstructured moving grid finite volume method was developed. Computational elements are added and eliminated according to motion of rotors, to keep the computation domain around rotors which mutually reverse. Also, the geometric conservation law is satisfied in the method, using four dimensional space time unified domain for control volume. Using the method, accurate computation is carried out without interpolation of physical quantities. Applying to a flow around a sphere, computation procedure was established with introduction of concept of a hierarchical grid distinction. Then, the results of application to the flow around intermeshing rotors showed efficacy of the method. The results also showed applicability of the method to compute flows around any complicated motion.