Flow Field Analysis around the Forced Oscillating Plate under the Free Surface by Vortex Method — 2D Viscous Fluid Analysis Based on Fundamental Equations Using Velocity and Vorticity as Unknown Quantities —

Abstract

Fins are often installed on submerged parts of a floating structure to reduce its motion in waves. It is expected that its kinetic energy is reduced by vortex generated from fins because its energy is converted into vortex energy around fins. To utilize this method, numerical analysis method for viscous fluid is required to decide the optimum shape and installation position of these fins. For this problem, authors proposed 2D numerical analysis method in time domain, using vortex method that can consider the fluid viscosity and calculated motions and primary conversion efficiency of a floating OWC-type wave energy converter in waves. In this method, unknown quantities are vorticity and stream function. As a next step, vortex method should be expanded to 3D problem so that it will be applied to actual design for floating structure, however its method can't be applied because stream function isn't defined in 3D problem. Therefore, development of vortex method using vorticity and velocity as unknown quantities is required. In this paper, by restricting to 2D problem, the vortex method using these unknown quantities is applied to flow field around a 2D cylinder in uniform flow and a forced oscillation problem of a submerged plate under the free surface. We carry out the comparison between calculation and experimental results, confirming its effectivity and reliability.