등류 내에서 연성체 고리의 쌍안정성

Abstract

The immersed boundary method for simulating a flexible ring clamped at one point in a uniform flow has been developed. The penalty method derived from fluid compressibility is used to ensure the conservation of the internal volume of the flexible ring. We observed bistable states, one stationary stable state and the other a self-sustained periodically flapping state, which coexist over a range of flow velocities depending on the initial inclination angle. The Reynolds number range of the bistability region and the flapping amplitude were determined for various aspect ratios a/b. For a/b=0.5, the bistable region arises at the highest Reynolds number and the flapping amplitude in the self-sustained flapping state is minimized. A new bistability phenomenon was observed: for certain aspect ratios, two periodically flapping states coexist with different amplitudes in a particular Reynolds number range, instead of the presence of a stationary stable state and a periodically flapping state.