Self-Excited Oscillation of Equilateral Triangular Wedge

This paper investigates the characteristics of a particular fluid-structure interaction phenomenon, i.e. the continuous oscillation in rotational mode of an equilateral triangular wedge in the uniform incoming flow in the water tunnel. We propose the explanation of this self-excited oscillation. It is the unbalance force acting on the wedge’s side faces that causes such movement. If the wedge is positioned initially asymmetrically against the freestream, on one side, the flow will be flow-past-flat-plate like, whereas the other side will be flow-past-sharp-edge like. Due to the unbalanced pressure exerting on the two sides, the wedge will rotate. When the wedge moves, these mechanisms switch side interchangeably, and bring the wedge to continuous oscillation. To understand more thoroughly, several experiments were conducted to investigate such behavior by means of Food coloring dye and Laser Induced Fluorescence flow visualization. The oscillating frequency is governed by Strouhal numbers, which appears within limited range of 0.12 < Str < 0.18. Beyond this range, the wedge is either stationary or rotates only in one direction. Accompanied with, the simple wedge’s dynamic behavior is examined, by considering incoming freestream flow’s hydrodynamic force acting on the wedge.