A FLUID DYNAMICS STUDY OF A MODIFIED LOW-REYNOLDS-NUMBER FLAPPING MOTION

Abstract

ABSTRACT The objective of the present study is to investigate the low Reynolds number (LRN) fluid dynamics of an elliptic airfoil performing a novel figure-eight-like motion. To this mean, the influence of phase angle between the pitching and translational (heaving and lagging) motions and the amplitude of translational motions on the fluid flow is simulated. NavierStokes (NS) equations with Finite Volume Method (FVM) are used and the instantaneous force coefficients and the fluid dynamics performance, as well as the corresponding vortical structures are analyzed. Both the phase angle and the amplitudes of horizontal and vertical motions are of great importance to the fluid dynamic characteristics of the model as they are shown to change the peaks of the fluid forces, fluid dynamic performance, and the vortical patterns around the model. INTRODUCTION Forced and flow-induced oscillations are highly prevalent in a wide range of fluid engineering applications. These unsteady conditions could be useful when assisting in the generation of the fluid forces such as wing flapping, or be destructive when becoming the undesired oscillations such as wing flutter. Flapping motions are the most common means of force generation in micro aerial vehicles and swimming robots. The physical characteristics and the fluid phenomena of such motions strongly depend on the governing flow and system parameters. LRN flapping flows are mostly accompanied with non-linear vortex dynamics, such as dynamic stal