Flow Characteristics of a Circular Cylinder behind an Impinging Airfoil Near Wake with Different Lateral Spacing

Abstract

A computational model is formulated to investigate the unsteady flow characteristics of a circular cylinder behind an impinging airfoil near-wake at Re=200. The distance between the airfoil trailing edge and the downstream cylinder axis is fixed at 1.5D where D is the diameter of circular cylinder and the lateral spacing is varied from 5 to 5 so as to numerically investigate the effect of lateral spacing on the flow characteristics. The present work is concerned on the following aspects: the general flow patterns, the vortex shedding frequency, force fluctuations and spectra, as well as the effect of lateral spacing on the flow features at low Reynolds number and small axial spacing. The calculated flow pattern and its comparison with the visualization by Laser-Induced Fluorescence (LIF) technique are conducted. It is determined that three regimes can be defined in terms of H/D, where H is the distance between the cylinder center and the line extended from the airfoil leading edge to trailing edge. And four kinds of typical flow pattern associated with the three regimes can be identified accordingly. It is interesting to find that both the fluctuations of lift and drag forces on the circular cylinder exhibit symmetric features centered at H/D=0 and the dump distribution of C′SUBD/SUB is found as well.