Wake Dynamics of a Longitudinally Oscillating Cylinder at Low Reynolds Number

A longitudinally oscillating cylinder in a steady fluid stream has been shown to exhibit some interesting wake dynamics. The wake dynamics of a circular cylinder of diameter, d in a steady air stream at a velocity, \(U_{\infty }\) oscillating longitudinally in the streamwise direction with an amplitude, a and forced excitation frequency, fe is considered in the current studies at a low Reynolds number, Re = 500. The non-dimensional parameters governing the flow dynamics are amplitude ratio, a/d, frequency ratio, fe/fs, and Reynolds number, Re =  \(U_{\infty }\) d/ν, where fs is the frequency of the shed vortices, when the cylinder is stationary (A = 0) and ν is kinematic viscosity of air. Our simulations have been carried out at Re = 500, and we identify various wake geometry such as, A-I mode, harmonic synchronous A-I mode, A-IV mode, and SA mode at several combinations of amplitude and frequency ratios. The observed wake geometry has an effect on the unsteady drag and lift forces and their associated frequency of fluctuations. The results are relevant to physical systems where vortex-induced vibrations (VIV) are important.