LARGE EDDY SIMULATION OF THE NEAR WAKE OF A CIRCULAR CYLINDER AT SUB-CRITICAL REYNOLDS NUMBER

This paper investigates the unsteady, near wake of a circular cylinder in cross flow at a Reynolds number of 5.5 x 10(3) using Large Eddy Simulation (LES). The near and intermediate wake velocity fields and unsteady aerodynamic forces compare well against available experimental data. Flow visualisation results show the presence of intermittent Kelvin Helmholtz (KH) instabilities in the very near wake. An empirical relation is presented for the spanwise length scales associated with KH instability that compares favourably with LES data. A wavelet analysis technique is used to investigate the frequency content of near wake. This analysis shows the existence of vortex pairing and breakdown in the near wake, providing further evidence that the near wake shear layer behaves in a similar manner to a mixing layer.