FEATURES OF THE SUPERCRITICAL TRANSITION IN THE WAKE OF A CIRCULAR CYLINDER

The features of the wake behind a uniform circular cylinder atRe=200, which is just beyond the critical Reynolds number of 3-D transition, areinvestigated in detail by direct numerical simulations by solving 3-D incompressibleNavier-Stokes equations using mixed spectral-spectral-element method. The high-order splitting algorithm based on the mixed stiffly stable scheme is employed inthe time discretization. Due to the nonlinear evolution of the secondary instabilityof the wake, the spanwise modes with different wavelengths emerge. The spanwisecharacteristic length determines the transition features and global properties of thewake. The existence of the spanwise phase difference of the primary vortices sheddingis confirmed by Fourier analysis of the time series of the spanwise vorticity and at-tributed to the dominant spanwise mode. The spatial energy distributions of variousmodes and the velocity profiles in the near wake are obtained. The numerical resultsindicate that the near wake is in 3-D quasi-periodic laminar state with transitionalbehaviors at this supercritical Reynolds number.