Direct numerical simulation of the initial evolution of a turbulent axisymmetric wake

Abstract

The initial evolution of a turbulent axisymmetric wake at a macroscale Reynolds number of 1500 has been simulated by direct solution of the unsteady three-dimensional Navier-Stokes equations using a (temporal) spectral scheme on the Flosolver Mk3 parallel computer at NAL. A visualization of the flow is presented in terms of constant-vorticity surfaces. The simulation shews a complete sequence of events from formation of vortex rings through generation of azimuthal instability and appearance of streamwise structures to eventual break - down into turbulent flow, and reveals explicitly certain interesting features of the development of streamwise vorticity.