Direct numerical simulation of the turbulence characteristics in a cylinder wake

Abstract

The primary vortex street, turbulent kinetic energy and energy dissipation rate in the wake of a circular cylinder are examined at a Reynolds number of 1000 and up to 120 cylinder diameters downstream of the cylinder. The turbulence characteristics are quantified using direct numerical simulation (based on the framework of Nektar++), which provides a comprehensive dataset that is almost impossible to acquire from physical experiments. The energy dissipation rate is decomposed into the components due to the mean flow, the coherent primary vortices and the remainder. It is found that the remainder component, which develops only in a three-dimensional turbulent wake, accounts for the majority of the total dissipation rate for almost the entire wake. The turbulence dissipation in the wake is largely locally homogeneous, but not locally isotropic or axisymmetric, even after the annihilation of the primary vortex street. The spatial distribution of the turbulence characteristics relative to the spatial distribution of the primary and streamwise vortices is also examined.