Experimental and Theoretical Studies of Coherent Structures in the Near Wake of aCircular Cylinder at Mach Number 2

摘要

The coherent structures in the supersonic wake of a circular cylinder are assumedto be spatially growing instability waves superimposed on the mean flow. The aim of this presentation is to determine the amplified waves and to evaluate the effects of the mean velocity, temperature and density profiles on the stability characteristics. The linear viscous compressible stability theory of parallel mean flow is applied. The basic state is determined by measurements and by solving the compressible Navier-Stokes equations with a Taylor-Galerkin-Finite-Element approach. To get a right description of the turbulence in the near wake a special algebraic turbulent model is introduced. It was possible to show that the near wake behind a circular cylinder is an absolute unstable region.