On Turbulent Separated Flows in Axisymmetric Diffusers

Summary

This paper describes experimental and numerical investigations concerning the turbulent flow through axisymmetric expansions having different diffuser half-angles (6 deg < α < 90 deg). Special attention is given to flow separation and reattachment as well as to flow relaxation downstream of reattachment. First, mean flow results (velocity field, pressure and wall shear stress distributions) including their similarity structures are presented. Further investigations refer to measurements concerning turbulent flow quantities (Reynolds stresses, turbulent kinetic energy) in comparison with calculations carried out with a finite-volume method that involved the standard k-ε-turbulence model. Finally, investigations concerning turbulent transport quantities (diffusion, convection, production and dissipation) are discussed by taking as an example the terms contained in the transport equation for the turbulent kinetic energy. In this investigation first experimental results concerning pressure diffusion are also included, which were carried out with a recently developed X-P probe.