ABSTRACT

Velocity gradient tensor (VGT) analysis of high-order accurate DNS data of compressible pipe, nozzle and diffuser flows is performed. Joint pdfs of second and third invariants conditioned on positive and negative dilatation levels are presented in the viscous layer, buffer layer, log layer and core regions of these flows. For flow regions with positive dilatation there is a preference for unstable flow topology, while regions with negative dilatation show a preference for stable flow topology.