Vortex dynamics over a dihedral plane in a transitional slightly compressible flow: a computational study

In this paper, three different vortex diagnostic methods are compared to obtain a better understanding of boundary layer influence on the transport of vortical structures involving a complete analysis of vorticity, the Vorticity Threshold Criterion (VTC), and the Weiss Criterion (WC). These three techniques are basically confronted to find a suitable understanding of all flow characteristics (the swirling dynamics produced downstream of the discontinuity point of the dihedral) for a range of laminar to transitional Reynolds numbers. The computations on this dihedral plane are made using a 2D DNS method. The Weiss criterion, coming from the analysis of the incompressible Euler equations is validated and applied to low speed compressible flows ( M=0.2). A detailed analysis of the swirling procedure is performed for Reynolds numbers 242, 400 (laminar), 565 and 800 (transitional). Finally, different averaged or instantaneous, local or global quantities are used to analyse and characterize Concentrated Structures as a function of the Reynolds number evolution.