Synthesis on compressible mixing layers

Abstract

In the workshop, five computations of compressible mixing layers have been presented; three of them (INRIA Sophia-Antipolis, University of Seville, ECL, Laboratoire de Mécanique des Fluides et d’Acoustique) were relative to TC100 (Steady supersonic mixing layer) and two of them (IMFT Toulouse and NTUA-Aerodynamics Athens) were performed to represent TC102 (unsteady supersonic mixing layers). For clarity, it may be recalled that TC 100 is dedicated to the computation of supersonic mixing layers, statistically steady and fully developed: similarity solutions are expected for flows with unity Prandtl numbers, and averages are made on all the scales of turbulence. The importance of having this test-case was to compare the results of computation on the same formulation for the normalized spreading rate vs. convective Mach number M _c (Langley curve). In TC 102, the large scale structures (or organized eddies) are computed explicitly, while the fine grained turbulence is modelled: there is no periodic forcing of the layer, only the natural modes of the layer are computed as unsteady perturbation. In TC 100, asymptotic properties were computed (compilation of several experiments), while TC 102 was made for one particular flow in which the unsteadiness is documented, and in which the development of an asymptotic mixing layer from out of similarity conditions at the trailing edge of a separating plate is given.