Visualization of large-scale structures in spatially developing compressible mixing layers

Large - scale structures in two- and three-dimensional, spatially developing, compressible mixing layers are visualized. The convective Mach number Mc is prescribed to be 0.4 and 0.8. Direct numerical simulations were performed using a Discontinuous Galerkin method. Special attention is paid on the panorama of spatial evolution of large - scale structures, as well as on the compressibility effect on these structures. Fine structures such as the sonic waves at the inlet, and shocklet structures for the Mc = 0.8 case are also visualized. For the three-dimensional cases, in order to show the spatial evolution of the large - scale structures more clearly, both the λ 2 and Q 2 structure extraction methods colored with stream-wise velocity magnitude are utilized. The “H-type” secondary instability structure and the “forest” structures are evident. It is found that the λ 2 method gives better results in the case of high compressibility effect shear flows. Graphical Abstract