Direct numerical simulation of a three-dimensional spatially evolving compressible mixing layer laden with particles. I. Turbulent structures and asymmetric properties

Abstract

With the Eulerian–Lagrangian point-source method, the effects of dispersed particles on turbulent structures and asymmetric properties are systematically investigated in a three-dimensional spatially evolving compressible mixing layer with the convective Mach number up to 1.2. Particles interact with the mixing layer through two-way coupling, and three simulations with different particle diameters are conducted and compared with the particle-free flow. The underlying mechanisms responsible for the mixing layer asymmetry are also revealed through analyzing the self-similar equations of the particle-laden spatially evolving compressible mixing layer. The compressible mixing layer is significantly asymmetric on the high- and low-speed sides. The low-speed layer possesses more vortices and less shocklets compared with the high-speed layer in the fully developed region, and the shear layer center tends to skew toward the low-speed stream, which is due to the streamwise momentum gradient. Small particles augment the mixing layer asymmetry with more vortices and shocklets in the low-speed stream, which is attributed to the small inertia and the larger streamwise velocity of particles than fluid across the mixing layer. However, large particles attenuate the asymmetry of the mixing layer where the vortical structures on the low-speed side are further reduced and the shocklets are barely existent in both the layers, which is ascribed to the large inertia and the stronger effect of particle back-reaction on the low-speed fluid than that on the high-speed fluid.