Numerical Study Of Inter-phase Interaction Three-dimensional Particle Laden Plane Mixing Laver By Direct Numerical Simulation

With regard to the fluid-particle interaction and inter-particle collision in gas-solid turbulence, the direct numerical simulation of a three-dimensional gas-solid two-phase plane mixing layer is conducted. Researches on the plane mixing layer include the theories of heat transfer, mass transfer and flow dynamics of two parallel streams with different velocities. These researches are important both for scientists and engineers, but numerical studies of inter-phase coupling interaction between fluid and particles are few, especially for numerical researches using direct numerical simulation for the enormous calculated amount.Under the above background, the present paper uses direct numerical simulation to investigate three-dimensional gas-solid two-phase plane mixing layer, focusing on the inter-phase interactions. The two flow models: temporally evolving mixing layer and spatially evolving mixing layer are both conducted. The particle motion is based on the one-way and two-way coupling method respectively, and inter-particle collision is simulated by using the hard-sphere model. Additionally, a large scale parallel computing is presented to simulate spatially evolving mixing layer for the requirement of calculated amount.Calculations are performed for a bunch of particles Stokes numbers of3when investigating temporally evolving mixing layer under one-way coupling method. The results show that the preferential concentration phenomenon of particles is found after the beginning of the rolling up of the large-scale vortex structures due to the influence of the vortex. It is also found that the inter-particle collision occurs frequently in the local regions with higher particle concentration of the flow field. The evolution of inter-particle collision can be divided into3stages under the influence of the growth of the vortex and the particle dispersion. The results under the two-way coupling show that the particle distribution is more uniform.In the two-way coupling case of temporally evolving mixing layer, the results show that the inter-particle collision influence on the mixing process of fluid positively, and the Reynolds stresses and turbulence kinetic energy of the flow field and particles are strengthened, but the mean stream-wise velocity of fluid phase and particle phase decrease due to the inter-particle collision. We reveal the rolling-up of span-wise vortexes, the mixing progress of vortexes, and the fully developed status in the gas-phase spatially evolving mixing layer without forcing, in the parallel computing environment. The flow field statistical results, include the stream-wise velocity and the Reynolds stress are compared match well with the experimental data. The inflow forcing is exert on three-dimensional plane mixing layer. Because of inflow forcing on the mixing layer, the positions of rolling-up vortexes is shifted upward.Two-way interactions are considered in parallel computing, and the particles collisions are solved by the hard-sphere model in the parallel computing when simulating gas-solid two-phase spatially evolving mixing layer. The particle distribution is more uniform after considering collision. Particles in different sizes exhibit diverse dispersion behaviors and the statistics of the stream-wise velocity are matched well with the experimental data. Particles Stokes numbers of100under different mass loading is injected into fluid field.Particle phase breaks the large-scale vortex strucrures and strengthen the mixing of fluid and the turbilence kinetic energy of the flow field.