Direct simulation of particle dispersion in a three-dimensional temporal mixing layer

A three-dimensional temporally evolving mixing layer and particle dispersion patterns with different Stokes numbers were investigated. The coherent structures in a plane mixing layer between two parallel streams were numerically simulated using a pseudo-spectral method. Particles with different Stokes numbers were traced using the Lagrangian approach. The results showed that particle dispersion patterns were strongly governed by large-scale vortex structures and three-dimensionality. Particles with Stokes number of the order of unity were found to be concentrated near the outer edges of the large-scale vortex structures. With the development of three-dimensionality, the variation of particle distribution increased along the spanwise direction. Some particles were thrown out of the high-concentration area due to the pairs of counter-rotating 'rib' vortices. and finally developed into a 'mushroom' pattern of the particle distribution in the spanwise direction.