直接数值模拟三维气固两相混合层中颗粒与流体的双向耦合

该文对随时间发展模式的三维气固两相混合层中颗粒与流体的双相偶合作用进行了直接数值模拟。气相流场采用拟谱方法对N—S方程组进行直接求解，计算颗粒场时，选取Stokes数等于5的颗粒，采用Lagrangian方法跟踪其运动。重点考察了颗粒相与流体相间的相互作用，分析了不同质量携带率的颗粒对流场特性的修正以及对颗粒扩散的影响。模拟结果表明：混合层流动在考虑颗粒的反作用时大涡结构的卷起和配对仍然占支配地位：颗粒延滞了混合层中大涡结构的发展，降低了大涡结构的长度尺寸；在大涡卷起过程中，颗粒会衰减气相湍流的能量，衰减的程度随颗粒质量携带率的增大而增大。而在大涡配对过程中，颗粒使气相湍流的能量增加，并且增加的程度随颗粒质量携带率的增大而增大。此外，颗粒的出现，增加了流体的混合程度，削弱了颗粒在流场中的扩散程度。

DIRECT NUMERICAL SIMULATION OF THE TWO-WAY COUPLING EFFECTS BETWEEN PARTICLES AND FLUID IN THE THREE-DIMENSIONAL PARTICLE-LADEN MIXING LAYER

Direct numerical simulation is employed to study the two-way coupling effects between the particles and the fluid in a three-dimensional temporal mixing layer. By using the pseudospectral method, N-S equations are directly solved. Particles with Stokes number of 5 distributed uniformity initially in the mixing layer were traced using the Lagrangian approach. The feedback effect of a particle is approximated to the point force linearly distributed to the grid points. The results show that the roll-ups and pairing of the large-scale vortex structures are still in dominant in the two-way coupled mixing layer. But the particles delay the development of the large-scale vortex structures and shorten the length of the vortex structures. In the process of vortex roll-ups, the particles decrease the turbulent kinetic energy of the fluid, and higher mass loading results in lower turbulent kinetic energy. While in the course of vortex pairing, the particles increase the turbulent kinetic energy of the fluid, and higher mass loading leads to higher turbulent kinetic energy. The development of momentum thickness is similar with the development of the turbulent kinetic energy. In addition, the particles increase the energy of all the Fourier mode with non-zero spanwise wavenumber and the mixed fluid thickness of the fluid, but they depress the dispersion of the particles in turn.