入流滑移条件对两相射流特性影响的大涡模拟研究

Influence of Inlet Velocity Differences Between Two Phases on LES of Particle Dispersions in Planar Jet

研究了入流滑移条件对空间发展的气粒两相平面湍射流的非定常流动特性的影响。以 Re数 130 0 0的平面不可压缩湍射流流动为例 ,气相场用 Euler方法求解 ,通过大涡模拟 ( large- eddy simulation,L ES) ,直接求解大尺度涡运动的 Navier- Stokes方程 ,小尺度涡用标准 Smagorinsky亚格子模式模拟。颗粒相的运动用 L agrangian方法直接求解。在不同入流滑移条件下 ( Up0 / U0 =α) :α=1,两相无滑移 ;α=0 .5 ,中等滑移情况 ;α=0 ,颗粒相以静止状态进入射流 ,分别求解了 5种尺度 ,共 2 5× 10 4个颗粒的运动方程。结果表明 :对于 Stokes数远小于 1或量级在 O( 1)附近的颗粒 ,颗粒与气相拟序结构的相互作用行为对入流滑移条件的变化不敏感。但是 Stokes数显著大于 1的颗粒 。

The influence of the inlet velocity difference between the two phases on the large eddy simulation (LES) of particle dispersions in an unsteady spatially developing free planar jet at a moderate Reynolds number.Re=13 000,has been investigated using an Eulerian/Lagrangian approach.LES is used to simulate the turbulence of the continuous phase with a Smagorinsky sub grid model,and the discrete particles are tracked in a Lagrangian approach.The acceleration and motion equations of 25×10 4 individual spherical particles with five kinds of diameters have been computed under three inlet velocity differences conditions:U p0 /U 0=α,where α=1 means that the particles are in dynamic equilibrium with the flow,α=0.5 refers to the medium inlet velocity difference and α=0 means that the particles are released into the flow in a stationary state.The simulations provide that the dispersion of particles with Stokes numbers far less than or of the same order of 1 are insensitive to the changes of the inlet velocity differences.However,the Stokes number only can not describe the interactions between the particles and the coherent structures well when even the dispersion process of particles with a Stokes number much larger than the order of 1 are influenced by the coherent structures under α=0.