重力对水平两相湍射流中颗粒行为的影响

Effect of Gravity on the Particle Behaviors in a Horizontal Two-Phase Jet

研究了重力对空间发展的水平两相平面湍射流中颗粒运动的影响。气相场用 Euler方法求解 ,通过大涡模拟直接求解大尺度涡运动的 Navier- Stokes方程 ,小尺度涡采用 Smagorinsky亚格子模式模拟。颗粒相的运动采用L agrangian方法直接求解。射流 Re数为 1130 0。模拟发现 ,对于 St 1及 St～ 0 (1)的颗粒 ,其在平面射流下游的瞬时分布对重力的影响不敏感。随着颗粒 St数的增大 ,重力对平面射流场中颗粒行为的影响逐渐明显 ,但其作用效果还明显地与两相入射流滑移系数的大小有着直接联系。在小两相入流滑移系数情况下 ,对于 St～ 0 (10 )的颗粒 ,在重力作用下的沉降过程还受到了湍流拟序结构的作用 ,而重力作用导致的更大 St数颗粒的沉降 ,将引起固相粒子在射流下游的非对称分布 ,但它既不是均匀各向同性湍流中颗粒的梯度扩散结果 。

Numerical simulations of the particle-vortex interaction under gravity for an incompressible spatially developing horizontal two-phase turbulent jet flow are reported. The large-eddy simulation finite-difference scheme was used to perform the continuous phase simulations at a moderate Reynolds number, Re=11300. The Lagrangian equations of particle motions were solved directly. Extensive results of the particle-laden jet flow were obtained. It has been shown that the instantaneous distributions of St<1 and St - 0 (1) particles are insensitive to the effect of gravity. The need for the consideration of gravity for horizontal particle-laden jet is emphasized with the increasing particles St number values. The particle sedimentation of St - 0 (10) is modified by the jet coherent structures when the initial inlet two-phase velocity coefficients is small. An asymmetrical dispersion pattern is caused when the initial inlet two-phase velocity coefficients is small. An asymmetrical dispersion pattern is caused when the gravity is included for larger 100 μm and 200 μm glass beads, whose St number is much larger than the order of unit. However these phenomena belong neither to the gradient-driven diffusion in a homogeneous isotropic turbulence nor to the dispersion of small stokes number.