论文标题
充满粒子湍流的动力学。部分2：修改的波动力模型（M-FFS）
Dynamics of particle-laden turbulent Couette flow. Part2: Modified fluctuating force model (M-FFS)
论文作者
论文摘要
在体积分数制度$ ϕ> 10^{ - 4} $的双向耦合DNS模拟[1]中，显示出湍流强度的不连续降低，超出了关键体积分数$ ϕ_ {CR} _ {CR} \ sim7.875 \ sim7.875 \ times10^{-4 4} $。由于存在高惯性颗粒，发现湍流的剪切产生的急剧减少是湍流不连续衰减的主要原因。在本文中，探索了粒子相统计。双向耦合的DNS表明，横流（y）和跨度（z）方向的均方速度曲线是平坦的，并且随着$ ϕ $的增加而增加，因为较高的碰撞频率有助于将流向动量转移到跨度和壁式正常方向上。而流动的波动会减少并趋于随着负载的增加而变得更加平坦。在具有$ ϕ> ϕ_ {Cr} $的策略中，粒子速度波动驱动流体相位速度波动。此外，观察到单向耦合的DNS和波动力模拟（FFS）[2]能够在粒子$ ϕ <ϕ <ϕ_ {CR} $中以合理的精度预测粒子相统计，其中壁式碰撞时间和粒子跨粒子碰撞时间比粒子的粘性时间较小。对于，$ ϕ> ϕ_ {Cr} $，由于FFS限制了捕获湍流衰减和平均流体速度曲线的变化，因此观察到单向耦合DNS和FFS的预测有重大错误。在本文中成功开发了修改的FFS模型（M-FFS），其平均流体速度曲线和零散布性。
Two-way coupled DNS simulation of particle-laden turbulent Couette-flow [1], in the volume fraction regime $ϕ>10^{-4}$, showed a discontinuous decrease of turbulence intensity beyond a critical volume fraction $ϕ_{cr}\sim7.875\times10^{-4}$. Due to the presence of high inertial particles, the drastic reduction of shear production of turbulence is found to be the main cause for the discontinuous attenuation of turbulence. In this article, particle-phase statistics is explored. The two-way coupled DNS reveal that the mean-square velocity profiles in cross-stream (y) and span-wise (z) directions are flat and increase with $ϕ$ as the higher frequency of collision helps in transferring streamwise momentum to span-wise and wall-normal directions. Whereas, streamwise fluctuations decrease and tend become flatter with increase in loading. In the regime with $ϕ>ϕ_{cr}$, the particle velocity fluctuations drive the fluid phase velocity fluctuations. Additionally it is observed that one-way coupled DNS and Fluctuating Force Simulation (FFS) [2] are capable to predict the particle phase statistics with reasonable accuracy in the regime $ϕ<ϕ_{cr}$ where wall-particle collision time and inter-particle collision time is lesser than viscous relaxation time of the particles. For, $ϕ>ϕ_{cr}$, a significant error in the prediction from one-way coupled DNS and FFS is observed due to the limitation of FFS in capturing the turbulence attenuation and the change in mean fluid velocity profile. A modified FFS model (M-FFS) is successfully developed in this article with modified mean fluid velocity profile and zero-diffusivity.
