Granular pressure and particle velocity fluctuations prediction in liquid fluidized beds
Granular pressure and particle velocity fluctuations prediction in liquid fluidized beds
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DOI：
10.1016/j.ces.2008.01.031
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发表时间：
2008-05
影响因子：
4.7
通讯作者：
F. Gevrin;O. Masbernat;O. Simonin
中科院分区：
文献类型：
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作者：
F. Gevrin;O. Masbernat;O. Simonin
介绍了一种用于固液流化床动态模拟的数值模拟方法。这种方法是基于质量、动量和波动动能输运方程的欧拉双流体公式。在颗粒介质动力学理论的框架下，推导了考虑间隙液相粘滞阻力影响的固相波动运动模型。采用Zenit等人[1997]的实验成果，对固液流化床的流动形态进行了二维模拟。固液流动中碰撞颗粒压力的测量。流体力学学报[353]，261-283]，在高粒子雷诺数（尼龙，玻璃和钢珠）的水中三种类型的固体颗粒的对比惯性。实验和数值颗粒压力对低惯性粒子和高惯性粒子都表现出满意的一致性，对大多数惯性粒子的预测水平最好。预测对模型中使用的现象学定律的敏感性也被提出，并且由于非线性相关性，床层中的平均颗粒压力是一个比波动动能（或颗粒温度）更不敏感的变量。因此，分析了床层中平均颗粒温度的输运机制，作为固体分数和颗粒惯性的函数。在低、中等斯托克斯数（尼龙和玻璃珠）和固相分数的所有范围内，波动动能的主要产生机制是平均速度梯度，而主要耗散项是粘性阻力引起的。在较高的斯托克斯数（钢珠）和浓度下，颗粒温度的产生受颗粒压力的可压缩性效应控制。在这种情况下，耗散主要由粒子间碰撞提供。
A numerical modelling approach for the dynamic simulation of solid–liquid fluidized beds is evaluated. This approach is based on an Eulerian two-fluid formulation of the transport equations for mass, momentum and fluctuating kinetic energy. The solid-phase fluctuating motion model is derived in the frame of granular medium kinetic theory accounting for the viscous drag influence of the interstitial liquid phase. Solid–liquid fluidized bed two-dimensional simulations were performed for flow configurations taken from the experimental work of Zenit et al. [1997. Collisional particle pressure measurements in solid–liquid flows. Journal of Fluid Mechanics 353, 261–283], for three types of solid particles of contrasted inertia in water at high particle Reynolds number (nylon, glass and steel beads). Experimental and numerical granular pressures exhibit a satisfactory agreement with both low and high inertia particles, the best level of prediction being observed with the most inertial particles. Sensitivity of the predictions to the phenomenological laws used in the model is also presented and it appears that, due to non-linear correlations, the average granular pressure in the bed is a less sensitive variable than the fluctuating kinetic energy (or granular temperature). The transport mechanisms of the mean granular temperature in the bed are therefore analyzed as a function of the solid fraction and the particle inertia. At low and moderate Stokes number (nylon and glass beads) and in all range of solid-phase fraction, the dominant production mechanism of fluctuating kinetic energy is due to the mean velocity gradient, whereas the main dissipation term is that induced by the viscous drag. At higher Stokes number (steel beads) and concentration, the production of the granular temperature is controlled by the compressibility effects via the granular pressure. In this case, the dissipation is mainly provided by inter-particle collisions.