Oblique particle–wall collisions in a liquid
Oblique particle–wall collisions in a liquid
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DOI：
10.1017/s002211200400919x
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发表时间：
2004-06
影响因子：
3.7
通讯作者：
G. Joseph;M. Hunt
中科院分区：
文献类型：
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作者：
G. Joseph;M. Hunt
本文介绍了粘性流体中颗粒斜撞壁的接近和反弹的实验测量。使用直径为12.7 mm的钢和玻璃颗粒。实验使用厚的Zerodur壁（玻璃状材料）与甘油和水的各种混合物进行。法向和切向恢复系数的定义，从各自的速度分量的比例在接触点之前和之后的影响。这些系数考虑了由于润滑效应和非弹性而引起的损失。第三个参数，滑动摩擦系数，提供了在碰撞过程中当颗粒滑动时作用在颗粒上的切向力的测量。流体中的倾斜碰撞在性质上类似于干燥系统中的倾斜碰撞，具有取决于表面粗糙度的较低摩擦系数。对于光滑表面，由于润滑作用，摩擦系数急剧降低。提出了一个理论模型，考虑到粘度对压力的依赖性，以解释所观察到的切向力作用在一个光滑的球体在斜碰撞。该模型依赖于推断均匀的润滑层内的温度增加，在影响过程中的粘性加热的结果。由颗粒感受到的切向力表示为取决于润滑层内的粘度的摩擦系数。粘度由于压力效应而增加，并且由于热效应而降低。对于粗糙表面，摩擦系数与在干燥系统中测量的摩擦系数相当，因为表面粗糙度可以通过润滑层彼此相互作用。
This paper presents experimental measurements of the approach and rebound of a particle colliding obliquely with a wall in a viscous fluid. Steel and glass particles 12.7 mm in diameter were used. The experiments were performed using a thick Zerodur wall (a glass-like material) with various mixtures of glycerol and water. Normal and tangential coefficients of restitution were defined from the ratios of the respective velocity components at the point of contact just prior to and after impact. These coefficients account for losses due to lubrication effects and inelasticity. A third parameter, a coefficient of sliding friction, provides a measure of the tangential force acting on the particle as it slides during a collision. Oblique collisions in a fluid are qualitatively similar to oblique collisions in a dry system, with a lowered friction coefficient dependent on surface roughness. For smooth surfaces the friction coefficient is drastically reduced due to lubrication effects. A theoretical model that takes into account the dependence of viscosity on pressure is proposed to explain the observed tangential force acting on a smooth sphere during an oblique collision. The model relies on an inferred uniform temperature increase within the lubrication layer, a consequence of viscous heating during impact. The tangential force felt by the particle is expressed as a friction coefficient dependent on the viscosity within the lubrication layer. The viscosity increases owing to pressure effects and decreases owing to thermal effects. For rough surfaces the friction coefficient is comparable to that measured in dry systems, since the surface asperities may interact with each other through the lubrication layer.