喷雾清洗中微颗粒受到流体作用力的研究

对喷雾清洗过程中微颗粒所受到的流体力进行了研究.由于液滴撞击在平面上产生的不稳定流,无法用现有的层流作用力公式来预测颗粒所受到的作用力,本文采用了计算流体力学模拟的方法对流场分布进行了模拟,并且计算颗粒上相应受到的作用力.通过计算结果,讨论了影响颗粒清除效果的关键因素.研究表明,在微米尺度内,平面的可湿性质对液滴展开的初始阶段流场分布有显著影响,从而也大大影响了平面上颗粒所受到的作用力.此外,撞击在干燥表面时,颗粒受到的拖拽力会比撞击到湿表面上时大三个数量级以上.而在湿表面上时,提高撞击速度会比增大液滴大小来得更有效,主导颗粒去除的力为拖拽力.

Numerical Study on Hydrodynamic Forces for Micro Particle Detachment by Droplet Impact

This paper presents the results of a numerical investigation of micro-sized particle removal by droplet impact.Computational fluid dynamics simulation is used to calculate the flow distribution of droplet impact on a flat surface.The hydrodynamic forces exerted on the particle are then computed.Key factors controlling particle removal are discussed.Both hydrophilic and hydrophobic surfaces are considered.The flow distributions,especially the front edge expanding upon impact at microscale,strongly depend on surface wettability.The associated hydrodynamic forces on the particles vary accordingly.In addition,the impact on a dry surface can produce higher removal efficiency than that on a wet surface.Under the same impact conditions,the drag force exerted on a particle residing on a dry surface can be three orders of magnitudes larger than on a wet surface.Improving droplet impact velocity is more effective than improving droplet size.