液滴撞击湿壁面实验研究

Experiment Study of Droplet Impacting on Wetted Surface

采用高速摄像仪以11 000帧/s的拍摄速度对3种不同尺寸的液滴以不同速度分别撞击湿壁面(水平及不同倾斜角度)的过程进行了观测。研究了铺展、产生冠状不飞溅、飞溅3种实验现象。定性分析了初始液滴直径、液滴撞击速度、湿壁面倾斜角度对飞溅现象的作用。定量统计出液滴撞击湿壁面产生飞溅现象的各项临界参数,给出飞溅判据的经验关系式并进行误差分析。结果表明:随液滴撞击速度的增大,撞击湿壁面后会依次出现铺展、产生冠状不飞溅、产生二次液滴飞溅等现象。液滴直径的增加与湿壁面倾斜角度的降低均对飞溅的产生有促进作用。并通过拟合实验数据得到用于判别液滴撞击湿壁面是否发生产生二次液滴飞溅现象的无量纲参数K与无量纲液膜层厚度H*关系:K=3 210-122 284.48 H*+2.234 26×10~6 H*2(0.008 56<H*<0.033 18)。

A high-speed camera was used to observe the process of three different sizes of droplet impact at different speeds on the wetted surface(horizontal and different tilt angles)at 11 000 frames per second.Three experimental phenomena,including spreading,crown without splashing and splashing,were studied.The effects of initial droplet diameter,droplet impact velocity and inclination angle of the surface on splashing phenomenon were qualitatively analyzed.The critical parameters of splashing phenomenon resulted by droplet impacting on wetted surface were counted quantitatively,and the empirical relation of the splashing criterion was given whose error analysis was also made.The results show that with the increase of the impact velocity of droplets,after impacting on the wetted surface,the phenomena of spreading,formation of liquid crown without splashing and splashing with secondary droplet generated occur in sequence.The increase of the droplet diameter and the decrease of the surface inclination angle both promote the emergence of splashing.By fitting the experimental data,the relationship between the dimensionless parameter K,which is used to determine whether the splashing occurs after the droplet impacting on the wetted surface,and the dimensionless liquid film thickness H*is acquired:K=3 210-122 284.48 H*+2.234 26×10 6 H*2(0.008 56<H*<0.033 18).