液滴在受热倾斜固体壁面上的“爬坡”特性

“Climbing”Characteristic of Droplet on Heated Inclined Solid Substrate

为研究液滴在倾斜固体壁面上的"爬坡"特性,基于润滑理论,建立了液滴的二维演化模型,模拟了壁温分布、壁面倾角和邦德数取不同值时液滴的"爬坡"特征。结果表明:随着壁面温度梯度增大,液滴运动状态由"下坡"变为"爬坡",且速率逐渐加快,液滴身后的薄液膜由"逆坡而上"变为"顺坡而下","爬坡"时刻先从无到有,后又从大到小,直至零;当温度梯度较小时,液滴左侧接触角迅速减小,而右侧接触角虽逐渐减小,但变化缓慢,而当温度梯度较大时,接触角变化规律与之相反;壁面倾角和邦德数的增大都将使液滴"爬坡"速率减慢,"单峰"结构的峰值降低,且原因类似,同时,还将使液滴覆盖范围的增速先减后增,但原因相反。

This paper established an evolution model based on the lubrication theory to analyze the＂climbing＂characteristic of a droplet on a heated inclined solid substrate when the temperature distribution,substrate inclination and the Bond number were different. The results show that with the increase of the temperature gradient,the motion of the droplet changed from ＂going downhill＂to ＂climbing uphill＂,and this change tended to occur earlier. The velocity of＂climbing＂accelerated gradually,and the thin liquid film behind the droplet turned from＂upward slope＂to＂downward slope＂. When the temperature gradient was small,the left and right contact angles of the droplet decreased rapidly and slowly respectively,but when the temperature gradient was large,the opposite was true. For similar reason,the increase of the substrate inclination and the Bond number both can slow down the ＂climbing＂of the droplet,and reduce the summit value of its‘single peak＇structure. Meanwhile,it can also cause the growth rate of the droplet coverage to decrease first and increase then,but for the opposite reason.