A coupled level set and volume–of–fraction method is applied to investigate hollow oil droplet impacts on heated walls. Results show that given the increase in impact velocity, three evolutionary processes of spreading, transition, and central jet occur after the hollow oil droplet impact on a heated wall. The variation in the spreading length of hollow oil droplets is similar in different evolutionary processes, but the variation in the center height of hollow oil droplets is relatively different. The wall heat flux and the position of the maximum heat flux increase with impact velocity. In addition, the wall temperature influences the flow and heat transfer characteristics of the hollow oil droplet impingement. Considering the viscosity–temperature characteristics of the lubricating oil, the spreading length of the hollow oil droplet increases with the wall temperature, but the central height of the hollow oil droplet is unaffected by the wall surface temperature. The wall heat flux and the position of the maximum heat flux also increase with the impact velocity. Pressure and velocity distribution indicate that the bubble rupture at the central jet originates from the combined effect of inertial force and surface tension. The results of this study provide a basis for an improved understanding of the flow and heat transfer characteristics of hollow oil droplet impact on a heated wall and serve as a theoretical reference for investigating the effect of bubbles on oil–gas lubrication processes.

中文翻译：

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空心油滴撞击受热壁的形态演化及扩散流

应用耦合水平集和体积分数方法来研究空心油滴对加热壁的影响。结果表明，随着撞击速度的增加，空心油滴撞击受热壁后会发生扩散、过渡和中心射流三个演化过程。空心油滴扩散长度的变化在不同的演化过程中是相似的，但空心油滴中心高度的变化相对不同。壁面热通量和最大热通量的位置随着冲击速度的增加而增加。此外，壁温影响空心油滴撞击的流动和传热特性。考虑润滑油的粘温特性，空心油滴的扩散长度随着壁温的增加而增加，但空心油滴的中心高度不受壁面温度的影响。壁面热通量和最大热通量的位置也随着冲击速度的增加而增加。压力和速度分布表明，中心射流处的气泡破裂源于惯性力和表面张力的共同作用。该研究结果为深入了解空心油滴撞击受热壁的流动和传热特性奠定了基础，并为研究气泡对油气润滑过程的影响提供了理论参考。壁面热通量和最大热通量的位置也随着冲击速度的增加而增加。压力和速度分布表明，中心射流处的气泡破裂源于惯性力和表面张力的共同作用。该研究结果为深入了解空心油滴撞击受热壁的流动和传热特性奠定了基础，并为研究气泡对油气润滑过程的影响提供了理论参考。壁面热通量和最大热通量的位置也随着冲击速度的增加而增加。压力和速度分布表明，中心射流处的气泡破裂源于惯性力和表面张力的共同作用。该研究结果为深入了解空心油滴撞击受热壁的流动和传热特性奠定了基础，并为研究气泡对油气润滑过程的影响提供了理论参考。