加热平板上水滴内部流场数值模拟和实验研究

Numerical Simulation and Experiment of Internal Flow Field of Water Droplets Evaporation on Heating Substrate

本文利用Fluent软件模拟了水滴在加热平板上蒸发时其内部温度分布和流场运动情况。在蒸发初期,随着气液界面处低温极值点的变化,水滴内的Marangoni对流漩涡呈现出不同的演变,并且在这一阶段水滴内部温度分布受Marangoni对流影响较大。随着水滴内部温度逐渐趋于均匀,水滴内部形成一对左右对称的对流漩涡。在相同条件下进行实验研究,将模拟所得与实验结果进行对比分析,两者吻合较好;通过改变加热板温度,得到水滴内部流场平均速度随时间的变化关系,加热板温度越高,流场运动速度越快,随时间下降得也越显著;流场速度在蒸发初期下降幅度较大,而到了中期和后期则趋于平稳。

The software Fluent was used to simulate evaporation of water droplets on the surface of a flat heating substrate, where temperature distribution and flow-field motion conditions were studied. The results show that, in the initial stage of evaporation, along with the change of the low temperature extreme points of the liquid-gas interface, the Marangoni convection vortices in the water droplets present different evolution, and at the same stage the temperature distribution inside the droplets are greatly influenced by Marangoni convection. Furthermore, with the uniformization of temperature distribution inside the water droplet, a pair of symmetrical convection vortices form inside the water droplet, on the left and right side, rotating in opposite direction. Conducting experimental studies under the same conditions, and comparing experimental and simulation results, both are in good agreement; also changing the surface temperature of the heating substrate, the results show that the increment of the temperature has the following effects on the droplet internal velocity field： the higher the heating substrate temperature is, the faster the flow field motion is, and more significant the decline of the average velocity is; in the initial stage of evaporation the flow field velocity has larger decline, stabilizing after between the medium and final stages.