三维模型液滴蒸发的Bénard-Marangoni对流模拟

Bénard-Marangoni convection simulation of evaporating droplet with three-dimensional model

现有液滴的数值模拟多为二维模型,难以与实验观察到的Bénard-Marangoni对流现象进行比较说明。因此考虑液滴蒸发的冷却效应,通过建立三维的液滴蒸发模型,模拟恒接触角模式液滴在加热基板上的蒸发过程,研究Bénard-Marangoni涡胞的变化,Ma数对Bénard-Marangoni涡胞产生的影响。当Ma数大于临界Ma数时,液滴出现Bénard-Marangoni涡胞,并处于不稳定状态,涡胞不断出现、消失,液滴的滞止点在蒸发过程中不维持在液滴中心位置,直至液滴趋于稳定。在低接触角时,液滴出现Bénard-Marangoni涡胞所需的临界Ma值较小,随着接触角增大,液滴出现Bénard-Marangoni涡胞所需临界Ma呈线性增加。当接触半径一致时,液滴蒸发趋于稳定时的Bénard-Marangoni涡胞随Ma数的增加而增加;当基板温度与液滴温差一定时,液滴蒸发趋于稳定时的Bénard-Marangoni涡胞随液滴接触半径的增加而增加。

The existing numerical simulations of droplets are mostly two-dimensional models,which are difficult to compare with the Bénard-Marangoni convection observed in experiments.Considering the cooling effect of droplet evaporation,a three-dimensional droplet evaporation model was established to simulate the evaporation process of droplets on the heated substrate with constant contact angle mode.The change of Bénard-Marangoni cells and the effect of Ma number on Bénard-Marangoni cells was further studied.When the Ma number is greater than the critical Ma number,the Bénard-Marangoni cells appear in the droplet,and the droplet is in an unstable state.The cells appear and disappear alternately,and the stagnation point of the droplet does not maintain at the center of the droplet during evaporation until the droplet tends to be stable.When the contact angle is low,the critical Ma value required for the appearance of Bénard-Marangoni cells is smaller.With the contact angle increasing,the critical Ma value of Bénard-Marangoni cells increases linearly.When the contact radius is the same,the Bénard-Marangoni cells increase with the Ma number increasing in the case of the droplet evaporation tending to be stable.When difference of the substrate temperature and the droplet temperature is constant,the Bénard-Marangoni cells increase with the droplet contact radius increasing in the case of the droplet evaporation tending to be stable.