Abstract In this paper, we numerically investigated the evolution of flow pattern inside an evaporating sessile drop using a transient numerical model based on the Arbitrary Lagrangian–Eulerian (ALE) frame that fully couples fluid flow and heat and mass transfer. Effects of both liquid volatility and initial contact angle on the transient flow pattern were explored. The results show that stronger volatile drops have more vortices whereas multi-vortices circulation lasts for shorter time. With the increasing of contact angle, the maximum number of vortices at first increases gently and then rapidly, while the duration of the multi-vortices circulation at first decreases rapidly and then increases a little bit. Marangoni flow is found to dominate the formation of vortices in most of the simulated cases, whereas natural convection plays a role in drops of large contact angles. These conclusions agree with the judgement criteria based on Marangoni number and Grashof number. Besides the classical symmetrical vortices, encompassing vortices are observed during the transient development of internal flow. These encompassing vortices normally form either through the merging of a big vortex with its adjacent small one or through the splitting of a big vortex into two smaller ones.

中文翻译：

---

蒸发固着液滴中的瞬态流动模式：挥发性和接触角影响的数值研究

摘要 在本文中，我们使用基于任意拉格朗日-欧拉 (ALE) 框架的瞬态数值模型对蒸发的固着液滴内部流动模式的演变进行了数值研究，该模型完全耦合了流体流动和传热传质。研究了液体挥发性和初始接触角对瞬态流动模式的影响。结果表明，较强的挥发性液滴具有更多的涡流，而多涡流循环持续的时间较短。随着接触角的增加，最大涡流数先平缓后迅速增加，而多涡流循环的持续时间则先迅速减少，然后略有增加。在大多数模拟情况下，发现 Marangoni 流主导涡旋的形成，而自然对流在大接触角的液滴中起作用。这些结论与基于 Marangoni 数和 Grashof 数的判断标准一致。除了经典的对称涡流，在内流的瞬态发展过程中还观察到包围涡流。这些环绕的漩涡通常是通过一个大漩涡与其相邻的小漩涡合并形成的，或者通过一个大漩涡分裂成两个较小的漩涡而形成。