Numerical investigation of surface curvature effect on the self-propelled capability of coalesced drops
Numerical investigation of surface curvature effect on the self-propelled capability of coalesced drops
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DOI：
10.1063/5.0026163
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发表时间：
2020-12
影响因子：
4.6
通讯作者：
Yan Chen;Ahmed Islam;M. Sussman;Y. Lian
中科院分区：
文献类型：
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作者：
Yan Chen;Ahmed Islam;M. Sussman;Y. Lian
我们数值研究曲率对聚结液滴自推进能力的影响。数值方法是基于一个经过验证的多相流求解器，解决了三维Navier-Stokes方程。采用流体矩法捕捉气液界面，并采用方向分裂法对界面进行平流。然后，采用近似投影法将速度和压力的计算解耦。通过实验结果与仿真结果的对比，验证了不同情况下的有效性。使用这种数值方法仔细捕获的合并引起的跳跃行为在一个平面上。为了研究弯曲基底的曲率对自跳跃行为的影响，还研究了单液滴撞击凸表面和两液滴在光纤上聚合的情况，并与实验结果进行了比较。单滴在凸面上的不对称反弹导致接触时间减少40%，如我们的研究所示。我们的研究还表明，由于楔形体的曲率，液滴在楔形体的对称侧上形成了一个瓣形区域。叶状区域迫使液滴在向上的方向上将更多的表面能转化为动能。通过增加曲面曲率提高了跳跃能力。我们的研究还表明，在较低的接触角下，液滴可以很容易地附着在基底上，同时，很难从基底上分离。
We numerically investigate the curvature effect on the self-propelled capability of coalesced drops. The numerical method is based on a well validated multiphase flow solver that solves the three-dimensional Navier–Stokes equations. The liquid–air interface is captured using the moment of fluid method, and a direction splitting method is applied to advect the interface. Afterward, an approximate projection method is used to decouple the calculation of velocity and pressure. Different cases were validated by comparing the experimental results with the simulation results. The coalescence-induced jumping behavior on a flat surface is carefully captured using this numerical method. To investigate the effect of curvature of a curvy substrate on the self-jumping behavior, a case with a single drop impinging on a convex surface and a case with two drops’ coalescence on a fiber are also studied and compared with the experimental results. The asymmetric bouncing of a single drop on the convex surface leads to 40% reduction in contact time, as found in our study. Our study also reveals that due to the curvature of the wedge, the drop forms a lobe shaped region on the symmetric sides of the wedge. The lobed region forces the drop to convert more surface energy into kinetic energy in the upward direction. The jumping capability is improved by increasing the surface curvature. Our study also shows that at lower angles of contact, the drops can easily get attached to the substrate and, at the same time, have difficulty detaching from the substrate.