Two-dimensional numerical simulations of underwater vapor bubble on a hot spot have been performed to investigate the thermocapillary-driven flow generated at the bubble interface and the accompanying flow near the contact line. With fixing the bubble diameter of 10 μm, several contact angle and hot-spot temperatures have been considered to discuss the flow characteristics relevant to a mechanism of the particle accumulation in the bubble underneath, which was demonstrated experimentally in literature. In this study, the volume-of-fluid method was employed to capture the vapor-water interface, in the framework of OpenFOAM, an open-source CFD toolbox. We found that a bilayer structure is formed near the contact line, and the lower layer forms a flow approaching the contact line along the wall surface. In addition, a region where the wall shear rate decreases locally occurs slightly outside of the contact line. These two features are especially pronounced in the condition with contact angle of 30° and with a high temperature of the hot spot. The thickness of this lower layer depends on the hot-spot temperature, and is estimated approximately at 200 nm in a present condition.

中文翻译：

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局部加热壁上微气泡的热毛细驱动流动的数值研究

已经对热点上的水下蒸气气泡进行了二维数值模拟，以研究在气泡界面处产生的热毛细管驱动流动以及接触线附近的伴随流动。在将气泡直径固定为10μm的情况下，已考虑了几种接触角和热点温度来讨论与下方气泡中颗粒堆积机理相关的流动特性，这在文献中已得到实验证明。在这项研究中，在开源CFD工具箱OpenFOAM的框架中，采用了流体体积方法来捕获汽水界面。我们发现在接触线附近形成了双层结构，并且下层沿着壁表面形成接近接触线的流。此外，壁剪切速率局部降低的区域出现在接触线的外侧。在接触角为30°且热点温度较高的情况下，这两个特征尤其明显。该下层的厚度取决于热点温度，并且在当前条件下估计为约200nm。