Thermocapillary convection in double-layer fluid structures within a two-dimensional open cavity.
Thermocapillary convection in double-layer fluid structures within a two-dimensional open cavity.
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DOI：
10.1016/j.jcis.2007.06.017
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发表时间：
2007-11
影响因子：
9.9
通讯作者：
N. Gupta;H. Haj-Hariri;A. Borhan
中科院分区：
文献类型：
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作者：
N. Gupta;H. Haj-Hariri;A. Borhan
考虑了在不考虑重力作用的情况下，含两层不混溶液体的矩形空腔内的热毛细对流。在这两个层的温度场和流场计算使用域映射结合有限差分格式上交错网格。允许熔体-密封剂和空气-密封剂界面变形，接触线固定在固体边界上。在顶部的自由表面的存在下，导致在密封剂相的对流增加，同时延迟熔体中的热毛细流动。当密封剂的粘度增加或密封剂层的厚度减小时，密封层中的热毛细对流的强度减小。选择具有更大的界面张力对温度的敏感性（与熔体相相比）的密封剂几乎可以完全抑制熔体中的热毛细对流。在一个开放的腔体中的熔体-密封剂界面的变形被发现是大于那些在一个封闭的腔体与刚性的顶面，由于较高的压力梯度实现在密封剂相。与先前报道的封闭腔中双层系统的界面变形行为相反，熔体-密封剂界面的形状对于所有粘度比值而言在性质上是相似的，其中界面浸入冷壁附近的熔体中，并且浸入热壁附近的密封剂中。对于在这项研究中考虑的双层，在密封剂层的顶部的自由表面被发现是更有效的比一个刚性的顶部在降低熔体中的热毛细对流的强度。
Thermocapillary convection within a differentially-heated open rectangular cavity containing two immiscible liquid layers is considered in the absence of gravitational effects. The temperature and flow fields in the two layers are computed using domain mapping in conjunction with a finite-difference scheme on a staggered grid. The melt–encapsulant and air–encapsulant interfaces are allowed to deform, with the contact lines pinned on the solid boundaries. The presence of a free surface at the top leads to increased convection in the encapsulant phase while retarding thermocapillary flow in the melt. The intensity of thermocapillary convection in the encapsulated layer is reduced as the viscosity of the encapsulant is increased or the thickness of the encapsulant layer is decreased. Choosing an encapsulant with a greater sensitivity of interfacial tension to temperature (as compared to that of the melt phase) can almost completely suppress thermocapillary convection in the melt. Deformations of the melt–encapsulant interface in an open cavity are found to be larger than those in a closed cavity with a rigid top surface, due to higher pressure gradients realized in the encapsulant phase. In contrast to interface deformation behavior reported earlier for a double-layer system in a closed cavity, the shape of the melt–encapsulant interface is qualitatively similar for all values of the viscosity ratio, with the interface dipping into the melt near the cold wall, and into the encapsulant near the hot wall. For the double-layers considered in this study, a free surface at the top of the encapsulant layer was found to be more effective than a rigid top in reducing the intensity of thermocapillary convection in the melt.