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首页> 外文学位 >THERMOCAPILLARY-BUOYANCY CONVECTION IN DROP-SHAPED SYSTEM BY PHASE CHANGE.
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THERMOCAPILLARY-BUOYANCY CONVECTION IN DROP-SHAPED SYSTEM BY PHASE CHANGE.

机译：相位变化导致液滴状系统中的热毛细对流换热。

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摘要

Based on the experimental finding of certain convection patterns inside evaporating sessile drops, and also because of the increasing interest in surface-tension driven flows, a finite difference code is developed using an ADI scheme to study the thermocapillary-buoyancy convection induced by phase change in a drop-shaped system.; The intercoupling relation between thermocapillary force, buoyancy force, heat transfer, and phase change, along with their effects on the induced flow patterns, is disclosed. Three types of convection can be classified based on MaRa: thermocapillary-dominant, competing, and buoyancy-dominant. Among these three types, the competing type of convection simulates the experimental observations quite well, the basic mechanism of the observed convection inside evaporating sessile drops is thus understood.; A critical Ma number of 10('4) is found for transition from linear flow behavior to nonlinear in the thermocapillary-dominant case. For the more familiar buoyancy-dominant convection, onset of flow separation is found at Ra = 10('6) with Pr = 17.6.; Both evaporation and condensation are examined; only evaporation initiates the unstable convection, while condensation always brings out a stable density distribution that eventually damps out all the fluid agitation. A simple numerical model is also presented to study the effect of boundary recession due to evaporation and the peeling-off effect (the removal of the surface layer of fluid by evaporation) is shown to be relevant.
机译：基于蒸发无滴内某些对流模式的实验发现，并且由于对表面张力驱动流的兴趣不断增加，使用ADI方案开发了一种有限差分码，用于研究由相变引起的热毛细管浮力对流。水滴形系统。公开了热毛细作用力，浮力，传热和相变之间的相互耦合关系，以及它们对感应流型的影响。基于MaRa可以将对流分为三种类型：热毛细作用为主，竞争作用和浮力为主。在这三种类型中，对流的竞争类型很好地模拟了实验观察结果，因此，了解了蒸发的无柄液滴内部对流的基本机理。发现在热毛细管占主导地位的情况下，临界Ma数为10（'4），可从线性流动行为过渡到非线性行为。对于更熟悉的浮力主导对流，在Ra = 10（'6）且Pr = 17.6时发现了流动分离的开始。同时检查蒸发和冷凝；仅蒸发会引发不稳定的对流，而凝结始终会带来稳定的密度分布，从而最终抑制所有流体搅动。还提出了一个简单的数值模型来研究由于蒸发引起的边界退缩的影响，并且剥离效应（通过蒸发去除流体表面层）被证明是相关的。

著录项

  • 作者

    DUH, JEN-CHOW.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 1987
  • 页码 122 p.
  • 总页数 122
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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