Rarefied gas flow in a rectangular enclosure induced by non-isothermal walls
Rarefied gas flow in a rectangular enclosure induced by non-isothermal walls
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DOI：
10.1063/1.4875235
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发表时间：
2014-05-01
影响因子：
4.6
通讯作者：
Stefanov, Stefan
中科院分区：
文献类型：
--
作者：
Vargas, Manuel;Tatsios, Giorgos;Stefanov, Stefan
研究了稀薄气体在无外力场协同作用的矩形封闭腔内的非等温流动。顶壁和底壁保持在恒定但不同的温度，并且假定沿侧壁沿着为线性温度分布。模型建立在直接数值求解Shakhov动力学方程和直接模拟Monte Carlo（DSMC）方法的基础上。解决问题的确定性和随机允许系统的比较和验证的结果，以及利用每种方法在所涉及的流动和传热现象的调查的数值优势。热诱导流模拟的三个无量纲参数表征的问题，即，参考克努森数，温度比的底部的顶板，和外壳的纵横比。他们的流动配置和散装量的影响进行了彻底的检查。沿着侧壁，气体以小的努森数从冷到热流动，而随着努森数的增加，气体从热到冷流动，并且热诱导流动配置变得更加复杂。即使在小的温差下，也可以存在热-冷流动延伸到非等温侧壁的整个长度的这些流动模式，然后，随着顶板和底板之间的温差增加，它们被增强。空腔的长宽比也影响这种流动结构，随着空腔深度与宽度相比的增加，热-冷流动变得更加主导。为了进一步分析流动模式，引入了一种新的解决方案分解成弹道和碰撞部分。这是通过相应地修改典型DSMC算法的索引过程来实现的。的解决方案的每个部分的贡献分别检查和物理解释的流动配置，包括热到冷的流动靠近侧壁，在整个范围内的努森数提供。(C)2014 AIP出版有限责任公司。
The flow of a rarefied gas in a rectangular enclosure due to the non-isothermal walls with no synergetic contributions from external force fields is investigated. The top and bottom walls are maintained at constant but different temperatures and along the lateral walls a linear temperature profile is assumed. Modeling is based on the direct numeri cal solution of the Shakhov kinetic equation and the Direct Simulation Monte Carlo (DSMC) method. Solving the problem both deterministically and stochastically allows a systematic comparison and verification of the results as well as the exploitation of the numerical advantages of each approach in the investigation of the involved flow and heat transfer phenomena. The thermally induced flow is simulated in terms of three dimensionless parameters characterizing the problem, namely, the reference Knudsen number, the temperature ratio of the bottom over the top plates, and the enclosure aspect ratio. Their effect on the flow configuration and bulk quantities is thoroughly examined. Along the side walls, the gas flows at small Knudsen numbers from cold-to-hot, while as the Knudsen number is increased the gas flows from hot-to-cold and the thermally induced flow configuration becomes more complex. These flow patterns with the hot-to-cold flow to be extended to the whole length of the non-isothermal side walls may exist even at small temperature differences and then, they are enhanced as the temperature difference between the top and bottom plates is increased. The cavity aspect ratio also influences this flow configuration and the hot-to-cold flow is becoming more dominant as the depth compared to the width of the cavity is increased. To further analyze the flow patterns a novel solution decomposition into ballistic and collision parts is introduced. This is achieved by accordingly modifying the indexing process of the typical DSMC algorithm. The contribution of each part of the solution is separately examined and a physical interpretation of the flow configuration, including the hot-to-cold flow close to the side walls, in the whole range of the Knudsen number is provided. (C) 2014 AIP Publishing LLC.