DSMC investigation on flow characteristics of rarefied hypersonic flow over a cavity with different geometric shapes
DSMC investigation on flow characteristics of rarefied hypersonic flow over a cavity with different geometric shapes
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不同几何形状空腔稀薄高超声速流流动特性的DSMC研究
DOI：
10.1016/j.ijmecsci.2018.09.022
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发表时间：
2018-11
影响因子：
7.3
通讯作者：
Qin Luo
中科院分区：
文献类型：
--
作者：
Guangming Guo;Qin Luo
空泡作为最基本的气动外形之一，在各种气动表面上经常会遇到不同几何形状的空泡。本文采用粒子模拟中最成功的方法之一--直接模拟蒙特卡罗（DSMC）方法，对长深比为1-8，后壁与前壁高度比为0.5 ~ 2，在马赫数为8、高度为60公里的情况下，自由流的倾斜前壁为20° ~ 70°。模拟结果表明，改变长深比可以显著改变空腔内的剪切层和回流区，当长深比为6时，空腔转变为封闭型。对于长深比一定的空腔，后壁高度的增加会将剪切层推离空腔底面，从而增加回流区的面积。相反，后壁高度的减小会将剪切层拉入空腔内部，最后回流区会分裂成两个较小的分离区，分别位于空腔的左右角。一个重要的发现是，标准（即，长度与深度之比）不是一个常数，而是随着自由落体条件而变化。同时适当倾斜前壁和后壁，可以完全消除空腔内的回流区，同时对剪切层的影响较小。
As one of the most fundamental configurations, the cavities with different geometric shapes are frequently encountered on various aerodynamic surfaces. In this paper, the direct simulation Monte Carlo (DSMC) which is one of the most successful particle simulation methods in treating rarefied gas dynamics is employed to investigate the flow characteristics of the cavity with a length-to-depth ratio of 1–8, a rearwall-to-frontwall height ratio of 0.5–2, and an inclined frontwall ranging from 20° to 70° for the free stream at a Mach number of 8 and an altitude of 60 km. The simulation results indicate that the shear layer and recirculation region within the cavity are changed greatly by varying length-to-depth ratio and the cavity is transformed into a closed type at the length-to-depth ratio of 6. For the cavity with a fixed length-to-depth ratio, the increase in rearwall height would push the shear layer away from cavity floor and hence increases the area of recirculation region. Conversely, the decrease in rearwall height would draw the shear layer into the interior of the cavity and finally the recirculation region would be split into two smaller and separated ones located at the left and right corners of the cavity respectively. A significant finding is that the criterion (i.e., length-to-depth ratio) for classifying the cavity type is not a constant but changes with freestream conditions. In addition, recirculation region(s) within the cavity can be eliminated completely by simultaneously inclining the frontwall and rearwall with an appropriate angle and meanwhile the shear layer is affected slightly.
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DOI：
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发表时间：
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期刊：
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