High-speed unsteady flows around spiked-blunt bodies
High-speed unsteady flows around spiked-blunt bodies
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DOI：
10.1017/s0022112009006235
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发表时间：
2009-07
影响因子：
3.7
通讯作者：
A. Panaras;D. Drikakis
中科院分区：
文献类型：
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作者：
A. Panaras;D. Drikakis
本文详细研究了钝头体的超声速和高超音速非定常绕流，包括流场初始化对流场结果的影响。过去的实验研究表明，如果一个尖钝体的几何形状是这样的，即出现了由斜前震和弓形余震组成的激波群，那么流动可能是非定常的。非定常流动的特征是周期性的径向膨胀和崩溃的锥形分离泡周围的尖峰（脉动）形成。超过一定的尖峰长度，流动是“稳定的”，即在径向方向上稳定或轻微振荡。不稳定和“稳定”的条件下，增加或减少穗长度在实验测试，此外，滞后效应已被观察到。本研究表明，对于某些几何形状的数值模拟流强烈依赖于假设的初始流场，包括由于固有的滞后效应和非定常流动模式的外观分叉的发生。使用几种不同的配置的计算表明，瞬态（初始）流的发展对应于一个几乎无粘流场的特点是由前震余震相互作用。当流动是脉动的时，进一步的流动发展对初始条件不敏感，而对于振荡或几乎“稳定”的流动，流动发展强烈地依赖于假定的初始流场。
This paper presents a detailed investigation of unsteady supersonic and hypersonic flows around spiked-blunt bodies, including the investigation of the effects of the flow field initialization on the flow results. Past experimental research has shown that if the geometry of a spiked-blunt body is such that a shock formation consisting of an oblique foreshock and a bow aftershock appears, then the flow may be unsteady. The unsteady flow is characterized by periodic radial inflation and collapse of the conical separation bubble formed around the spike (pulsation). Beyond a certain spike length the flow is ‘stable’, i.e. steady or mildly oscillating in the radial direction. Both unsteady and ‘stable’ conditions have been reported when increasing or decreasing the spike length during an experimental test and, additionally, hysteresis effects have been observed. The present study reveals that for certain geometries the numerically simulated flow depends strongly on the assumed initial flow field, including the occurrence of bifurcations due to inherent hysteresis effects and the appearance of unsteady flow modes. Computations using several different configurations reveal that the transient (initial) flow development corresponds to a nearly inviscid flow field characterized by a foreshock–aftershock interaction. When the flow is pulsating, the further flow development is not sensitive to initial conditions, whereas for an oscillating or almost ‘steady’ flow, the flow development depends strongly on the assumed initial flow field.