Instabilities in oblique shock wave/laminar boundary-layer interactions
Instabilities in oblique shock wave/laminar boundary-layer interactions
复制标题
斜激波/层流边界层相互作用的不稳定性
DOI：
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发表时间：
2016
影响因子：
3.7
通讯作者：
J. Robinet
中科院分区：
文献类型：
--
作者：
F. Guiho;F. Alizard;J. Robinet
采用数值模拟和全局线性稳定性分析的方法，研究了斜激波与平板上层流边界层的相互作用。在选定的流动条件下（自由流动马赫数、雷诺数和激波角），来流边界层由于逆压梯度而发生分离。对于大范围的流动参数，斜激波/边界层相互作用（OSWBLI）被认为是全局稳定的。我们表明，二维大尺度结构的开始是由选择性噪声放大产生的，在线性框架中，由几个全局模态组成的波包序列对每个频率进行了描述。对特征谱和特征函数的详细分析使我们对空间尺度（形状和定位）和频率之间的关系有了一些深入的了解。特别是，OSWBLI表现出一种普遍的行为。最低频率对应的结构主要位于分离激波附近，以马赫波的形式发射辐射，并按相互作用长度进行缩放。中频与主要局限于剪切层的结构有关，并与冲击时的位移厚度有关。利用全局解析分析了OSWBLI选择频率的线性过程。结果表明，失稳主要与剪切层引起的失稳有关。对于较低的频率范围，在线性框架中没有特别的选择性。二维数值模拟表明，非线性机制改变了中等强迫振幅下的线性行为，导致低频显著放大。最后，基于目前的结果，我们提出了一些关于在激波/湍流边界层相互作用中观察到的非定常开始的假设。
The interaction of an oblique shock wave and a laminar boundary layer developing over a flat plate is investigated by means of numerical simulation and global linear-stability analysis. Under the selected flow conditions (free-stream Mach numbers, Reynolds numbers and shock-wave angles), the incoming boundary layer undergoes separation due to the adverse pressure gradient. For a wide range of flow parameters, the oblique shock wave/boundary-layer interaction (OSWBLI) is seen to be globally stable. We show that the onset of two-dimensional large-scale structures is generated by selective noise amplification that is described for each frequency, in a linear framework, by wave-packet trains composed of several global modes. A detailed analysis of both the eigenspectrum and eigenfunctions gives some insight into the relationship between spatial scales (shape and localization) and frequencies. In particular, OSWBLI exhibits a universal behaviour. The lowest frequencies correspond to structures mainly located near the separated shock that emit radiation in the form of Mach waves and are scaled by the interaction length. The medium frequencies are associated with structures mainly localized in the shear layer and are scaled by the displacement thickness at the impact. The linear process by which OSWBLI selects frequencies is analysed by means of the global resolvent. It shows that unsteadiness are mainly associated with instabilities arising from the shear layer. For the lower frequency range, there is no particular selectivity in a linear framework. Two-dimensional numerical simulations show that the linear behaviour is modified for moderate forcing amplitudes by nonlinear mechanisms leading to a significant amplification of low frequencies. Finally, based on the present results, we draw some hypotheses concerning the onset of unsteadiness observed in shock wave/turbulent boundary-layer interactions.
影响因子：
3.7
作者：
M. Grilli;P. Schmid;S. Hickel;N. Adams
通讯作者：
M. Grilli;P. Schmid;S. Hickel;N. Adams
影响因子：
2.2
作者：
E. Touber;N. Sandham
通讯作者：
E. Touber;N. Sandham
影响因子：
1.8
作者：
Barkley, D.;Blackburn, H. M.;Sherwin, S. J.
通讯作者：
Sherwin, S. J.