Complete first-mode oblique breakdowns under wall transpirations in a Mach 2 flat-plate boundary layer are investigated by direct numerical simulations. The parameters of oblique waves are determined by linear stability analysis, while air transpiration is modeled by a wall-injection boundary condition. Wall transpiration with various blowing ratios is imposed at two distinct streamwise regions to assess its effects. When wall transpiration is located in the linear and early nonlinear region, the transition shifts upstream with increasing blowing ratios. This promotion effect arises from the destabilization of the oblique mode, steady vortex mode and higher-harmonic modes. Wall transpiration also leads to reduced skin friction and heat transfer in the transpiration and downstream turbulent regions. Through integral analysis, the impacts of transpiration on the generation mechanisms of skin friction and heat transfer are gained. The reduced skin friction and heat transfer in the transpiration region are mainly attributed to the amplified negative contributions from mean convection. In the turbulent region, the reduction of skin friction can be attributed to the heightened negative contributions from mean convection and the diminished positive contributions from turbulent convection. Concurrently, heat transfer experiences a decrease as a consequence of reduced positive contributions from spatial development and augmented negative contributions from mean convection. When wall transpiration is located in the late nonlinear region, its impacts resemble those observed when transpiration is located in the linear and early nonlinear region. However, the transition-promoting effect weakens, and the heat-transfer reduction effect becomes more pronounced.

中文翻译：

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壁蒸腾下超音速边界层第一模式倾斜击穿的直接数值模拟

通过直接数值模拟研究了马赫 2 平板边界层中壁蒸腾作用下的完全第一模式倾斜击穿。斜波的参数由线性稳定性分析确定，而空气蒸腾则由壁注入边界条件建模。在两个不同的流向区域施加具有不同吹风比的壁蒸腾以评估其效果。当壁蒸腾位于线性和早期非线性区域时，随着鼓风比的增加，过渡向上游移动。这种促进效应源于斜模态、稳态涡模态和高次谐波模态的失稳。壁蒸腾还导致蒸腾和下游湍流区域的表面摩擦和热传递减少。通过积分分析，得出蒸腾作用对表面摩擦和传热产生机制的影响。蒸腾区域的表面摩擦和传热减少主要归因于平均对流的负贡献放大。在湍流区域，表面摩擦的减少可归因于平均对流的负贡献增加和湍流对流的正贡献减少。同时，由于空间发展的积极贡献减少和平均对流的消极贡献增加，传热减少。当壁蒸腾位于晚期非线性区域时，其影响类似于蒸腾位于线性和早期非线性区域时观察到的影响。然而，促进转变的效果减弱，传热减少的效果变得更加明显。