钝体驻点附近的扰动放大
Perturbation amplification near the stagnation point of blunt bodies
AI总结：
针对钝体绕流转捩中自由流扰动进入边界层的机制不明确的问题，研究了扰动通过驻点进入边界层的线性机制，发现低湍流强度下其占主导，并揭示了随雷诺数、马赫数的变化趋势。
摘要：
钝体绕流存在多种不同的转捩至湍流的路径。近期已有研究探索了通过抬升效应实现的扰动非模态放大，用以解释轴对称体驻点附近的转捩现象。然而，只有已存在于边界层中的扰动才能被放大，而自由流扰动进入边界层的机制尚未得到充分探究。本研究针对扰动如何通过驻点进入边界层展开了研究。在低湍流强度水平下，这种线性机制预计将比此前确定的、与边界层扰动形成相关的非线性机制占主导地位。本文还开展了参数化研究，揭示了该机制随雷诺数和马赫数变化的趋势。
英文摘要：
Different transition to turbulence routes for the flow around blunt bodies are possible. Non-modal amplification of perturbations via the lift-up effect has recently been explored to explain transition near the stagnation point in axisymmetric bodies. However, only perturbations already present in the boundary layer can be amplified, and the mechanisms by which free-stream perturbations enter the boundary layer have not yet been fully explored. In this study, we present an investigation of how disturbances enter the boundary layer via the stagnation point. This linear mechanism is expected to dominate over non-linear mechanisms previously identified on the formation of boundary layer perturbations at low turbulence intensity levels. A parametric investigation is presented, revealing trends with Reynolds and Mach numbers.
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