High-speed laminar-to-turbulent transition over blunt bodies is relevant to a variety of aerodynamic applications. Experiments have observed that beyond a critical value of the nose radius the initially downstream movement of transition location is reversed. Linear stability and receptivity analyses have been unsuccessful at predicting this reversal. The current Paper uses a random forcing approach in conjunction with the Navier–Stokes equations to understand this phenomenon using blunted flat plates of different nose radii at $M_{\infty }=6.0$. Specifically, steady validated base flows are perturbed to generate multiple scales associated with both the boundary layer as well as the entropy layer. The dominant frequencies and corresponding growth rates in the frequency spectrum are identified with spectral decomposition techniques. With increasing nose bluntness, a reversal in growth rate of maximum amplified frequency is observed beyond a critical value. At low bluntness, the invariance of the scaled frequency parameter indicates that the dominant instability is the Mack mode, as confirmed with through dynamic mode decomposition. For nose radii higher than the critical value, the mode associated with the peak frequency is different, with more prominent support in the entropy layer, indicating the presence of non-Mack modes.

钝体上的高速层流到湍流过渡与各种空气动力学应用有关。实验已经观察到，超出鼻子半径的临界值，过渡位置的最初下游移动是相反的。线性稳定性和接受性分析未能成功预测这种逆转。当前的论文结合Navier – Stokes方程使用了一种随机强迫方法，以使用不同鼻半径的钝化平板来了解这种现象。${\mathrm{中号}}_{\infty }=6.0$。具体而言，对稳定的经过验证的基本流进行扰动，以生成与边界层以及熵层均相关的多个比例。用频谱分解技术确定频谱中的主频和相应的增长率。随着鼻子钝度的增加，可以观察到最大放大频率的增长率超过临界值。在低钝度下，缩放的频率参数的不变性表明主要的不稳定性是Mack模式，这已通过动态模式分解得到了证实。对于高于临界值的鼻半径，与峰值频率相关的模式是不同的，在熵层中具有更突出的支持，表明存在非麦克模式。