Experiments on shock–shock interactions were conducted in a transonic–supersonic wind tunnel with variable free-stream Mach number functionality. Transition between the regular interaction (RI) and the Mach interaction (MI) was induced by variation of the free-steam Mach number for a fixed interaction geometry, as opposed to most previous studies where the shock generator angles are varied at constant Mach number. In this paper, we present a systematic flow-based post-processing methodology of schlieren data that enables an accurate tracking of the evolving shock system including the precise and reproducible detection of RI\(\rightleftarrows \)MI transition. In line with previous experimental studies dealing with noisy free-stream environments, transition hysteresis was not observed. However, we show that establishing accurate values of the flow deflections besides the Mach number is crucial to achieve experimental agreement with the von Neumann criterion, since measured flow deflections deviated significantly, up to \(1.2^{\circ }\), from nominal wedge angles. We also report a study conducted with a focusing schlieren system with variable focal plane that supported the image processing by providing insights into the three-dimensional side-wall effects integrated in the schlieren images.

在具有可变自由流马赫数功能的跨音速-超音速风洞中进行了冲击-冲击相互作用的实验。常规相互作用 (RI) 和马赫相互作用 (MI) 之间的过渡是由固定相互作用几何形状的自由蒸汽马赫数的变化引起的，这与大多数先前的研究相反，其中激波发生器角度在恒定马赫数下变化。在本文中，我们提出了一种系统的基于流的纹影数据后处理方法，该方法能够准确跟踪不断演变的冲击系统，包括对 RI \(\rightleftarrows \)MI 过渡。与先前处理嘈杂自由流环境的实验研究一致，未观察到过渡滞后。然而，我们表明，除了马赫数外，建立准确的流动偏转值对于实现与冯诺依曼准则的实验一致至关重要，因为测量的流动偏转与标称值偏差显着，最高可达\(1.2^{\circ }\)楔角。我们还报告了使用具有可变焦平面的聚焦纹影系统进行的一项研究，该系统通过提供对集成在纹影图像中的 3 维侧壁效应的洞察来支持图像处理。