Regular reflection to Mach reflection (RR–MR) transition in short wedges

• Published in: Journal of fluid mechanics 2024-10, Vol.998, Article A38
• Main Authors: Baby, Vinod Yeldho, Paramanantham, Vinoth, Rajesh, G.
• Format: Article
• Language: English
• Subjects: Angle of reflection; Configurations; Criteria; Distance; JFM Papers; Mach number; Mach reflection; Method of characteristics; Reflection; Shock waves; Supersonic flow; Symmetry; Trailing edges; Wave interaction; Wave interactions; Wave reflection
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2024.826

Regular reflection (RR) to Mach reflection (MR) transitions (${\rm RR}\leftrightarrow {\rm MR}$) on long wedges in steady supersonic flows have been well studied and documented. However, in a short wedge where the wedge length is small, the transition prediction becomes really challenging owing to the interaction of the expansion fan emanating from the trailing edge of the wedge with the incident shock and the triple/reflection point. The extent of this interaction depends on the distance between the wedge trailing edge and the symmetry line (Ht). This distance is a geometric combination of the distance of the wedge leading edge from the symmetry line $(H)$, the wedge angle ($\theta$) and the wedge length $(w)$. In the present study, we used the method of characteristics to model the complete wave interactions which accurately predicted shock curvatures and the reflection configurations for all ranges of the incoming flow Mach number. In the case of short wedges, the transition criterion strongly depends on the wedge length, which can be so adjusted even to eliminate the ${\rm RR}\rightarrow {\rm MR}$ transitions till the wedge angle reaches the no-reflection domain. Transition lines for both the detachment criterion and von Neumann criterion are also drawn to investigate the dual solution domain, and the reflection configurations were verified experimentally for the first time on short wedges. By using proper input configuration parameter ($w/H$), various types of shifts in the dual solution domain for short wedges are studied and categorised into three types, namely Type I, Type II and Type III.