Screech tones from rectangular jets with spanwise oblique shock-cell structures

摘要: Understanding screech is especially important for the design of advanced aircraft because can cause sonic fatigue failure structures. Although connection between shock-cell spacing and frequency well understood, relation non-uniformities in structures resulting amplitude, mode, steadiness have remained unexplored. This paper addresses above issues by intentionally producing spanwise (larger nozzle dimension) variations studying mode. The spanwise-oblique were produced using imperfectly expanded convergent-divergent rectangular nozzles (aspect ratio = 5) with non-uniform exit geometries. Three geometries studied: (a) a uniform edge, (b) oblique (single-bevelled) (c) that had two (double-bevelled) cuts to form an arrowhead-shaped nozzle. For all considered, mode was antisymmetric transverse (smaller direction allowing focus on changes direction. types modes observed: symmetric (I), (II), (III). following significant results emerged: (i) cases corresponds structure, (ii) when multiple are present, technique presented here makes it possible distinguish coexisting mutually exclusive modes, (iii) strength shocks 3 4 influences source amplitude determines whether unsteady. offer hope better understanding tailoring shock-containing jets minimize components.