Numerical Study of Shock-Reflection Hysteresis in an Underexpanded Jet

Shock-ree ection hysteresis and plume structure in a low-density, axisymmetric highly underexpanded air jet is examined using a Navier ‐Stokes e ow solver. This type of jet is found in a number of applications, e.g., rocket exhausts and fuel injectors. The plume structure is complex, involving the interaction of several e ow features, making this a demanding problem. Two types of shock ree ection appear to occur in the plume, regular and Mach, depending on the jet pressure ratio. The existence of a dual solution domain where either type may occur has been predicted, in agreement with experiment where the same phenomenon has been observed for a nitrogen jet. There is a hysteresis in the shock-ree ection type; the ree ection type observed in the dual-solution domain depends on the time history of the plume development. A quasi-steady approach is employed to calculate the entire hysteresis loop. An implicit, multiblock structured, e nite volume e ow solver is used. The results of the computational study are used to examine the structure of the plume and are compared with experimental data where possible. Some e ow features not initially recognized from experiment have been identie ed, notably curvature of the Mach disk, recirculation behind the Mach disk, and the regular ree ection having Mach-ree ection characteristics.