Low-Dimensional Dynamical Characteristics of Shock Wave /Turbulent Boundary Layer Interaction in Conical Flows.

摘要

Shock wave / boundary layer interaction is studied in a large area ratio axisymmetric nozzle comprising a design exit Mach number of 5.58. Shock motion unsteadiness is captured by way of the dynamic wall pressure and is evaluated during overexpanded operations of the nozzle up to a nozzle pressure ratio of 65. Stationary SWBLI is considered whereby the nozzle is operated at a nozzle pressure ratio of 28.7 such that the internal flow structure is in a restricted-shock separated state; the annular separation shock resides within a fixed intermittent region of the flow. Conditional averages of the wall pressure fluctuations show how the motion of the incipient separation shock is out of phase with pressure fluctuations measured in the separated region downstream of the shock; pressure decreases when the shock moves downstream and vice versa. This is indicative of a long intermittent region, in terms of the boundary layer thickness, as the observed phenomena can be explained by translating the static wall pressure profile along with the shock motion. Non-stationary SWBLI is also considered by increasing the nozzle pressure ratio over time (transient start-up). Under these conditions, the shock pattern is shown to vary in strength and structure as it sweeps through the nozzle.