Characteristics of the Unsteady Shock-Induced Laminar Boundary Layer on a Flat Plate

The unsteady shock-induced laminar boundary layer on a flat plate is theoretically studied for shock speeds ranging from 1.12 to 9 km/sec. Boundary layer flows for real air, assumed to be in thermochemical equilibrium, are analyzed by extending Lam's work on shock-induced laminar boundary layers to equilibrium dissociated and ionized flows. A complete description of the unsteady nature of the boundary layer is presented in terms of heat transfer and several boundary layer thickness quantities as functions of a single time-position variable. Boundary layer development is considered for two points of view. Time-dependent boundary layer development and approach to steady state for any fixed position on the plate is described, as is the configuration of the boundary layer with position on the plate at any point in time. Quantities presented in graphical form permit accurate values for descriptive boundary layer quantities to be easily obtained for post shock pressures at or near 1 atm. Results indicate that in shock-tube experiments where observations of the flow are made through a boundary layer that influences experimental measurements, it is desirable to employ a flat plate to generate a boundary layer that minimizes the boundary layer thickness and diminishes or eliminates boundary layer unsteadiness.