Turbulent Boundary Layers In Subsonic And Supersonic Flow

A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.

Summary: The present report consists of two parts. The first part deals with the two-dimensional stationary flow in the presence of local supersonic zones. A numerical method of integration of the equation of gas dynamics is developed. Proceeding from solutions at great distance from the body the flow pattern is calculated step by step. Accordingly the related body form is obtained at the end of the calculation. The second part treats the relationship between the displacement thickness of laminar and turbulent boundary layers and the pressure distribution at high speeds. The stability of the boundary layer is investigated, resulting in basic differences in the behavior of subsonic and supersonic flows. Lastly, the decisive importance of the boundary layer for the pressure distribution, particularly for thin profiles, is demonstrated.

For flow over a two-dimensional ramp compression corner case, an experimental investigation to determine the incipient separation was carried out at Mach numbers between 0.55 and 0.9 and Reynolds numbers (based on undisturbed boundary layer thickness) between 350,000 and 690,000. Detailed surface pressure, pitot traversing and oil flow data were obtained for each ramp angle case. Two-dimensionality of the ramp compression corners was verified by the surface oil flow. A major finding of this study is that the incipient separation ramp angle is relatively independent of Mach number and Reynolds number within the range studied. The incipient separation ramp angle was found to be about 22.5 degrees.