A combined experimental and computational study of pressure-driven three-dimensional separation in a turbulent boundary layer

Abstract

Experimental data and computational results are compared for a pressure-driven three-dimensional separation in a two-dimensional turbulent boundary layer. The comparisons include surface-flow visualizations, wall static pressures, and skin-friction coefficients. With the use of an open-circuit low-speed wind tunnel, the separation pattern was generated by a streamwise adverse pressure gradient combined with localized overhead suction that represented 6% of the test section entrance flow. This separation pattern was characterized by its topological critical points: a saddle point of separation, a nodal point of attachment, two additional saddle points, and two foci. Calculations of the experiment were made by using the INS3D computer code with the Spalart-Allmaras one-equation turbulence model. The topology of the computed near-wall particle traces was similar to the experimental separation pattern having the same geometric aspect ratio and the same number and types of critical points seen in the experiment. Comparisons between experimental data and computed results for static-pressure coefficient and skin-friction coefficient also showed good agreement. Results from the use of another turbulence model, Baldwin-Barth, had a much larger separated region. This experiment provides new data that isolate a three-dimensional separation pattern driven by pressure gradient and the amount of turbulent mixing.