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Bono Wasistho
Mechanical and Aerospace Engineering Department Arizona State University Tempe, Arizona 85287-6106, USA

Kyle D. Squires
School for Engineering of Matter, Transport and Energy Department of Mechanical and Aerospace Engineering Arizona State University Tempe, Arizona 85287-6106, USA


Large Eddy Simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) calculations have been used to predict the development, separation, reattachment and downstream recovery of the flow over a smoothly contoured ramp. The statistically two-dimensional upstream flow separates along the ramp surface and then reattaches downstream on a flat section. A canonical flat-plate turbulent boundary layer at a momentum thickness Reynolds number 1100, and having a boundary layer thickness 0.13Lr, is introduced four ramp lengths upstream of the onset of curvature. Subgrid-scale (SGS) stresses in the LES are closed using the dynamic eddy viscosity model of Germano et al (1991). RANS calculations of the steady-state solution are performed using two leading models: Spalart-Allmaras (Spalart-Allmaras 1994) and v2-f (Durbin 1991). Mean flow predictions obtained using all the models agree well with the experimental measurements of Song et al (2000). Boundary layer detachment occurs along the curved section (x/Lr ~ 0.4) with reattachment at roughly x/Lr ~ 1.4. The primary turbulent shear stress sharply increases in the separated region and LES predictions of the shear stress development are accurate. RANS estimations of the shear stress are below the data in the separated region, though reasonable further downstream.