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A computational investigation has been performed to better understand the impact of surface roughness on the flow o ver a c ontaminated s u rface. T h is r eport h i ghlights t he i mplementation a nd d evelopment of the roughness amplification m odel i n t he fl ow so lver OV ER FLOW-2. Th e mo del, or iginally pr oposed by Dassler, Kozulovic, and Fiala, introduces an additional scalar field r oughness a mplification qu an tity. This value is explicitly set at rough wall boundaries using surface roughness parameters and local flow quantities. The additional transport equation allows non-local effects of surface roughness to be accounted for downstream of rough sections. This roughness amplification v ariable i s c oupled w ith t he Langtry-Menter model and used to modify the criteria for transition. Results from flat plate test cases show good agreement with experimental transition behavior on the flow o ver v arying s and g rain r oughness h e ights. Additional validation studies were performed on a NACA 0012 airfoil with leading edge roughness. The computationally predicted boundary layer development demonstrates good agreement with experimental results. New tests using varying roughness configurations have been carried out at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel to provide further calibration of the roughness amplification m ethod. An overview and preliminary results are provided of this concurrent experimental investigation. ∗The work described in this report was performed for Sandia National Laboratories under Contract No. 1228734

A Transport Equation Approach to Modeling the Influence of Surface Roughness on Boundary Layer Transition