YIP-Low-Order Representations of Irregular Surface Roughness and Their Impact on Wall Turbulence
Final rept. Feb 2007-Feb 2010
ILLINOIS UNIV AT URBANA-CHAMAPAIGN
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This effort explored the impact of topographical scales present within irregular surface roughness on a turbulent boundary layer. Low-order representations of a surface replicated from a turbine blade damaged by deposition of foreign materials were generated using singular value decomposition to decompose the complex topography into a set of basis functions of decreasing importance to the original full surface. The low-order surface models were then formed by truncating the basis functions at the first 5 and 16 modes containing 71 and 95 of the full surface content, respectively, so that only the largest-scale topographical features were included. Physical replications of these surfaces were rapid prototyped and particle-image velocimetry was used to measure the flow over these surfaces in the streamwise-wall-normal plane and in a streamwise-spanwise plane deep within the roughness sublayer. A 16-mode model of the full surface faithfully reproduced most of the characteristics of flow over the full surface for both developing and developed flow conditions. However, both models failed to reproduce important details of the Reynolds-shear-stress-producing events within the roughness sublayer. The final report details these observations.
- Manufacturing and Industrial Engineering and Control of Production Systems
- Fluid Mechanics