TED-AJ03-595 PREDICTING HEAT TRANSFER FOR TURBULENT FLOW OVER RANDOMLY-ROUGH SURFACES USING THE DISCRETE-ELEMENT METHOD
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概要
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The discrete-element method considers heat transfer from a rough surface to be the sum of convection through the fluid on the flat part of the surface and the convection from each of the roughness elements. The discrete-element method has been widely used and validated for roughness composed of sparse, ordered, and deterministic elements. Modifications made to the discrete-element roughness method to extend the validation to real surface roughness are detailed. These modifications include accounting for the deviation of the roughness element cross sections from circular configurations and determining the location of the computational ""surface that differs from the physical surface. Two randomly-rough surfaces found on high-hour gas-turbine blades were characterized using a Taylor-Hobson Form Talysurf Series 2 profilometer. Two randomly-rough surfaces and two elliptical-analog surfaces were generated for wind-tunnel testing using a three-dimensional printer. The printed surfaces were scaled to maintain similar boundary layer thickness to roughness height ratio in the wind-tunnel as is found in gas-turbine operation. The analog surfaces were created by replacing each roughness element from the original randomly-rough surface with an elliptical roughness element with the equivalent plan-form area and eccentricity. The results of the wind tunnel Stanton number measurements and the discrete-element method predictions for each of the four surfaces are presented and discussed. The discrete-element predictions are within 16% of the experimentally measured Stanton numbers for the randomly-rough and analog surfaces.
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著者
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Mcclain Stephen
Department Of Mechanical Engineering The University Of Alabama At Birmingham
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Hodge Keith
Department of Mechanical Engineering Mississippi State University
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Bons Jeffrey
Department of Mechanical Engineering Brigham Young University