This project focuses on fundamental research to relate friction and thermal effects of flow path surfaces to "real" detailed surface roughness from actual applications. These include the complex, spatially-varying roughness on internal turbine airfoil cooling passages, external turbine airfoil surfaces (as employed in gas turbine engines), and heat exchanger surfaces. Such roughness plays major roles in augmenting heat loading, pressure drop, drag, and aerodynamic losses.
The "real" rough surfaces employed for testing are prepared using similar procedures and environments employed for actual operating engine components, and are provided by General Electric Corporate Research and Development Center, and General Electric Aircraft Engines. Experimental data are obtained in an internal channel flow, as well as on an external airfoil with the same Reynolds numbers, Mach numbers, pressure gradients, free-stream turbulence levels, passage flow rates, boundary layer development, and physical dimensions as those that exist in operating gas turbine engines. Two principal goals are: (i) the development of a rough surface Reynolds Analogy for flows over the rough surfaces encountered in the actual applications, and (ii) the development of new predictive models to account for roughness in boundary layer numerical prediction schemes. The results obtained as part of this study are also useful for the development of improved surface manufacturing techniques.
