Measurements of Stanton numbers, velocity profiles, temperature profiles, and turbulence intensity profiles are reported for turbulent flat plate boundary layer flows with a step change in surface roughness. The first 0.9 m length of the test surface is roughened with 1.27-mm-dia hemispheres spaced 2 base diameters apart in a staggered array. The remaining 1.5 m length is smooth. The experiments show that the step change from a rough to a smooth surface has a dramatic effect on the convective heat transfer. In many cases, the Stanton number drops below the smooth-wall correlation immediately downstream of the change in roughness. The Stanton number measurements are compared with predictions using the discrete element method with excellent results.
Heat Transfer in the Turbulent Boundary Layer With a Step Change in Surface Roughness
Taylor, R. P., Taylor, J. K., Hosni, H. H., and Coleman, H. W. (October 1, 1992). "Heat Transfer in the Turbulent Boundary Layer With a Step Change in Surface Roughness." ASME. J. Turbomach. October 1992; 114(4): 788–794. https://doi.org/10.1115/1.2928032
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