Conference Proceedings

Experimental study of a high Reynolds number turbulent boundary layer evolving over a rough-to-smooth change in surface condition

M Li, CM de Silva, R Baidya, D Chung, I Marusic, N Hutchins

11th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2019 | Darmstadt University of Technology | Published : 2019

Abstract

The evolution of turbulent boundary layers downstream of a rough-to-smooth transition is investigated at a range of Reynolds numbers. Measurements are performed at friction Reynolds numbers of 4100, 7100, 14000 and 21000 using hotwire anemometry. The wall-shear stress on the smooth surface in each case is measured directly using oil film interferometry. The growth of the internal layer is studied, and a full recovery of all energetic scales in the energy spectrum of the streamwise velocity fluctuations is observed at 80 boundary layer thicknesses downstream of the roughness transition. A comparison of recovery lengths required for various flow statistics (skin-friction coefficient and energy..

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