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Seminar: Fluid Mechanics

Turbulent boundary layer over heterogeneous rough surfaces

Speaker: Bharathram Ganapathisubramani
Organization: Univ. Southampton
Time: 2017-11-23 10:30
Place: Teknikringen 8

Abstract

The enormous impact and significance of surface roughness on turbulent wall-flows in engineering applications and the natural environment cannot be understated. Surface roughness in most of these problems usually possess spatially varying properties. In meteorological applications, grasslands /cities are found to border wind farms or forests are situated at the edge of cities. In engineering, surface heterogeneities are caused due to manufacturing inconsistencies or due to gradual degradation of the surface such as ablated turbine blades or a biofouled hull of a ship. It is impossible to characterize the impact of surface heterogeneity on wall-turbulence with simple “one size fits all” correlations such as the Moody diagram. In this talk, I will present some results where we attempt to characterize the impact of two different varieties of heterogeneous surface roughness and its influence on wall-turbulence. First, I will show results from a systematic study in which the surface roughness heterogeneity is dominant along the spanwise direction. Second, I will present results from experiments where the effects of sudden change in surface roughness in the streamwise direction on a boundary layer is examined.