Analysis of the flow over Checkerboard Heterogenous Roughness using Particle Tracking Velocimetry and Hot Wire Anemometry

While the impact of homogeneous roughness on wall-bounded turbulence is established to be similar between turbulent channel and boundary layer flows (Chung et al., 2021, Ann. Rev. Fl. Mech.), this similarity and thus transferability of obtained physical understanding is not obvious for heterogeneous rough surfaces. The heterogeneous roughness investigated here is that of a checkerboard arrangement of smooth and rough surface sections whose dimensions exceed the outer length scale of the flow. The turbulent flow fields that emerge over such a heterogenous rough surface are investigated and compared between turbulent channel flow and turbulent boundary layer. In both cases, it is observed that flow heterogeneity remains confined to a very near-wall region despite the large characteristic scale of the checkerboard pattern relative to the outer scales of the flows. The flow heterogeneity appears to increase in strength with increasing Reynolds number.