The drag of artificial biofilm-like surfaces in a turbulent channel flow

Drag penalties and performance degradation are some of the adverse effects induced by soft and hard biofouling in a marine environment. Understanding the mechanisms by which the compliance, effective roughness, and morphology of soft biofouling streamers interact with the flow is essential. However, studying soft biofilms in a laboratory setting is challenging due to sloughing and growth non-uniformities. In this study, two commercial fur surfaces are used as models to understand the interaction between streamers and the flow. The two Faux-Fur surfaces are studied in a turbulent channel flow and their coefficient of friction subjected to flow is determined and compared to their time averaged rigid replicas produced from profile scans. Spectral modal analysis is performed on high-speed videos of fur motion to extract relevant spatial and temporal scales of the studied surfaces, and compared to the characteristic scales of the flow. Furthermore, 2D planar PIV is performed at a downstream location to highlight the effect of streamer morphology (mainly height) on the skin-friction profile across a wide range of friction based Reynolds number. Additionally, a compliant scientific-fur of known material properties is manufactured and studied to isolate the effect of fur morphological and mechanical parameters.