The impact of bio-inspired micro-textures on turbulence and implications for bio-fouling settlement

Abstract

Biomimetic textures originally developed as an anti-fouling strategy for static immersion, have been studied for application on marine hydro-turbines. Turbulent flow Simulations have been performed to characterize hydrodynamic stresses in area where micro-organisms are expected to settle. The study relies on Large Eddy Simulations of fully developed channel flow in the transitionally rough regime to study the fluid flow interaction around the texture prisms. The analysis focusses on the sensitivity to the texture layout and orientation and considers three different gap sizes S+=10,40,80, scaled in inner units, where the smallest gap S+=10 corresponds to the physical gap between textures at full scale when applied over a turbine blade operating under nominal conditions. Results indicate that the smallest gap which has been shown previously to be most effective at hindering micro-organism attachment also creates an effective shelter against mean turbulent stresses. Interestingly, however, strong infrequent turbulent fluctuations are predicted within the gap. These may be sufficient to avoid unwanted accumulation of the smallest organisms and passive particles. Exposed surfaces including within groves between textures, where organisms would be most expected to settle in static immersions, are also found to experience significant stresses as the gap size is increased.