Turbulent drag reduction over air and liquid impregnated surfaces
Results on turbulent skin friction reduction over air and liquid impregnated surfaces are presented for aqueous Taylor Couette flow. The surfaces are fabricated by mechanically texturing the inner cylinder and chemically modifying the features to make them either non wetting with respect to water (air infused, or superhydrophobic case) or wetting with respect to an oil that is immiscible with water (liquid infused case) The drag reduction, which remains fairly constant over the Reynolds number range tested (100 Ret 140) is approximately 10% for the superhydrophobic surface and 14% for the best liquid infused surface. Our results suggest that liquid infused surfaces may enable robust drag reduction in high Reynolds number turbulent flows without the shortcomings associated with conventional superhydrophobic surfaces, namely, failure under conditions of high hydrodynamic pressure and turbulent flow fluctuations.