PIV investigation of the flow around a superhydrophobic obstacle

The flow around a semi-cylindrical two-dimensional obstacle is studied using Particle Image Velocimetry, comparing the case of a superhydrophobic surface with the case of a smooth surface. Measurements were carried out in a closed-loop water tunnel for a relatively low Reynolds number. Results show that the von Karman type vortex shedding observed in the canonical case is almost suppressed in the superhydrophobic case. As consequence of this suppression the whole flow field around the obstacle shows a much less unsteady behavior. It is argued that the shedding suppression is a consequence of the fact that the superhydrophobic surface avoids a critical accumulation of surface vorticity around the body due to modified slip conditions.