Streamwise and spanwise slip over a superhydrophobic surface

Abstract

The near-wall turbulent flow over a superhydrophobic surface (SHS) with random texture was studied using three-dimensional Lagrangian particle tracking velocimetry (3D-PTV). The channel was operated at a constant mass flow rate over the SHS and a smooth surface at a Reynolds number of 7000 based on the bulk velocity of and the full channel height. The friction Reynolds number was 217, based on the friction velocity and half channel height. The 3D-PTV processing was based on the shake-the-box algorithm applied to images of fluorescent tracers recorded using four high-speed cameras. The SHS was obtained by spray coating, resulting in a root-mean-square roughness of and an average texture width..