Influence of Superhydrophobic Coatings on Turbulence and Vortical Structures in a Submerged Impinging Jet.

The impact of liquid jets on solid surfaces is a critical hydrodynamic mechanism in applications like cooling and cleaning. Surface properties, particularly superhydrophobicity, can significantly alter flow development throughout the impingement process. This work uses particle image velocimetry (PIV) to investigate a submerged water jet impinging on smooth and superhydrophobic surfaces. The jet, with a 4 mm diameter (D), was operated at a Reynolds number of 4500 and a nozzle-to-surface distance of 10D. Results demonstrate that the superhydrophobic surface (SHS) modifies the flow behavior significantly. Compared to the smooth surface, the peak jet velocity on the SHS increased by 26% in the axial direction and 19% in the radial direction. Furthermore, turbulent kinetic energy (TKE) at the impingement point was substantially higher on the coated surface. These findings are attributed to reduced wall friction on the superhydrophobic surface, which enhances momentum retention and alters turbulent production.