Turbulent heat transfer over super-hydrophobic and liquid-infused surfaces

Recently, super-hydrophobic (SHS) and liquid-infused surfaces (LIS) have been proposed as a method to achieve drag reduction in turbulent flows. SHS consist of a textured surface with a thin-film hydrophobic coating, which allows entrapment of air in the cavities when wetted with water. LIS are conceptually similar, except for the infusion of a second liquid that replaces the air pockets in the surface features. Conceptually, the flow over LIS and SHS reproduces a two-layer configuration over a rough surface, where the roughness elements are constituted by the surface textures. Turbulent drag reduction is possible because the second fluid (air trapped in the textures for SHS, and lubricant liquid for LIS) creates a slip interface with the primary fluid, thus reducing friction drag. Experimental and numerical studies have shown great potential in terms of drag reduction. The objective of this work is to study heat transfer performance over these surfaces and the correlation between the velocity and thermal fields (Reynolds analogy). Direct numerical simulation of turbulent flow and heat transfer are performed using different textured geometries (modeled with immersed boundary method) and varying the viscosity ratio and interfacial tension between the two fluids.