Sustainable drag reduction of fatty acid amide-based oleogel surface under high-speed shear flows

Abstract

Nepenthes alata-inspired micro/nano-textured liquid-infused surface (LIS) has shown strong potential in the fields of drag reduction (DR), anti-biofouling and self-cleaning. However, its surface slippery property is largely degraded under turbulent shear flow conditions due to the loss of the impregnated oil. This inhibits its practical applications to marine vehicles. The mucus-impregnated tissue systems of marine creatures are primarily based on fatty acid amides (FAAs) such as erucamide or oleamide, which has been commercially utilized as solid-slip additives. A stable lubricant interface of erucamide-PDMS composite (EPC) oleogel is formed by cross-linking erucamide with PDMS gel network before infusion of silicon oil. In this study, the surface stability and lubricant retention of EPC was investigated in consideration of DR applications. The fabricated EPC-oleogel surface exhibits shear stable DR under harsh conditions such as high-pressure, temperature, and shear flow conditions. The surface shows a shear stable DR performance of 12-16 % even up to a high speed of 12 m𝑠−1, corresponding friction Reynolds number (𝑅𝑒𝜏) of about 5,000. This kind of DR performance at turbulent high-speed shear flow is not easy for conventional structured LIS surfaces. The superior lubrication stability of FAA-oleogel at the flow conditions of a cruising ship ensures its strong potential for sustainable fuel economy of marine vehicles.