Slip flow through microchannels with lubricant-infused bi-dimensional textured surfaces

Abstract

Lubricant-infused textured surfaces, where a secondary liquid impregnates textures, have been employed as an alternative to gas-cushioned textured surfaces. However, the drag reduction capabilities of this new class of textured surfaces in the laminar regime have not been explored. In this work, a pressure-driven flow through microchannels containing lubricant-infused bi-dimensional textures was numerically investigated to assess their slippage properties. A large parameter ranges, Reynolds numbers 1–1000; viscosity ratio 0–1; constriction ratio 0.1–10; lubricant fraction 0–1, were employed in the simulations. Upon balancing the velocity continuity and shear stress at the liquid–lubricant interface, we could capture the viscous effects of lubricant on the amount of slippage. The effective slip length was computed as a function of relevant non-dimensional flow and geometrical parameters for texture configurations such as posts and holes. A significant amount of dissipation in the lubricant phase was observed for a viscosity ratio greater than 0.1 for both the texture configurations investigated. However, an increased viscosity ratio between the lubricant and liquid bettered the performance of the posts compared to holes at low-lubricant fractions. The inertial effects on the effective slip length were alleviated with an increase in viscosity of the underlying lubricant, for a surface covered with holes compared to posts. Furthermore, it was shown that the validity of scaling laws for the effective slip length from the gas-cushioned textured surfaces to liquid-infused textured surfaces could be extended upon incorporating the effects of inertia and viscosity ratio. The results presented here will help in designing efficient lubricant-infused textured surfaces for drag reduction both in internal and external flow settings.