Turbulent flow and heat transfer of superhydrophobic cylinders with measured slip length

This study investigates the impact of surface-engineered wall slip on flow dynamics and heat transfer in tandem cylinder configurations at a subcritical Reynolds number (Re = 3900). Utilizing large eddy simulation (LES) with experimentally calibrated slip lengths, the research examines how the slip conditions modify boundary layer behavior, wake structures, turbulence characteristics, and overall thermal performance. LES predictions reveal significant modifications in flow physics and heat transfer characteristics. Slip conditions lead to thinner boundary layers on both cylinders and delayed flow separation. This modification enhances aerodynamic performance by reducing drag and lift forces, particularly for the upstream cylinder. The wakes become narrower and more elongated, increasing the vortex-shedding frequencies while attenuating the energy associated with vortex shedding. Furthermore, the implementation of slip boundary conditions significantly alters turbulence characteristics toward one-component “cigar-shaped” turbulence in the Lumley triangle. Both spatial and temporal turbulence scales undergo substantial modifications, with integral length scales typically reducing. Heat transfer performance quantified through Nusselt number distributions exhibits a nuanced response to slip conditions. While the upstream cylinder consistently shows enhanced heat transfer, the downstream cylinder's thermal response strongly depends on the center-to-center ratio. The research highlights the potential for optimizing heat transfer and aerodynamic performance through the strategic application of surface-engineered wall slip, opening new avenues for innovation in various engineering applications, including heat exchangers and thermal management systems.