Lattice Boltzmann investigation of the influence of slip distributions on the flow past a diamond cylinder at low-Reynolds-number

Abstract

Two-dimensional flow past a diamond cylinder with varying slip distributions is numerically investigated using the lattice Boltzmann method at a Reynolds number of 100. Nine slip distributions, namely, fore-up (FU), after-up (AU), fore-up + fore-down (FU–FD), after-up + after-down (AU–AD), FU–AU, FU–AD, FU–FD–AU, FU–AU–AD, and full-slip, are examined and compared with the no-slip case. Fore-side and after-side slip were found to have opposite effects on the friction drag of the diamond cylinder, and the combination of the fore-up and after-up (FU–AU) slip is beneficial for pressure reduction. A maximum drag reduction of 13.6% is achieved by the full-slip case mainly contributed by the pressure reduction. Furthermore, comparison of two typical slip distributions with a non-uniform slip length is investigated. A uniform slip length for the FU and AU (or the FD and AD) is found to be very helpful for pressure reduction. The asymmetric slip distributions could also result in torque on the cylinder, which can be utilized to achieve flow control by adjusting the slip length and the slip length difference between different locations of the cylinder edges.