THREE-DIMENSIONAL VOF SIMULATIONS OF LAMINAR FLUID FLOWS IN MICRO-PIPES CONTAINING SUPERHYDROPHOBIC WALLS WITH MICRO-POSTS AND MICRO-RIDGES

This paper investigates water flowfield characteristics inside micro-pipes containing superhydrophobic walls under laminar flow conditions. It also investigates the effects of solid fraction, wall pattern, and Reynolds number on both skin friction drag and flow field characteristics. A transient, incompressible, three-dimensional, volume-of-fluid (VOF) methodology has been employed to continuously track the air-water interface and to visualize the dynamic behavior of the complex flows inside micro-pipes containing different superhydrophobic wall features (square micro-posts and longitudinal micro-ridges). The results of the present simulations show that micro-pipes containing superhydrophobic walls with longitudinal micro-ridges features have a better frictional performance than those having square posts features. The predicted results also show that the frictional performance of micro-pipes is a monotonically decreasing function of Reynolds number for both patterns examined in the present study. In addition, as the solid fraction decreases, the flow enhancenient of superhydrophobic micro pipes increases and it seems, based on the studied cases, to reach an asymptotic value. However, a further study is needed to confirm this latter issue.