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

摘要

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 enhancement 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.