Flow Characterizations and Drag Reduction on the Hydrophobic Surface with a Full Covering Gas Film

Characteristics of the flow on hydrophobic surfaces with a full covering gas film are investigated using the single-component multi-phase (SCMP) Lattice Boltzmann (LB) simulation. By adopting the Shan-Doolen force model and incorporating equations of state (EOS) of real fluids, large density ratios are achieved. The height of the air film maintained is observed to increase with the improvement of the surface hydrophobicity. In the laminar flow, the state of the gas-liquid interface is not influenced by the Reynolds number (Re). On the gas layer, the slip effect and wall shear stress reduction are sustained continuously regardless of their positions (on the space or on the micro-structure). Even so, decreasing the solid area fraction is also significant to enhance the slip effect and decrease the wall shear stress on hydrophobic surfaces.