Abstract
We studied the influence of gas-liquid interface on the drag reduction effect by numeric simulation. Level set method was used for an analysis of gas-liquid interface. The liquid penetrates in the microstructure when the surface is hydrophilic. But for hydrophobic surface, it was clarified that a gas layer keeps the shape in the microstructure in the flow condition. And the position of gas-liquid interface can move due to velocity of main channel. In addition, from the analytical result using the model that alternately applied slip and no-slip boundary condition to the wall surface, the drag reduction effect is dependent on not only Reynolds number but also the position of gas-liquid interface.
