Abstract
Drag reduction have been reported in a lot of experiments in microchannels with hydrophobic cavities. In order to understand the mechanism, analytical simulations is performed. The analytical model is a rectangular channel of height h = 5 μm and width w = 20 μm with hydrophobic micro cavities on bottom and top of the channel. In this channel, water does not penetrate into micro cavities, and air remains in micro cavities. As a result, air and water form gas-liquid interface in micro cavities. It was found that the gas-liquid interface plays an important role in the drag reduction effect, and the drag reduction rate depends on the shape of the gas-liquid interface. Moreover, it was obtained that the penetrating depth of water is important for drag reduction.
