Simulation of Microbubbles Drag Reduction on Nonsmooth Surface with Hydrophobic Property

Abstract

The friction resistance accounts for a large proportion of the total resistance, during the navigation of ships and underwater vehicles. Drag reduction techniques can significantly reduce the friction resistance of the wall and improve the speed of navigation. This paper combine microbubbles drag reduction technology and nonsmooth and hydrophobic surface technology. Building different analysis models, considering the dimples size of nonsmooth surface , the contact angle of surface and wall roughness, study the law between drag reduction and parameters of the wall by gas-liquid two-phase flow model. Under the same conditions, analysis results show that the performance of drag reduction is mainly determined by the dimple size of nonsmooth surface. The lager dimples cause stronger turbulence and loss more energy. The drag reduction effect is declined. There is a linear relationship between the drag reduction and the contact angle of hydrophobic surface. The drag reduction is enhanced by increasing the contact angle. But the principle is complicated between drag reduction and the roughness of the wall. There are different roughness to achieve the best effect under different flow velocities.