Research Of Ship Bionic Drag-reduction Based On Micro-nano Structure

At the macro scale, there is enough collision between the molecules and the wal, so we usually use no-slip conditions in the flow problem. But at microscale, because of the small geometry, the collision frequency is not fully high. This may lead to the velocity slip on the wall."Velocity slip"is the tangential speed difference between the fluid and the surface at interface. When their tangential speeds are equality, then it comes to the no-slip boundary condition as the conventional hydromechanics. On the other hand, with the miniaturization of feature size, the microstructure of the wall becomes an important factor affecting to the flow characteristics.This article simulates the slip phenomenon in the channel of different diameters and discusses the effects of the wall structure to velocity slip. We want to analysis the affect law of the velocity slip in micro scale flow. Then we can take advantage of this law and find a special kind of micro-nano structure which can be used on the ship, to reduce the frictional resistance. In order to get the wall condition which has the maximum velocity slip, we focus on the parameters which can impact the velocity slip, including the diameter of channel, the wall shape, the micro-nano structure and so on. The scope of channel diameter involves the continuous media zone, slip zone and the transition zone. Then we can contrast and analysis the affect of Kn to the fluid velocity distribution. The wall shape includes rectangular wave, triangle wave and sine wave. We hope to find a kind of wall shape which is favorable to the velocity slip.The research on the micro-nano structure begins with"lotus leaf effect". The lotus leaf has hydrophobicity. It can self-clean, reduce friction and prevent to be glued. It has great value on the preparation of biomimetic function surface. The unique super-hydrophobic of micro-nano structure has a significant impact on the distribution of the fluid. This article analyzes the mechanism of micro-nano structure by numerical simulation. Then we can make use of the special nature of micro-nano structure and reduce the flow resistance.