导　　师： 孙江龙

学科专业： H2401

授予学位： 硕士

作　　者： ;

机构地区： 华中科技大学

摘　　要： 在宏观尺度下，由于有足够多的分子与壁面发生碰撞，所以流动问题的壁面条件多采用速度无滑移条件。但是在微尺度问题中，几何尺寸的微小不能保证充分高的分子与壁面的碰撞频率，这就必然引起壁面处的速度滑移。“速度滑移”是指流体在固体表面流动时流体和表面之间在界面处的切向速度差。流体流动和表面的切向速度相等时即为常规流体力学中常采用的无滑移边界条件。特征尺度的微小化使得壁面的微观结构也成为一个影响流动特性的重要因素。
　　 本文主要从速度滑移方面入手，模拟流体在不同直径的通道流动时的滑移现象，研究壁面结构对速度滑移的影响，分析速度滑移对微纳尺度流动的影响规律，进而利用这一规律，寻找到一种特殊的微纳结构，以达到减摩降阻的效果。重点研究微流动各项参数对流体速度滑移的影响，包括通道直径、壁面形状、微纳结构等，以求得达到最大速度滑移的壁面条件。其中，通道直径的范围包括连续介质区、滑移区和过渡区，对比分析KN数对流体速度分布的影响。壁面形状则包括矩形波、三角波和正弦波三种形状的壁面，希望通过对比能够找到对速度滑移有利的壁面形状。
　　 对于微纳结构的研究始于对“荷花效应”的认识。荷花效应具有疏水自洁、减摩防粘的功能，对制备仿生功能表面具有很大的应用价值。由于微纳结构特有的超疏水性，对流速的分布情况也有重要影响，本文通过数值模拟，分析微纳结构的作用机制，从而对微纳结构的特殊性质加以利用，以达到减小流动阻力的效果。 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.

关 键 词： 舰船仿生减阻 微纳结构 速度滑移 微纳尺度流动 超疏水性

分 类 号： [U661.311 Q811.6]

领　　域： [交通运输工程] [交通运输工程] [生物学]