沟槽面减阻效果影响因素及减阻机理的分析

采用雷诺平均N-S方程和RNG k-ε湍流模型计算V型沟槽面的湍流边界层流动和粘性阻力,研究了沟槽尖峰形状和雷诺数对减阻效果的影响规律,初步分析了沟槽面减阻机理.指出:沟槽尖峰处的圆角半径越小其减阻效果越好,沟槽斜面中下部的壁面应力随着圆角半径的减小而降低,但尖峰处的局部壁面应力会随之增大;来流速度对沟槽减阻率的影响很大,对于一种尺度的V型沟槽,存在着一个具有较好减阻效果的来流速度范围,而沟槽面在沿来流方向上的布置位置对减阻效果的影响非常小;沟槽尺度对减阻效果很剧烈;沟槽尖峰处生成的二次涡是产生减阻效果的根本原因,二次涡的强弱与沟槽减阻率的大小紧密相关.

Analysis on Factors and Mechanism of Drag Reduction by Grooved Surface

The flow in turbulent boundary layer and the viscous drag over V-groove surface are numerically simulated using the RANS formula and RNG k-ε turbulence model. The influences of the tip shape of V-groove and Reynolds number on the drag reduction effect are studied; and the mechanism of drag reduction effect is analyzed, too. It is shown that, the smaller the fillet radius of the tip is, the better the effect of drag reduction is. As the fillet radius of the tip becomes smaller, the wall shear stress on the middle and low part of the groove surface becomes less,but the local wall shear stress on the tip becomes greater; the flow velocity has a great influence on the ratio of drag reduction, and the favorable flow velocity range is related to a certain groove dimension, but the locations where the groove surface is set along the flow direction have very little influence on the ratio of drag reduction,while the dimension of groove has very strongly influence on the drag reduction effect. The secondary vortices generated at the groove peaks are the fundamental reasons of the drag reduction,and the drag reduction ratio is closely related to the intensity of the second vortex.