“大涡破碎”的紊流减阻实验研究

The Experimental Approach to the LEBU on Turbulent Drag Reduction

本文对当今国外曾提出的紊流表面摩擦减阻新概念——“大涡破碎”(LEBU)进行了初步的风洞实验探索。将具有对称流线型剖面的二元小肋,沿垂直于气流的方向安置在平板表面的紊流附面层内某一高度处,收到了不同程度的减阻效果。实验中分别考察了小肋的安置位置L,安置高度H,迎角θ及相对厚度b等参数对减阻效果的不同影响。从紊流附面层涡结构的观点出发,提出紊流的“细化”作用是小肋对平扳减阻的根本原因,并认为改善紊流附面层的速度型是研究紊流减阻的一种手段。实验使用自制的高灵敏度摩擦天平,测得的减阻效果与Ludwieg—Tillman公式的计算结果基本一致。

Setting a thin two-dimensional airfoil with a symmetric streamline section at a certain location within the turbulent boundary layer, the auther has made the preliminary experimental approach to the 'Large Eddy Break Up (LEBU)' in wind tunnel, which is the newest concept of turbulent skin friction drag reduction proposed abroad currently, and gets some efficiency of the drag reduction to a different extent. In this experiment, the different effects on the drag reduction of the parameters, such as the location L, height H, angle of attack 9 and thickness/chord ratio 6 of the airfoil, are investigated. The 'fining' action for turbulent flow of the airfoil is proposed as a basic reason of the drag reduction from the point of view of the vortex construction of turbulent boundary layer, and the improvement of the velocity pattern of turbulent boundary layer is considered as a means of approaching to turbulent drag reduction.The results measured with a high-sensitivity balance, home-made for the experiment, are in good agreement with those calculated using Ludwieg-Tillman formula.