跨音速翼型实验侧壁效应机理

 在西德宇航院跨音速风洞（TWB）进行的翼型油流实验结果表明,传统的关于侧壁效应的概念和理论只能适用于亚临界流动。超临界情况下,侧壁效应现象更复杂,影响更严重。实验中观察到的流油谱可分为五类。油流谱的发展规律说明侧壁干扰主要来源于侧壁边界层的位移效应。实侧壁“二元风洞”对跨音速翼型实验不能模拟真实情况。油流照片表明,即使风洞宽度达到翼型弦长的3.4倍,侧壁对中心截面的流动仍会有明显影响,侧壁抽气技术作为克服侧壁效应的手段是很有希望的。

MECHANISM OF SIDE WALL EFFECT FOR TRANSONIC AIRFOIL TESTING

Based on the results of oil flow visualization tests the mechanism of side wall effect for airfoil testing is investigated.It is shown that the traditional theory and concept of side wall effect are suitable only for subcritical flow conditions.In supercritical cases, the manifestation of side wall effect is much more complicated, and its influence much more pronounced. It is shown in the present paper that the oil flow patterns on the airfoil fall into five types. The main features for each of them are described. The mechanism o?side wall effect is interpreted both for supercritical and subcritical conditions. A systematic exposition of the development of oil flow patterns is made. It is pointed out that the old fashioned "two dimensional wind tunnel" of solid side wall is improper for transonic airfoil testing. Wind tunnel of large width may reduce the side wall effect,but it is not a final solution.It is shown that even for tunnel width of 3.4 chordlength, there may still be evident of side wall effect in the middle section of the model. It is believed that proper application of suction may be a promising solution for the side wall problem.