前缘形状对空腔模型气动特性影响试验

Experiment on influence of leading-edge shape on aerodynamic characteristics of cavity model

与安装在风洞侧壁的空腔模型相比,位于风洞核心流中的空腔模型在模拟边界层厚度方面具有明显优势。然而,核心流空腔模型在试验中却暴露出入口边界层厚度显著高于理论估计值、腔内声压级明显小于数值计算结果等问题,严重影响了试验结果的准确性。以C201空腔模型为研究对象,通过更换不同形状的模型前缘,综合采用边界层测量、脉动压力测量和表面荧光油流等试验方法,系统评估了亚、超声速下前缘形状对空腔风洞试验的影响。试验结果表明:亚声速条件下,椭圆形前缘有助于消除前缘流动分离,获得与计算结果相一致的入口边界层厚度和腔内声压级分布;超声速条件下,小角度尖劈前缘有利于避免形成脱体激波。研究结果可为空腔模型外形设计提供指导,避免前缘流动分离和脱体激波对空腔流动试验带来的不利影响。

Compared with the cavity model installed into the side wall of the wind tunnel, the cavity model located in the core-flow of the wind-tunnel has obvious advantages in simulating the thickness of the boundary layer. However, the core-flow cavity model suffers from the problems that the thickness of the approaching boundary layer is significantly higher than the theoretical estimate and the sound pressure level in the cavity is significantly lower than the numerical result, which seriously affects the accuracy of the test results. In the present study, effects of leading-edge shapes on cavity flow tests at the subsonic and supersonic speeds are comprehensively evaluated, using the technologies including boundary layer measurement, pressure fluctuation measurement and surface fluorescent oil flow. The C201 cavity model is investigated, whose leading-edge shape can be changed during the tests. The test results show that at the subsonic speed, the elliptical leading-edge helps to eliminate flow separation. The obtained approaching boundary layer thickness and sound pressure level distribution in the cavity is consistent with the calculated results. At the supersonic speed, the leading-edge of the small-angle wedge shape helps to avoid formation of detached shock waves. The research results could provide guidance for the design of cavity model shape, so that the adverse effects of leading-edge flow separations and detached shock waves on cavity flow tests can be avoided.