针对受壁面限制的涡对融合问题,以多段翼型的二元风洞试验为例,用雷诺平均的NS方程进行了模拟。结合侧壁面的表面摩擦力线、不同x向横截面流线的拓扑结构分析及总压分布云图,刻画了多段翼型的涡流流场结构,进而分析了受侧壁面干扰的涡对融合过程。并与无侧壁面干扰的涡对融合过程进行了比较。结果发现,壁面对涡对融合过程的影响,包括了对旋涡发展速度的延迟、旋涡诱导速度的限制及壁面摩擦引起的能量损失等方面,明显延长了涡对融合所需的时间。但是侧壁面干扰的影响范围有限。根据以上结果,建议二元风洞试验中,试验段宽度应考虑侧壁面影响范围;对展弦比较大的半模,应对机身加上垫块或者采用镜像法来消除侧壁面对襟翼涡等的干扰;对于展弦比较小的模型,则应采用全模进行试验。
Two dimensional wind tunnel tests of multi-element airfoil are simulated by using Reynolds averaged Navier-Stokes equations. Skin friction lines on side wall, streamlines and total pressure contours at different cross sections are combined together to depict the topology of vortex flow of multi-element airfoil. And the side-wall interference on the merging process of vortex pairs is studied. The wall confined merging process of vortex pair is evidently different compared with the unconfined merging process. The formation of focus from shear layers, the development process from focus to center (vortices) by absorbing shear layers, are both slowed down by the intrusion of sidewall. Side wall also dissipates the vorticity and decreases the kinetic energy of vortices by skin friction, but its interference is limited to certain zones. According to the numerical results, it is suggested that, the test section of wind tunnel must be wide enough for two dimensional tests; for semi-span model tests of high aspect ratio airplane, stand-off method or fuselage image can be employed. Full model test is necessary for small aspect ratio model.