低背鳍对细长平板三角翼流场影响的

 对细长平板三角翼及其对称面上加低背鳍组合体在低速风洞进行了二维粒子图像测速（PIV）实验，三角翼后掠角为82.5°，背鳍当地高度与三角翼当地半展长的比值为0.6，实验迎角为30°，无侧滑角，基于三角翼根弦长的雷诺数为2.33×10⁶。实验结果表明：单独细长平板三角翼分离涡流场对称、定常；加上背鳍后，组合体分离涡流场变得定常、非对称和非锥型。实验结果证实了低高度背鳍对细长平板三角翼分离涡的稳定性起着削弱和破坏的作用，初步验证了前人关于细长锥体分离涡的稳定性理论，并给出了30°迎角下分离涡失稳后的具体表现特性。

Particle Image Velocimetry Study of Flow over Slender Delta Wing with Low Dorsal Fin

A two-dimensional particle image velocimelry (PIV) measurement experimental study is performed on a flat-plate delta wing of 82.5° sweep angle and velocimetry of the identical delta wing with a low dorsal fin. The test is conducted at a low-speed wind tunnel using a two-dimensional PIV technique at 30° angle of attack and zero sideslip. The ratio of the local fin height to the local wing semi-span is 0.6.The Reynolds number based on the root chord of the wing is 2.33×10~6. The test results clearly indicate that the vortices over the wing-alone model are symmetric and steady. The vortices still keep steady but become asymmetric and nonconical over the model with the low fin for the same flow conditions. The results confirm that the low dorsal fin may weaken and even destroy the stability of the vortex pair of the slender delta wing, and provide for the first time experimental evidence of the theoretical predictions and depict the flow behavior at 30° angle of attack when the vortex instability onset occurs.