The impact of skewness angle on the effectiveness of vortex generators (VGs) and the behavior of streamwise vortices on flow separation behind a backward-facing ramp (BFR) with a sharp transition were experimentally investigated using surface oil flow visualizations, planar and stereoscopic particle image velocimetry measurements. Counter/corotating streamwise vortices were generated by a set of boundary layer-type rectangular VG located upstream of the BFR that comprised a flat- and 30-inclined sections with different skewness angles of 10°, 20°, and 30°. Local Reynolds number based on the VG location was Re_x ≈ 3 × 10⁶. Results show that the reattachment length was reduced by ∼45% when the VG was located five times its height ahead of the transition. Additionally, the behavior of the vortex core generated by the left vane displayed strong dependence on the skewness angle, whereby its vorticity magnitude and vortex instability increase with the skewness angle. Circulation magnitude and vortex radius of the left vortex core are also observed to be physically larger and less stable. In contrast, the vortex core produced by the right vane displays opposite behavior as the skewness angle increases. Lastly, the vortex core location is observed to fluctuate more in the vertical direction than horizontal direction.

使用表面油流可视化，平面和立体粒子图像，通过实验研究了偏斜角对涡流发生器（VGs）的有效性的影响以及向后涡流（BFR）后面具有急剧过渡的流向涡流对流动分离行为的影响。测速仪测量。由位于BFR上游的一组边界层型矩形VG产生了逆向/顺流涡流，该边界VG包括具有10°，20°和30°不同偏斜角的平坦部分和30°倾斜部分。基于所述VG位置局部雷诺数为重新_X ≈3×10 ⁶。结果表明，当VG位于过渡之前其高度的五倍时，重新连接长度减少了约45％。另外，由左叶片产生的涡旋芯的行为表现出对偏斜角的强烈依赖性，由此其涡度大小和涡旋不稳定性随偏斜角而增加。还观察到左旋涡芯的循环量和旋涡半径在物理上更大且不稳定。相反，随着偏斜角的增加，右叶片产生的涡旋核表现出相反的行为。最后，观察到涡流芯位置在垂直方向上比水平方向上波动更大。