As a novel passive flow control device, a ring-shaped Karman-vortex generator (KVG) is employed to alleviate the severe flow separation of a conical diffuser with a total divergence angle of ${36}^{\circ }$ at a $Re=1.0\times {10}^4$. The baseline diffuser and 18 controlled schemes with different KVG sizes and location combinations are studied by an implicit large-eddy simulation method. The flow control mechanisms and design principles are discussed based on current simulations and relevant researches. The diameter of the KVG $D_K$ is suggested to be 3–4% of the length of the expansion section. The length to the throat and the distance from the wall are suggested to be 7.5–10.0$D_K$ and $2.0\text{–}3.0D_K$, respectively. For the optimal combinations, the alternately shedding Karman vortex street is seldom affected by the wall, and the unsteady wake can directly arrive downstream at the near-wall region and effectively enhance the flow mixing. The results demonstrate that a properly designed KVG can suppress massive flow separation in the expansion section and downstream region and promote pressure recovery performance.

作为一种新颖的被动式流量控制装置，采用了环形Karman涡旋发生器（KVG）来缓解圆锥形扩散器的严重流动分离，其总发散角为 ${36}^{\circ }$ 在 $\mathrm{[R}Ë=1.0\times {10}^4$。通过隐式大涡模拟方法研究了具有不同KVG尺寸和位置组合的基线扩散器和18种受控方案。基于目前的仿真和相关研究，讨论了流量控制机制和设计原理。KVG的直径$d_{ķ}$建议为膨胀段长度的3-4％。建议到喉咙的长度和与墙壁的距离为7.5–10.0$d_{ķ}$ 和 $2.0\text{–}3.0d_{ķ}$， 分别。对于最佳组合，交替脱落的卡曼涡流街很少受到墙的影响，不稳定的尾流可以直接到达下游的近墙区域，并有效地增强了流动混合。结果表明，设计合理的KVG可以抑制膨胀段和下游区域的大量流动分离，并提高压力恢复性能。