Vortex interaction mechanism and control technology of canard configuration at high angle of attack

The vortex interaction mechanism and control technology of the close-coupled canard configuration at high angles of attack have been reviewed, and the vortex control technology of canard-span wise continuous or pulse blowing have been analyzed and discussed in detail. The results show that the aerodynamic performances could be improved at middle and large angles of attack in canard configuration through the interactions between the canard vortex and the wing vortex. The flow field near the apex of the main wing is affected by the down-wash effect of the canard, in the following downstream development, the co-rotating vortex pair gradually merges into a single stable concentrated vortex by mutual introduction, and finally develops into the concentrated vortex breakdown. Through canard-spanwise blowing, the vortex interactions on the wing might be transformed so the vortex breakdown could be delayed, therefore the maximum lift and stall angle could be further enlarged and the drag force could be reduced. The canard-spanwise pulse blowing can save the blow volume through the hysteresis effect. Either larger duty ratio or higher pulse frequency is conducive to achieve the target lift with a lower bleed air volume. With the same lift increment, the higher the pulse frequency, the smaller the corresponding pulse duty ratio, and the greater the amount of blowing could be saved. For instance, compared with continuous blowing with volume coefficient of 0.25 at 28°, the pulse blowing with volume coefficient of 0.3 could achieve the same lift amplitude under the frequency of 5 Hz and duty cycle of 0.2, which saves the air volume up to 76%.