鸭翼高度对动态俯仰鸭式布局升力特性的影响

Effect of canard’s vertical position on dynamic lift characteristics of pitching canard configurations

摘要:

为揭示鸭式布局非定常运动中鸭翼高度对战机纵向气动特性的影响,采用回流水槽测力实验和CFD数值模拟两种手段研究不同鸭翼高度下的鸭式布局（g/c_w分别为-0.15、-0.05、0、0.05和0.15）进行低频与高频（k分别为0.037 5和0.600 0）俯仰振荡的过程。结果表明:与主翼升力系数相比,鸭翼高度的变化对鸭翼升力产生的影响更为明显。在低频上仰阶段,低置布局的鸭翼涡更易受到下游主翼的干扰作用发生双螺旋破裂,导致鸭翼升力系数明显减小；在低频下俯阶段,低置布局的鸭翼涡也更难重新恢复。在高频上仰阶段,由于鸭翼前缘有效迎角的明显减小,低置与高置布局的鸭翼涡均优先生成于下翼面；在高频下俯阶段,与高置布局相比,低置布局鸭翼涡残留的对流速度更快,导致同等迎角下后者鸭翼的升力系数更低。对主翼而言,高置布局在低频上仰时拥有更高的最大主翼升力系数,但在高频下俯阶段,受到主翼前缘涡破裂与鸭翼高度的影响,高置布局丧失了主翼前缘涡对鸭翼涡尾流的干扰效应,导致主翼升力有所降低。研究结果为进一步深入研究不同鸭翼高度对鸭式布局气动特性的影响提供了参考。

Abstract:

To unveil the effect of canard’s vertical position (g/c_w=-0.15, -0.5,0, 0.05 and 0.15) on longitudinal aerodynamic characteristics of a dynamic canard configuration, both water-tunnel force measurements and CFD numerical simulations are conducted to research the unsteady pitching oscillations (k=0.037 5 and 0.600 0) of canard configurations. It has been found that the variations of canard’s vertical position bring more influences on the lift coefficients of the canard than the ones of wing. During the low-frequency pitching-up process, the canard vortex of the lower deployed case becomes more sensitive to the interaction from the downstream wing, which brings an earlier double-spiral breakdown of canard vortex. When undergoing the low-frequency pitching-down process, the canard vortex of the lower deployed case is harder to rebuild than the higher deployed one. During the high-frequency upstroke process, due to the large reduction of canard leading-edge effective attack angle, the canard vortex initially develops on the lower surface of the canard for both lower and higher deployed cases. When undergoing the high-frequency downstroke process, the convection flow of canard vortex for the lower deployed case is faster than the higher deployed one, thus the canard lift coefficients of the former case become smaller. In addition, compared to the canard configuration with a lower deployed canard, the higher deployed case can own a larger maximum lift coefficient of wing during the low frequency pitching oscillations. When undergoing a high-frequency downstroke stage, due to the breakdown of wing vortex and canard’s vertical position, the wing lift coefficients of the higher deployed case become smaller.