基于前缘合成双射流的飞翼布局纵向气动控制特性研究

Research on longitudinal aerodynamic control characteristics of flying wing based on leading-edge dual synthetic jets

  • 摘要: 为兼顾飞翼布局飞行器的隐身性和气动操控性,提出了一种基于合成双射流的飞翼布局纵向气动控制技术,研究其对小后掠飞翼布局大攻角下的气动操控能力。采用数值模拟方法,分析了前缘阵列式合成双射流与不同攻角飞翼布局流场的相互作用,探究其对飞翼布局纵向气动特性的影响,最后对比了传统合成射流控制,突出了其优势。结果表明:前缘阵列式合成双射流可有效提高大攻角升力、减小阻力,增大升阻比,同时还会使俯仰力矩出现非线性变化,具备大攻角滚转姿态操控能力;合成双射流在前缘形成周期性涡结构,增强了边界层底部低速流体与主流的动量交换,提高了边界层抗逆压梯度的能力;攻角8°~10°时,合成双射流可完全抑制前缘分离,但攻角10°时,在靠近后缘处形成分离区,使升力略有减小;攻角12°时,合成双射流可推迟流动分离,分离线移动至机翼中段;攻角14°~16°时,合成双射流虽然仅可有效抑制靠近展向分离起始位置处的流动分离,但同时也增加了分离区内的流动能量,有效提高升力;攻角18°时,吸力面近乎完全分离,合成双射流虽未能有效抑制分离,但会使前缘吸力峰值回升,仍有增升、减阻的效果;与合成射流相比,合成双射流控制产生的气动变化量更大,更具应用潜力。

     

    Abstract: This paper proposes a longitudinal aerodynamic control strategy for flying-wing aircraft utilizing dual synthetic jets to compromise the stealth performance and aerodynamic maneuverability. The performance of this method for a small-swept-angle flying wing at large attack-of-angle (AOA) is examined by investigating the interaction between leading-edge dual synthetic jets and flow fields at different AOAs. Results show that an array of dual synthetic jets at the leading edge can effectively increase lift, reduce drag, and increase the lift-to-drag ratio at large angle of attack. The nonlinearly varying pitch moment indicates that the roll attitude control at high AOAs can be realized. Dual synthetic jets induce periodically evolving vortices at the leading edge, strengthening the momentum mixing across the wall-normal direction and enhancing the capability to resist reverse pressure gradient. Depending on AOA, dual synthetic jets have varied performance. At the AOAs of 8−10 degrees, they can completely suppress the leading-edge separation, while at the AOA of 10 degrees, a small separation area around the trailing edge leads to a slight decrease of lift. At the AOA of 12 degrees, the separation line moves to the middle section of the wing. At the AOA of 14−16 degrees, they can only effectively suppress the flow separation around the spanwise front of the separation zone, but they can still improve the lift efficiency by intensifying the energy in the separation zone. At the AOA of 18 degrees, the flow over the suction surface is almost completely separated. Nevertheless, the suction at the leading edge increases so that a relatively high lift-to-drag ratio remains. Compared with traditional synthetic jets, dual synthetic jets can significantly improve aerodynamic performance, manifesting their great potential.

     

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