类X?47B无人机菱形编队气动干扰数值模拟

设计了一种由4架类X?47B飞翼布局无人机（UAVs）组成的菱形编队。通过求解RANS方程的数值模拟方法，研究了菱形编队无人机气动干扰问题，详细分析了影响机理，定量给出了编队减阻效果。计算结果表明:头机气动性能基本保持不变。两侧僚机受上洗气流影响，其减阻效果明显。尾机主要受下洗气流影响，其阻力增大，对编队久航和远航不利。在重力配平条件下，两侧僚机飞行阻力的减小是由攻角减小和诱导阻力减小共同引起的。尾机在编队中飞行阻力的增大主要是攻角增大带来的阻力增加，诱导阻力增大仅带来了20%的阻力增量。从减小下洗气流对尾机的不利影响出发，对不同垂向间距的尾机升阻特性进行了研究，并参考雁群头鸟变换行为机制，给出了无人机菱形编队飞行建议。 

Numerical simulation on aerodynamic interference of UAVs like X-47B in rhombus formation

A rhombus formation composed of 4 unmanned aerial vehicles (UAVs) like X-47B with flying wing configuration was designed.By solving the RANS equations,the aerodynamic interference of UAVs in rhombus formation flight was studied,and the related mechanism was analyzed in detail.The effect of formation drag reduction was given quantitatively.Computational results showed that the aerodynamic performance of head UAV remained unchanged,and the drag reduction of wing UAVs affected by upwash flow was obvious,but the drag of tail UAV mainly affected by downwash flow increased,making it unfavorable to the long voyage of formation.Under the condition of gravity balancing,the reduction of flight drag of wing UAVs was caused by the decrease of attack angle and induced drag,while the increase of flight drag of tail UAV was mainly caused by the increase of attack angle,and the induced drag only brought 20% of flight drag increase of tail UAV.In order to reduce the adverse effect of downwash flow on tail UAV,the aerodynamic characteristics of tail UAV with different vertical spacing were studied.According to the behavior mechanism of head bird transformation in geese,the flying suggestions of rhombus formation were given.