多桨倾转旋翼飞行器地面/地面耦合非定常流场特征研究

Analyses on the Characteristics of the Ground/Ground Coupled Unsteady Field Flow of Multi Blade Tiltrotor Aircraft

采用分离涡(DES)方法对地面效应下的多桨倾转旋翼飞行器的非定常气动特性展开了研究。采用运动嵌套网格方法和动量源模型相结合的方式对旋翼/机身/地面耦合流场进行了不同精细程度的模拟,并重点从速度场、涡量场以及非定常气动载荷特征角度分析了地效下多桨倾转旋翼飞行器气动载荷非定常波动的形成机理。结果表明:相同机翼上的两副旋翼存在非定常干扰,使旋翼拉力出现非定常波动,波幅达到12.9%;前、后旋翼桨尖涡向下运动与地面碰撞后,部分气流向上卷起,在前后机翼之间融合形成尺度更大的涡结构,该涡结构向上运动并被前、后旋翼重新吸入;此外,该涡结构在前后机翼之间前后移动,被前后旋翼吸入的时刻不一致,从而导致全机在俯仰方向力出现非定常载荷波动,波幅为37.7%。

The unsteady aerodynamic characteristics of multi blade tiltrotor in ground effect were analyzed by DES method.Among them,the rotor/fuselage/ground coupled flow field was simulated with varying degrees of detail by the combination of moving overset grid method and momentum source model,and the formation mechanism of unsteady fluctuation of aerodynamic load on multi blade tiltrotor in ground effect was analyzed from the perspective of velocity field,vortex interior field and characteristics of unsteady aerodynamic load.The result indicated that there was unsteady interference between the rotors on the same wing,causing unsteady pulse fluctuations in the lift propeller thrust with a wave amplitude of 12.9%.The rotor blade tip moved downward and collided with the ground,causing some of the airflow to curl up.The fusion of the curled up front and rear rotors formed a larger vortex structure,which moved upward and resucked in by the rotors.This structure moved back and forth between the front and rear wings,resulting in inconsistent moments of suction by the front and rear rotors,resulting in unsteady load fluctuations in the pitching direction of the aircraft,with a wave amplitude of 37.7%.