Research of effect of aerodynamic interference between rotors on vortex ring state of quadrotor aircraft

旋翼间气动干扰对四旋翼飞行器涡环状态影响研究

National Key Laboratory of Helicopter Aeromechanics(China Helicopter Research and Development Institute), Jingdezhen 333001, China

Received: 4 December 2024

Abstract

To investigate the impact of the aerodynamic interference among multirotors on the characteristics of vortex rings and their underlying mechanisms, a combination of detached eddy simulation (DES) and overset grid methods to simulate the unsteady aerodynamic load variations of quadrotor aircraft under vortex ring conditions is employed. The results indicate that for the quadrotor drone used in this study, in the early stage of the vortex ring state, due to aerodynamic interference between the rotors, a large-scale circulation structure covering the entire rotor disk is formed. The rotor thrust increases by 17% comparing to the average value of isolated rotors, and the magnitude of unsteady fluctuations decreases by 28%. The aerodynamic interference between the rotors alleviates the adverse effects of the vortex ring state. In the mid-stage, the circulation structure shifts upward and becomes more symmetrical, with the positive effects of aerodynamic interference weakening; however, it still results in a thrust increase of 11% comparing to isolated rotors and a drop of 21% in unsteady fluctuations. In the later stage, the circulation phenomenon above the rotor disk disappears, resulting in a 27% thrust increase comparing to isolated rotors and a drop of 40% in unsteady fluctuations. The interference effects between the rotors accelerate the aircraft's escape from the vortex ring circulation. Aerodynamic interference between the rotors plays a significant role in the performance of the quadrotor drone at different stages of the vortex ring state, particularly showing a remarkable positive effect in the later stage.

摘要

为探究多旋翼之间气动干扰对涡环特性的影响及内在机理, 运用分离涡模拟(DES)与嵌套网格相结合的方法, 对涡环状态下四旋翼飞行器非定常气动载荷变化特征进行了模拟研究。结果表明: 对于文中使用的四旋翼飞行器, 在涡环状态前期, 由于旋翼间的气动干扰, 形成了覆盖整个桨盘的大尺度环流结构, 旋翼拉力较孤立旋翼的时均值增加17%, 非定常波动幅度减少28%, 旋翼间气动干扰缓解了涡环状态的不利影响。进入中期, 环流结构向上偏移并趋于对称, 气动干扰的积极作用有所减弱, 但仍使旋翼拉力较孤立旋翼增加11%, 非定常波动幅度减少21%。发展至后期, 桨盘上方环流现象消失, 拉力较孤立旋翼增加27%, 非定常波动幅度减少40%, 旋翼间干扰效应加速飞行器摆脱涡环环流。旋翼间的气动干扰在涡环状态的不同阶段均对四旋翼飞行器的性能产生了重要影响, 尤其在后期阶段表现出显著的积极作用。