Rotor interactional effects on aerodynamic and noise characteristics of a small multirotor unmanned aerial vehicle
Rotor interactional effects on aerodynamic and noise characteristics of a small multirotor unmanned aerial vehicle
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DOI：
10.1063/5.0003992
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发表时间：
2020-04-01
影响因子：
4.6
通讯作者：
Lee, Duck-Joo
中科院分区：
文献类型：
--
作者：
Lee, Hakjin;Lee, Duck-Joo
近年来，使用多旋翼推进系统的小型无人机由于广泛的军事和商业应用而受到相当大的关注。在多转子结构中，由于转子位置非常接近，转子干扰现象严重。因此，相邻旋翼桨尖之间的间距对尾迹结构和流场有很大的影响，从而对多旋翼飞行器的气动性能和噪声水平起着重要的作用。在本研究中，四旋翼直升机悬停飞行条件下的数值模拟进行调查的相互转子干扰的气动性能，尾流结构，和声压级使用非线性涡格法与涡粒子法和声学模拟的基础上Farassat的公式1A。对不同间距的多旋翼构型的计算表明，随着旋翼间距的减小，平均推力显著减小，推力波动显著增大。此外，由于相邻旋翼的存在，旋翼后的尾迹几何形状和诱导流结构倾向于被径向向下拖向飞行器中心，从而导致尽管多旋翼在悬停状态下工作，但尾迹与尾迹之间仍存在强烈的相互作用，并形成不对称的尾迹结构。还观察到，转子相互作用引入的非定常载荷导致声压级的相当大的增加，特别是转子平面的法线方向。
Small scale unmanned aerial vehicles using multirotor propulsion systems have received considerable attention for a wide range of military and commercial applications in recent years. In the multirotor configuration, the rotor interaction phenomenon occurs severely because the rotors are located in close proximity to each other. Therefore, the separation distance between the adjacent rotor tips has a strong effect on the wake structures and flow fields, which consequently play an important role in determining the aerodynamic performance and noise level of the multirotor vehicle. In the present study, numerical simulations of a quadcopter under hover flight conditions are conducted to investigate the mutual rotor-to-rotor interactional effects on the aerodynamic performance, wake structures, and sound pressure level using the nonlinear vortex lattice method with the vortex particle method and acoustic analogy based on Farassat's formulation 1A. Calculations for the multirotor configurations with different separation distances show that the average thrust force decreases significantly and force fluctuation is found to increase dramatically as the rotor spacing gets smaller. In addition, the wake geometry and induced flow structure behind the rotor tend to be radially dragged down toward the center of the vehicle due to the existence of the adjoining rotor, which consequently results in strong wake-to-wake interaction and the formation of asymmetric wake structures although the multirotor operates under the hovering condition. It is also observed that unsteady loading introduced by rotor interaction leads to a considerable increase in the sound pressure level, particularly the normal direction of the rotor plane.