多旋翼飞行器涡环状态数值模拟

旋翼类飞行器在进入涡环状态时极易发生安全事故。采用基于非结构网格的滑移网格技术对多旋翼飞行器的气动特性进行了数值模拟,并进行了试验验证。分别模拟了多旋翼飞行器垂直下降状态和30°斜向下下降状态时的流场,得到该状态下多旋翼飞行器的气动特性和滑流区流场规律,并分析了力与功率的变化规律。研究发现:多旋翼飞行器在垂直下降状态和30°斜向下状态均会进入涡环状态,在垂直下降速度为4 m/s时,多旋翼飞行器已经处于涡环状态,旋翼的拉力损失会达到15%,旋翼功率随下降速度的增大先增大后减小,且不同旋翼拉力大小和功率大小不一致。当30°斜下降速度为4~6 m/s时,多旋翼飞行器处于涡环状态。该结论可为多旋翼无人机的安全飞行提供参考。

Numerical simulation of multi-rotor aircraft in vortex ring state

A dynamic grid technology based on unstructured grid was used to simulate the aerodynamic characteristics of multi-rotor aircraft in the descent state, and experimental verification was performed. This method was used to simulate the flowfield of the aircraft in the vertical descent state and the 30° oblique descent state. The aerodynamic characteristics of the multi-rotor aircraft and the law of the flowfield in the slipstream region were obtained in this state, and the variations of force and power were also obtained. The study found that the multi-rotor aircraft would enter the vortex ring state in both vertical descent and 30° oblique descent. When the vertical descent speed dropped to 4 m/s, the multi-rotor aircraft was already in the vortex ring state, the loss of the thrust reached 15%, the rotor power increased first and then decreased with the increase of vertical descent speed, the thrust and power of different rotor of the aircraft were not consistent. When the 30° oblique descent speed reached 4-6 m/s, the multi-rotor aircraft was in vortex ring state. This conclusion can provide a reference for the safe flight of multi-rotor drones.