Static aeroelastic analysis of very flexible wings coupled with distributed propellers

耦合分布螺旋桨的大柔性机翼静气弹研究

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 2 December 2022

Abstract

Distributed propellers are widely used as propulsion for high-aspect-ratio long-endurance UAVs, and their load and slipstream will change the structural and aerodynamic characteristics of the wing, making geometric nonlinear effects more prominent. To address the aeroelastic interference of distributed propellers on the large flexible wing, firstly, on the basis of the vortex theory, a slipstream tube model is used to rapidly calculate the induced velocity of the slipstream, realizing the coupled aerodynamic modeling of the propeller and wing. Secondly, the coupled modelling of propellers and the nonlinear structure is achieved through the derivation and transformation of the coordinate system in the co-rotation method. Finally, combined with the space beam spline, a nonlinear static aeroelastic analysis framework for the large flexible wing considering the effects of distributed propellers is established. The simulation example of flexible wing with distributed propellers shows that the propeller pull will cause negative twisting of the wing due to large deformations, resulting in approximately 10% loss of lift and 20%-40% decrease in static stability margin; the propeller slipstream will change the local flow velocity and the angle of attack, bringing about 2.5% lift gain and 2%-8% increase in static stability margin; propellers increase lift when it is close to the wing root, but decrease when close to the wing tip, and the closer to the wing tip, the more significant the effect is. The analysis method established in this paper can provide guidance for the coupling design of distributed propellers and large flexible wings.

摘要

分布式螺旋桨被广泛用作为大展弦比长航时无人机提供推进动力, 其载荷和滑流会改变机翼的结构和气动特性, 使几何非线性效应更加突出。针对分布式螺旋桨对大柔性机翼的气弹干扰问题, 在涡流叶素理论基础上, 采用滑流管模型快速计算滑流对机翼的诱导速度, 实现螺旋桨与机翼的耦合气动建模; 在共旋转法中通过坐标系的推导与转换, 实现展向分布的螺旋桨与机翼非线性结构耦合建模; 结合空间梁样条插值, 建立了考虑分布式螺旋桨载荷和滑流影响的大柔性机翼非线性静气弹分析框架。大柔性机翼与分布式螺旋桨耦合的算例结果表明: 非线性大变形使螺旋桨拉力产生机翼结构负扭转, 造成约10%的升力损失和20%~40%的静稳定裕度减小; 螺旋桨滑流通过影响机翼当地流速和绕流攻角, 改变了结构变形分布, 带来约2.5%的升力收益和2%~8%的静稳定裕度增加; 螺旋桨靠近翼根时增升, 靠近翼尖时减升且越靠近翼尖影响越显著; 所建立的分析方法可为分布式螺旋桨与大柔性机翼的耦合设计提供指导。