摘要
大柔性太阳能无人机在气动力的作用下产生较大的弯曲变形,引起气动载荷的重新分布及作用方向的改变,线性理论难以获得足够的精度。基于共旋转有限元理论,推导了几何非线性空间梁单元的切线刚度矩阵和内力求解格式,几何精确的描述了无人机机翼结构的几何非线性弹性变形;编写了空间共旋坐标有限元求解代码,利用计算流体力学软件FLUENT计算气动力,构造了流固耦合求解器;研究了类"太阳神"布局太阳能无人机几何大变形下的静气动弹性响应问题。研究结果表明:无人机受载变形后导致升阻比降低,翼尖弯曲变形为展长的13%时,升阻比降低4.2%,滚转力矩导数增加了300%,偏航力矩导数增加了350%;几何非线性效应改善了气动载荷在展向的分布,有利于机翼结构设计。研究工作对大柔性太阳能无人机的设计具有一定的参考意义。
Very flexible solar powered UAV under aerodynamic loading undergoes large deformation and aerody-namic load distribution is not possible to be obtained sufficiently precisely by means of linear theory. Starting from Ref.12 by Crisfield et al, we develop a static aeroelastic characteristics analysis algorithm suitable to very flexible aircraft;this is explained in sections 1 and 2 of the full paper. The core of section 1 is that, using the co-rotational theory, we derive the expression of tangent stiff matrix and that of internal force of a spatial two-node beam element of a geometrically nonlinear structure. The static aeroelastic equations are set up in section 2. Section 3 analyzes the static aeroelastic characteristics of a solar powered UAV with the layout similar to Helios. The results given in Figs.5 through 8 and their analysis show preliminarily that：the distortion of the flexible wing leads to lift loss, when the wingtip displacement is 13% of span, the lift-drag ratio decreases by 4？2%, the rolling moment coefficient deriva-tive increases by 300%, and the yawing moment coefficient derivative increases by 350%; the geometrical nonlinear bending effect improves the aerodynamic load distribution along the span, thus benefiting structure design. The investigation is believed to be of some reference value to the design of very flexible solar powered UAV.
出处
《西北工业大学学报》
EI
CAS
CSCD
北大核心
2014年第4期499-504,共6页
Journal of Northwestern Polytechnical University
基金
国家自然科学基金(11202162
11302178)资助
关键词
几何非线性
CR理论
柔性结构
横航向稳定性
静气动弹性
太阳能无人机
aeroelasticity, aircraft, algorithms, computer software, deformation, design, elastic deformation,flexible structures, flow fields, lift, lift drag ratio, matrix algebra, Navier Stokes equations, Newton-Raphson method, schematic diagrams, solar energy, stability, stiffness matrix, turbulence models,unmanned aerial vehicles（ UAV）, wings
co-rotational （CR） theory, geometrically nonlinear structures, lateral-directional stability, solar powered UAV, static aeroelasticity
