大展弦比等剖面多段折叠翼颤振特性

Flutter Characteristics of High Aspect Ratio Multi-segment Folding Wings with Equal Section

对大展弦比多段折叠翼的颤振特性进行研究,使用弯扭组合梁元模拟机翼弯曲和扭转两种变形形态,结合修正的气动片条理论,得到大展弦比机翼不同折叠姿态下的颤振速度和颤振频率数据。考虑到各段机翼折叠角的变化,基于有限元理论建立包含折叠角参数的结构动力学模型,并通过模态截断将其缩减并解耦。根据Theodorsen非定常气动力理论在频域内修正弯扭组合梁元上的气动升力和俯仰力矩,并基于V-g(V为机翼与未扰空气之间的相对速度,g为人工结构阻尼)法引入人工结构阻尼,对在不同折叠状态下的多段折叠翼进行颤振计算。研究结果表明:机翼结构的固有频率会随着折叠角的变化呈现非线性增长形态,而颤振速度和颤振频率随折叠角的变化规律基本相同,且外侧机翼折叠角的存在可有效提高机翼的颤振速度;当固定最外侧段机翼的折叠角时,机翼段数的增加对颤振速度的影响不明显。

Flutter characteristics of high aspect ratio multi-segment folding wings are studied.A beam element considering bending and torsion deformations is used to simulate the two deformation modes of bending and torsion.Combined with the modified aerodynamic strip theory,flutter velocities and flutter frequencies of the high aspect ratio wing at different folding angles are obtained.Considering changes of the folding angle of each segment of the wing,a structural dynamic model including the parameter of folding angles is established based on the finite element theory.Then the dynamic model is reduced and decoupled by modal truncation.According to Theodorsen s unsteady aerodynamic theory,aerodynamic lifts and pitching moments on the bending-torsion beam element are modified in the frequency domain.And an artificial structural damping is introduced based on the V-g method for flutter calculation.The flutter calculations for the multi-segment folding wings under different folding angles reveal that:the natural frequencies of the wing structures show nonlinear growth with the change of folding angles;the variation laws of flutter velocities and flutter frequencies with folding angles are basically the same;the existence of the outer wing folding angle can effectively improve the flutter velocity of the wing;the number of wing segments has no obvious effect on flutter velocities when the outermost wing folding angle is fixed.