Z型折叠机翼的气动力计算及非线性动力学分析

AERODYNAMIC FORCE CALCULATION AND NONLINEAR DYNAMIC ANALYSIS OF Z-TYPE MORPHING WINGS

近年来,由于变体飞行器能够通过改变结构几何参数从而有效地改善飞行特性,成为了各国研究的热点问题.然而气动弹性问题一直是制约变体飞行器发展的瓶颈.所以,通过计算特殊形状变体飞行器的气动特性并分析结构的动态稳定性,能更多的了解变形结构的气动特性,也将推动变体飞行器中气动力计算的发展及相关领域的研究.本文主要研究了Z型折叠机翼的气动力计算及非线性动力学分析.根据亚音速下气流的特点,采用薄翼型理论计算Z型折叠机翼的环量分布,然后利用Kutta-Joukowski升力定理,推导了在理想不可压流体来流条件下定常气动升力的解析公式.将上述得到的气动力作用在Z型折叠机翼中,将Z型折叠机翼简化为以刚性铰链相连接的三块碳纤维复合材料层合板,应用Hamilton原理建立了在亚音速气动载荷作用下Z型折叠机翼结构的非线性动力学方程,并根据特殊的边界条件得到了结构的模态函数.利用Galerkin方法离散得到了结构带有折叠角度的常微分运动控制方程.利用数值方法分析了一定气动力作用下Z型折叠机翼结构在折叠过程中的非线性动力学特性,分析了折叠角度对变形机翼结构稳定性的影响.

In recent years,morphing aircrafts,which is able to improve the lift-drag characteristics of the aircraft by changing wingspans and aspect ratios,has become a popular research issue around the world. However,the aeroelastic problem is still a bottleneck for the development of the morphing wing. Therefore,it is necessary to calculate the aerodynamic forces of morphing aircrafts by combining with the particular deformable structures and analyse the dynamic characteristics of the morphing aircrafts. Through this way,we will promote the development of the aerodynamic calculation in the morphing aircrafts and related researches fields. In this paper,the aerodynamics of a Z-type morphing wing in the subsonic air flow are further promoted and the nonlinear dynamic analysis of the Z-type morphing wing is conducted. Under the flow condition of ideal incompressible fluid,the thin airfoil theory is applied to calculate the effects of the mean camber line. Based on the Kutta-Joukowski lift theorem,the steady aerodynamic lift on the Z-type morphing wing is derived by the analytic formulation. The Z-type wing are considered as three carbon fiber composite laminated plates connected with the hinges. Based on Hamilton＇s principle,the nonlinear partial differential governing equations of motion for the Z-type folding wing are established subjected to the aerodynamic force in subsonic air flow,and the mode-shape functions are obtained with the boundary conditions of the Z-type wing structure. Then,the Galerkin method is used to transform the partial differential equation into nonlinear ordinary differential equations with rotation angle. Numerical simulations are also performed for the nonlinear dynamic responses of the Z-type folding wing subjected to the aerodynamic force,and the influence of folding angles on the stability of the wing are then analyzed.