发动机推力对大展弦比机翼颤振边界的影响

Effects of the Engine Propulsion on Flutter Boundary of High-Aspect-Ratio Wing

为解决现有线性气动力模型对大柔性机翼受发动机推力影响的气动稳定性分析方法的不足,提出了基于计算流体力学(CFD)与Simo几何精确梁模型的非线性气动弹性分析方法。以翼吊式发动机的大展弦比机翼为研究对象,采用横向随动力和集中质量模拟发动机推力和吊挂质量,分别研究了单纯发动机推力和考虑气动载荷联合作用时,发动机推力、结构弯扭刚度比、发动机集中质量以及发动机安装位置等参数对机翼结构颤振特性的影响。数值模拟所采用的大展弦比柔性机翼非线性气动弹性模型耦合了Simo几何精确梁模型和雷诺平均N-S非定常气动力模型,考虑了结构和流场的两场非线性耦合。模拟结果表明:发动机推力对机翼颤振边界影响很大,具体的影响效果取决于上述其他参数的变化;发动机吊舱靠近翼根布置、发动机尽量布置在机翼弹性轴之前、减小机翼弯扭刚度比等布局或设置有利于扩大机翼的颤振包线范围。因此,在进行翼吊式气动布局的设计或分析时,必须考虑发动机推力及其相关参数的影响。

An interaction method of CFD combined with geometrically exact beam based on Simo theory for fluid-structure interaction (FSI) is proposed to analyze the effects of engine propulsion on stability of very flexible structures,which have been discussed via the existing linear aerodynamic forces models.Aiming at the high-aspect-ratio wing with engines,the mentioned method is adopted to evaluate the wing flutter boundary with variations of the parameters,including propulsion,bending-torsion stiffness ratio,engine mass,and engine position,where the lateral follower force and concentrated mass are simulated as the engine thrust and nacelle mass respectively.The geometrically exact beam based on Simo theory for nonlinear structure is coupled with Reynold-averaged Navier-Stokes aerodynamic equation to construct the nonlinear aeroelastic model used in numerical simulation of the high-aspect-ratio flexible wing.The nonlinear coupling of both structure and flow is considered in the aeroelastic model.The numerical results show that the engine propulsion has remarkable influence on the stability performance of the wing,and the influence is determined greatly by the mentioned parameters.The aerodynamic stability can be improved by such configurations as installation of the engine close to the wing root and the leading edge,and reduction of the bending-torsion stiffness ratio.It is necessary to consider the engine propulsion and its affiliated parameters in aerodynamic design or analysis of the flexible wing with engine mounted.