民用飞机大变形静气动弹性载荷设计

通过对气动非线性和结构非线性的几何非线性问题进行研究,结合型号经验,提出考虑非线性效应的大型客机静气动弹性载荷设计方法,建立了基于曲面涡格的曲面定常气动力模型和非线性有限元模型,结合曲面样条插值实现了气动模型随结构变形的自适应,即载荷的随动加载。对某大柔性客机进行静气动弹性载荷分析表明,考虑几何非线性效应的弹性载荷与线性弹性载荷有较大差异。

民用飞机策略化气动弹性载荷方法研究

针对现代大型民用飞机静气动弹性载荷分析的需求,建立了策略化的弹性载荷设计方法。采用工程梁法、平板面元法、高阶面元法和大变形法,并引入风洞试验或CFD气动压力数据对飞机压力分布进行修正,对某大型民用飞机进行弹性载荷分析。研究表明:在飞机概念设计阶段,可采用工程梁法实现几十万种工况弹性载荷快速分析;在初步设计阶段,可采用优化的工程梁法和平板面元法进行几千种工况的弹性载荷分析;在详细设计阶段,可采用高阶面元法和大变形法进行几百种工况的弹性载荷分析。该策略化的静气动弹性载荷设计方法精度高、效率高,满足了大型民用飞机弹性载荷不同设计阶段需求,具有较强的工程适用性。

Wind-induced responses of super-large cooling towers

Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Aeroelastic trim and flight loads analysis of flexible aircraft with large deformations

A method for static aeroelastic trim analysis and flight loads computation of a flexible aircraft with large deformations has been presented in this paper,which considers the geometric nonlinearity of the structure and the nonplanar effects of aerodynamics.A nonplanar vortex lattice method is used to compute the nonplanar aerodynamics.The nonlinear finite element method is introduced to consider the structural geometric nonlinearity.Moreover,the surface spline method is used for structure/aerodynamics coupling.Finally,by combining the equilibrium equations of rigid motions of the deformed aircraft,the nonlinear trim problem of the flexible aircraft is solved by iterative method.For instance,the longitudinal trim analysis of a flexible aircraft with large-aspect-ratio wings is carried out by both the nonlinear method presented and the linear method of MSC Flightloads.Results obtained by these two methods are compared,and it is indicated that the results agree with each other when the deformation is small.However,because the linear method of static aeroelastic analysis does not consider the nonplanar aerodynamic effects or structural geometric nonlinearity,it is not applicable as the deformations increase.Whereas the nonlinear method presented could solve the trim problem accurately,even the deformations are large,which makes the nonlinear method suitable for rapid and efficient analysis in engineering practice.It could be used not only in the preliminary stage but also in the detail stage of aircraft design.