基于径向基函数的网格变形及非线性气动弹性时域仿真研究

为开展非线性气动弹性研究,基于非线性结构有限元软件NASTRAN和自主研制的多块结构化计算流体力学(CFD)求解器,开发了一套基于计算流体力学/计算结构动力学(CFD/CSD)耦合求解方法的气动弹性时域仿真程序.该程序采用径向基函数(RBF)交换两套求解器之间的数据并进行网格变形.为提高RBF方法的效率,构造了基于多次插值的空间待插值点精简算法.在多次插值过程中,每次插值的对象为上次插值的误差,并同时限制插值区域,以此实现了空间待插值网格数的精简.数个网格变形的算例表明该方法可支持大变形运动,并且具有较高的计算效率.采用此程序开展了AGARD 445.6机翼颤振计算、大展弦比机翼的静气动弹性计算与切尖三角翼极限环振荡(LCO)现象的动气动弹性仿真,结果揭示了当机翼展弦比较大或者响应幅值较大时,结构非线性对于气动弹性有显著影响.

Research of Mesh Deforming Method Based on Radial Basis Functions and Nonlinear Aeroelastic Simulation

To carry out research of nonlinear aeroelasticity, this paper presents a nonlinear time-domain aeroelastic simulation program which adopts computational fluid dynamics/computational structural dynamics (CFD/CSD) couple method. The program couples the nonlinear structural finite element software NASTRAN with a multi-block structured grid-based CFD solver developed by myself. Radial basis function (RBF) is used to transfer information between the two solvers and deform grid. To improve the efficiency of the RBF method, a space point reduction algorithm based on multi-level interpolation is constructed. For the purpose of reducing the number of space points, the interpolation object of each interpolation step is the error of previous step, and interpolation region is limited simultaneously. Results of some mesh deformation examples show that this way can support the movement of large deformation with high computational efficiency. With the use of this program, flutter computation of AGARD 445.6 wing is completed, static aeroelastic computation of a wing with a large aspect ratio is performed and a dynamic aeroelastic simulation of limit-cycle-oscillation (LCO) of a cropped delta wing is carried out. Results demonstrate that structural nonlinearity has strong influences on aeroelastic phenomenas when the aspect ratio of the wing is large or the amplitude of response is great.