跨音速后掠翼抖振边界计算

本文提出一种确定跨音速后掠翼抖振边界的数值计算方法,现有的确定跨音速翼型抖振边界的F.Thomas 准则被推广到包括具有大后掠角的后掠翼,计算是对侧滑翼进行,其中用积分法对三维可压缩湍流边界层的计算是根据本文作者听发展的方法,对于跨音速压强分布是利用A.Eberle的解全速位方程的有限元素法给出,按本文方法计算出F-86A 飞机的抖振边界与相同雷诺数下飞行试验所得结果符合得很好。     

求非线性转子－轴承系统周期响应的一种计算方法

本文把求非线性转子－轴承系统瞬态响应的分块Ｎｅｗｍａｒｋ方法与打靶法结合求系统的周期解，该方法利用了分块Ｎｅｗｍａｒｋ方法求解速度快的优点和Ｊａｃｏｂｉ矩阵求解时每步不需迭代的特点。本文首先给出周期解的求解公式，然后用一个算例，讨论了周期解的稳定性及失稳后的分岔行为。     

带窗口准等熵压缩实验的流场反演技术

在一维拉格朗日平面准等熵压缩流体力学的基础上,建立了带窗口准等熵压缩实验流场反演方法,给出了界面处压力历史的求法,编制了实现流场反演技术的程序,并与一般流体力学计算进行了比较;对Z575号实验给出的界面速度历史进行了反演计算,给出了的Al 6061-T6等熵压缩线。     

A Fast,Matrix-free Implicit Method for Computing Low Mach Number Flows on Unstructured Grids

A fast, matrix-free implicit method has been developed to solve low Mach number flow problems on unstructured grids. The preconditioned compressible Euler and Navier-Stokes equations are integrated in time using a linearized implicit scheme. A newly developed fast, matrix-free implicit method, GMRES + LU?SGS, is then applied to solve the resultant system of linear equations. A variety of computations has been made for a wide range of flow conditions, for both in viscid and viscous flows, in both 2D and 3D to validate the developed method and to evaluate the effectiveness of the GMRES + LU?SGS method. The numerical results obtained indicate that the use of the GMRES + LU?SGS method leads to a significant increase in performance over the LU?SGS method, while maintaining memory requirements similar to its explicit counterpart. An overall speedup factor from one to more than two order of magnitude for all test cases in comparison with the explicit method is demonstrated.     

结构几何非线性分析的一种修正的有限元迁移矩阵法

本文提出一种修正的有限元法与迁移矩阵法相结合的方法用于结构几何非线性劳力分析。该法可克服一般的ＦＥ－ＴＭ法只适用于规则边界结构的缺点，同时可避免由于传递矩阵连续相乘而产生的误差传递。采用修正的步长增量法与修正的牛顿。拉斐逊方法相结合的算法于非线性问题的求解，编制了在ＩＢＭ－ＰＣ／ＡＴ上实现该方法的计算机程序ＴＮＯＮＤＬＷ１，数值计算结果表明了本文方法及所编制程序的有效性。     

A boundary-value problem for a nonlinear heat-conduction equation

Methods for the numerical solution of the boundary-value problem are comidered. One method is related to the method of successive approximations and the other employs the collocation method [1]. A relationship between the latter method and the Ritz and Galerkin methods [2] is shown. An application of the collocation method to the nonstationary problem is given. The approximate solution is represented in analytic form. A way of finding the absolute error of the approximate solution is given.     

Modified Adams-Moulton Predictor-Corrector Method in Solving Multibody Dynamical Systems

A modified Adams-Moulton predictor-corrector method is proposed to solve multibody dynamical systems. The proposed method is obtained by combining an Adams-Bashforth predictor method and an Adams-Moulton corrector method with derived weighting coefficients. With the modification, the accuracy of the proposed method is almost one order of magnitude better than the Adams-Moulton predictor-corrector method with the same step size. Stability limits of the proposed method are also studied. Because the present method has greater stability limits than Adams-Moulton predictor-corrector methods, the proposed method has good robustness during the process of time integration. A crank-slider mechanism is used as an example to investigate the capability of the proposed method in solving multibody dynamic systems.     

Uncoupled finite element solution of biharmonic problems for vector potentials

A method for the uncoupled solution of three-dimensional biharmonic problems for the vector potential in viscous incompressible flow is presented. The strategy applied in a previous work on vector Poisson equations is employed to reduce the vector fourth-order problem to a sequence of scalar biharmonic problems. A finite element aimed at the implementation of the method in a discrete version is considered. A conjugate gradient algorithm which is particularly efficient for the uncoupled solution method is also described.     

HOMOTOPY CONTINUATION ALGORITHM FOR STRUCTURAL DAMAGE IDENTIFICATION

I. INTRODUCTIONStructural damages due to the loss of sti?ness such as crack, localization bulking have remarkablein?uences on the physical properties of structure such as deformation, stress, frequency and modelshape. So the change of these properties can be used to identify the damage location and degree ofstructures. The damage identification techniques based on these properties’ changes have attractedmuch attention in recent years, and many approaches have been developed[1??5].Nowaday…     

Penalty functions in constrained variational principles for element free Galerkin method

An improved formulation of the Element Free Galerkin (EFG) method is presented in this paper. In the Element Free Galerkin method, enforcement of essential boundary conditions is awkward as the approximations do not satisfy the Kronecker delta condition. A method of generating admissible approximations to the essential boundary conditions is given, using a constrained variational principle with a penalty function. Several examples of Laplace equation are solved and compared with analytical solutions and flux Lagrange multipliers, to demonstrate the performance of the method. A parametric study comparing three different weight functions is made. A guide on the EFG/penalisation method is given, considering the possibility of using irregular grids with a variable domain of influence for each point.     

有杆抽油系统动态特性的计算机仿真

本文建立了有杆抽油系统动态特性仿真的综合数学模型．即应用数值积分法建立转子运动规律的仿真模型和应用差分法建立抽油杆柱纵向振动的仿真模型。本文提出了一种叠代方法较好地解决了两子系统之间相互耦合的问题，给出了一种便于应用的井下边界条件的仿真方法。     

基于柔度的桁架结构损伤定位方法

建立了一种基于模态柔度的桁架结构损伤定位方法。从结构柔度矩阵与刚度矩阵的正交关系出发,将损伤结构在观测模态下的节点误差作为损伤定位的动力指纹,通过采用模态参数的一阶矩阵摄动技术,以近似解析的方式推导了本文方法的损伤定位原理。并且通过对一个典型桁架结构的数值模拟研究,验证了本文损伤定位方法的有效性和鲁棒性。研究结果表明,本文基于柔度的损伤定位方法能够在实际观测条件下,准确地识别桁架结构的损伤单元位置。     

板壳结构弹塑性稳定性的有限元分析

构造了20参数圆柱壳拟协调单元,同时采用分层模型的弹塑性稳定性分析.根据塑性屈曲的Stowell形变理论,用基于切线刚度矩阵的增量法和修正的Newton-Raphson方法,计算屈曲前的弹塑性内力分布,并用逆幂迭代法求解弹塑性屈曲荷载.     

ITERATIVE ALGORITHM FOR AXIALLY ACCELERATING STRINGS WITH INTEGRAL CONSTITUTIVE LAW

A numerical method is proposed to simulate the transverse vibrations of a viscoelastic moving string constituted by an integral law. In the numerical computation, the Galerkin method based on the Hermite functions is applied to discretize the state variables, and the Runge- Kutta method is applied to solve the resulting differential-integral equation system. A linear iterative process is designed to compute the integral terms at each time step, which makes the numerical method more efficient and accurate. As examples, nonlinear parametric vibrations of an axially moving viscoelastic string are analyzed.     

基于水平集方法的均布式柔性机构的拓扑优化设计

提出一种利用水平集方法进行均布武柔性机构设计的新方法.根据水平集边界表达方法中具有几何信息的特点,将图像分析中的二次能量函数引入到水平集模型中,以控制柔性机构拓扑优化设计结果的几何尺寸,得到等宽带状均布的柔性机构,较好地解决了传统柔性机构拓扑优化中容易出现单点铰链问题.应用半隐式的加性分裂算子(AOS)算法求解水平集方程,松弛了逆风格式中CFL(Courant-Frie drichs-Lewy)条件对时间步长的限制,提高了求解效率.通过一个典型的二维算例来验证方法的有效性.     

A HYBRID SPECTRAL/FINITE VOLUME METHOD FOR VISCOUS FLOWS

Abstract

This paper presents a hybrid spectral/finite volume method for steady-state compressible viscous flows. The method is evaluated for accuracy via test cases for various Mach numbers. The domain is divided into a viscous region and an inviscid region. The viscous region uses the full Navier-Stokes equations, while the inviscid region employs the Euler equations. A high order Chebyshev collocation spectral method is developed for the viscous region to resolve boundary layers. This method avoids the dense grids needed by finite-volume methods to resolve the viscous areas. A low order finite-volume method based on a Lax-Wendroff type scheme is employed for the inviscid region. A special interface formulation is developed for coupling the spectral with the finite-volume method. Comparisons with analytic results as well as convergence histories are presented.     

密集模态摄动的新方法

本文提出了一种密集模态结构系统(M_0,K_0)振动分析的矩阵摄动新方法.它将密集模态结构系统特征解的摄动问题转化为重特征值的摄动问题.文中给出了一个数值例子.     

Méthode couplée CVFE/BE pour les calculs acoustiques en domaine non borné

A new method based on the flux conservation for acoustic computations in unbounded domain is presented. The domain is divided in outer and inner regions by a fictitious boundary. The inner problem is solved by a control volume finite element method while the outer flow is treated with a boundary element method. The coupling of the two sub-domains is performed using an appropriate expression for the outgoing fluxes satisfying the Sommerfeld condition. A two-dimensional configuration with a circular interface is considered to show that the method is effective. Results of this method are compared to an analytical solution and to results from the literature.     

Forced Axisymmetric Nonlinear Vibrations of Reinforced Conical Shells

A numerical method for analysis of the axisymmetric nonlinear vibrations of conical shells is developed based on the integro-differential method of constructing difference schemes. A prediction analysis is conducted of the response of shells with various taper angles to an impulsive load     

基于实验设计法的工程结构优化设计

基于实验设计法,提出了一种新的工程结构优化设计方法,这种方法将设计变量的水平值配列于正关表中,按正交表的参数组合条件进行结构解析,通过对设计变量对于目标函数值的方差分析和F检验,改变设计变量的水平值,进而通过迭代计算使设计变量趋地最优解,本文以杵架结构为计算例,验证了本方法的全局收敛性和优化精度,由于无需构建目标函数和约束函数以及微分计算,此方法具有简单而又适应广泛的优点。