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 共查询到19条相似文献,搜索用时 62 毫秒
1.
单点子域积分与差分   总被引:20,自引:0,他引:20  
通过稳定性分析、显式与隐式积分,表明了单点子域积分相对于差分法的优越性.  相似文献   

2.
综合隐式和显式时间积分技术,对结构非线性动力反应分析提出一种并行混合时间积分算法.该算法采用区域分解技术.将并发性引入到算法中,即利用显式时间积分技术进行界面节点积分而利用隐式算法求解局部子区域.为实现并行混合时间积分算法,设计了灵活的并行数据信息流.编写了该算法的程序,在工作站机群实现了数值算例,验证了算法的精度和性能.计算结果表明该算法具有良好的并行性能,优于隐式算法.  相似文献   

3.
?????? 《力学与实践》2010,32(3):96-100
合隐式和显式时间积分技术,对结构非线性动力反应分析提出一种并行混合时间积分算 法. 该算法采用区域分解技术. 将并发性引入到算法中,即利用显式时间积分技术进行界面 节点积分而利用隐式算法求解局部子区域. 为实现并行混合时间积分算法,设计了灵活的并 行数据信息流. 编写了该算法的程序,在工作站机群实现了数值算例,验证了算法的精度和 性能. 计算结果表明该算法具有良好的并行性能,优于隐式算法.  相似文献   

4.
老亮 《力学与实践》1983,5(6):54-55
用D-M模型来推导J积分与COD的关系式J=σ,δ时,不少书用图1的ABC表示积分回路,并由式(1),或式(2),或式(3): ...  相似文献   

5.
胡海昌 《力学季刊》1993,14(1):1-11
本文用非解析开拓法严格地导出了任意区域内双调和函数的一个边界积分表示式,在这个表示式中有两个边界函数和四个常数,它们与双调和函数之间存在一一对应的关系。因此依据这个表示式建立的间接变量边界积分方程与原微分方程边值问题等价。  相似文献   

6.
本文建立多圆荷载作用下弹性半空间体上薄板的挠度与应力的计算式。荷载数量及分布任意,每个圆荷载密度与轮迹半径彼此相异。对计算式中的反常积分及级数的收敛性予以证明。对含振荡函数反常积分建议一种方便的算法。  相似文献   

7.
一类奇异积分计算方法及其在断裂力学中的应用任传波,云大真(大连理工大学,大连116023)在力学及其它的工程计算中,常常遇到奇异积分,不同奇异程度的积分可以采用不同的方法来解决。本文提出的方法可以解决如下一类的奇异积分问题其中1求解方法对于式(1)的...  相似文献   

8.
刘钊  王有成 《力学季刊》1993,14(4):48-55
本文对边界元方法中的各类积分根据其奇异性作分类,并对主值积分的收敛条件、变量替换等进行了讨论,又给出了变替换附加项显式。文中提供的主值积分配项消奇术在边界元方法中是有普遍意义的。  相似文献   

9.
边界元法中计算几乎奇异积分的一种无奇异算法   总被引:9,自引:0,他引:9  
边界元法中存在几乎奇异积分的计算困难。引起边界单元上几乎奇异积分的因素是源点到其邻近单元的最小距离δ。本文拓展文[1]的思想,进一步采用分部积分将δ移出奇异积分式中积分核之外,转换后积分核是δ的正则函数。所以几乎强奇异和超奇异积分被化为无奇异的规则积分与解析积分的和,可由通常的Gauss数值积分解。文中应用此正则化技术求解了弹性力学平面问题的近边界点位移和应力。  相似文献   

10.
陈光敬  于立 《力学季刊》1998,19(3):265-274
利用Mindlin竖向附加应力公式,通过积分得到地基内矩形面积上三角形分布荷载作用下角点下竖向附加应力解析式,并通过对地基内矩形面积上均布和三角形分布载荷作用下角点下竖向附加应力公式关于深度进行积分,得到了计算角点下竖附加应力面积的解析式,根据解析式制表格,可供运用应力面积法进行群桩实体基础等的最终沉降计算时查用。  相似文献   

11.
RETHINKINGTOFINITEDIFFERENCETIME-STEPINTEGRATIONSZhongWanxie(钟万勰)(ReseartchInstituteofEngineeringMechanics,DalianUniversityof...  相似文献   

12.
结构动力分析中时间积分方法进展   总被引:2,自引:1,他引:1  
叙述了结构动力分析中时间积分方法的最新发展情况,对这一领域的基本原理和思想进行了总结,重点介绍一些新型计算方法的基本性质,为时间积分方法的进一步研究奠定基础。  相似文献   

13.
The application of exponential integrators based on Krylov techniques to large‐scale simulations of complex fluid flows with multiple time‐scales demonstrates the efficiency of these schemes in reducing the associated time‐step restrictions due to numerical stiffness. Savings of approximately 50% can be achieved for simulations of the three‐dimensional compressible Navier–Stokes equations while still maintaining a truncation error typical of explicit time‐stepping schemes. Exponential time integration techniques of this type are particularly advantageous for fluid flows with a wide range of temporal scales such as low‐Mach number, reactive or acoustically dominated flows. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

14.
Several explicit Taylor-Galerkin-based time integration schemes are proposed for the solution of both linear and non-linear convection problems with divergence-free velocity. These schemes are based on second-order Taylor series of the time derivative. The spatial discretization is performed by a high-order Galerkin spectral element method. For convection-diffusion problems an operator-splitting technique is given that decouples the treatment of the convective and diffusive terms. Both problems are then solved using a suitable time scheme. The Taylor-Galerkin methods and the operator-splitting scheme are tested numerically for both convection and convection-diffusion problems.  相似文献   

15.
In this paper, an exact formula for the integration of the constitutive equations of kinematic hardening material is presented. Its algorithms are simple and clear. For isotropic hardening or mixed hardening material, the formula is still an exact solution for the case of radial loading, and it is an approximate solution with reasonable accuracy for the case of non-radial loading. The computation results show that the procedure proposed in this paper improves both accuracy and efficiency of numerical integration schemes adopted widely in elastic-plastic finite element analysis.  相似文献   

16.
Extending fixed‐grid time integration schemes for unsteady CFD applications to moving grids, while formally preserving their numerical stability and time accuracy properties, is a nontrivial task. A general computational framework for constructing stability‐preserving ALE extensions of Eulerian multistep time integration schemes can be found in the literature. A complementary framework for designing accuracy‐preserving ALE extensions of such schemes is also available. However, the application of neither of these two computational frameworks to a multistage method such as a Runge–Kutta (RK) scheme is straightforward. Yet, the RK methods are an important family of explicit and implicit schemes for the approximation of solutions of ordinary differential equations in general and a popular one in CFD applications. This paper presents a methodology for filling this gap. It also applies it to the design of ALE extensions of fixed‐grid explicit and implicit second‐order time‐accurate RK (RK2) methods. To this end, it presents the discrete geometric conservation law associated with ALE RK2 schemes and a method for enforcing it. It also proves, in the context of the nonlinear scalar conservation law, that satisfying this discrete geometric conservation law is a necessary and sufficient condition for a proposed ALE extension of an RK2 scheme to preserve on moving grids the nonlinear stability properties of its fixed‐grid counterpart. All theoretical findings reported in this paper are illustrated with the ALE solution of inviscid and viscous unsteady, nonlinear flow problems associated with vibrations of the AGARD Wing 445.6. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

17.
Sansour  C.  Wriggers  P.  Sansour  J. 《Nonlinear dynamics》1997,13(3):279-305
The paper is concerned with a dynamical formulation of a recently established shell theory capable to catch finite deformations and falls within the class of geometrically exact shell theories. A basic aspect is the design of time integration schemes which preserve specific features of the continuous system such as conservation of momentum, angular momentum, and energy when the applied forces allow to. The integration method differs from the one recently proposed by Simo and Tarnow in being applicable without modifications to shell formulations with linear as well as nonlinear configuration spaces and in being independent of the nonlinearities involved in the strain-displacement relations. A finite element formulation is presented and various examples of nonlinear shell dynamics including large overall and chaotic motions are considered.  相似文献   

18.
Introducing fractional operators in the adaptive control loop, and especially in Model Reference Adaptive Control (MRAC), has proven to be a good mean for improving the plant dynamics with respect to response time and disturbance rejection. The idea of introducing fractional operators in adaptation algorithms is very recent and needs to be more established, that is why many research teams are working on the subject. Previously, some authors have introduced a fractional model reference in the adaptation scheme, and then fractional integration has been used to deal directly with the control rule. Our original contribution in this paper is the use of a fractional derivative feedback of the plant output, showing that this scheme is equivalent to the fractional integration, one with a certain benefit action on the system dynamical behaviour and a good robustness effect. Numerical simulations are presented to show the effectiveness of the proposed fractional adaptive schemes.  相似文献   

19.
We present a new unconditionally positivity‐preserving (PP) implicit time integration method for the DG scheme applied to shallow water flows. This novel time discretization enhances the currently used PP DG schemes, because in the majority of previous work, explicit time stepping is implemented to deal with wetting and drying. However, for explicit time integration, linear stability requires very small time steps. Especially for locally refined grids, the stiff system resulting from space discretization makes implicit or partially implicit time stepping absolutely necessary. As implicit schemes require a lot of computational time solving large systems of nonlinear equations, a much larger time step is necessary to beat explicit time stepping in terms of CPU time. Unfortunately, the current PP implicit schemes are subject to time step restrictions due to a so‐called strong stability preserving constraint. In this work, we hence give a novel approach to positivity preservation including its theoretical background. The new technique is based on the so‐called Patankar trick and guarantees non‐negativity of the water height for any time step size while still preserving conservativity. In the DG context, we prove consistency of the discretization as well as a truncation error of the third order away from the wet–dry transition. Because of the proposed modification, the implicit scheme can take full advantage of larger time steps and is able to beat explicit time stepping in terms of CPU time. The performance and accuracy of this new method are studied for several classical test cases. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

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