共查询到20条相似文献,搜索用时 10 毫秒
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针对三维不规则非灰吸收介质的辐射传递问题,提出用混合有限体积侑限元法对其求解.在直角坐标系下,详细推导了混合有限体积/有限元法的计算过程;并结合向量和矩阵运算的相关理论,给出一种能够耦合边界条件的有限元方程的总体合成方法.以姿控推进器喷管扩张段和其内部的吸收介质之间的辐射传递为求解对象,采用该方法得到喷口的光谱辐射亮度... 相似文献
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W. Rachowicz A. Zdunek 《International journal for numerical methods in engineering》2005,62(9):1226-1249
An hp‐adaptive finite element (FE) approach is presented for a reliable, efficient and accurate solution of 3D electromagnetic scattering problems. The radiation condition in the far field is satisfied automatically by approximation with infinite elements (IE). Near optimal discretizations that can effectively resolve local rapid variations in the scattered field are sought adaptively by mesh refinements blended with graded polynomial enrichments. The p‐enrichments need not be spatially isotropic. The discretization error can be controlled by a self‐adaptive process, which is driven by implicit or explicit a posteriori error estimates. The error may be estimated in the energy norm or in a quantity of interest. A radar cross section (RCS) related linear functional is used in the latter case. Adaptively constructed solutions are compared to pure uniform p approximations. Numerical, highly accurate, and fairly converged solutions for a number of generic problems are given and compared to previously published results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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针对传统有限元法求解Oldroyd-B本构方程时需加入稳定化方案的缺点,本文基于非结构网格给出了统一间断有限元求解框架.该框架包含采用IPDG(interior penalty discontinuous Galerkin)求解质量方程和动量方程,与采用RKDG(RungeKutta discontinuous Galerkin)求解本构方程这两个核心.数值结果表明:该方法在求解Oldroyd-B本构方程时无需加入稳定化方案,实施比有限元法简便,且具有较高的计算精度,可有效地模拟包含应力奇异点的复杂粘弹流动问题,进而揭示非牛顿粘弹流动的基本特征. 相似文献
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Michael Junge Dominik Brunner Lothar Gaul 《International journal for numerical methods in engineering》2011,87(7):664-676
To predict the vibro‐acoustic behavior of structures, both a structural problem and an acoustic problem have to be solved. For thin structures immersed in water, a strong interaction between the structural domain and fluid domain occurs. This significantly alters the resonance frequencies. In this work, the structure is modeled by the finite element method. The exterior acoustic problem is solved by a fast boundary element method employing hierarchical matrices. An FE‐BE formulation is presented, which allows the solution of the coupled eigenvalue problem and thus the prediction of the coupled eigenfrequencies and mode shapes. It is based on a Schur complement formulation of the FE‐BE system yielding a generalized eigenvalue problem. A Krylov–Schur solver is applied for its efficient solution. Hereby, the compressibility of the fluid is neglected. The coupled eigensolution is then used for a model reduction strategy allowing fast frequency sweep calculations. The efficiency of the proposed formulations is investigated with respect to memory consumption, accuracy, and computation time. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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通过单元正交展开的余项中添加若干待定的低次项,得到所需的超接近于有限元解的逼近函数,由此导出了一类非线性两点边值问题的强超收敛性。最后给出了一个数例验证了这一结论。 相似文献
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边界元法是边界积分方程的数值解法 ,是随着计算机技术的发展而出现的。建立声学边界积分方程分两种方法 :直接法与间接法。本文介绍了边界元法在环境声学中的应用 ,如声屏障和不同情况下道路周围的声场分布、复杂气象条件对声传播的影响的问题等。由于边界元法是半解析半数值解法。在解边界积分方程时会遇到解的存在与唯一性问题。 相似文献
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We show that local quantities of interest such as displacements or stresses of a FE–solution can be calculated with improved accuracy if fundamental solutions are employed. The approach is based on Bettis theorem and an integral representation of the local quantities via Greens function. The unknown Greens function is split into a regular part and a fundamental solution so that only the regular part must be approximated on the finite element ansatz space. Some numerical studies for linear elasticity will illustrate our approach. 相似文献
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目的伞降-气囊回收方式是目前无人机回收的主要方式,气囊能够在回收过程中很好地起到降低过载、限制反弹、保护设备的作用,研究气囊在回收过程中的回收特性对于加快无人机研制进度,提高无人机的回收质量具有重要意义。方法采用有限元模拟方法对无人机回收过程中气囊的减震特性进行研究,以单个气囊为研究对象,分析气囊充气后压力、气囊排气孔面积和气囊放气压力对气囊减震性能的影响,并对气囊参数进行优化。将优化过的气囊应用于某型高亚音速无人机,并对其减震特性进行验证。结果充气后压力、排气孔面积和放气压力等气囊参数无论过大还是过小都会影响减震性能,实际应用中必须根据实物具体情况,确定一组合理的气囊参数。某型高亚音速无人机采用双气囊减震方案,在进行气囊参数优化后,回收时其重心位置的加速度明显减小,飞机回弹速度及剩余速度也得到明显改善,满足了机体及机载设备对回收过载的要求。结论采用有限元对气囊的分析和优化方法对于气囊的设计具有较强的指导意义。 相似文献
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One of the important features of flanging process is elastic recovery during unloading leading to springback. The elastic recovery is associated with various tool and material parameters. It is difficult to analytically predict the elastic recovery accurately owing to the complex material deformation behavior. In this investigation, a commercially available Finite Element software is used for elasto-plastic analysis of flanging process. The springback is studied varying geometrical, material and friction parameters. The results of the simulation are validated with a few published experimental results. 相似文献
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中高频段下的粘弹性材料声学参数测量 总被引:1,自引:0,他引:1
为了实现粘弹性材料在高频段上的声学参数测量,提出一种自由场测量方法,通过测量目标的水下散射声场指向性,计算目标散射场声压的前几阶勒让德系数,建立以目标的材料声学参数为变量的数学模型,并运用遗传算法进行参数反演.仿真结果表明以铝球的杨氏模量(E)为例,不存在声场误差的情况下反演精度可达0.0014%,铝球散射场的实验数据也提供了较高的参数反演精度.将此方法应用于中高频段上某种成分的粘弹性材料参数测量,成功地获取了其在此频段上的声学参数.提高目标散射场的测量精度有利于目标材料反演精度的提高.此方法避免了对声压相位的测量,减少了影响精度的因素. 相似文献
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粘弹性材料具有良好的阻尼性能,在工程振动与噪声处理上的应用非常广泛。利用粘弹性材料进行阻尼结构设计并预测其动力学特性,需要知道准确的动力学参数。回顾粘弹性材料动力学参数测试的经典方法,并着重介绍共振法测试技术。研究共振法测试中细棒的动力学响应与动力学参数间的关系,在此基础上,基于共振法测试数据和有限元仿真,提出一种反演粘弹性材料动力学参数的新方法。首先根据幅值比反演出损耗因子,再根据共振频率反演出储能模量。通过具体算例验证可知,反演得出的动力学参数的相对误差均在4 % 以内,该反演方法不仅结果收敛、准确可靠且反演速度快,为在连续频率范围内的动力学参数反演奠定基础。 相似文献
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In a previous paper, a general method was presented for constructing the solution to the problem of a semi-infinite, mode
III crack propagating dynamically through an infinite, general linear viscoelastic body. The only restrictions placed upon
the crack tip speed were that it have constant sign and in magnitude not exceed the glassy shear wave speed. In the present
contribution, those previous analytical results are applied to a study of dynamic unsteady crack growth in a linear viscoelastic
body. In particular, a numerical algorithm for computing the stress intensity factor is given along with example simulations
of running cracks using the Achenbach-Chao viscoelastic model and a stress intensity factor (SIF) fracture criterion. We also
compare the transient SIF with the dynamic steady state SIF, and examine the transition to constant crack speed for a dynamically
accelerating crack in a viscoelastic material. 相似文献
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岩石工程渐进破坏分析的边界元法 总被引:1,自引:0,他引:1
本文根据内变量理论,应用均匀化技术处理岩石的变形与破坏过程,建立了岩石渐进破坏的本构关系以及相应的边界元公式并系统地给出了初应力表示下的非线性边界元计算步骤和方法。由此可有效地处理岩石的软化、膨胀、不抗拉等特性。实例计算表明本文所建立的边界元方法是有效而可靠的。 相似文献
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I. T. Pearson 《Strain》2001,37(3):113-122
Abstract: The sensitivity of the joint's stiffness to changes in certain parameters (geometric and material properties) has been investigated and an understanding of the joint's behaviour gained from this parametric study. This insight into simple overlap joint behaviour has been used to fashion some design guidelines aimed at increasing joint stiffness. A representation that can be successfully substituted for certain adhesively bonded overlap joints in finite element (FE) analyses is also suggested. 相似文献