共查询到19条相似文献,搜索用时 203 毫秒
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针对传统边界元法在数值求解大规模声学问题时的超大计算量问题,将快速多极算法与伽辽金边界元法相结合,提出了基于Burton-Miller方程的伽辽金多极边界元法。在已有二维快速多极算法的基础上,引入核函数的对角展开形式及自适应树结构算法,同时使用经过近似求逆预处理的广义极小残差法求解系统线性方程组,最后将该方法应用于二维矩形管道与刚性圆柱面声散射问题的求解。数值计算结果表明:在求解无限域声学问题时,Burton-Miller方程保证了全频率段解的唯一性,特别是在特征频率处解的稳定性。与传统边界元方法相比,伽辽金多极边界元法的计算量由原来的I(n~2)降到了O(nlog~2n)量级,该方法非常适合用于求解大规模声学问题。 相似文献
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针对注射模三维冷却系统,以修正的三维边界元法为基础给出型腔表面温度的计算方法。在此基础上,以冷却管道线单元节点和冷管半径为设计变量,通过构造边界积分灵敏度方程得到型腔温度对设计变量的灵敏度。在优化设计中,以型腔表面各点温度与某一设定目标温度的均方差为目标函数,在一定的约束条件下,通过寻求目标函数的最小值求出冷却管道的优化位置和尺寸,并在实例进行验算。 相似文献
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发动机进气系统噪声是车辆最主要的噪声源之一,为了满足车辆舒适性越来越高的要求,控制和匹配进气系统的声学性能至关重要.依据三维几何模型建立进气系统的声学模型,其中四分之一波长管的声学模型为参数化模型.基于管道声学理论,研究发动机进气系统噪声仿真方法--无源法,并应用"无源法",进行进气系统管口噪声的模拟仿真.以试验设计分析为基础,研究基于管口噪声的四分之一波长管灵敏度分析方法,并应用该方法,进行四分之一波长管的各个参数灵敏度分析.在不具备发动机仿真模型的情况下,仍然能进行进气系统管口噪声的模拟仿真,并通过灵敏度分析确定四分之一波长管的设计参数.基于管口噪声的四分之一波长管灵敏度分析方法具有很高的工程应用价值,并为进气系统四分之一波长管的参数化设计提供了理论依据. 相似文献
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灵敏度分析在结构优化设计和可靠性分析中起着至关重要的作用。针对特征值敏度的解析法在有限元分析中不足,本文提出了一种基于半解析的伴随变量特征值敏度分析方法,用有限差分法代替了常规的解析求导。另外,针对导数矩阵稀疏性的特点提出了一种新颖的存储方法,并将这种方法应用于伴随变量法涉及到的导数矩阵存储,节省了存储空间。最后将本文提出的伴随变量方法与常见的解析法敏度分析方法进行对比,证实本文方法在精确性和计算效率上得到了较大的提高,且非常适合于大型结构的敏度分析。 相似文献
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微机电系统中基于模态展开和边界元法的静电-结构耦合高效分析方法 总被引:1,自引:0,他引:1
为了提高微机电系统中静电-结构耦合数值计算速度,提出了一种新的针对微结构小变形的静电-结构耦合高效率数值计算方法。该方法将用于结构分析的微梁线性方程与用于静电场分析的边界积分方程相结合,微梁方程部分用标准的模态分析法处理,静电边界元方程则采用边界元法处理,并且将边界元方程用Taylor级数在微梁未变形的位置展开,以使静电计算能在微梁未变形的位置进行。同以往的常规算法相比,当微结构变形微小时,使用该方法,微结构变形后的面电荷密度可以在微结构未变形中计算,从而大大提高了静电-结构耦合数值计算效率。将该方法的计算结果与已有的文献计算结果和ANSYS的计算结果做了对比,验证了本方法的正确性,并且计算效率有显著提高。 相似文献
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Tae Hee Lee 《Journal of Mechanical Science and Technology》1999,13(6):470-476
New adjoint variable method for design sensitivity analysis of distinct eigenvlaues and eigenvectors is presented. In the
viewpoint of efficiency for the design sensitivity analysis of eigenvectors especially, the developed adjoint variable method
is required to compute adjoint variables from simultaneous linear equations, the so-called adjoint equations, instead of linear
combination of eigenvectors. Once we obtain the adjoint variables, design sensitivity analysis of response function that is
given in terms of eigenvalues, eigenvectors and design variables can be computed directly. In this way, design sensitivity
analysis of eigenvectors can be obtained by using eigenvalues and their corresponding eigenvectors of the mode being differentiated
only. To verify the proposed method, numerical examples are demonstrated. This can have considerable impact on computer implementation
of the developed method in the design sensitivity analysis of eigenproblem needed for practical applications. 相似文献
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Tae Hee Lee 《Journal of Mechanical Science and Technology》1999,13(3):246-252
Design sensitivity analysis of structural problems obeying an elastoplastic material behavior is developed using adjoint variable
method. An elastoplastic constitutive equation with yield surface and kinematic hardening is considered to describe the material
behavior. The traditional incremental procedure and its design variation need special treatments in order to predict the discontinuity
of the structural response sensitivity because the contribution from the design sensitivity at the material transition point
is lost during the calculation. In this study, discontinuities of the design variations at the material transition points
are alleviated in the adjoint variable method. Analytical and numerical examples are used not only to demonstrate the developed
sensitivity procedure but also to gain insights of numerical implementation for the design sensitivity analysis of the elastoplastic
structure based on the adjoint variable method. The comparisons between adjoint variable and direct variation methods are
also discussed. 相似文献
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采用基于半解析有限元的激励响应计算方法来求解薄板中Lamb波的激励响应结果,替代常规的实验方法,实现对薄板中Lamb波传播特性的仿真分析。与三维有限元仿真方法相比,采用激励响应计算方法仿真导波在波导介质中的传播过程可以节省计算量,提高效率。通过求解薄板中Lamb波的一般均质方程,基于频谱叠加原理,可以计算薄板中Lamb波激励响应结果。分别提取激励响应计算结果和实验测量数据,通过小波分析计算两种数据的Lamb波群速度。经验证,激励响应仿真计算结果与实验数据有很好的一致性,通过群速度频散曲线对比两种方法获取的数据,模态分析结论一致。激励响应计算方法还可以仿真计算任意截面波导介质中导波的传播过程,具有较好的通用性。 相似文献
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提出一种新型双夹爪变刚度夹持器,每个夹爪是一个由四根对称旋转柔性支链组成的变刚度柔性并联机构(VSFPM)。夹持器由两个电动机驱动,其中一个宏动电动机用于控制夹爪的开合运动,适应被抓取物体的几何尺寸;另一个微动电动机用于控制柔性支链的旋转角度,以调整夹爪在开合方向的刚度,实现变刚度柔顺抓取,提高对被抓取物体几何形状、材料属性的适应能力。基于刚度投影方法,分析了基于旋转支链柔性并联机构在夹持方向上的变刚度原理;应用基于伴随变换的刚度分析方法,求得了夹爪在任意旋转角度下的刚度模型;通过有限元仿真分析,验证了刚度模型的准确性。此外,有限元分析结果表明,提出的VSFPM机构具有较大的刚度调整范围(0.178~9.663 N/mm),为变刚度柔性夹持器设计提供了新的思路和方法。 相似文献
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A procedure for shape design sensitivity analysis is developed using a standard boundary integral equation (BIE) formulation for elliptic problems with static response. The performance functional to be considered involves both the domain and boundary integrals, and a complete consideration is given in describing the shape variation by including the tangential as well as the normal component of the velocity field. The material derivative concept and the adjoint variable method as applied to the BIE formulation are basic tools for the derivation. This has opened a new unfied approach using the BIE to the shape design sensitivity problems. 相似文献
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In this study, a topological design sensitivity of the air bearing surface (ABS) is suggested by using an adjoint variable
method. The discrete form of the generalized lubrication equation based on a control volume formulation is used as a compatible
condition. A residual function of the slider is considered as an equality constraint function, which represents the slider
in equilibrium. The slider thickness parameters at all grid cells are chosen as design variables since they are the topological
parameters determining the ABS shape. Then, a complicated adjoint variable equation is formulated to directly handle the highly
nonlinear and asymmetric coefficient matrix and vector in the discrete system equation of air-lubricated slider bearings.
An alternating direction implicit (ADI) scheme is utilized for the numerical calculation. This is an efficient iterative solver
to solve large-scale problem in special band storage. Then, a computer program is developed and applied to a slider model
of a sophisticated shape. The simulation results of design sensitivity analysis (DSA) are directly compared with those of
FDM at the randomly selected grid cells to show the effectiveness of the proposed approach. The overall distribution of DSA
results are reported, clearly showing the region on the ABS where special attention should be given during the manufacturing
process. 相似文献
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Mohamad Hamed Hekmat Masoud Mirzaei Ehsan Izadpanah 《Journal of Mechanical Science and Technology》2009,23(9):2479-2491
In this research, the continuous adjoint method is applied to optimize an airfoil in subsonic and transonic flows. An inverse
design problem is solved to evaluate the ability of the optimization algorithm and then, two types of optimizations, constrained
and non-constrained, are investigated in a drag minimization problem. In the non-constrained drag minimization problem, the
optimization is performed in a fixed angle of attack with neither geometric nor aerodynamic constraint, but in the constrained
drag minimization problem, the optimization is performed in a fixed lift coefficient. Comparison of the results of these two
optimizations shows the effects of the constraint on the optimization trend and the optimized geometry. Moreover, imposing
the aerodynamic constraint increased the computational costs of the adjoint method. In constrained and non-constrained drag
minimization problems, the surface points are adopted as design variables to show the performance of the adjoint equations
approach in problems with numerous design variables. 相似文献