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Fast Simulation of Wheel-Rail Contact Using Proper Generalized Decomposition 基于适当广义分解的轮轨接触快速仿真
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.073
C. Ansin, F. Larsson, R. Larsson, M. Ekh, B. Pålsson
Degradation of the railhead in curved tracks caused by high lateral contact forces between wheel and rail is associated with high maintenance costs, which motivates the need for predictive methodologies. The damage mechanisms include plastic deformation, wear, and surface (or subsurface) initiated cracks due to rolling contact fatigue (RCF). Numerical computations of the long-term evolution and degradation of the rail head are computationally demanding due to a large number of load cycles, large variation in vehicle loads and wheel rim geometries. An existing framework [1] considers feed-back loops between dynamic vehicle-track interaction, elastic-plastic wheel-rail contact, and accumulated rail damage due to plasticity and surface wear to update the rail profile. In this work however, the contact simulation and the subsequent analysis of the evolution of plastic deformation is restricted to a meta-modeling strategy in 2D in order to reduce the computational cost. To increase computational efficiency, we adopt the Proper Generalized Decomposition (PGD) to solve a reduced order problem for each load cycle. In order to model the 3D contact situation, the rail cross section is modeled in 2D, while the coordinate along the rail constitutes a parameter in the PGD approximation. Furthermore, the varying contact load, predicted from dynamic train-track simulations, is parametrized in terms of spatial distribution. In addition to formulating the problem, we discuss and evaluate the accuracy and efficiency of the proposed strategy through a set of verification examples for elastic contact under varying traffic loads. Finally, we also discuss the outlook towards elastic-plastic simulations.
由于车轮和钢轨之间的侧向接触力大,弯曲轨道中轨道头的退化与高维护成本有关,这激发了对预测方法的需求。损伤机制包括塑性变形、磨损和由滚动接触疲劳(RCF)引起的表面(或次表面)裂纹。由于载荷循环次数多,车辆载荷变化大,轮辋几何形状变化大,钢轨头部长期演化和退化的数值计算要求很高。现有的框架[1]考虑了车辆-轨道动态相互作用、弹塑性轮轨接触以及由于塑性和表面磨损导致的轨道累积损伤之间的反馈回路来更新轨道轮廓。然而,在这项工作中,接触模拟和塑性变形演变的后续分析仅限于二维元建模策略,以减少计算成本。为了提高计算效率,我们采用适当的广义分解(PGD)来解决每个负载周期的降阶问题。为了模拟三维接触情况,将钢轨截面建模为二维,而沿钢轨的坐标构成PGD近似中的一个参数。此外,根据动态列车轨道模拟预测的接触载荷变化,根据空间分布参数化。除了提出问题外,我们还通过一组不同交通负载下的弹性接触验证实例来讨论和评估所提出策略的准确性和效率。最后,我们还讨论了弹塑性模拟的发展前景。
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引用次数: 0
A Posteriori Error Estimation and Adaptivity for Second-Order Optimally Convergent G/XFEM and FEM 二阶最优收敛G/XFEM和FEM的后验误差估计和自适应
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.042
M. E. Bento, S. Proença, C. Duarte
The Generalized/eXtended Finite Element Method (G/XFEM) is known to efficiently and accurately solve problems that are challenging for standard methodologies. The method can deliver optimal convergence rates in the energy norm and global matrices with a scaled condition number that has the same order as in the Finite Element Method (FEM). This is achieved even for problems of Linear Elastic Fracture Mechanics (LEFM), which have solutions containing singularities and discontinuities. Despite delivering optimal convergence rates, it has been shown [1], however, that first-order G/XFEM are not competitive with second-order FEM that uses quarter-point elements, especially for three-dimensional (3-D) problems. Because of this, optimally convergent second-order G/XFEM, customized to solve LEFM problems, have been recently proposed [1, 2, 3]. The formulations presented in these works augment both standard lagrangian FEM approximation spaces [3] and p FEM approximation spaces [1, 2] in order to insert into the G/XFEM numerical approximation the discontinuous and singular behaviors of fractures. It is important to note that, in addition to using enrichment functions, G/XFEM still needs local mesh refinement around crack fronts in order to achieve optimal convergence. This must be considered especially for 3-D problems that violate the assumptions of the adopted singular enrichments. While this local mesh refinement can be easily performed for simple cases, the level of refinement
广义/扩展有限元法(G/XFEM)以高效、准确地解决标准方法难以解决的问题而闻名。该方法在能量范数和全局矩阵上具有最优的收敛速度,且条件数与有限元法具有相同的阶数。即使对于具有包含奇异点和不连续点的解的线弹性断裂力学(LEFM)问题,也可以实现这一点。尽管提供了最佳的收敛速度,但已经证明[1],一阶G/XFEM与使用四分之一点单元的二阶FEM没有竞争力,特别是对于三维(3-D)问题。正因为如此,最近提出了最优收敛的二阶G/XFEM,专门用于解决LEFM问题[1,2,3]。这些工作中提出的公式扩充了标准拉格朗日有限元近似空间[3]和p有限元近似空间[1,2],以便在G/XFEM数值近似中插入断裂的不连续和奇异行为。值得注意的是,除了使用富集函数外,G/XFEM还需要在裂缝前缘周围进行局部网格细化,以实现最优收敛。对于违反所采用的奇异富集假设的三维问题,必须特别考虑这一点。虽然这种局部网格细化可以很容易地执行简单的情况下,细化的水平
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引用次数: 0
Adaptive mixed isogeometric analysis of a highly convective benchmark problem for the Boussinesq equations 高对流Boussinesq方程基准问题的自适应混合等几何分析
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.045
Abdullah Abdulhaque¹, Trond Kvamsdal, Mukesh Kumar, A. Kvarving
In this article, we study a special benchmark problem for the Boussinesq equations. This is the Navier-Stokes equations coupled with the Advection-Diffusion equation, and it is used for modelling buoyancy-driven flow. The solution process is mixed isogeometric discretization combined with adaptive mesh refinement [4]. We discretize the equation system with the recently proposed isogeometric versions of the Taylor-Hood, Sub-Grid and Raviart-Thomas elements [1]. The adaptive refinement is based on LR B-splines [2] and recovery estimators [3]. We investigate the suitability of our adaptive methods for Rayleigh numbers in the range 10 1 -10 5 , by comparing with high-resolution reference solution.
本文研究了一类特殊的Boussinesq方程的基准问题。这是Navier-Stokes方程与平流-扩散方程的耦合,它用于模拟浮力驱动的流动。求解过程采用混合等几何离散化与自适应网格细化相结合的方法[4]。我们用最近提出的Taylor-Hood、Sub-Grid和Raviart-Thomas单元的等几何版本对方程组进行离散化[1]。自适应细化是基于LR b样条[2]和恢复估计[3]。通过与高分辨率参考溶液的比较,我们研究了我们的自适应方法在10 1 -10 5范围内的瑞利数的适用性。
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引用次数: 0
An Efficient hp-Adaptive Approach for Compressible Two-Phase Flows using the Level-Set Ghost Fluid Method 基于水平集鬼流法的可压缩两相流的高效hp自适应方法
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.039
P. Mossier, D. Appel, A. Beck, C. Munz
We present an efficient hp-adaptive discretization for sharp interface simulations of compressible two-phase flows using the level-set ghost fluid method. The discretization employs a high order p-adaptive Discontinuous Galerkin (DG) scheme in regions of high regularity, whereas discontinuities are captured by a more robust Finite Volume (FV) scheme on an element-local sub-grid. The h-refinement strategy effectively carries over the subscale resolution capability of the DG scheme to shocks and the phase interface, while preserving an essentially non-oscillatory behavior of the solution. The p-refinement and the FV-limiting are controlled by a common indicator that evaluates the modal decay of the solution polynomials. The resulting adaptive hybrid DG/FV operator is used for the governing equations of both, the fluid flow and the level-set transport. However, the hp-adaptive discretization, together with solving the computationally expensive level-set equations only in the vicinity of the phase interface, causes pronounced variations in the element costs throughout the domain. In parallel computations, these variations imply a significant workload imbalance among the processor units. To ensure parallel scalability, the proposed discretization thus needs to be complemented by a dynamic load balancing (DLB) approach. We introduce a DLB scheme that determines the current workload distribution accurately through element-local walltime measurements and repartitions the elements efficiently along a space-filling curve. We provide strong scaling results to underline the parallel efficiency of the presented hp-adaptive sharp interface framework. Moreover, complex benchmark problems demonstrate that it handles efficiently and accurately the inherent multiscale physics of compressible two-phase flows.
本文提出了一种有效的高自适应离散化方法,用于可压缩两相流的尖锐界面模拟。在高正则性区域采用高阶p自适应间断伽辽金(DG)格式进行离散化,而在单元局部子网格上采用更鲁棒的有限体积(FV)格式进行离散化。h-细化策略有效地保留了DG方案对冲击和相界面的亚尺度分辨率能力,同时保留了溶液的基本非振荡行为。p-细化和fv限制是由一个共同的指标来控制的,该指标评估了解多项式的模态衰减。所得到的自适应混合DG/FV算子用于流体流动和水平集输运的控制方程。然而,高自适应离散化,加上只在相位界面附近求解计算昂贵的水平集方程,导致整个域内元件成本的显著变化。在并行计算中,这些变化意味着处理器单元之间存在显著的工作负载不平衡。为了确保并行可扩展性,所提出的离散化因此需要辅以动态负载平衡(DLB)方法。我们介绍了一种DLB方案,该方案通过测量元素本地的运行时间准确地确定当前的工作负载分布,并沿着空间填充曲线有效地重新划分元素。我们提供了强大的缩放结果来强调所提出的hp自适应锐接口框架的并行效率。此外,复杂的基准问题表明,该方法能够有效、准确地处理可压缩两相流固有的多尺度物理特性。
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引用次数: 0
Verifying and applying LES-C turbulence models for turbulent incompressible flow and fluid-fluid interaction problems LES-C湍流模型在湍流不可压缩流动和流体-流体相互作用问题中的验证与应用
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.040
Mustafa Aggul, Yasasya Batugedara, A. Labovsky, Eda Onal, J. Kyle, Schwiebert
The large eddy simulation (LES) models for incompressible flow have found wide application in computational fluid dynamics (CFD), including areas relevant to aeronautics such as computing drag and lift coefficients and fluid-structure interaction problems [1, 2]. LES models have also found application in climate science through modeling fluid-fluid (atmosphere-ocean) problems. Large eddy simulation with correction (LES-C) turbulence models, introduced in 2020, are a new class of turbulence models which rely on defect correction to build a high-accuracy turbulence model on top of any existing LES model [3, 4, 5]. LES-C models have two additional benefits worth serious consideration. First, LES-C models are easy to run in parallel: One processor can compute the defect (LES) solution, while the other processor computes the LES-C solution. Thus, if one has access to a machine with more than one computational core (essentially ubiquitous in modern architectures), the improved solution comes at nearly no cost in terms of the “wall time” it takes a simulation to complete. Second, LES-C models readily lend themselves to coupling with other
不可压缩流动的大涡模拟(LES)模型在计算流体动力学(CFD)中得到了广泛的应用,包括与航空相关的领域,如计算阻力和升力系数以及流固耦合问题[1,2]。LES模式还通过模拟流体-流体(大气-海洋)问题在气候科学中得到应用。大涡模拟校正(Large eddy simulation with correction, LES- c)湍流模型是2020年推出的一类新的湍流模型,它依靠缺陷校正在现有的LES模型之上建立高精度的湍流模型[3,4,5]。LES-C模型还有两个值得认真考虑的额外好处。首先,LES- c模型很容易并行运行:一个处理器可以计算缺陷(LES)解决方案,而另一个处理器计算LES- c解决方案。因此,如果您可以访问具有多个计算核心的机器(在现代体系结构中基本上无处不在),则改进的解决方案几乎不需要花费模拟完成的“墙时间”。其次,LES-C模型很容易与其他模型耦合
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引用次数: 0
On the Use of Neural Networks for Inverse Problems 神经网络在反问题中的应用
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.018
L. Herrmann, T. Bürchner, S. Kollmannsberger
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引用次数: 0
A Convergence Proof for Adaptive Parametric PDEs with Unbounded Coefficients 系数无界自适应参数偏微分方程的收敛性证明
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.005
N. Farchmin, M. Eigel
Numerical methods for random parametric PDEs can greatly benefit from adaptive refinement schemes, in particular when functional approximations are computed as in stochastic Galerkin methods with residual based error estimation. From the mathematical side, especially when the coefficients of the PDE are unbounded, solvability is difficult to prove and numerical approximations face numerous challenges. In this talk we generalize the adaptive refinement scheme for elliptic parametric PDEs introduced in [1, 2] to unbounded (lognormal) diffusion coefficients [3]. The algorithm is guided by a reliable error estimator which steers both the refinement of the spacial finite element mesh and the enlargement of the stochastic approximation space. As the algorithm relies solely on (a sufficiently good approximation of) the Galerkin projection of the PDE solution and the PDE coefficient, it can be used in a non-intrusively manner, allowing for applications in many different settings. We prove that the proposed algorithm converges and even show evidence that similar convergence rates as for intrusive approaches can be observed.
随机参数偏微分方程的数值方法可以极大地受益于自适应改进方案,特别是当计算函数逼近时,如基于残差误差估计的随机伽辽金方法。从数学角度看,特别是当偏微分方程系数无界时,其可解性难以证明,数值逼近面临诸多挑战。在本演讲中,我们将[1,2]中引入的椭圆参数偏微分方程的自适应改进方案推广到无界(对数正态)扩散系数[3]。该算法以可靠的误差估计量为指导,既指导了空间有限元网格的细化,又指导了随机逼近空间的扩大。由于该算法仅依赖于PDE解和PDE系数的Galerkin投影(足够好的近似值),因此可以以非侵入式的方式使用,允许在许多不同的环境中应用。我们证明了所提出的算法是收敛的,甚至表明可以观察到与入侵方法相似的收敛速度。
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引用次数: 0
Space-Time Goal Oriented Error Estimation and Adaptivity for Discretization and Reduced Order Modeling Errors 面向空时目标的误差估计与自适应离散化与降阶建模误差
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.026
J. Roth, H. Fischer, J. Thiele, U. Köcher, A. Fau, L. Chamoin, T. Wick
In this presentation, we present a uniform framework in which the dual-weighted residual (DWR) method is used for spatial and temporal discretization error control [1], as well as the control of the reduced order modeling error for the proper orthogonal decomposition (POD). In the first part of this presentation, the DWR method is applied to a space-time formulation of non-stationary Navier-Stokes flow. Tensor-product space-time finite elements are being used to discretize the variational formulation with discontinuous Galerkin finite elements in time and inf-sup stable Taylor-Hood finite element pairs in space. To estimate the error in a quantity of interest and drive adaptive refinement in time and space, we demonstrate how the DWR method for incompressible flow [2] can be extended to a partition of unity based error localization [3, 4]. Our methodology is being substantiated on the two dimensional flow around a cylinder benchmark problem. In the second
在本报告中,我们提出了一个统一的框架,其中双加权残差(DWR)方法用于时空离散化误差控制[1],以及适当正交分解(POD)的降阶建模误差控制。在本报告的第一部分,DWR方法应用于非平稳Navier-Stokes流的时空公式。用张量积空时有限元在时间上离散不连续的Galerkin有限元,在空间上离散不稳定的Taylor-Hood有限元对。为了估计感兴趣量的误差并在时间和空间上驱动自适应改进,我们演示了不可压缩流的DWR方法[2]如何扩展到基于单位的误差定位划分[3,4]。我们的方法在圆柱体周围的二维流动基准问题上得到了证实。在第二个
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引用次数: 0
Adaptive mesh refinement procedures for the virtual element method 自适应网格细化程序的虚元法
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.064
D. van Huyssteen, F. López-Rivarola, G. Etse, P. Steinmann
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引用次数: 0
A posteriori error estimates of elliptic and parabolic equations for the weak Galerkin finite element methods 弱伽辽金有限元法椭圆型和抛物型方程的后验误差估计
Pub Date : 1900-01-01 DOI: 10.23967/admos.2023.043
Y. Nie, Y. Liu
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引用次数: 0
期刊
XI International Conference on Adaptive Modeling and Simulation
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