Multiscale Model. Simul.最新文献_第3页

Generalized multiscale finite element method for highly heterogeneous compressible flow 高非均质可压缩流动的广义多尺度有限元方法

Multiscale Model. Simul. Pub Date : 2022-01-19 DOI: 10.1137/21m1438475

Shubin Fu, Eric T. Chung, Lina Zhao

引用次数: 1

Speckle Memory Effect in the Frequency Domain and Stability in Time-Reversal Experiments 频域散斑记忆效应与时间反转实验稳定性

Multiscale Model. Simul. Pub Date : 2022-01-14 DOI: 10.1137/22m1470414

J. Garnier, K. Sølna

{"title":"Speckle Memory Effect in the Frequency Domain and Stability in Time-Reversal Experiments","authors":"J. Garnier, K. Sølna","doi":"10.1137/22m1470414","DOIUrl":"https://doi.org/10.1137/22m1470414","url":null,"abstract":"When waves propagate through a complex medium like the turbulent atmosphere the wave field becomes incoherent and the wave intensity forms a complex speckle pattern. In this paper we study a speckle memory effect in the frequency domain and some of its consequences. This effect means that certain properties of the speckle pattern produced by wave transmission through a randomly scattering medium is preserved when shifting the frequency of the illumination. The speckle memory effect is characterized via a detailed novel analysis of the fourth-order moment of the random paraxial Green's function at four different frequencies. We arrive at a precise characterization of the frequency memory effect and what governs the strength of the memory. As an application we quantify the statistical stability of time-reversal wave refocusing through a randomly scattering medium in the paraxial or beam regime. Time reversal refers to the situation when a transmitted wave field is recorded on a time-reversal mirror then time reversed and sent back into the complex medium. The reemitted wave field then refocuses at the original source point. We compute the mean of the refocused wave and identify a novel quantitative description of its variance in terms of the radius of the time-reversal mirror, the size of its elements, the source bandwidth and the statistics of the random medium fluctuations.","PeriodicalId":313703,"journal":{"name":"Multiscale Model. Simul.","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125512418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Constraint energy minimizing generalized multiscale finite element method for inhomogeneous boundary value problems with high contrast coefficients 高对比系数非齐次边值问题的约束能量最小化广义多尺度有限元法

Multiscale Model. Simul. Pub Date : 2022-01-13 DOI: 10.1137/21m1459113

Changqing Ye, Eric T. Chung

引用次数: 2

Improved uniform error bounds on time-splitting methods for the long-time dynamics of the Dirac equation with small potentials 小势狄拉克方程长时间动力学时分裂方法的改进一致误差界

Multiscale Model. Simul. Pub Date : 2021-12-07 DOI: 10.1137/22m146995x

W. Bao, Yue Feng, Jia Yin

{"title":"Improved uniform error bounds on time-splitting methods for the long-time dynamics of the Dirac equation with small potentials","authors":"W. Bao, Yue Feng, Jia Yin","doi":"10.1137/22m146995x","DOIUrl":"https://doi.org/10.1137/22m146995x","url":null,"abstract":"We establish improved uniform error bounds on time-splitting methods for the long-time dynamics of the Dirac equation with small electromagnetic potentials characterized by a dimensionless parameter $varepsilonin (0, 1]$ representing the amplitude of the potentials. We begin with a semi-discritization of the Dirac equation in time by a time-splitting method, and then followed by a full-discretization in space by the Fourier pseudospectral method. Employing the unitary flow property of the second-order time-splitting method for the Dirac equation, we prove uniform error bounds at $C(t)tau^2$ and $C(t)(h^m+tau^2)$ for the semi-discretization and full-discretization, respectively, for any time $tin[0,T_varepsilon]$ with $T_varepsilon = T/varepsilon$ for $T>0$, which are uniformly for $varepsilon in (0, 1]$, where $tau$ is the time step, $h$ is the mesh size, $mgeq 2$ depends on the regularity of the solution, and $C(t) = C_0 + C_1varepsilon tle C_0+C_1T$ grows at most linearly with respect to $t$ with $C_0ge0$ and $C_1>0$ two constants independent of $t$, $h$, $tau$ and $varepsilon$. Then by adopting the regularity compensation oscillation (RCO) technique which controls the high frequency modes by the regularity of the solution and low frequency modes by phase cancellation and energy method, we establish improved uniform error bounds at $O(varepsilontau^2)$ and $O(h^m +varepsilontau^2)$ for the semi-discretization and full-discretization, respectively, up to the long-time $T_varepsilon$. Numerical results are reported to confirm our error bounds and to demonstrate that they are sharp. Comparisons on the accuracy of different time discretizations for the Dirac equation are also provided.","PeriodicalId":313703,"journal":{"name":"Multiscale Model. Simul.","volume":"4564 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122196346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 11

Two-scale elastic shape optimization for additive manufacturing 增材制造的双尺度弹性形状优化

Multiscale Model. Simul. Pub Date : 2021-11-29 DOI: 10.1137/21m1450859

S. Conti, M. Rumpf, Stefan Simon

{"title":"Two-scale elastic shape optimization for additive manufacturing","authors":"S. Conti, M. Rumpf, Stefan Simon","doi":"10.1137/21m1450859","DOIUrl":"https://doi.org/10.1137/21m1450859","url":null,"abstract":"In this paper, a two-scale approach for elastic shape optimization of fine-scale structures in additive manufacturing is investigated. To this end, a free material optimization is performed on the macro-scale using elasticity tensors in a set of microscopically realizable tensors. A database of these realizable tensors and their cost values is obtained with a shape and topology optimization on microscopic cells, working within a fixed set of elasticity tensors samples. This microscopic optimization takes into account manufacturability constraints via predefined material bridges to neighbouring cells at the faces of the microscopic fundamental cell. For the actual additive manufacturing on a chosen fine-scale, a piece-wise constant elasticity tensor ansatz on grid cells of a macroscopic mesh is applied. The macroscopic optimization is performed in an efficient online phase, whereas the associated cell-wise optimal material patterns are retrieved from the database that was computed offline. For that, the set of admissible realizable elasticity tensors is parametrized using tensor product cubic B-splines over the unit square matching the precomputed samples. This representation is then efficiently used in an interior point method for the free material optimization on the macro-scale.","PeriodicalId":313703,"journal":{"name":"Multiscale Model. Simul.","volume":"36 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120969465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

A Hierarchy of Network Models Giving Bistability Under Triadic Closure 三合一闭包下双稳定性网络模型的一个层次

Multiscale Model. Simul. Pub Date : 2021-11-10 DOI: 10.1137/21m1461290

Stefano Di Giovacchino, D. Higham, K. Zygalakis

引用次数: 0

Computational Modeling for High-Fidelity Coarsening of Shallow Water Equations Based on Subgrid Data 基于子网格数据的浅水方程高保真粗化计算建模

Multiscale Model. Simul. Pub Date : 2021-10-15 DOI: 10.1137/21m1452871

S. Ephrati, Erwin Luesink, G. Wimmer, P. Cifani, B. Geurts

{"title":"Computational Modeling for High-Fidelity Coarsening of Shallow Water Equations Based on Subgrid Data","authors":"S. Ephrati, Erwin Luesink, G. Wimmer, P. Cifani, B. Geurts","doi":"10.1137/21m1452871","DOIUrl":"https://doi.org/10.1137/21m1452871","url":null,"abstract":"Small-scale features of shallow water flow obtained from direct numerical simulation (DNS) with two different computational codes for the shallow water equations are gathered offline and subsequently employed with the aim of constructing a reduced-order correction. This is used to facilitate high-fidelity online flow predictions at much reduced costs on coarse meshes. The resolved small-scale features at high resolution represent subgrid properties for the coarse representation. Measurements of the subgrid dynamics are obtained as the difference between the evolution of a coarse grid solution and the corresponding DNS result. The measurements are sensitive to the particular numerical methods used for the simulation on coarse computational grids and can be used to approximately correct the associated discretization errors. The subgrid features are decomposed into empirical orthogonal functions (EOFs), after which a corresponding correction term is constructed. By increasing the number of EOFs in the approximation of the measured values the correction term can in principle be made arbitrarily accurate. Both computational methods investigated here show a significant decrease in the simulation error already when applying the correction based on the dominant EOFs only. The error reduction accounts for the particular discretization errors that incur and are hence specific to the particular simulation method that is adopted. This improvement is also observed for very coarse grids which may be used for computational model reduction in geophysical and turbulent flow problems.","PeriodicalId":313703,"journal":{"name":"Multiscale Model. Simul.","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129254939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

The Narrow Capture Problem with Partially Absorbing Targets and Stochastic Resetting 目标部分吸收和随机重置的窄捕获问题

Multiscale Model. Simul. Pub Date : 2021-10-13 DOI: 10.1137/21m1449580

P. Bressloff, Ryan D. Schumm

引用次数: 5

The Heterogeneous Multiscale Method for dispersive Maxwell systems 色散Maxwell系统的非均质多尺度方法

Multiscale Model. Simul. Pub Date : 2021-10-04 DOI: 10.1137/21M1443960

P. Freese

引用次数: 1

NonReciprocal Wave Propagation in Space-Time Modulated Media 时空调制介质中的非互反波传播

Multiscale Model. Simul. Pub Date : 2021-09-15 DOI: 10.1137/21m1449427

H. Ammari, Jinghao Cao, Erik Orvehed Hiltunen

引用次数: 7