Journal of Computational Physics: X最新文献

Relative acceleration of orthonormal basis vectors for the geometric conduction blocks of the cardiac electric signal propagation on anisotropic curved surfaces 各向异性曲面上心电信号几何传导块正交基向量的相对加速度

Journal of Computational Physics: X Pub Date : 2023-11-01 DOI: 10.1016/j.jcpx.2023.100135

Sehun Chun

{"title":"Relative acceleration of orthonormal basis vectors for the geometric conduction blocks of the cardiac electric signal propagation on anisotropic curved surfaces","authors":"Sehun Chun","doi":"10.1016/j.jcpx.2023.100135","DOIUrl":"10.1016/j.jcpx.2023.100135","url":null,"abstract":"<div><p>Geometric conduction blocks stop cardiac electric propagation due to the shape or conductivity properties of the domain. The blocks are considered to cause many abnormal cardiac electric propagations, leading to cardiac electrophysiological pathologies, such as cardiac fibrillation and arrhythmia. Locating such multidimensional conduction blocks is challenging, particularly in a complex domain with a complex shape and strong anisotropy, such as the heart. To address this problem, we propose a novel mathematical model of the geometric conduction block using the relative acceleration adopted from space-time physics. An efficient numerical scheme for the mathematical model is also proposed to predict the unidirectional conduction block effectively, even in a complex domain. The relative acceleration in the cardiac electric propagation corresponds to the sink-source relationship between the excited (after repolarization) and excitable (before depolarization) cardiac cells, representing the geometric growth rate of the volume of metric balls. The trajectory is constructed from the wavefront of diffusion-reaction equations by aligning orthonormal basis vectors along the gradient of the action potential. Relative acceleration is computed along the propagational direction from the connection 1-form of the basis vectors. The proposed mathematical model and numerical scheme are applied to demonstrate geometric conduction blocks in two-dimensional (2D) simple curved domains with strong anisotropy.</p></div>","PeriodicalId":37045,"journal":{"name":"Journal of Computational Physics: X","volume":"17 ","pages":"Article 100135"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590055223000136/pdfft?md5=ab2847b27f86f9bb7689e05fdaa1d88d&pid=1-s2.0-S2590055223000136-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Monte Carlo radiative transfer peel off mechanism for spatially extended detectors 空间扩展探测器的蒙特卡罗辐射传递剥离机制

Journal of Computational Physics: X Pub Date : 2023-11-01 DOI: 10.1016/j.jcpx.2023.100132

Christian Peest, Oliver Reich, Lena Bressel

引用次数: 0

Ensemble transport smoothing. Part I: Unified framework 集合输运平滑。第一部分:统一框架

Journal of Computational Physics: X Pub Date : 2023-11-01 DOI: 10.1016/j.jcpx.2023.100134

Maximilian Ramgraber , Ricardo Baptista , Dennis McLaughlin , Youssef Marzouk

{"title":"Ensemble transport smoothing. Part I: Unified framework","authors":"Maximilian Ramgraber , Ricardo Baptista , Dennis McLaughlin , Youssef Marzouk","doi":"10.1016/j.jcpx.2023.100134","DOIUrl":"10.1016/j.jcpx.2023.100134","url":null,"abstract":"<div><p>Smoothers are algorithms for Bayesian time series re-analysis. Most operational smoothers rely either on affine Kalman-type transformations or on sequential importance sampling. These strategies occupy opposite ends of a spectrum that trades computational efficiency and scalability for statistical generality and consistency: non-Gaussianity renders affine Kalman updates inconsistent with the true Bayesian solution, while the ensemble size required for successful importance sampling can be prohibitive. This paper revisits the smoothing problem from the perspective of measure transport, which offers the prospect of consistent prior-to-posterior transformations for Bayesian inference. We leverage this capacity by proposing a general ensemble framework for transport-based smoothing. Within this framework, we derive a comprehensive set of smoothing recursions based on nonlinear transport maps and detail how they exploit the structure of state-space models in fully non-Gaussian settings. We also describe how many standard Kalman-type smoothing algorithms emerge as special cases of our framework. A companion paper <span>[35]</span> explores the implementation of nonlinear ensemble transport smoothers in greater depth.</p></div>","PeriodicalId":37045,"journal":{"name":"Journal of Computational Physics: X","volume":"17 ","pages":"Article 100134"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590055223000124/pdfft?md5=5628d601649f468d0e56d36b3987da03&pid=1-s2.0-S2590055223000124-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Ensemble transport smoothing. Part II: Nonlinear updates 整体传输平滑。第二部分:非线性更新

Journal of Computational Physics: X Pub Date : 2023-11-01 DOI: 10.1016/j.jcpx.2023.100133

Maximilian Ramgraber , Ricardo Baptista , Dennis McLaughlin , Youssef Marzouk

引用次数: 3

The 3D Elliptical Parcel-In-Cell (EPIC) method 三维椭圆单元包(EPIC)方法

Journal of Computational Physics: X Pub Date : 2023-11-01 DOI: 10.1016/j.jcpx.2023.100136

Matthias Frey , David Dritschel , Steven Böing

{"title":"The 3D Elliptical Parcel-In-Cell (EPIC) method","authors":"Matthias Frey , David Dritschel , Steven Böing","doi":"10.1016/j.jcpx.2023.100136","DOIUrl":"https://doi.org/10.1016/j.jcpx.2023.100136","url":null,"abstract":"<div><p>We present the three-dimensional version of the Elliptical Parcel-In-Cell (EPIC) method for the simulation of fluid flows and analogous continuum systems. The method represents a flow using a space-filling set of ellipsoidal parcels, which move, rotate and deform in the flow field. Additionally, parcels may carry any number of attributes, such as vorticity, density, temperature, etc, which generally evolve in time on the moving parcels. An underlying grid is used for efficiency in computing the velocity field from the interpolated vorticity field, and in obtaining parcel attribute tendencies. Mixing is enabled by permitting parcels to split when excessively deformed, and by merging very small parcels with the nearest other parcel. Several tests are provided which illustrate the behaviour of the method and demonstrate its effectiveness in modelling complex, buoyancy-driven turbulent fluid flows. The results are compared with a large eddy simulation (LES) and a direct numerical simulation (DNS) model.</p></div>","PeriodicalId":37045,"journal":{"name":"Journal of Computational Physics: X","volume":"17 ","pages":"Article 100136"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590055223000148/pdfft?md5=b80b927c5faff1329ce80f89f5b41be0&pid=1-s2.0-S2590055223000148-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138413547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Efficient variable cell shape geometry optimization 高效的可变单元格形状几何优化

Journal of Computational Physics: X Pub Date : 2023-07-25 DOI: 10.1016/j.jcpx.2023.100131

Moritz Gubler, Marco Krummenacher, Hannes Huber, Stefan Goedecker

引用次数: 2

Fast hierarchical low-rank view factor matrices for thermal irradiance on planetary surfaces 行星表面热辐照度的快速分层低阶视图因子矩阵

Journal of Computational Physics: X Pub Date : 2023-07-22 DOI: 10.1016/j.jcpx.2023.100130

Samuel F. Potter , Stefano Bertone , Norbert Schörghofer , Erwan Mazarico

{"title":"Fast hierarchical low-rank view factor matrices for thermal irradiance on planetary surfaces","authors":"Samuel F. Potter , Stefano Bertone , Norbert Schörghofer , Erwan Mazarico","doi":"10.1016/j.jcpx.2023.100130","DOIUrl":"https://doi.org/10.1016/j.jcpx.2023.100130","url":null,"abstract":"<div><p>We present an algorithm for compressing the radiosity view factor model commonly used in radiation heat transfer and computer graphics. We use a format inspired by the hierarchical off-diagonal low rank format, where elements are recursively partitioned using a quadtree or octree and blocks are compressed using a sparse singular value decomposition—the hierarchical matrix is assembled using dynamic programming. The motivating application is time-dependent thermal modeling on vast planetary surfaces, with a focus on permanently shadowed craters which receive energy through indirect irradiance. In this setting, shape models are comprised of a large number of triangular facets which conform to a rough surface. At each time step, a quadratic number of triangle-to-triangle scattered fluxes must be summed; that is, as the sun moves through the sky, we must solve the same view factor system of equations for a potentially unlimited number of time-varying righthand sides. We first conduct numerical experiments with a synthetic spherical cap-shaped crater, where the equilibrium temperature is analytically available. We also test our implementation with triangle meshes of planetary surfaces derived from digital elevation models recovered by orbiting spacecraft. Our results indicate that the compressed view factor matrix can be assembled in quadratic time, which is comparable to the time it takes to assemble the full view matrix itself. Memory requirements during assembly are reduced by a large factor. Finally, for a range of compression tolerances, the size of the compressed view factor matrix and the speed of the resulting matrix vector product both scale linearly (as opposed to quadratically for the full matrix), resulting in orders of magnitude savings in processing time and memory space.</p></div>","PeriodicalId":37045,"journal":{"name":"Journal of Computational Physics: X","volume":"17 ","pages":"Article 100130"},"PeriodicalIF":0.0,"publicationDate":"2023-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50191210","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: 0

A conformal mapping approach to modelling two-dimensional stratified flow 二维分层流建模的保角映射方法

Journal of Computational Physics: X Pub Date : 2023-06-02 DOI: 10.1016/j.jcpx.2023.100129

Heidi J. Dritschel , David G. Dritschel , Magda Carr

{"title":"A conformal mapping approach to modelling two-dimensional stratified flow","authors":"Heidi J. Dritschel , David G. Dritschel , Magda Carr","doi":"10.1016/j.jcpx.2023.100129","DOIUrl":"https://doi.org/10.1016/j.jcpx.2023.100129","url":null,"abstract":"<div><p>Herein we describe a new approach to modelling inviscid two-dimensional stratified flows in a general domain. The approach makes use of a conformal map of the domain to a rectangle. In this transformed domain, the equations of motion are largely unaltered, and in particular Laplace's equation remains unchanged. This enables one to construct exact solutions to Laplace's equation and thereby enforce all boundary conditions.</p><p>An example is provided for two-dimensional flow under the Boussinesq approximation, though the approach is much more general (albeit restricted to two-dimensions). This example is motivated by flow under a weir in a tidal estuary. Here, we discuss how to use a dynamically-evolving conformal map to model changes in the water height on either side of the weir, though the example presented keeps these heights fixed due to limitations in the computational speed to generate the conformal map.</p><p>The numerical approach makes use of contour advection, wherein material buoyancy contours are advected conservatively by the local fluid velocity, while a dual contour-grid representation is used for the vorticity in order to account for vorticity generation from horizontal buoyancy gradients. This generation is accurately estimated by using the buoyancy contours directly, rather than a gridded version of the buoyancy field. The result is a highly-accurate, efficient numerical method with extremely low levels of numerical damping.</p></div>","PeriodicalId":37045,"journal":{"name":"Journal of Computational Physics: X","volume":"17 ","pages":"Article 100129"},"PeriodicalIF":0.0,"publicationDate":"2023-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50191213","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: 0

Numerical simulation of temperature-driven free surface flows, with application to laser melting and polishing 温度驱动自由表面流动的数值模拟及其在激光熔化和抛光中的应用

Journal of Computational Physics: X Pub Date : 2023-06-01 DOI: 10.1016/j.jcpx.2023.100127

Alexandre Caboussat , Julien Hess , Alexandre Masserey , Marco Picasso

引用次数: 2

Natural grid stretching for DNS of compressible wall-bounded flows 可压缩壁有界流DNS的自然网格拉伸

Journal of Computational Physics: X Pub Date : 2023-05-30 DOI: 10.1016/j.jcpx.2023.100128

Alessandro Ceci, Sergio Pirozzoli

引用次数: 0