Journal of Computational Physics最新文献

{"title":"On a two-phase incompressible diffuse interface fluid model with curvature-dependent mobility","authors":"Junxiang Yang ,&nbsp;Junseok Kim","doi":"10.1016/j.jcp.2025.113764","DOIUrl":"10.1016/j.jcp.2025.113764","url":null,"abstract":"<div><div>A mass-conserved diffuse interface two-phase fluid model is developed to capture more fluid details without introducing a large number of meshes. The original Cahn–Hilliard (CH) model satisfies the energy dissipation law by minimizing the total length of the interface. Although the total mass is conserved, the original CH dynamics will lead to the local mass loss of small fluids. The traditional approaches for fixing the local mass loss are to increase the number of mesh grids and to utilize the adaptive mesh refinement technique. However, these approaches either require significant computational time or increase the difficulty in numerical implementation. To reduce the local mass loss with the same computational resources, we propose a curvature-dependent mobility. In the regions with large curvature, this mobility minimizes the shrinking dynamics of the interface in the diffuse interface. In regions with small curvature, this mobility only minimizes the interfacial dynamics on the fluid interface. Since the new mobility is always nonnegative, the proposed model still satisfies the total mass conservation and energy dissipation property. Compared with the original CH model, the present model has better capability for local mass conservation. For two-phase fluid flow problems where the density and viscosity ratios are equal, we develop a linear, second-order accurate, and energy-stable time-marching scheme. The leap-frog-type method is adopted to discretize the proposed CH model in time and the simplified auxiliary variable method with correction is used to discretize the incompressible Navier–Stokes equations in time. We name this new scheme the leap-frog-auxiliary-variable (LFAV) method. For an arbitrary time step, we analytically prove the time-discretized energy stability. In each time step, we only need to separately solve several parabolic equations for the velocities, a Poisson equation for pressure, and a parabolic equation with variable coefficients for the phase-field variable. Several numerical experiments have been performed to validate the accuracy, stability, and capability of interface capturing of the developed model and method. The proposed model is further extended to simulate a dam break in three-dimensional space. The numerical results show that this new model has good potential in capturing large fluid deformation and small splashing liquids.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113764"},"PeriodicalIF":3.8,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A front-tracking immersed-boundary framework for simulating Lagrangian melting problems","authors":"Kevin Zhong ,&nbsp;Christopher J. Howland ,&nbsp;Detlef Lohse ,&nbsp;Roberto Verzicco","doi":"10.1016/j.jcp.2025.113762","DOIUrl":"10.1016/j.jcp.2025.113762","url":null,"abstract":"<div><div>In so-called Lagrangian melting problems, a solid immersed in a fluid medium is free to rotate and translate in tandem with its phase-change from solid to liquid. Such configurations may be classified as a fluid-solid interaction (FSI) problem coupled to phase-change. Our present work proposes a numerical method capable of simulating these Lagrangian melting problems and adopts a front-tracking immersed-boundary (IB) method. We use the moving least squares IB framework, a well-established method for simulating a diverse range of FSI problems <span><span>[1]</span></span>, <span><span>[2]</span></span> and extend this framework to accommodate melting by additionally imposing the Stefan condition at the interface. In the spirit of canonical front-tracking methods, the immersed solid is represented by a discrete triangulated mesh which is separate from the Eulerian mesh in which the governing flow equations are solved. A known requirement for these methods is the need for comparable Eulerian and Lagrangian grid spacings to stabilise interpolation and spreading operations between the two grids. For a melting object, this requirement is inevitably violated unless interventional remeshing is introduced. Our work therefore presents a novel dynamic remeshing procedure to overcome this. The remeshing is based on a gradual coarsening of the triangulated Lagrangian mesh and amounts to a negligible computational burden per timestep owing to the incremental and local nature of its operations, making it a scalable approach. Moreover, the coarsening is coupled to a volume-conserving smoothing procedure detailed by Kuprat et al. <span><span>[3]</span></span>, ensuring a zero net volume change in the remeshing step to machine precision. This added feature makes our present method highly specialised to the study of melting problems, where precise measurements of the melting solid's volume is often the primary predictive quantity of interest.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113762"},"PeriodicalIF":3.8,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of the forcing and sub-filter scale terms in the volume-filtering immersed boundary method","authors":"Himanshu Dave ,&nbsp;Marcus Herrmann ,&nbsp;Peter Brady ,&nbsp;M. Houssem Kasbaoui","doi":"10.1016/j.jcp.2025.113765","DOIUrl":"10.1016/j.jcp.2025.113765","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We present a characterization of the forcing and sub-filter scale terms produced in the volume-filtering immersed boundary (VF-IB) method by Dave et al. &lt;span&gt;&lt;span&gt;[5]&lt;/span&gt;&lt;/span&gt;. The process of volume-filtering produces bodyforces in the form of surface integrals to describe the boundary conditions at the interface. Furthermore, the approach also produces unclosed terms called &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. The level of contribution from &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; on the numerical solution depends on the filter width &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. In order to understand these terms better we take a 2 dimensional, varying coefficient hyperbolic equation shown by Brady and Livescu &lt;span&gt;&lt;span&gt;[3]&lt;/span&gt;&lt;/span&gt;. This case is chosen for two reasons. First, the case involves 2 distinct regions separated by an interface, making it an ideal case for the VF-IB method. Second, an existing analytical solution allows us to properly investigate the contribution from &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; for varying &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. The filter width controls how well resolved the interface is. The smaller the filter width, the more resolved the interface will be. A thorough numerical analysis of the method is presented, as well as the effect of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; on the numerical solution. In order to perform a direct comparison, the numerical solution is compared to the filtered analytical solution. Through this we highlight three important points. First, we present a methodical approach to volume filtering a hyperbolic PDE. Second, we show that the VF-IB method exhibits second order convergence with respect to decreasing &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (i.e. making the interface sharper). Finally, we show that &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; scales with &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;. Large filter widths would require a modeling approach to sufficiently resolve &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. However for finer filter widths that have a sufficiently sharp interface, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;sfs&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; can be ignored without any significant reduction in the accuracy of solution. We show that through the inclusion of these unclosed terms, the VF-IB method can bridge the gap between fully modeled and fully resolved methods by providing accurate results when the filter width is of the same ord","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113765"},"PeriodicalIF":3.8,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Projected Langevin Monte Carlo algorithms in non-convex and super-linear setting","authors":"Chenxu Pang ,&nbsp;Xiaojie Wang ,&nbsp;Yue Wu","doi":"10.1016/j.jcp.2025.113754","DOIUrl":"10.1016/j.jcp.2025.113754","url":null,"abstract":"&lt;div&gt;&lt;div&gt;It is of significant interest in many applications to sample from a high-dimensional target distribution &lt;em&gt;π&lt;/em&gt; with the density &lt;span&gt;&lt;math&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mtext&gt;d&lt;/mtext&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;∝&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mtext&gt;d&lt;/mtext&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;, based on the temporal discretization of the Langevin stochastic differential equations (SDEs). In this paper, we propose an explicit projected Langevin Monte Carlo (PLMC) algorithm with non-convex potential &lt;em&gt;U&lt;/em&gt; and super-linear gradient of &lt;em&gt;U&lt;/em&gt; and investigate the non-asymptotic analysis of its sampling error in total variation distance. Equipped with time-independent regularity estimates for the associated Kolmogorov equation, we derive the non-asymptotic bounds on the total variation distance between the target distribution of the Langevin SDEs and the law induced by the PLMC scheme with order &lt;span&gt;&lt;math&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;max&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mi&gt;ln&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;em&gt;d&lt;/em&gt; is the dimension of the target distribution and &lt;span&gt;&lt;math&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt; characterizes the growth of the gradient of &lt;em&gt;U&lt;/em&gt;. In addition, if the gradient of &lt;em&gt;U&lt;/em&gt; is globally Lipschitz continuous, an improved convergence order of &lt;span&gt;&lt;math&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; for the classical Langevin Monte Carlo (LMC) scheme is derived with a refinement of the proof based on Malliavin calculus techniques. To achieve a given precision &lt;em&gt;ϵ&lt;/em&gt;, the smallest number of iterations of the PLMC algorithm is proved to be of order &lt;span&gt;&lt;math&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;max&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;mo&gt;⋅&lt;/mo&gt;&lt;mi&gt;ln&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;⋅&lt;/mo&gt;&lt;mi&gt;ln&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;. In particular, the classical Langevin Monte Carlo (LMC) scheme with the non-convex potential &lt;em&gt;U&lt;/em&gt; and the globally Lipschitz gradient of &lt;em&gt;U&lt;/em&gt; can be guaranteed by order &lt;span&gt;&lt;math&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;mo&gt;⋅&lt;/mo&gt;&lt;mi&gt;ln&lt;/mi&gt;&lt;mo&gt;⁡&lt;/mo&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;. Numerical experim","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"526 ","pages":"Article 113754"},"PeriodicalIF":3.8,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regularized reduced order Lippmann-Schwinger-Lanczos method for inverse scattering problems in the frequency domain","authors":"J. Baker ,&nbsp;E. Cherkaev ,&nbsp;V. Druskin ,&nbsp;S. Moskow ,&nbsp;M. Zaslavsky","doi":"10.1016/j.jcp.2025.113725","DOIUrl":"10.1016/j.jcp.2025.113725","url":null,"abstract":"<div><div>Inverse scattering is broadly applicable in quantum mechanics, remote sensing, geophysical, and medical imaging. This paper presents a robust direct non-iterative reduced order model (ROM) method for solving inverse scattering problems based on an efficient approximation of the resolvent operator, resulting in the regularized Lippmann-Schwinger-Lanczos (LSL) algorithm. We show that the efficiency of the method relies upon the weak dependence of the orthogonalized basis on the unknown potential in the Schrödinger equation by demonstrating that the Lanczos orthogonalization is equivalent to performing Gram-Schmidt on the ROM time snapshots. We then develop the LSL algorithm in the frequency domain with two levels of regularization. The proposed bi-level regularization of the algorithm represents a significant advancement in computational stability, enabling its application to real data sets that are larger than used previously with LSL and inherently contain errors. We show that the same procedure can be extended beyond the Schrödinger formulation to the diffusive Helmholtz equation, e.g., to imaging the conductivity using diffusive electromagnetic fields in conductive media with localized positive conductivity perturbations. Numerical experiments for diffusive Helmholtz and Schrödinger problems show that the proposed bi-level regularization scheme significantly improves the performance of the LSL algorithm, allowing for accurate reconstructions with noisy data and large data sets.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113725"},"PeriodicalIF":3.8,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"GSIS-ALE for moving boundary problems in rarefied gas flows","authors":"Jianan Zeng,&nbsp;Yanbing Zhang,&nbsp;Lei Wu","doi":"10.1016/j.jcp.2025.113761","DOIUrl":"10.1016/j.jcp.2025.113761","url":null,"abstract":"<div><div>Multiscale rarefied gas flows with moving boundaries pose significant challenges to the numerical simulation, where the primary difficulties involve robustly managing the mesh movement and ensuring computational efficiency across all flow regimes. Build upon recent advancements of the general synthetic iterative scheme (GSIS), this paper presents an efficient solver to simulate the large displacement of rigid-body in rarefied gas flows. The newly developed solver utilizes a dual time step method to solve the mesoscopic kinetic and macroscopic synthetic equations alternately, in an arbitrary Lagrangian-Eulerian framework. Additionally, the overset mesh is used and the six degree-of-freedom rigid body dynamics equation is integrated to track the motion of solids. Four moving boundary problems encompassing a wide range of flow velocities and gas rarefaction are simulated, including the periodic pitching of airfoil, particle motion in lid-driven cavity flow, two-body separation in supersonic flow, and three-dimensional lunar landing, demonstrating the accuracy and efficiency of the GSIS in handling multi-scale moving boundary problems within an overset framework.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113761"},"PeriodicalIF":3.8,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MOOSE-based finite element framework for mass-conserving two-phase flow simulations on adaptive grids using the diffuse interface approach and a Lagrange multiplier","authors":"Ali Mostafavi ,&nbsp;Mohammadmahdi Ranjbar ,&nbsp;Vitaliy Yurkiv ,&nbsp;Alexander L. Yarin ,&nbsp;Farzad Mashayek","doi":"10.1016/j.jcp.2025.113755","DOIUrl":"10.1016/j.jcp.2025.113755","url":null,"abstract":"<div><div>A numerical framework capable of simulating incompressible laminar two-phase flows has been developed within the Multiphysics Object-Oriented Simulation Environment (MOOSE). The fully-coupled and fully-implicit-in-time methodology relies on the continuous Galerkin finite element discretization of the coupled Cahn-Hilliard Navier-Stokes (CHNS) equations. Despite the computational advantages of adaptive mesh refinement (AMR), mass-conserving interpolation schemes do not exist for transferring the solution to a newly adapted mesh. This paper introduces a new time-dependent scalar Lagrange multiplier to ensure mass conservation on adaptive grids while efficiently handling the interpolation errors involved in mesh coarsening. To assess the accuracy of the numerical implementation, several two-phase flow benchmark problems have been studied and validated against reference solutions. The comparisons demonstrate the accuracy of the code and the overall methodology. The proposed method can be effectively applied to any 2D, 2D axisymmetric and 3D complex immiscible two-phase flows, leveraging conservative AMR without compromising conservation principles.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"527 ","pages":"Article 113755"},"PeriodicalIF":3.8,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical methods and improvements for simulating quasi-static elastoplastic materials","authors":"Jiayin Lu ,&nbsp;Chris H. Rycroft","doi":"10.1016/j.jcp.2025.113756","DOIUrl":"10.1016/j.jcp.2025.113756","url":null,"abstract":"<div><div>Hypo-elastoplasticity is a framework suitable for modeling the mechanics of many hard materials that have small elastic deformation and large plastic deformation. In laboratory tests for these materials the Cauchy stress is often in quasi-static equilibrium. Rycroft et al. discovered a mathematical correspondence between this physical system and the incompressible Navier–Stokes equations, and developed a projection method similar to Chorin's projection method (1968) for incompressible Newtonian fluids. Here, we improve the original projection method to simulate quasi-static hypo-elastoplasticity, by making three improvements. First, drawing inspiration from the second-order projection method for incompressible Newtonian fluids, we formulate a second-order in time numerical scheme for quasi-static hypo-elastoplasticity. Second, we implement a finite element method for solving the elliptic equations in the projection step, which provides both numerical benefits and flexibility. Third, we develop an adaptive global time-stepping scheme, which can compute accurate solutions in fewer timesteps. Our numerical tests use an example physical model of a bulk metallic glass based on the shear transformation zone theory, but the numerical methods can be applied to any elastoplastic material.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113756"},"PeriodicalIF":3.8,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust full-layer prismatic mesh generation based on bijective mapping","authors":"Hongfei Ye ,&nbsp;Taoran Liu ,&nbsp;Haonan Ni ,&nbsp;Jianjun Chen","doi":"10.1016/j.jcp.2025.113744","DOIUrl":"10.1016/j.jcp.2025.113744","url":null,"abstract":"<div><div>Prismatic/tetrahedral hybrid meshes are widely used in CFD simulations involving RANS calculations. However, premature termination during <em>Advancing Layer Method</em> (ALM) generation often necessitates using highly distorted pyramidal elements, compromising overall mesh quality and hindering subsequent tetrahedral mesh generation. To address this, we propose a robust full-layer prismatic mesh generation scheme based on recent advances in piecewise linear bijective mapping. Our scheme iteratively deforms an initial mesh towards an orthogonal target, minimizing the bijective mapping energy via a robust, area/volume-preserving As-Rigid-As-Possible mapping method. Extending to complex geometry in 3D, we further introduce an interpolation-based prismatic mesh generation method, enabling the generation of computationally suitable meshes for complex geometries.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"524 ","pages":"Article 113744"},"PeriodicalIF":3.8,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143131969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A finite difference method for turbulent thermal convection of complex fluids","authors":"Jiaxing Song ,&nbsp;Chang Xu ,&nbsp;Olga Shishkina","doi":"10.1016/j.jcp.2025.113732","DOIUrl":"10.1016/j.jcp.2025.113732","url":null,"abstract":"<div><div>An efficient and robust finite difference algorithm for three-dimensional direct numerical simulations (DNS) of turbulent thermal convection of complex fluids has been developed. To study the complicated fluid elasticity and plasticity, the simulated non-Newtonian fluids are modelled by either viscoelastic Oldroyd-B or FENE-P, or Saramito elastoviscoplastic constitutive equations based on the conformation tensor. The non-Newtonian solver is built on top of the open-source AFiD (<span><span>www.afid.eu</span><svg><path></path></svg></span>) code, which uses a pencil distributed parallel strategy to efficiently handle the large-scale wall-bounded turbulence computations. The present algorithm is demonstrated to preserve the properties of symmetry, boundedness and positive definiteness of the conformation tensor up to large Weissenberg numbers <span><math><mi>W</mi><mi>i</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>2</mn></mrow></msup></math></span> and high Rayleigh number <span><math><mi>R</mi><mi>a</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>10</mn></mrow></msup></math></span>. To validate and assess the code, both two-dimensional and three-dimensional DNS of viscoelastic Rayleigh–Bénard convection are performed. A comparison with available DNS results in the literature shows a very good agreement. Moreover, the results for the heat transport modification for highly turbulent thermal convection with polymer additives agree not only qualitatively but also quantitatively with previous experiments in a similar parameter range. To validate the elastoviscoplastic model used in the code, the DNS of elastoviscoplastic turbulent channel flows at friction Reynolds number <span><math><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>=</mo><mn>180</mn></math></span> and different Bingham numbers <em>Bi</em> are performed, which also show good agreement with the available results. Single plume dynamics and turbulent Rayleigh–Bénard convection of Newtonian, viscoplastic, viscoelastic and elastoviscoplastic fluids are also studied in the DNS to show the versatility of the code.</div></div>","PeriodicalId":352,"journal":{"name":"Journal of Computational Physics","volume":"525 ","pages":"Article 113732"},"PeriodicalIF":3.8,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}