Philipp L. Kinon , Riccardo Morandin , Philipp Schulze
{"title":"Discrete gradient methods for port-Hamiltonian differential-algebraic equations","authors":"Philipp L. Kinon , Riccardo Morandin , Philipp Schulze","doi":"10.1016/j.apnum.2025.12.006","DOIUrl":"10.1016/j.apnum.2025.12.006","url":null,"abstract":"<div><div>Discrete gradient methods are a powerful tool for the time discretization of dynamical systems, since they are structure-preserving regardless of the form of the total energy. In this work, we discuss the application of discrete gradient methods to the system class of nonlinear port-Hamiltonian differential-algebraic equations - as they emerge from the port- and energy-based modeling of physical systems in various domains. We introduce a novel numerical scheme tailored for semi-explicit differential-algebraic equations and further address more general settings using the concepts of discrete gradient pairs and Dirac-dissipative structures. Additionally, the behavior under system transformations is investigated and we demonstrate that under suitable assumptions port-Hamiltonian differential-algebraic equations admit a representation which consists of a parametrized port-Hamiltonian semi-explicit system and an unstructured equation. Finally, we present the application to multibody system dynamics and discuss numerical results to demonstrate the capabilities of our approach.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 45-75"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Two-grid mixed finite element method with backward Euler fully discrete scheme for the nonlinear schrödinger equation","authors":"Zhikun Tian , Jianyun Wang , Jie Zhou","doi":"10.1016/j.apnum.2025.12.009","DOIUrl":"10.1016/j.apnum.2025.12.009","url":null,"abstract":"<div><div>We consider the two-dimensional time-dependent nonlinear Schrödinger equation by the backward Euler fully discrete mixed finite element method and obtain optimal error order in <em>L</em><sup>2</sup>-norm. We develop a two-grid algorithm within the backward Euler fully discrete mixed finite element scheme. This algorithm reduces the solution of the nonlinear Schrödinger equation on a fine grid to solving the original nonlinear problem on a much coarser grid, coupled with a linear problem on the fine grid. Moreover, we demonstrate that the two-grid solution achieves the same error order as the standard mixed finite element solution when the coarse and fine mesh sizes satisfy <span><math><mrow><mi>H</mi><mo>=</mo><mi>O</mi><mo>(</mo><msup><mi>h</mi><mfrac><mn>1</mn><mn>2</mn></mfrac></msup><mo>)</mo></mrow></math></span>. Finally, a numerical experiment in the RT<sub>0</sub> space is provided to partly verify theoretical results.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 1-15"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145915173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Finite element simulation of modified Poisson-Nernst-Planck/Navier-Stokes model for compressible electrolytes under mechanical equilibrium","authors":"Ankur Ankur , Ram Jiwari , Satyvir Singh","doi":"10.1016/j.apnum.2026.01.011","DOIUrl":"10.1016/j.apnum.2026.01.011","url":null,"abstract":"<div><div>This work presents a finite element method for a modified Poisson–Nernst–Planck/Navier–Stokes (PNP/NS) model under the mechanical equilibrium, developed for compressible electrolytes. The modification is based on the new model proposed by Dreyer, Guhlke and M<span><math><mover><mi>u</mi><mo>¨</mo></mover></math></span>ller [1], where the diffusion flux in the classical PNP system is replaced with an implicitly involved new diffusion flux, leading to fractional nonlinearity. He and Sun [2] previously developed a numerical approach for another type of modification, where the Poisson equation in the PNP system was substituted with a fourth-order elliptic equation. Another key contribution of this work is the reduction of the equilibrium system to a modified Poisson–Boltzmann system. The proposed numerical scheme is capable of handling both compressible and incompressible regimes by employing a bulk modulus parameter, which governs the fluid’s compressibility and enables seamless transition between these regimes. To emphasize practical relevance, we discuss the implications of compressible electrolytes in the context of double-layer capacitance behavior. We also conduct numerical simulations over various domains to demonstrate its applicability under various operating conditions, including temperature fluctuations and variations in the bulk modulus. The numerical results validate the accuracy and robustness of our computational scheme and demonstrate that the observed limiting behavior for the incompressible regime aligns with the theoretical trends anticipated by Dreyer et al. <span><span>[1]</span></span>.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 255-278"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147384758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Neethu Suma Raveendran , Md. Abdul Aziz , Sivaguru S. Ravindran , Muhammad Mohebujjaman
{"title":"Efficient, accurate, and robust penalty-projection algorithm for parameterized stochastic Navier-Stokes flow problems","authors":"Neethu Suma Raveendran , Md. Abdul Aziz , Sivaguru S. Ravindran , Muhammad Mohebujjaman","doi":"10.1016/j.apnum.2026.01.010","DOIUrl":"10.1016/j.apnum.2026.01.010","url":null,"abstract":"<div><div>This paper presents and analyzes a fast, robust, efficient, and optimally accurate fully discrete splitting algorithm for the Uncertainty Quantification (UQ) of convection-dominated flow problems modeled by parameterized Stochastic Navier-Stokes Equations (SNSEs). The time-stepping algorithm is an implicit backward-Euler linearized method, grad-div and Ensemble Eddy Viscosity (EEV) regularized, and split using discrete Hodge decomposition. Moreover, the scheme’s sub-problems are all designed to have different Right-Hand-Side (RHS) vectors but the same system matrix for all realizations at each time-step. The stability of the algorithm is rigorously proven, and it has been shown that appropriately large grad-div stabilization parameters cause the splitting error to vanish. The proposed UQ algorithm is then combined with the Stochastic Collocation Methods (SCMs). Several numerical experiments are presented to verify the predicted convergence rates and performance of this superior scheme on benchmark problems with high expected Reynolds numbers (<em>Re</em>).</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 235-254"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147384759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A stable multistep scheme for the transient Wigner equation: Efficient handling of scattering","authors":"Yidan Wang , Haiyan Jiang , Tiao Lu , Wenqi Yao","doi":"10.1016/j.apnum.2026.01.009","DOIUrl":"10.1016/j.apnum.2026.01.009","url":null,"abstract":"<div><div>For the transient Wigner equation including scattering, we develop a second-order two-step scheme inspired by the Crank-Nicolson (CN) scheme. The resulting CN-like scheme retains favorable stability while exhibiting higher computational efficiency than any of the existing multi-stage one-step time integration schemes. Unconditional <em>L</em><sup>2</sup>-stability and convergence of the CN-like scheme are rigorously proved. Numerical experiments are conducted by simulating a typical resonant tunneling diode, and the results validate the second-order temporal accuracy, remarkable stability and high efficiency of the CN-like scheme. We also reveal the effects of the scattering mechanism on the Wigner function, and the subsequent impact on the I-V characteristics and the electron densities.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 196-210"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146024187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Santhosh George , Muniyasamy M , Laurence Grammont
{"title":"Derivative-free convergence analysis for Steffensen-type schemes for nonlinear equations","authors":"Santhosh George , Muniyasamy M , Laurence Grammont","doi":"10.1016/j.apnum.2026.01.003","DOIUrl":"10.1016/j.apnum.2026.01.003","url":null,"abstract":"<div><div>Steffensen schemes have been constructed to approximate the solution of an operator equation, with the goal of avoiding the use of its derivatives. It is the reason why these schemes involve the first order divided difference operator. Until now, results on convergence order have been provided using Taylor series expansion, which implies that the operator must be several times differentiable. To be consistent with the nature of the Steffensen schemes, we propose a proof of the convergence order under assumptions that involve only the first and second order divided difference operators. In addition, the convergence order analysis for these Steffensen schemes is done here for the general case of Banach spaces, while it has been done only for finite-dimensional spaces so far. Until now, the assumptions required for semi-local analysis and those required for local analysis have been of a very different nature. A new idea was to unify these hypotheses; hence, we give a single set of convergence conditions. Moreover, our local convergence analysis provides consistently explicit convergence balls that are computable.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"223 ","pages":"Pages 101-120"},"PeriodicalIF":2.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A separate preconditioned primal-dual splitting algorithm for composite monotone inclusion problems","authors":"Xiaokai Chang , Xingran Zhao , Long Xu","doi":"10.1016/j.apnum.2025.12.004","DOIUrl":"10.1016/j.apnum.2025.12.004","url":null,"abstract":"<div><div>We propose a separable preconditioned primal-dual splitting (SP-PDS) method for solving composite monotone inclusion problems. The linear subproblem arising in this method can be selected or generated by comprehensively considering factors such as computational complexity and numerical convergence speed. We prove weak convergence in Hilbert space by reformulating the proposed SP-PDS as a decomposed proximal point algorithm, where the preconditioner is decomposed nonsymmetrically. In particular, various efficient preconditioners are introduced in this framework for which only a few inner iterations are needed to implement preconditioning, instead of computing an inexact solution and controlling the error. The performance of separate preconditioning strategy is verified through preliminary numerical experiments on the image denoising and LASSO problems.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"222 ","pages":"Pages 108-123"},"PeriodicalIF":2.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jikun Zhao , Kangcheng Deng , Chao Wang , Bei Zhang
{"title":"Error analysis on the mixed finite element method for a quad-curl problem with low-order terms in three dimensions","authors":"Jikun Zhao , Kangcheng Deng , Chao Wang , Bei Zhang","doi":"10.1016/j.apnum.2025.11.011","DOIUrl":"10.1016/j.apnum.2025.11.011","url":null,"abstract":"<div><div>This paper aims to develop a mixed finite element method for the three-dimensional quad-curl problem with low-order terms. We prove the regularity estimates on the solution to the primal weak problem under the assumption that the domain is a convex polyhedron. Subsequently, we introduce an auxiliary variable to reformulate the original problem as a mixed problem that consists of two curl-curl equations. Based on the regularity estimates, we establish the equivalence between the primal and mixed formulations. In this mixed finite element method, the primal and auxiliary variables are discretized by the Nédélec’s edge elements. We first derive the suboptimal error estimates for the mixed finite element method. In order to prove the optimal convergence, we construct a special projection with some good properties by using the Maxwell equation under the natural boundary condition. Then, by the duality argument, we prove the optimal error estimates for the approximation to the primal solution in the quad-curl equation. The numerical results illustrate the viability and optimal convergence of this method.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"222 ","pages":"Pages 17-31"},"PeriodicalIF":2.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Linear minimum-variance approximants for noisy data","authors":"Sergio López-Ureña, Dionisio F. Yáñez","doi":"10.1016/j.apnum.2025.12.002","DOIUrl":"10.1016/j.apnum.2025.12.002","url":null,"abstract":"<div><div>Inspired by recent developments in subdivision schemes founded on the Weighted Least Squares technique, we construct linear approximants for noisy data in which the weighting strategy minimizes the output variance, thereby establishing a direct correspondence with the Generalized Least Squares and the Minimum-Variance Formulas methodologies. By introducing annihilation-operators for polynomial spaces, we derive usable formulas that are optimal for general correlated non-uniform noise. We show that earlier subdivision rules are optimal for uncorrelated non-uniform noise and, finally, we present numerical evidence to confirm that, in the correlated case, the proposed approximants are better than those currently used in the subdivision literature.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"222 ","pages":"Pages 46-52"},"PeriodicalIF":2.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"High-order orthogonal spline collocation schemes for two-dimensional nonlinear problems","authors":"Meirong Cheng, Qimin Li, Leijie Qiao","doi":"10.1016/j.apnum.2025.12.001","DOIUrl":"10.1016/j.apnum.2025.12.001","url":null,"abstract":"<div><div>To address the nonlinear control of transverse vibrations in a clamped square plate, we design and analyze an orthogonal spline collocation (OSC) scheme combined with a discrete-time approximation. Two new Crank–Nicolson (CN) OSC variants are introduced for temporal discretization. By applying a Taylor expansion to the nonlinear term, the original fourth-order nonlinear problem is transformed into a linear one, enabling efficient computation. The theoretical investigation is provided. Numerical experiments on several practical examples confirm the effectiveness of the schemes, achieving second-order temporal accuracy and optimal spatial convergence.</div></div>","PeriodicalId":8199,"journal":{"name":"Applied Numerical Mathematics","volume":"222 ","pages":"Pages 32-45"},"PeriodicalIF":2.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}