{"title":"The Estimate of Singular Set of Weak Solution to MHD Equations","authors":"Zhong Tan, Jianfeng Zhou","doi":"10.1007/s00021-026-01019-4","DOIUrl":"10.1007/s00021-026-01019-4","url":null,"abstract":"<div><p>We are concerned with the estimate of singular set of weak solution to Magneto-hydrodynamical (MHD) equations. First, we show that if the pressure <i>P</i> associated to a Leray-Hopf weak solution (<i>u</i>, <i>b</i>) satisfies some additional assumptions, then there is a reduction in the Hausdorff dimension of singular set at a first potential blow up time. Next, instead of imposing the assumption on the pressure, we prove that if the initial data satisfies an extra assumption, then (<i>u</i>, <i>b</i>) possess finite number singular points at first potential blow up time.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Standing Wave Solutions of abcd-systems for Water Waves","authors":"Peifei Song, Yuhao Xie, Min Chen, Shenghao Li","doi":"10.1007/s00021-026-01013-w","DOIUrl":"10.1007/s00021-026-01013-w","url":null,"abstract":"<div><p>We continue the study for standing wave solutions of <i>abcd</i>-systems which was started by Chen and Iooss (Chen, M., Iooss, G.: <i>Eur. J. Mech. B, Fluids</i>, 24(1):113–124, 2005) for the BBM system via the Lyapunov-Schmidt method. In this paper, we will first discuss the feasibility of the Lyapunov-Schmidt method for bifurcating standing wave solutions of <i>abcd</i>-systems. These systems will be characterized into three categories: feasible, infeasible and uncertain feasible ones. In particular, we prove the existence of nontrivial bifurcating standing waves for the Bona-Smith system.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Non-Uniqueness and BV Blowup for Vacuously Liu-Admissible Solutions to P-System Via Computer-Assisted Proof","authors":"Sam G. Krupa","doi":"10.1007/s00021-026-01018-5","DOIUrl":"10.1007/s00021-026-01018-5","url":null,"abstract":"<div><p>In this paper, we consider non-uniqueness and finite time blowup of the BV-norm for exact solutions to genuinely nonlinear hyperbolic systems in one space dimension, in particular the <i>p</i>-system. The recent Bressan-De Lellis result [<i>Arch. Ration. Mech. Anal.</i>, 247(6):Paper No. 106, 12, 2023] shows that whenever a BV solution exists, with finite (but possibly very large total variation), it is unique if each shock verifies the Liu <i>E</i>-condition. We show non-uniqueness of solutions by convex integration. The solutions we construct are Liu-admissible for a trivial reason: there are no shocks, so the Liu <i>E</i>-condition is vacuously satisfied. But our construction shows exactly that there is an issue, a qualitative difference between small data solutions (for example in the BV class) and large data solutions, where this exact type of phenomenon might occur. Our result can be interpreted as a cautionary example to show that the Liu <i>E</i>-condition is satisfactory for small oscillations but <i>not for large oscillations</i> where typically these type of constructions appear. In particular, we present Riemann initial data which admits infinitely many bounded solutions, each of which experience, not just finite time, but in fact <i>instantaneous</i> blowup of the BV norm. The Riemann initial data is allowed to come from an open set in state space. Our method provably does not admit the natural strictly convex entropy. The proof of our theorem is computer-assisted. Our code is available on the GitHub.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147643168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Existence of All Wilton Ripples of the Kawahara Equation","authors":"Ryan P. Creedon","doi":"10.1007/s00021-026-01014-9","DOIUrl":"10.1007/s00021-026-01014-9","url":null,"abstract":"<div><p>We investigate the existence of Wilton ripple solutions of the Kawahara equation. Without loss of generality, these are <span>(2pi )</span>-periodic, traveling-wave solutions whose profiles at zero amplitude have a codimension-1 bifurcation from a linear combination of <span>(cos (x))</span> and <span>(cos (Kx))</span> for <span>(K in mathbb {N} setminus {1})</span>. Using a Lyapunov-Schmidt reduction, we prove the existence of these solutions for all <i>K</i>, in contrast to previous work demonstrating existence only for <span>(K = 2)</span>. Although the proof holds only for the Kawahara equation, many ideas introduced in the proof can be applied to more general contexts, including Wilton ripples of the gravity-capillary water wave equations.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Solution Formula and (H^2)-Solvability for the Stokes System in An Infinite Layer with Upper Stress-Free and Lower Slip-Type Boundary Conditions","authors":"Daisuke Hirata","doi":"10.1007/s00021-026-01015-8","DOIUrl":"10.1007/s00021-026-01015-8","url":null,"abstract":"<div><p>In this paper, we study the initial-boundary value problem for the Stokes system in the three-dimensional infinite layer domain <span>(Omega = (0,frac{pi }{2}) times mathbb {R}^2)</span>, subject to upper stress-free and lower slip-type boundary conditions. Using the Fourier method, we derive an integral formulation for regular solutions. Based on this formula, we demonstrate the solvability of the problem in the <span>(L^2)</span>-based Sobolev space <span>(H^2(Omega ))</span>.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Spatial Pointwise Behavior of Gradient of Navier-Stokes Flow Around a Rigid Body Moving by Time-Periodic Motion, with Applications to Stability/attainability of time-periodic Flow","authors":"Tomoki Takahashi","doi":"10.1007/s00021-026-01016-7","DOIUrl":"10.1007/s00021-026-01016-7","url":null,"abstract":"<div><p>Let us consider the spatial pointwise behavior of time-periodic solutions to the Navier-Stokes equation in the exterior of a rigid body, moving by time-periodic motion. For the translational and angular velocity of the body, assuming besides smallness and regularity, either of the following conditions: (i) translation or rotation is absent; (ii) both velocities are parallel to the same constant vector. If time average over a period of translational velocity, <span>(lambda )</span> (say), is non-zero (resp. zero), we then show that gradient of the velocity of the fluid decays like the one of the gradient of the Oseen fundamental solution (resp. decays at the rate <span>(O(|x|^{-2}))</span>). As applications, in the case <span>(lambda =0)</span>, we show the attainability of the time-periodic solution for small data. In the case <span>(lambda ne 0)</span>, the stability/attainability of the time-periodic solution with sharp decay properties are also deduced.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00021-026-01016-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Convergence of a Second-Order Projection Method to Leray-Hopf Solutions of the Incompressible Navier-Stokes Equations","authors":"Franziska Weber","doi":"10.1007/s00021-025-00985-5","DOIUrl":"10.1007/s00021-025-00985-5","url":null,"abstract":"<div><p>We analyze a second-order projection method for the incompressible Navier-Stokes equations on bounded Lipschitz domains. The scheme employs a Backward Differentiation Formula of order two (BDF2) for the time discretization, combined with conforming finite elements in space. Projection methods are widely used to enforce incompressibility, yet rigorous convergence results for possibly non-smooth solutions have so far been restricted to first-order schemes. We establish, for the first time, convergence (up to subsequence) of a second-order projection method to Leray–Hopf weak solutions under minimal assumptions on the data, namely <span>(u_0 in L^2_{textrm{div}}(Omega ))</span> and <span>(f in L^2(0,T;L^2_{textrm{div}}(Omega )))</span>. Our analysis relies on two ingredients: A discrete energy inequality providing uniform <span>(L^infty (0,T;L^2(Omega )))</span> and <span>(L^2(0,T;H^1_0(Omega )))</span> bounds for suitable interpolants of the discrete velocities, and a compactness argument combining Simon’s theorem with refined time-continuity estimates. These tools overcome the difficulty that only the projected velocity satisfies an approximate divergence-free condition, while the intermediate velocity is controlled in space. We conclude that a subsequence of the approximations converges to a Leray–Hopf weak solution. This result provides the first rigorous convergence proof for a higher-order projection method under no additional assumptions on the solution beyond those following from the standard a priori energy estimate.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00021-025-00985-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147559770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Asymptotic Stability of Composite Waves of Two Viscous Shocks for Relaxed Compressible Navier-Stokes Equations","authors":"Renyong Guan, Yuxi Hu","doi":"10.1007/s00021-026-01010-z","DOIUrl":"10.1007/s00021-026-01010-z","url":null,"abstract":"<div><p>This paper investigates the time asymptotic stability of composite waves formed by two shock waves within the context of one-dimensional relaxed compressible Navier-Stokes equations. We establish the nonlinear stability of the composite waves consisting of two viscous shocks under the condition of having two small, independent wave strengths and the presence of small initial perturbations. Furthermore, the solutions of the relaxed system are observed to globally converge over time to those of the classical system as the relaxation parameter approaches zero. The methods are based on relative entropy, the <i>a</i>-contraction with shifts theory and fundamental energy estimates.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Global Small-Time Approximate Null and Lagrangian Controllability of the Viscous Non-Resistive MHD System in a 3 D Domain with Navier Type Boundary Conditions","authors":"Jiajiang Liao, Franck Sueur, Ping Zhang","doi":"10.1007/s00021-026-01012-x","DOIUrl":"10.1007/s00021-026-01012-x","url":null,"abstract":"<div><p>We consider the incompressible viscous MHD system without magnetic diffusion in a 3<i>D</i> bounded domain with Navier type boundary condition. We establish the global small-time approximate null controllability and the Lagrangian controllability of the system, in the class of smooth solutions, by following the approach initiated in [7] to establish the global small-time null controllability of the incompressible Navier-Stokes equations in the class of weak solutions and extended in [34] to establish the global small-time null and Lagrangian controllability of the incompressible Navier-Stokes equations in the class of strong solutions. This approach makes use of controls with an extra fast scale in time and some corresponding multi-scale asymptotic expansions of the controlled solution. This expansion is constructed by an iterative process which requires some regularity. The extra-difficulty here is that the MHD system at stake is mixed hyperbolic-parabolic, without any regularizing effect on the magnetic field. Although our strategy makes use of a quite precise asymptotic expansion, we succeed to cover the case where the initial velocity belongs the Sobolev space <span>(H^{24})</span> and the initial magnetic field belongs to the Sobolev space <span>(H^8)</span>.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147441137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Revisiting the Slip Boundary Condition: Surface Roughness as a Hidden Tuning Parameter","authors":"Matthias Maier, Peter Munch, Murtazo Nazarov","doi":"10.1007/s00021-026-01009-6","DOIUrl":"10.1007/s00021-026-01009-6","url":null,"abstract":"<div><p>In this paper, we investigate the effect of boundary surface roughness on numerical simulations of incompressible fluid flow past a cylinder in two and three spatial dimensions furnished with slip boundary conditions. The governing equations are approximated using a continuous finite element method, stabilized with a Galerkin least-squares approach. Through a series of numerical experiments, we demonstrate that: (<i>i</i>) the introduction of surface roughness through numerical discretization error, or mesh distortion, makes the potential flow solution unstable; (<i>ii</i>) when numerical surface roughness and mesh distortion are minimized by using high-order isoparametric geometry mappings, a stable potential flow is obtained in both two and three dimensions; (<i>iii</i>) numerical surface roughness, mesh distortion and refinement level can be used as control parameters to manipulate drag and lift forces resulting in numerical values spanning more than an order of magnitude. Our results cast some doubt on the predictive capability of the slip boundary condition for wall modeling in turbulent simulations of incompressible flow.</p></div>","PeriodicalId":649,"journal":{"name":"Journal of Mathematical Fluid Mechanics","volume":"28 2","pages":""},"PeriodicalIF":1.3,"publicationDate":"2026-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00021-026-01009-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}