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Experimental convergence rate study for three shock‐capturing schemes and development of highly accurate combined schemes 三种激波捕获方案的实验收敛率研究及高精度组合方案的开发
3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-06-14 DOI: 10.1002/num.23053
Shaoshuai Chu, Olyana A. Kovyrkina, Alexander Kurganov, Vladimir V. Ostapenko
Abstract We study experimental convergence rates of three shock‐capturing schemes for hyperbolic systems of conservation laws: the second‐order central‐upwind (CU) scheme, the third‐order Rusanov‐Burstein‐Mirin (RBM), and the fifth‐order alternative weighted essentially non‐oscillatory (A‐WENO) scheme. We use three imbedded grids to define the experimental pointwise, integral, and convergence rates. We apply the studied schemes to the shallow water equations and conduct their comprehensive numerical convergence study. We verify that while the studied schemes achieve their formal orders of accuracy on smooth solutions, after the shock formation, a part of the computed solutions is affected by shock propagation and both the pointwise and integral convergence rates reduce there. Moreover, while the convergence rates for the CU and A‐WENO schemes, which rely on nonlinear stabilization mechanisms, reduce to the first order, the RBM scheme, which utilizes a linear stabilization, is clearly second‐order accurate. Finally, relying on the conducted experimental convergence rate study, we develop two new combined schemes based on the RBM and either the CU or A‐WENO scheme. The obtained combined schemes can achieve the same high order of accuracy as the RBM scheme in the smooth areas while being non‐oscillatory near the shocks.
摘要研究了具有守恒定律的双曲型系统的三种激波捕获方案的实验收敛速率:二阶中心迎风(CU)方案、三阶Rusanov - Burstein - Mirin (RBM)方案和五阶可选加权本质非振荡(A - WENO)方案。我们使用三个嵌入网格来定义实验的逐点、积分和收敛速率。我们将所研究的格式应用于浅水方程,并对其进行了全面的数值收敛研究。我们验证了虽然所研究的格式在光滑解上达到了它们的形式精度阶,但在激波形成后,部分计算解受到激波传播的影响,并且点向和积分收敛速度都降低了。此外,CU和A‐WENO方案的收敛率降低到一阶,而采用线性稳定机制的RBM方案明显具有二阶精度。最后,基于已进行的实验收敛速率研究,我们开发了基于RBM和CU或A‐WENO方案的两种新的组合方案。所得到的组合格式可以在光滑区域获得与RBM格式相同的高阶精度,同时在冲击附近无振荡。
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引用次数: 0
Behavior of Lagrange‐Galerkin solutions to the Navier‐Stokes problem for small time increment 小时间增量Navier-Stokes问题的Lagrange‐Galerkin解的性质
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-06-04 DOI: 10.1002/num.23051
M. Tabata, Shinya Uchiumi
We consider two kinds of numerical quadrature formulas of Gauss type and Newton‐Cotes type, which are required in the real computation of Lagrange–Galerkin scheme for the Navier–Stokes problem. The Lagrange–Galerkin scheme with numerical quadrature, which has been used practically but not fully analyzed, is proved to be convergent at least for Gauss type quadrature under a condition on the time increment. As for the scheme with Newton‐Cotes type quadrature, it has more smooth convergent property than that of Gauss type, whose reason is discussed.
本文考虑了Navier-Stokes问题的Lagrange-Galerkin格式的实际计算中所需要的Gauss型和Newton‐Cotes型两种数值正交公式。具有数值正交的拉格朗日-伽辽金格式在一定的时间增量条件下,至少对高斯型正交是收敛的。对于具有Newton - Cotes型正交的格式,它具有比高斯型格式更光滑的收敛性,并讨论了其原因。
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引用次数: 0
At war or saving lives? On the securitizing semantic repertoires of Covid-19. 战争还是拯救生命?关于 Covid-19 的安全化语义再现。
3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-06-01 Epub Date: 2022-09-23 DOI: 10.1177/00471178221122957
Stephane J Baele, Elise Rousseau

This paper offers a multi-dimensional analysis of the ways and extent to which the US president and UK prime minister have securitized the Covid-19 pandemic in their public speeches. This assessment rests on, and illustrates the merits of, both an overdue theoretical consolidation of Securitization Theory's (ST) conceptualization of securitizing language, and a new methodological blueprint for the study of 'securitizing semantic repertoire'. Comparing and contrasting the two leaders' respective securitizing semantic repertoires adopted in the early months of the coronavirus outbreak shows that securitizing language, while very limited, has been more intense in the UK, whose repertoire was structured by a biopolitical imperative to 'save lives' in contrast to the US repertoire centred on the 'war' metaphor.

本文从多个维度分析了美国总统和英国首相在公开演讲中将科维德-19 大流行病安全化的方式和程度。这一评估立足于早该进行的安全化理论(ST)对安全化语言概念化的理论巩固,以及研究 "安全化语义剧目 "的新方法蓝图,并说明了两者的优点。通过比较和对比两位领导人在冠状病毒爆发的最初几个月中各自采用的安全化语义剧目,我们可以发现,英国的安全化语言虽然非常有限,但却更加强烈,其剧目是根据 "拯救生命 "的生物政治要求构建的,而美国的剧目则以 "战争 "隐喻为中心。
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引用次数: 0
A finite volume scheme preserving the invariant region property for a class of semilinear parabolic equations on distorted meshes 一类半线性抛物型方程在畸变网格上的有限体积格式
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-26 DOI: 10.1002/num.23050
Huifang Zhou, Yuanyuan Liu, Z. Sheng
In this article, we present a finite volume scheme preserving invariant‐region‐property (IRP) for a class of semilinear parabolic equations with anisotropic diffusion coefficient on distorted meshes. The diffusion term is discretized by the finite volume scheme preserving the discrete maximum principle, and the time derivative is discretized by the backward Euler scheme. For the nonlinear system, a specially designed iteration is proposed to preserve the IRP. The IRPs are proved for both, the finite volume scheme and the nonlinear iteration. Numerical examples are presented to verify the accuracy and IRP of our scheme.
本文给出了一类具有各向异性扩散系数的半线性抛物型方程在畸变网格上保持不变量区域性质(IRP)的有限体积格式。扩散项采用有限体积格式离散化,保持离散极大值原则,时间导数采用后向欧拉格式离散化。对于非线性系统,提出了一种特殊设计的迭代方法来保持IRP。证明了有限体积格式和非线性迭代的irp。数值算例验证了该方法的精度和IRP。
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引用次数: 0
A mass‐ and energy‐preserving numerical scheme for solving coupled Gross–Pitaevskii equations in high dimensions 求解高维Gross–Pitaevskii耦合方程的保质量保能数值格式
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-24 DOI: 10.1002/num.23042
Jianfeng Liu, Q. Tang, Ting-chun Wang
This article is concerned with numerical study of a coupled system of Gross–Pitaevskii equations which describes the spin‐orbit‐coupled Bose–Einstein condensates. Due to the fact that this system possesses the total mass and energy conservation property and often appears in high dimensions, it brings a significant burden in designing and analyzing a suitable numerical scheme for solving the coupled Gross–Pitaevskii equations (CGPEs). In this article, an implicit finite difference scheme is proposed to solve the CGPEs, which is proved to be uniquely solvable, mass‐ and energy‐conservative in the discrete sense. In particular, it is proved in a rigorous way that, without any grid‐ratio restriction, the scheme is stable and convergent at the rate of O(h2+τ2)$$ Oleft({h}^2+{tau}^2right) $$ with time step τ$$ tau $$ and mesh size h$$ h $$ in the maximum norm, while previous works often require certain restriction on the grid ratio and only give the error estimates in the discrete L2$$ {L}^2 $$ norm or H1$$ {H}^1 $$ norm which could not imply the maximum error estimate. Numerical results are carried out to underline the error estimate and conservation laws, and investigate several dynamics of the CGPEs.
本文对描述自旋轨道耦合玻色-爱因斯坦凝聚体的Gross–Pitaevskii方程组的耦合系统进行了数值研究。由于该系统具有总质量和能量守恒特性,并且经常出现在高维中,因此在设计和分析求解Gross–Pitaevskii耦合方程(CGPE)的合适数值方案时带来了巨大的负担。在本文中,提出了一种求解CGPE的隐式有限差分格式,该格式被证明是唯一可解的,在离散意义上是质量和能量守恒的。特别地,以严格的方式证明了,在没有任何网格比率限制的情况下,该方案在O(h2+τ2)$Oleft({h}^2+{tau}^2 right)$$的速率下是稳定和收敛的,时间步长为τ$tau$$,网格大小为h$$h$$,而以前的工作通常需要对网格比率进行一定的限制,并且只给出离散L2$${L}^2$$范数或H1$${H}^1$$范数中的误差估计,这不能暗示最大误差估计。数值结果强调了误差估计和守恒定律,并研究了CGPE的几种动力学。
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引用次数: 0
Two‐level stabilized finite volume method for the stationary incompressible magnetohydrodynamic equations 稳态不可压缩磁流体动力学方程的两级稳定有限体积法
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-20 DOI: 10.1002/num.23043
X. Chu, Chuanjun Chen, T. Zhang
In this paper, a two‐level stabilized finite volume method is developed and analyzed for the steady incompressible magnetohydrodynamic (MHD) equations. The linear polynomial space is used to approximate the velocity, pressure and magnetic fields, and two local Gauss integrations are introduced to overcome the restriction of discrete inf‐sup condition. Firstly, the existence and uniqueness of the solution of the discrete problem in the stabilized finite volume method are proved by using the Brouwer's fixed point theorem. H2$$ {H}^2 $$ ‐stability results of numerical solutions are also presented. Secondly, optimal error estimates of numerical solutions in H1$$ {H}^1 $$ and L2$$ {L}^2 $$ ‐norms are established by using the energy method and constructing the corresponding dual problem. Thirdly, the stability and convergence of two‐level stabilized finite volume method for the stationary incompressible MHD equations are provided. Theoretical findings show that the two‐level method has the same accuracy as the one‐level method with the mesh sizes h=𝒪(H2) . Finally, some numerical results are provided to identify with the established theoretical findings and show the performances of the considered numerical schemes.
本文提出并分析了稳定不可压缩磁流体动力学方程的两级稳定有限体积法。利用线性多项式空间近似速度场、压力场和磁场,并引入两个局部高斯积分来克服离散inf - sup条件的限制。首先,利用browwer不动点定理证明了稳定有限体积法中离散问题解的存在唯一性;还给出了H2 $$ {H}^2 $$‐数值解的稳定性结果。其次,利用能量法构造相应的对偶问题,建立了H1 $$ {H}^1 $$和L2 $$ {L}^2 $$‐范数数值解的最优误差估计。第三,给出了稳定不可压缩MHD方程的两级稳定有限体积法的稳定性和收敛性。理论结果表明,当网格尺寸为h= (H2)时,二级方法与一级方法具有相同的精度。最后,给出了一些数值结果来验证已建立的理论结果,并展示了所考虑的数值格式的性能。
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引用次数: 0
Parameter robust higher‐order finite difference method for convection‐diffusion problem with time delay 时滞对流扩散问题的参数鲁棒高阶有限差分方法
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-16 DOI: 10.1002/num.23039
Sanjaya Sahoo, Vikas Gupta
This paper deals with the study of a higher‐order numerical approximation for a class of singularly perturbed convection‐diffusion problems with time delay. The method combines a higher‐Order Difference with an Identity Expansion (HODIE) scheme over a piece‐wise uniform mesh in the spatial direction and the backward Euler method on a uniform mesh for discretization in the temporal direction. A priori bounds for the continuous solution and its derivatives are derived by splitting the solution into regular and singular components. These bounds are useful in the error analysis of the proposed scheme. The present scheme converges ε$$ varepsilon $$ ‐uniformly with the order of convergence one in time and almost second‐order in space direction. Further, to increase the rate of convergence in the time variable, we implemented the Richardson extrapolation technique. Thus, finally, the resultant scheme with Richardson extrapolation in time becomes almost second‐order ε$$ varepsilon $$ ‐uniformly convergent in both the space and time variable. The detailed stability and convergence analysis have been done using the derived a priori estimates. We consider three test problems to validate the predicted theory and show that numerical results are in good agreement with our theoretical findings.
本文研究了一类具有时滞的奇摄动对流扩散问题的高阶数值逼近。该方法在空间方向上的逐片均匀网格上结合了高阶差分和恒等式展开(HODIE)方案,在时间方向上结合了均匀网格上的后向欧拉方法进行离散化。通过将连续解分解为正则分量和奇异分量,导出了连续解及其导数的先验界。这些边界在所提出的方案的误差分析中是有用的。本方案在时间上以一阶收敛,在空间方向上几乎以二阶收敛,使ε$$varepsilon$$一致收敛。此外,为了提高时间变量的收敛速度,我们实现了Richardson外推技术。因此,最后,在时间上进行Richardson外推的结果方案在空间和时间变量上几乎是二阶ε$$varepsilon$$一致收敛的。使用推导的先验估计进行了详细的稳定性和收敛性分析。我们考虑了三个测试问题来验证预测理论,并表明数值结果与我们的理论结果非常一致。
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引用次数: 2
Issue Information 问题信息
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-11 DOI: 10.1002/num.22889
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引用次数: 0
High order accurate and convergent numerical scheme for the strongly anisotropic Cahn–Hilliard model 强各向异性Cahn–Hilliard模型的高阶精确收敛数值格式
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-04 DOI: 10.1002/num.23034
Kelong Cheng, Cheng Wang, S. Wise
We propose and analyze a second order accurate in time, energy stable numerical scheme for the strongly anisotropic Cahn–Hilliard system, in which a biharmonic regularization has to be introduced to make the equation well‐posed. A convexity analysis on the anisotropic interfacial energy is necessary to overcome an essential difficulty associated with its highly nonlinear and singular nature. The second order backward differentiation formula temporal approximation is applied, combined with Fourier pseudo‐spectral spatial discretization. The nonlinear surface energy part is updated by an explicit extrapolation formula. Meanwhile, the energy stability analysis is enforced by the fact that all the second order functional derivatives of the energy stay uniformly bounded by a global constant. A Douglas‐Dupont type regularization is added to stabilize the numerical scheme, and a careful estimate ensures a modified energy stability with a uniform constraint for the regularization parameter A$$ A $$ . In turn, the combination with an appropriate treatment for the nonlinear double well potential terms leads to a weakly nonlinear scheme. More importantly, such an energy stability is in terms of the interfacial energy with respect to the original phase variable, which enables us to derive an optimal rate convergence analysis.
我们提出并分析了强各向异性Cahn–Hilliard系统的二阶精确时间、能量稳定的数值格式,其中必须引入双调和正则化才能使方程具有良好的适定性。各向异性界面能的凸性分析是克服其高度非线性和奇异性所带来的本质困难的必要条件。应用二阶后向微分公式时间近似,结合傅立叶伪谱空间离散化。非线性表面能部分通过显式外推公式进行更新。同时,能量的所有二阶泛函导数都一致地受一个全局常数的约束,这一事实加强了能量稳定性分析。添加了Douglas‐Dupont型正则化来稳定数值格式,并且仔细的估计确保了正则化参数A$$A$$具有一致约束的修正能量稳定性。反过来,与非线性双阱势项的适当处理相结合,得到了一个弱非线性格式。更重要的是,这种能量稳定性是根据相对于原始相变量的界面能,这使我们能够导出最优速率收敛分析。
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引用次数: 0
A positivity preserving high‐order finite difference method for compressible two‐fluid flows 可压缩双流体流动的保正高阶有限差分方法
IF 3.9 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-05-04 DOI: 10.1002/num.23037
Daniel Boe, Khosro Shahbazi
Any robust computational scheme for compressible flows must retain the hyperbolicity property or the real‐valued sound speed. Failure to maintain hyperbolicity, or the positivity of the square of the speed of sound, causes nonphysical distortions and the blow‐up of numerical simulations. Strong shock waves and interfacial discontinuities are ubiquitous features of the two‐fluid compressible dynamics that can potentially induce positivity‐related failure in a simulation. This article presents a positivity‐preserving algorithm for a high‐order, primitive variable‐based, weighted essentially non‐oscillatory finite difference scheme. The positivity preservation relies on a flux limiting technique that locally adapts high‐order fluxes towards the first order to retain the physical bounds of the solution without loss of high‐order convergence. This positivity preserving scheme has been devised and implemented up to eleventh order in one and two dimensions for a two‐fluid compressible model that consists of a single mass, momentum, and energy equations, as well as an advection of material parameters for capturing the interfaces. Several one‐ and two‐dimensional challenging test problems verify the performance. The scheme effectively retains high order accuracy while allowing for the simulation of several challenging problems that otherwise could not be successfully solved using the base scheme, without any penalty on the CFL condition requirement, and without any significant impact on the CPU times. The scheme represents the first high‐order (up to 11‐order) hyperbolicity‐preserving scheme for the considered two‐fluid compressible flows in the fully Eulerian formulation. The inherent efficiency of finite differences and the new robust positivity preserving quality enable modeling other challenging problems of two‐fluid and two‐phase problems.
可压缩流的任何鲁棒计算方案都必须保持双曲性或实值声速。未能保持双曲性或声速平方的正性,会导致非物理失真和数值模拟的爆炸。强冲击波和界面不连续性是双流体可压缩动力学的普遍特征,可能在模拟中引发正相关失效。本文提出了一种高阶、基于原始变量、加权本质上无振荡的有限差分格式的保正算法。正性保持依赖于通量限制技术,该技术将高阶通量局部调整为一阶,以在不损失高阶收敛的情况下保持解的物理边界。这种保正方案是为双流体可压缩模型设计和实现的,该模型由单个质量、动量和能量方程以及用于捕捉界面的材料参数平流组成,在一维和二维中达到十一阶。几个具有挑战性的一维和二维测试问题验证了性能。该方案有效地保持了高阶精度,同时允许模拟几个具有挑战性的问题,否则这些问题无法使用基本方案成功解决,不会对CFL条件要求造成任何惩罚,也不会对CPU时间产生任何重大影响。该方案代表了全欧拉公式中所考虑的双流体可压缩流的第一个高阶(高达11阶)双曲度保持方案。有限差分的固有效率和新的鲁棒保正质量使得能够对其他具有挑战性的双流体和两相问题进行建模。
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引用次数: 0
期刊
Numerical Methods for Partial Differential Equations
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