JournalTOCs

Communications on Applied Mathematics and Computation
Number of Followers: 1

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2096-6385 - ISSN (Online) 2661-8893
Published by Springer-Verlag

[2469 journals]

Global Existence of Smooth Solutions for the One-Dimensional Full Euler
System for a Dusty Gas
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  Abstract: Abstract We study the existence of global-in-time classical solutions for the one-dimensional nonisentropic compressible Euler system for a dusty gas with large initial data. Using the characteristic decomposition method proposed by Li et al. (Commun Math Phys 267: 1–12, 2006), we derive a group of characteristic decompositions for the system. Using these characteristic decompositions, we find a sufficient condition on the initial data to ensure the existence of global-in-time classical solutions.
  PubDate: 2022-06-24
Global Existence and Stability of Solutions to River Flow System
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  Abstract: Abstract In this short note, we are concerned with the global existence and stability of solutions to the river flow system. We introduce a new technique to set up a relation between the Riemann invariants and the finite mass to obtain a time-independent, bounded solution for any adiabatic exponent. The global existence of solutions was known long ago [Klingenberg and Lu in Commun. Math. Phys. 187: 327–340, 1997]. However, since the uncertainty of the function b(x), which corresponds physically to the slope of the topography, the \(L^{\infty }\) estimates growed larger with respect to the time variable. As a result, it does not guarantee the stability of solutions. By employing a suitable mathematical transformation to control the slope of the topography by the friction and the finite mass, we prove the uniformly bounded estimate with respect to the time variable. This means that our solutions are stable.
  PubDate: 2022-06-22
Two Energy-Preserving Compact Finite Difference Schemes for the Nonlinear
Fourth-Order Wave Equation
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  Abstract: Abstract In this paper, two fourth-order compact finite difference schemes are derived to solve the nonlinear fourth-order wave equation which can be viewed as a generalized model from the nonlinear beam equation. Differing from the existing compact finite difference schemes which preserve the total energy in a recursive sense, the new schemes are proved to perfectly preserve the total energy in the discrete sense. By using the standard energy method and the cut-off function technique, the optimal error estimates of the numerical solutions are established, and the convergence rates are of \(O(h^4+\tau ^2)\) with mesh-size h and time-step \(\tau \) . In order to improve the computational efficiency, an iterative algorithm is proposed as the outer solver and the double sweep method for pentadiagonal linear algebraic equations is introduced as the inner solver to solve the nonlinear difference schemes at each time step. The convergence of the iterative algorithm is also rigorously analyzed. Several numerical results are carried out to test the error estimates and conservative properties.
  PubDate: 2022-06-07
Recent Progress on Outflow/Inflow Problem for Viscous Multi-phase Flow
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  Abstract: Abstract According to the boundary condition with the zero, negative, or positive velocity, the initial boundary problem for compressible multi-phase flow with the Dirichlet-type boundary condition can be classified into three cases: impermeable problem, inflow problem, or outflow problem. In this paper, we review the recent progress on the existence and nonlinear stability of the stationary solution to the outflow/inflow problems for viscous multi-phase flow.
  PubDate: 2022-06-01
Superconvergent Interpolatory HDG Methods for Reaction Diffusion Equations
II: HHO-Inspired Methods
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  Abstract: Abstract In Chen et al. (J. Sci. Comput. 81(3): 2188–2212, 2019), we considered a superconvergent hybridizable discontinuous Galerkin (HDG) method, defined on simplicial meshes, for scalar reaction-diffusion equations and showed how to define an interpolatory version which maintained its convergence properties. The interpolatory approach uses a locally postprocessed approximate solution to evaluate the nonlinear term, and assembles all HDG matrices once before the time integration leading to a reduction in computational cost. The resulting method displays a superconvergent rate for the solution for polynomial degree \(k\geqslant 1\) . In this work, we take advantage of the link found between the HDG and the hybrid high-order (HHO) methods, in Cockburn et al. (ESAIM Math. Model. Numer. Anal. 50(3): 635–650, 2016) and extend this idea to the new, HHO-inspired HDG methods, defined on meshes made of general polyhedral elements, uncovered therein. For meshes made of shape-regular polyhedral elements affine-equivalent to a finite number of reference elements, we prove that the resulting interpolatory HDG methods converge at the same rate as for the linear elliptic problems. Hence, we obtain superconvergent methods for \(k\geqslant 0\) by some methods. We thus maintain the superconvergence properties of the original methods. We present numerical results to illustrate the convergence theory.
  PubDate: 2022-06-01
Convergence and Superconvergence of the Local Discontinuous Galerkin
Method for Semilinear Second-Order Elliptic Problems on Cartesian Grids
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  Abstract: Abstract This paper is concerned with convergence and superconvergence properties of the local discontinuous Galerkin (LDG) method for two-dimensional semilinear second-order elliptic problems of the form \(-\Delta u=f(x,y,u)\) on Cartesian grids. By introducing special Gauss-Radau projections and using duality arguments, we obtain, under some suitable choice of numerical fluxes, the optimal convergence order in \(L^2\) -norm of \({O}(h^{p+1})\) for the LDG solution and its gradient, when tensor product polynomials of degree at most p and grid size h are used. Moreover, we prove that the LDG solutions are superconvergent with an order \(p+ 2\) toward particular Gauss-Radau projections of the exact solutions. Finally, we show that the error between the gradient of the LDG solution and the gradient of a special Gauss-Radau projection of the exact solution achieves \((p+1)\) -th order superconvergence. Some numerical experiments are performed to illustrate the theoretical results.
  PubDate: 2022-06-01
Local Discontinuous Galerkin Methods for the abcd Nonlinear Boussinesq
System
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  Abstract: Abstract Boussinesq type equations have been widely studied to model the surface water wave. In this paper, we consider the abcd Boussinesq system which is a family of Boussinesq type equations including many well-known models such as the classical Boussinesq system, the BBM-BBM system, the Bona-Smith system, etc. We propose local discontinuous Galerkin (LDG) methods, with carefully chosen numerical fluxes, to numerically solve this abcd Boussinesq system. The main focus of this paper is to rigorously establish a priori error estimate of the proposed LDG methods for a wide range of the parameters a, b, c, d. Numerical experiments are shown to test the convergence rates, and to demonstrate that the proposed methods can simulate the head-on collision of traveling wave and finite time blow-up behavior well.
  PubDate: 2022-06-01
Dual-Wind Discontinuous Galerkin Methods for Stationary Hamilton-Jacobi
Equations and Regularized Hamilton-Jacobi Equations
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  Abstract: Abstract This paper develops and analyzes a new family of dual-wind discontinuous Galerkin (DG) methods for stationary Hamilton-Jacobi equations and their vanishing viscosity regularizations. The new DG methods are designed using the DG finite element discrete calculus framework of [17] that defines discrete differential operators to replace continuous differential operators when discretizing a partial differential equation (PDE). The proposed methods, which are non-monotone, utilize a dual-winding methodology and a new skew-symmetric DG derivative operator that, when combined, eliminate the need for choosing indeterminable penalty constants. The relationship between these new methods and the local DG methods proposed in [38] for Hamilton-Jacobi equations as well as the generalized-monotone finite difference methods proposed in [13] and corresponding DG methods proposed in [12] for fully nonlinear second order PDEs is also examined. Admissibility and stability are established for the proposed dual-wind DG methods. The stability results are shown to hold independent of the scaling of the stabilizer allowing for choices that go beyond the Godunov barrier for monotone schemes. Numerical experiments are provided to gauge the performance of the new methods.
  PubDate: 2022-06-01
Development of a Balanced Adaptive Time-Stepping Strategy Based on an
Implicit JFNK-DG Compressible Flow Solver
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  Abstract: Abstract A balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations. A proper relation between the spatial, temporal and iterative errors generated within one time step is constructed. With an estimate of temporal and spatial error using an embedded Runge-Kutta scheme and a higher order spatial discretization, an adaptive time-stepping strategy is proposed based on the idea that the time step should be the maximum without obviously influencing the total error of the discretization. The designed adaptive time-stepping strategy is then tested in various types of problems including isentropic vortex convection, steady-state flow past a flat plate, Taylor-Green vortex and turbulent flow over a circular cylinder at \({Re}=3\,900\) . The results indicate that the adaptive time-stepping strategy can maintain that the discretization error is dominated by the spatial error and relatively high efficiency is obtained for unsteady and steady, well-resolved and under-resolved simulations.
  PubDate: 2022-06-01
Capitalizing on Superconvergence for More Accurate Multi-Resolution
Discontinuous Galerkin Methods
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  Abstract: Abstract This article focuses on exploiting superconvergence to obtain more accurate multi-resolution analysis. Specifically, we concentrate on enhancing the quality of passing of information between scales by implementing the Smoothness-Increasing Accuracy-Conserving (SIAC) filtering combined with multi-wavelets. This allows for a more accurate approximation when passing information between meshes of different resolutions. Although this article presents the details of the SIAC filter using the standard discontinuous Galerkin method, these techniques are easily extendable to other types of data.
  PubDate: 2022-06-01
A Discontinuous Galerkin Method for Blood Flow and Solute Transport in
One-Dimensional Vessel Networks
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  Abstract: Abstract This paper formulates an efficient numerical method for solving the convection diffusion solute transport equations coupled to blood flow equations in vessel networks. The reduced coupled model describes the variations of vessel cross-sectional area, radially averaged blood momentum and solute concentration in large vessel networks. For the discretization of the reduced transport equation, we combine an interior penalty discontinuous Galerkin method in space with a novel locally implicit time stepping scheme. The stability and the convergence are proved. Numerical results show the impact of the choice for the steady-state axial velocity profile on the numerical solutions in a fifty-five vessel network with physiological boundary data.
  PubDate: 2022-06-01
Discontinuous Galerkin Methods for a Class of Nonvariational Problems
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  Abstract: Abstract We extend the finite element method introduced by Lakkis and Pryer (SIAM J. Sci. Comput. 33(2): 786–801, 2011) to approximate the solution of second-order elliptic problems in nonvariational form to incorporate the discontinuous Galerkin (DG) framework. This is done by viewing the “finite element Hessian” as an auxiliary variable in the formulation. Representing the finite element Hessian in a discontinuous setting yields a linear system of the same size and having the same sparsity pattern of the compact DG methods for variational elliptic problems. Furthermore, the system matrix is very easy to assemble; thus, this approach greatly reduces the computational complexity of the discretisation compared to the continuous approach. We conduct a stability and consistency analysis making use of the unified framework set out in Arnold et al. (SIAM J. Numer. Anal. 39(5): 1749–1779, 2001/2002). We also give an a posteriori analysis of the method in the case where the problem has a strong solution. The analysis applies to any consistent representation of the finite element Hessian, and thus is applicable to the previous works making use of continuous Galerkin approximations. Numerical evidence is presented showing that the method works well also in a more general setting.
  PubDate: 2022-06-01
Uniform Subspace Correction Preconditioners for Discontinuous Galerkin
Methods with hp-Refinement
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  Abstract: Abstract In this paper, we develop subspace correction preconditioners for discontinuous Galerkin (DG) discretizations of elliptic problems with hp-refinement. These preconditioners are based on the decomposition of the DG finite element space into a conforming subspace, and a set of small nonconforming edge spaces. The conforming subspace is preconditioned using a matrix-free low-order refined technique, which in this work, we extend to the hp-refinement context using a variational restriction approach. The condition number of the resulting linear system is independent of the granularity of the mesh h, and the degree of the polynomial approximation p. The method is amenable to use with meshes of any degree of irregularity and arbitrary distribution of polynomial degrees. Numerical examples are shown on several test cases involving adaptively and randomly refined meshes, using both the symmetric interior penalty method and the second method of Bassi and Rebay (BR2).
  PubDate: 2022-06-01
Hybrid High-Order Methods for the Acoustic Wave Equation in the Time
Domain
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  Abstract: Abstract We devise hybrid high-order (HHO) methods for the acoustic wave equation in the time domain. We first consider the second-order formulation in time. Using the Newmark scheme for the temporal discretization, we show that the resulting HHO-Newmark scheme is energy-conservative, and this scheme is also amenable to static condensation at each time step. We then consider the formulation of the acoustic wave equation as a first-order system together with singly-diagonally implicit and explicit Runge-Kutta (SDIRK and ERK) schemes. HHO-SDIRK schemes are amenable to static condensation at each time step. For HHO-ERK schemes, the use of the mixed-order formulation, where the polynomial degree of the cell unknowns is one order higher than that of the face unknowns, is key to benefit from the explicit structure of the scheme. Numerical results on test cases with analytical solutions show that the methods can deliver optimal convergence rates for smooth solutions of order \(\mathcal{O}(h^{k+1})\) in the \(H^1\) -norm and of order \(\mathcal{O}(h^{k+2})\) in the \(L^2\) -norm. Moreover, test cases on wave propagation in heterogeneous media indicate the benefits of using high-order methods.
  PubDate: 2022-06-01
Arbitrary Lagrangian-Eulerian Discontinuous Galerkin Methods for KdV Type
Equations
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  Abstract: Abstract In this paper, several arbitrary Lagrangian-Eulerian discontinuous Galerkin (ALE-DG) methods are presented for Korteweg-de Vries (KdV) type equations on moving meshes. Based on the \(L^2\) conservation law of KdV equations, we adopt the conservative and dissipative numerical fluxes for the nonlinear convection and linear dispersive terms, respectively. Thus, one conservative and three dissipative ALE-DG schemes are proposed for the equations. The invariant preserving property for the conservative scheme and the corresponding dissipative properties for the other three dissipative schemes are all presented and proved in this paper. In addition, the \(L^2\) -norm error estimates are also proved for two schemes, whose numerical fluxes for the linear dispersive term are both dissipative type. More precisely, when choosing the approximation space with the piecewise kth degree polynomials, the error estimate provides the kth order of convergence rate in \(L^2\) -norm for the scheme with the conservative numerical fluxes applied for the nonlinear convection term. Furthermore, the \((k+1/2)\) th order of accuracy can be proved for the ALE-DG scheme with dissipative numerical fluxes applied for the convection term. Moreover, a Hamiltonian conservative ALE-DG scheme is also presented based on the conservation of the Hamiltonian for KdV equations. Numerical examples are shown to demonstrate the accuracy and capability of the moving mesh ALE-DG methods and compare with stationary DG methods.
  PubDate: 2022-06-01
Extendible and Efficient Python Framework for Solving Evolution Equations
with Stabilized Discontinuous Galerkin Methods
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  Abstract: Abstract This paper discusses a Python interface for the recently published Dune-Fem-DG module which provides highly efficient implementations of the discontinuous Galerkin (DG) method for solving a wide range of nonlinear partial differential equations (PDEs). Although the C++ interfaces of Dune-Fem-DG are highly flexible and customizable, a solid knowledge of C++ is necessary to make use of this powerful tool. With this work, easier user interfaces based on Python and the unified form language are provided to open Dune-Fem-DG for a broader audience. The Python interfaces are demonstrated for both parabolic and first-order hyperbolic PDEs.
  PubDate: 2022-06-01
The Perturbed Riemann Problem for a Geometrical Optics System
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  Abstract: Abstract The perturbed Riemann problem for a hyperbolic system of conservation laws arising in geometrical optics with three constant initial states is solved. By studying the interactions among of the delta-shock, vacuum, and contact discontinuity, fourteen kinds of structures of Riemann solutions are obtained. The compound wave solutions consisting of delta-shocks, vacuums, and contact discontinuities are found. The single and double closed vacuum cavitations develop in solutions. Furthermore, it is shown that the solutions of the Riemann problem for the geometrical optics system are stable under certain perturbation of the initial data. Finally, the numerical results completely coinciding with theoretical analysis are presented.
  PubDate: 2022-05-16
Efficient WENO-Based Prolongation Strategies for Divergence-Preserving
Vector Fields
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  Abstract: Abstract Adaptive mesh refinement (AMR) is the art of solving PDEs on a mesh hierarchy with increasing mesh refinement at each level of the hierarchy. Accurate treatment on AMR hierarchies requires accurate prolongation of the solution from a coarse mesh to a newly defined finer mesh. For scalar variables, suitably high-order finite volume WENO methods can carry out such a prolongation. However, classes of PDEs, such as computational electrodynamics (CED) and magnetohydrodynamics (MHD), require that vector fields preserve a divergence constraint. The primal variables in such schemes consist of normal components of the vector field that are collocated at the faces of the mesh. As a result, the reconstruction and prolongation strategies for divergence constraint-preserving vector fields are necessarily more intricate. In this paper we present a fourth-order divergence constraint-preserving prolongation strategy that is analytically exact. Extension to higher orders using analytically exact methods is very challenging. To overcome that challenge, a novel WENO-like reconstruction strategy is invented that matches the moments of the vector field in the faces, where the vector field components are collocated. This approach is almost divergence constraint-preserving, therefore, we call it WENO-ADP. To make it exactly divergence constraint-preserving, a touch-up procedure is developed that is based on a constrained least squares (CLSQ) method for restoring the divergence constraint up to machine accuracy. With the touch-up, it is called WENO-ADPT. It is shown that refinement ratios of two and higher can be accommodated. An item of broader interest in this work is that we have also been able to invent very efficient finite volume WENO methods, where the coefficients are very easily obtained and the multidimensional smoothness indicators can be expressed as perfect squares. We demonstrate that the divergence constraint-preserving strategy works at several high orders for divergence-free vector fields as well as vector fields, where the divergence of the vector field has to match a charge density and its higher moments. We also show that our methods overcome the late time instability that has been known to plague adaptive computations in CED.
  PubDate: 2022-05-16
Preface to the Focused Issue on WENO Schemes
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  PubDate: 2022-05-13
Singularity Formation for the General Poiseuille Flow of Nematic Liquid
Crystals
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  Abstract: Abstract We consider the Poiseuille flow of nematic liquid crystals via the full Ericksen-Leslie model. The model is described by a coupled system consisting of a heat equation and a quasilinear wave equation. In this paper, we will construct an example with a finite time cusp singularity due to the quasilinearity of the wave equation, extended from an earlier result on a special case.
  PubDate: 2022-05-10