检索结果-内蒙古大学图书馆

high resolution finite difference schemes for a size structured coagulation-fragmentation model in the space of radon measures

引用

MATHEMATICAL BIOSCIENCES AND ENGINEERING 2023年第7期20卷 11805-11820页

作者： Ackleh, Azmy S. Lyons, Rainey Saintier, Nicolas Univ Louisiana Dept Math Lafayette LA 70504 USA Karlstad Univ Dept Math & Comp Sci S-65188 Karlstad Sweden Univ Buenos Aires Fac Ciencias Exactas & Nat Dept Matemat Pabellon 1 Ciudad Univ RA-1428 Buenos Aires DF Argentina

In this paper, we develop explicit and semi-implicit second-order high-resolution finite difference schemes for a structured coagulation-fragmentation model formulated on the space of Radon measures. We prove the convergence of each of the two schemes to the unique weak solution of the model. We perform numerical simulations to demonstrate that the second order accuracy in the Bounded-Lipschitz norm is achieved by both schemes.

关键词： Coagulation-fragmentation equation size structured populations radon measures equipped with Bounded-Lipschitz Norm finite difference schemes high resolution methods

来源：评论

学校读者我要写书评

暂无评论

An improved flux limiter using fuzzy modifiers for Hyperbolic Conservation Laws

引用

MATHEMATICS AND COMPUTERS IN SIMULATION 2021年 181卷 16-37页

作者： Lochab, Ruchika Kumar, Vivek Delhi Technol Univ Dept Appl Math Main Bawana Rd Delhi 110042 India

The objective of the work in this paper is to computationally tackle a range of problems in hyperbolic conservation laws, which is an interesting branch of computational fluid dynamics. For the simulation of issues in hyperbolic conservation laws, this work explores the concept of fuzzy logic-based operators. This research presents a unique mixture of fuzzy sets and logic with a new branch of conservation laws from fluid dynamics. The approach considers a computational procedure based on the reconstruction of several high-order numerical methods termed as flux-limited methods using some fuzzy logic operators. With the aid of fuzzy modifiers, these flux limiters are further modified. This approach results in improved convergence of approximations and maintains the problem's basic properties to be solved. Additionally, to ensure improved results, modified flux-limited methods are imposed on some famous test problems. The application results are provided wherever required. The work has demonstrated that it is possible to use such technique and apply it to complex areas of computational fluid dynamics to produce a more straightforward approach to studying other topics like flux-limited methods and hence opens up an exciting gateway for future work. (C) 2020 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词： Flux limiters Hyperbolic equations high resolution methods Fuzzy logic

来源：评论

学校读者我要写书评

暂无评论

A combined ghost:point-forcing/direct-forcing immersed boundary method (IBM) for compressible flow simulations

引用

COMPUTERS & FLUIDS 2018年 162卷 91-112页

作者： Boukharfane, Radouan Eugenio Ribeiro, Fabio Henrique Bouali, Zakaria Mura, Arnaud ENSMA CNRS ISAE Inst PprimeUPR 3346 Chasseneuil France Univ Poitiers Poitiers France Inst Estudos Avangados Sao Jose Dos Campos SP Brazil

The present manuscript describes the implementation of an immersed boundary method (IBM) into a compressible reactive multicomponent Navier-Stokes solver. The latter makes use of high-order accuracy discretization schemes applied on structured Cartesian grids. For the immersed boundary method, both direct-forcing and ghost-point-forcing schemes are considered. The direct-forcing source term, which is added to the three components of the Navier Stokes (NS) equations, i.e. the momentum equations, is used to impose the no-slip boundary conditions at the fluid-body interface. It is combined with a ghost point-forcing scheme to enforce both mass conservation and boundary conditions in the scalar equations (density, energy and species mass fractions). The discretization of the three-dimensional surface associated to the solid geometry is obtained from a triangulation, which is handled within the stereo lithography (STL) data format. The immersed boundary is thus represented with a finite number of La-grangian points, which are associated to the centers of gravity of the elementary triangles. The major components of the IBM procedure include the data structure itself, the determination of the status of the computational nodes, i.e. fluid, ghost or solid, the interpolation rules and the forcing model. The performance of the resulting immersed boundary scheme is investigated by considering a large set of two-dimensional benchmarks including a cylinder placed in either subsonic or supersonic flows, a subsonic airflow on a flat plate, moving-shock interactions with various obstacles. Numerical results are satisfactorily compared with available theoretical, experimental, and numerical data. The capabilities of the method are then illustrated on more representative flowfields such as two-dimensional non-reactive and reactive high-speed flows developing over rectangular cavities and three-dimensional supersonic flows over a rigid body. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Immersed boundary method Ghost-point-forcing approach Direct-forcing approach Compressible flows Shock-obstacle interaction high resolution methods

来源：评论

学校读者我要写书评

暂无评论

Application of high-resolution methods in compositional simulation

Application of high-resolution methods in compositional simu...

引用

International Conference on Computational Science (ICCS) on the Ascent of Computational Excellence

作者： Mikyska, Jiri Firoozabadi, Abbas Czech Tech Univ Fac Nucl Sci & Phys Engn Dept Math Trojanova 13 Prague 12000 Czech Republic Reservoir Engn Res Inst Palo Alto CA 94301 USA

Compositional simulation is an important tool in for evaluation of oil recovery and carbon sequestration. Several compositional models have been proposed in the past that are based on finite-difference, finite-volume or finite-element methods. These methods are typically of low order of approximation and suffer excessive numerical diffusion. These deficiencies can be significantly suppressed using the high resolution methods like mixed-hybrid and discontinuous Galerkin finite element methods. We have shown recently that these methods are much more sensitive to problem formulation than the conventional first-order methods. In this work we discuss several problems connected with application of high resolution schemes. These problems include formulation of boundary conditions, proper evaluation of phase fluxes, and formulation of the slope limiter in the discontinuous Galerkin method. The latter problem is common to all high resolution methods. We will present new examples of compositional simulations showing the advantages of our approach over the traditional first-order finite-volume schemes in single-phase and two-phase.

关键词： two-phase flow compositional simulation high resolution methods mixed-hybrid finite element method discontinuous Galerkin method slope limiter

来源：评论

学校读者我要写书评

暂无评论

Application of high-resolution methods in compositional simulation

引用

Procedia Computer Science 2011年 4卷 928-937页

作者： Jiří Mikyška Abbas Firoozabadi Czech Technical University in Prague Faculty of Nuclear Sciences and Physical Engineering Department of Mathematics Trojanova 13 120 00 Prague Czech Republic Reservoir Engineering Research Institute 595 Lytton Ave Palo Alto CA-94301 United States of America

Compositional simulation is an important tool in for evaluation of oil recovery and carbon sequestration. Several compositional models have been proposed in the past that are based on finite-difference, finite-volume or finiteelement methods. These methods are typically of low order of approximation and suffer excessive numerical diffusion. These deficiencies can be significantly suppressed using the high resolution methods like mixed-hybrid and discontinuous Galerkin finite element methods. We have shown recently that these methods are much more sensitive to problem formulation than the conventional first-order methods. In this work we discuss several problems connected with application of high resolution schemes. These problems include formulation of boundary conditions, proper evaluation of phase fluxes, and formulation of the slope limiter in the discontinuous Galerkin method. The latter problem is common to all high resolution methods. We will present new examples of compositional simulations showing the advantages of our approach over the traditional first-order finite-volume schemes in single-phase and two-phase.

关键词： two-phase flow compositional simulation high resolution methods mixed-hybrid finite element method discontinuous Galerkin method slope limiter

来源：评论

学校读者我要写书评

暂无评论

A detailed verification procedure for compressible reactive multicomponent Navier-Stokes solvers

引用

COMPUTERS & FLUIDS 2014年 89卷 88-110页

作者： Ferrer, Pedro Jose Martinez Buttay, Romain Lehnasch, Guillaume Mura, Arnaud ISAE ENSMA CNRS UPR 3346 Inst Pprime Chasseneuil France Univ Poitiers Poitiers France

The present manuscript reports a numerical verification study based on a series of tests that allows to evaluate the numerical performance of a compressible reactive multicomponent Navier-Stokes solver. The verification procedure is applied to a density-based finite difference numerical scheme suited to compressible reactive flows representative of either combustion in high speed flows or detonation. The numerical algorithm is based on a third-order accurate Total Variation Diminishing (TVD) Runge Kutta time integration scheme. It employs a seventh-order accurate Weighted Essentially Non-Oscillatory (WENO) scheme to discretize the non-linear advective terms while an eighth-order accurate centered finite difference scheme is retained for the molecular viscous and diffusive terms. These molecular contributions are evaluated with the library EGLIB that accounts for detailed multicomponent transport including Soret and Dufour effects. The developed numerical solver thus offers an interesting combination of existing methods suited to the present purpose of studying combustion in high speed flows and/or detonations. The numerical solver is verified by considering a complete procedure that gathers eight elementary verification subsets including, among others, the classical Sod's shock tube problem, the ignition sequence of a multi-species mixture in a shock tube, the unsteady diffusion of a smoothed concentration profile and a one-dimensional laminar premixed flame. Such verification analyses are seldom reported in the literature but constitute an important part of computational research activities. It is presently completed with the application of the verified finite difference scheme to the numerical simulation of (i) shock (reactive) mixing layer interaction and (ii) combustion ignition downstream of a highly under-expanded jet. The corresponding results shed some light onto the robustness (stability) and performance of the numerical scheme, and also provide some very v

关键词： Compressible flows Combustion Detonation high-order schemes high resolution methods Direct numerical simulation Under-expanded jet flames

来源：评论

学校读者我要写书评

暂无评论

VARIATIONAL BAYESIAN EM ALGORITHM FOR MODELING MIXTURES OF NON-STATIONARY SIGNALS IN THE TIME-FREQUENCY DOMAIN (HR-NMF)

VARIATIONAL BAYESIAN EM ALGORITHM FOR MODELING MIXTURES OF N...

引用

IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Badeau, Roland Dremeau, Angelique CNRS LTCI Telecom ParisTech Inst Mines Telecom Paris France

ISBN: (纸本)9781479903566

We recently introduced the high-resolution nonnegative matrix factorization (HR-NMF) model for analyzing mixtures of non-stationary signals in the time-frequency domain, and highlighted its capability to both reach high spectral resolution and reconstruct high quality audio signals. In order to estimate the model parameters and the latent components, we proposed to resort to an expectation-maximization (EM) algorithm based on a Kalman filter/smoother. The approach proved to be appropriate for modeling audio signals in applications such as source separation and audio inpainting. However, its computational cost is high, dominated by the Kalman filter/smoother, and may be prohibitive when dealing with high-dimensional signals. In this paper, we consider two different alternatives, using the variational Bayesian EM algorithm and two mean-field approximations. We show that, while significantly reducing the complexity of the estimation, these novel approaches do not alter its quality.

关键词： Nonnegative Matrix Factorization high resolution methods Expectation-Maximization algorithm Variational inference

来源：评论

学校读者我要写书评

暂无评论

MULTIPLICATIVE UPDATES FOR MODELING MIXTURES OF NON-STATIONARY SIGNALS IN THE TIME-FREQUENCY DOMAIN

MULTIPLICATIVE UPDATES FOR MODELING MIXTURES OF NON-STATIONA...

引用

21st European Signal Processing Conference (EUSIPCO)

作者： Badeau, Roland Ozerov, Alexey Telecom ParisTech Inst Mines Telecom CNRS LTCI Paris France Technicolor Res & Innovat Paris France

ISBN: (纸本)9781479936878

We recently introduced the high-resolution nonnegative matrix factorization (HR-NMF) model for representing mixtures of non-stationary signals in the time-frequency domain, and we highlighted its capability to both reach a high spectral resolution and reconstruct high quality audio signals. An expectation-maximization (EM) algorithm was also proposed for estimating its parameters. In this paper, we replace the maximization step by multiplicative update rules (MUR), in order to improve the convergence rate. We also introduce general MUR that are not limited to nonnegative parameters, and we propose a new insight into the EM algorithm, which shows that MUR and EM actually belong to the same family. We thus introduce a continuum of algorithms between them. Experiments confirm that the proposed approach permits to overcome the convergence rate of the EM algorithm.

关键词： Nonnegative Matrix Factorization high resolution methods Expectation-Maximization algorithm Multiplicative update rules

来源：评论

学校读者我要写书评

暂无评论

VARIATIONAL BAYESIAN EM ALGORITHM FOR MODELING MIXTURES OF NON-STATIONARY SIGNALS IN THE TIME-FREQUENCY DOMAIN (HR-NMF)

VARIATIONAL BAYESIAN EM ALGORITHM FOR MODELING MIXTURES OF N...

引用

IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Roland Badeau Angelique Dremeau Institut Mines-Telecom Telecom ParisTech CNRS LTCI

ISBN: (纸本)9781479903573