Abstract

The Active Flux scheme is a finite volume scheme with additional point values distributed along the cell boundary. It is third order accurate and does not require a Riemann solver. Instead, given a reconstruction, the initial value problem at the location of the point value is solved. The intercell flux is then obtained from the evolved values along the cell boundary by quadrature. Whereas for linear problems an exact evolution operator is available, for nonlinear problems one needs to resort to approximate evolution operators. This paper presents such approximate operators for nonlinear hyperbolic systems in one dimension and nonlinear scalar equations in multiple spatial dimensions. They are obtained by estimating the wave speeds to sufficient order of accuracy. Additionally, an entropy fix is introduced and a new limiting strategy is proposed. The abilities of the scheme are assessed on a variety of smooth and discontinuous setups.

Highlights

  • Hyperbolic m × m systems of conservation laws in d spatial dimensions have the form∂t q + ∇ · f(q) = 0 q : R+0 × Rd → Rm (1.1)The function f is called the flux

  • In order to evolve the cell average, finite volume methods require the knowledge of the flux through the intercell boundary

  • The Active Flux scheme is a finite volume scheme with additional pointwise degrees of freedom located at the cell boundary

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Summary

Introduction

Hyperbolic m × m systems of conservation laws in d spatial dimensions have the form. The function f is called the flux. Exact solutions of these equations are unavailable in general, and one needs to resort to numerical methods. Cell based methods consider the computational domain to be partitioned into cells. A certain number of discrete degrees of freedom are associated with every cell: e.g. finite.

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Finite volume Scheme
Pointwise Degrees of Freedom
Reconstruction
Evolution of Pointwise Degrees of Freedom
Overview of the Algorithm
Fix-Point Iteration
Comparison to Previous Results
Modification of the Fixpoint Iteration in Order to Account for Shocks
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Nonlinear Systems
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Estimating Curved Characteristics
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Runge–Kutta Scheme
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Limiting in One Spatial Dimension
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Notes:
Numerical Examples
Burgers’ Equation
Convergence Study
Self-steepening
Riemann Problems
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Other Scalar Equations
Riemann Problem
Interaction Between a Shock and a Sound Wave
Multi-dimensional Scalar Equations
Conclusion and Outlook
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Full Text
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