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Large time step asymptotic preserving evolution Galerkin methods for multidimensional system of hyperbolic balance laws.

Subject Area Mathematics
Term from 2008 to 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 70878602
 
Final Report Year 2017

Final Report Abstract

The aim of proposed project was development and analysis of large time step asymptotic preserving finite volume methods for two- and three-dimensional systems of hyperbolic balance laws with a singular parameter, such as low Froude or low Mach number. In order to approximate efficiently weakly compressible flows that typically arise in geophysical applications we build upon multiscale analysis that yields us suitable splittings of flux functions into fast and slow waves. We have followed two splitting strategies: (i) acoustic/advection splitting that is applied to the equations describing evolution of perturbations of the (hydrostatic) equilibrium and (ii) reference solution splitting that is based on the use a reference solution. The latter can be either the equilibrium solution or the singular limit solution. Our goal was to study asymptotic preserving properties of these methods and show that a suitable splitting into the linear stiff subsystem for fast acoustic/gravity waves and the nonlinear non-stiff subsystem for slow advection combined with the IMEX finite volume discretization yields asymptotic preserving schemes. In order to obtain large time step schemes, where the CFL stability condition is dictated only by the flow velocity, we have approximated fast waves implicitly and slow waves explicitly. This led us to use globally asymptotic accurate IMEX type methods for time discretization. We have studied theoretically asymptotic consistency and stability of the proposed IMEX finite volume methods. It turned out that in order to obtain an asymptotic preserving method, no artificial viscosity should be applied to the spatial approximation of fast waves. Furthermore, asymptotic stability of our IMEX FV methods has been analysed using both the energy and the modified equation method. For the isentropic Navier-Stokes equation asymptotic preserving error estimates have been proven for a combined finite element-finite volume scheme using the relative entropy approach. We have developed computational codes for two- and three-dimensional IMEX FV schemes and applied them to full compressible or isentropic Euler equations with small Mach number and the shallow water equations with small Froude number. Extensive experimental analysis confirm reliability and asymptotic preserving properties of the our new IMEX FV schemes.

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