35 research outputs found
The DUNE-ALUGrid Module
In this paper we present the new DUNE-ALUGrid module. This module contains a
major overhaul of the sources from the ALUgrid library and the binding to the
DUNE software framework. The main changes include user defined load balancing,
parallel grid construction, and an redesign of the 2d grid which can now also
be used for parallel computations. In addition many improvements have been
introduced into the code to increase the parallel efficiency and to decrease
the memory footprint.
The original ALUGrid library is widely used within the DUNE community due to
its good parallel performance for problems requiring local adaptivity and
dynamic load balancing. Therefore, this new model will benefit a number of DUNE
users. In addition we have added features to increase the range of problems for
which the grid manager can be used, for example, introducing a 3d tetrahedral
grid using a parallel newest vertex bisection algorithm for conforming grid
refinement. In this paper we will discuss the new features, extensions to the
DUNE interface, and explain for various examples how the code is used in
parallel environments.Comment: 25 pages, 11 figure
Asynchronous communication in spectral-element and discontinuous Galerkin methods for atmospheric dynamics – a case study using the High-Order Methods Modeling Environment (HOMME-homme_dg_branch)
The scalability of computational applications on current and next-generation supercomputers is increasingly limited by the cost of inter-process communication. We implement non-blocking asynchronous communication in the High-Order Methods Modeling Environment for the time integration of the hydrostatic fluid equations using both the spectral-element and discontinuous Galerkin methods. This allows the overlap of computation with communication, effectively hiding some of the costs of communication. A novel detail about our approach is that it provides some data movement to be performed during the asynchronous communication even in the absence of other computations. This method produces significant performance and scalability gains in large-scale simulations.publishedVersio
A Second-Order Finite Volume Method for Field-Scale Reservoir Simulation
Subsurface reservoirs are large complex systems. Reservoir flow models are defined on complex grids that follow geology with relatively large block sizes to make consistent simulations feasible. Reservoir engineers rely on established reservoir simulation software to model fluid flow. Nevertheless, fluid front position inaccuracies and front smearing on large grids may cause significant errors and make it hard to predict hydrocarbon production efficiency. We investigate higher-order methods that reduce these undesired effects without refining the grid, thus making reservoir simulation more accurate and robust. For this paper, we implemented a second-order finite volume method with linear programming (LP) reconstruction in the open-source industry-grade reservoir simulator OPM Flow (part of the open porous media initiative, OPM). We benchmark it against the first-order method on full-scale cases with standard coarse and refined grids. We prepared open refined-grid models of a synthetic reservoir with an unstructured grid and refined Norne field example. Our results confirm that the LP method predicts front positions as accurately as the first-order method on the refined grid for problems dominated by transport. These include the water alternating gas scenario on the synthetic reservoir and piston-type injection on the Norne field. Moreover, we study the gains from the LP method for CO2 injection problems on the Norne field with full multi-phase complexity beyond transport. We observe the relevant difference between the first- and the second-order methods in these cases. However, in some configurations, the reservoir complexity overshadows the gains from the second-order methods.publishedVersio
Python framework for HP adaptive discontinuous Galerkin methods for two phase flow in porous media
In this paper we present a framework for solving two-phase flow problems in porous media. The discretization is based on a Discontinuous Galerkin method and includes local grid adaptivity and local choice of polynomial degree. The method is implemented using the new Python frontend Dune-FemPy to the open source framework Dune. The code used for the simulations is made available as Jupyter notebook and can be used through a Docker container. We present a number of time stepping approaches ranging from a classical IMPES method to a fully coupled implicit scheme. The implementation of the discretization is very flexible allowing to test different formulations of the two-phase flow model and adaptation strategies
Python Framework for HP Adaptive Discontinuous Galerkin Method for Two Phase Flow in Porous Media
In this paper we present a framework for solving two phase flow problems in
porous media. The discretization is based on a Discontinuous Galerkin method
and includes local grid adaptivity and local choice of polynomial degree. The
method is implemented using the new Python frontend Dune-FemPy to the open
source framework Dune. The code used for the simulations is made available as
Jupyter notebook and can be used through a Docker container. We present a
number of time stepping approaches ranging from a classical IMPES method to
fully coupled implicit scheme. The implementation of the discretization is very
flexible allowing for test different formulations of the two phase flow model
and adaptation strategies.Comment: Keywords: DG, hp-adaptivity, Two-phase flow, IMPES, Fully implicit,
Dune, Python, Porous media. 28 pages, 9 figures, various code snippet
On discontinuous Galerkin approach for atmospheric flow in the mesoscale with and without moisture
We present and discuss discontinuous Galerkin (DG) schemes for dry and moist atmospheric flows in the mesoscale. We derive terrain-following coordinates on the sphere in strong-conservation form, which makes it possible to perform the computation on a Cartesian grid and yet conserves the momentum density on an f -plane. A new DG model, i.e. DG-COSMO, is compared to the operational model COSMO of the Deutscher Wetterdienst (DWD). A simplified version of the suggested terrain-following coordinates is implemented in DG-COSMO and is compared against the DG dynamical core implemented within the DUNE framework, which uses unstructured grids to capture orography. Finally, a few idealised test cases, including 3d and moisture, are used for validation. In addition an estimate of efficiency for locally adaptive grids is derived for locally and non-locally occurring phenomena.publishedVersio
Theoretical and Practical Aspects of Space-Time DG-SEM Implementations
We discuss two approaches for the formulation and implementation of
space-time discontinuous Galerkin spectral element methods (DG-SEM). In one,
time is treated as an additional coordinate direction and a Galerkin procedure
is applied to the entire problem. In the other, the method of lines is used
with DG-SEM in space and the fully implicit Runge-Kutta method Lobatto IIIC in
time. The two approaches are mathematically equivalent in the sense that they
lead to the same discrete solution. However, in practice they differ in several
important respects, including the terminology used to describe them, the
structure of the resulting software, and the interaction with nonlinear
solvers. Challenges and merits of the two approaches are discussed with the
goal of providing the practitioner with sufficient consideration to choose
which path to follow. Additionally, implementations of the two methods are
provided as a starting point for further development. Numerical experiments
validate the theoretical accuracy of these codes and demonstrate their utility,
even for 4D problems.Comment: updated 3D experiments, fixed typo
The Open Porous Media Flow Reservoir Simulator
The Open Porous Media (OPM) initiative is a community effort that encourages
open innovation and reproducible research for simulation of porous media
processes. OPM coordinates collaborative software development, maintains and
distributes open-source software and open data sets, and seeks to ensure that
these are available under a free license in a long-term perspective.
In this paper, we present OPM Flow, which is a reservoir simulator developed
for industrial use, as well as some of the individual components used to make
OPM Flow. The descriptions apply to the 2019.10 release of OPM.Comment: 43 pages, 22 figure