Oasis: a high-level/high-performance open source Navier-Stokes solver

TL;DR

Oasis is an open-source, high-performance Navier-Stokes solver in Python that leverages FEniCS and PETSc for large-scale, complex geometry simulations, emphasizing high-level programmability and flexibility.

Contribution

It introduces a Python-based, high-level Navier-Stokes solver that is scalable, flexible, and capable of reproducing classical turbulence simulations with high accuracy.

Findings

Successfully reproduces classical turbulent channel flow results.

Achieves high computational speed dominated by linear algebra solvers.

Demonstrates higher order accuracy and extensibility for new solvers.

Abstract

Oasis is a high-level/high-performance finite element Navier-Stokes solver written from scratch in Python using building blocks from the FEniCS project (fenicsproject.org). The solver is unstructured and targets large-scale applications in complex geometries on massively parallel clusters. Oasis utilizes MPI and interfaces, through FEniCS, to the linear algebra backend PETSc. Oasis advocates a high-level, programmable user interface through the creation of highly flexible Python modules for new problems. Through the high-level Python interface the user is placed in complete control of every aspect of the solver. A version of the solver, that is using piecewise linear elements for both velocity and pressure, is shown reproduce very well the classical, spectral, turbulent channel simulations of Moser, Kim and Mansour at $Re_{\tau}=180$ [Phys. Fluids, vol 11(4), p. 964]. The computational speed is strongly dominated by the iterative solvers provided by the linear algebra backend, which is arguably the best performance any similar implicit solver using PETSc may hope for. Higher order accuracy is also demonstrated and new solvers may be easily added within the same framework.