Fully and semi-implicit robust space-time DG methods for the incompressible Navier-Stokes equations

TL;DR

This paper introduces and analyzes fully and semi-implicit space-time discontinuous Galerkin methods for the incompressible Navier-Stokes equations, demonstrating stability, convergence, and efficiency improvements, especially at high Reynolds numbers.

Contribution

It presents a novel high-order semi-implicit DG scheme that reduces computational cost while maintaining stability and accuracy for Navier-Stokes simulations.

Findings

Proved pressure robustness and Reynolds semi-robustness of the schemes.

Established unconditional stability and quasi-optimal convergence rates.

Validated theoretical results with numerical experiments.

Abstract

We carry out a stability and convergence analysis of a fully discrete scheme for the time-dependent Navier-Stokes equations resulting from combining an $H(\mathrm{div}, \Omega)$-conforming discontinuous Galerkin spatial discretization, and a discontinuous Galerkin time stepping scheme. Such a scheme is proven to be pressure robust and Reynolds semi-robust. Standard techniques can be used to analyze only the case of lowest-order approximations in time. Therefore, we use some nonstandard test functions to prove existence of discrete solutions, unconditional stability, and quasi-optimal convergence rates for any degree of approximation in time. In particular, a continuous dependence of the discrete solution on the data of the problem, and quasi-optimal convergence rates for low and high Reynolds numbers are proven in an energy norm including the term $L^{\infty}(0, T; L^2(\Omega)^d)$ for the velocity. In addition to the standard discontinuous Galerkin time stepping scheme, which is fully implicit, we propose and analyze a novel high-order semi-implicit version that avoids the need of solving nonlinear systems of equations after the first time slab, thus significantly improving the efficiency of the method. Some numerical experiments validating our theoretical results are presented.