On the use of kinetic energy preserving DG-schemes for large eddy simulation

• Published in: Journal of computational physics Vol. 350; pp. 782 - 795
• Main Authors: Flad, David, Gassner, Gregor
• Format: Journal Article
• Language: English
• Published: Cambridge Elsevier Inc 01-12-2017; Elsevier Science Ltd
• Subjects: Aliasing; Compressibility; Computational physics; Computer simulation; Control stability; De-aliasing; Discontinuous Galerkin method; Dispersion; Energy dissipation; Flux; Galerkin method; High frequencies; Industrial applications; Interpolation; Kennedy and Gruber; Kinetic energy; Kinetic energy preserving; Kinetics; Large eddy simulation; Mach number; Mathematical analysis; Mathematical models; Numerical dissipation; Polynomials; Riemann solver; Scale models; Simulation; Solvers; Split form; Strategy; Turbulence; Vortices; Discontinuous Galerkin method; Turbulence; De-aliasing; Large eddy simulation; Kinetic energy preserving; Split form; Kennedy and Gruber
• ISSN: 0021-9991; 1090-2716
• DOI: 10.1016/j.jcp.2017.09.004

Recently, element based high order methods such as Discontinuous Galerkin (DG) methods and the closely related flux reconstruction (FR) schemes have become popular for compressible large eddy simulation (LES). Element based high order methods with Riemann solver based interface numerical flux functions offer an interesting dispersion dissipation behavior for multi-scale problems: dispersion errors are very low for a broad range of scales, while dissipation errors are very low for well resolved scales and are very high for scales close to the Nyquist cutoff. In some sense, the inherent numerical dissipation caused by the interface Riemann solver acts as a filter of high frequency solution components. This observation motivates the trend that element based high order methods with Riemann solvers are used without an explicit LES model added. Only the high frequency type inherent dissipation caused by the Riemann solver at the element interfaces is used to account for the missing sub-grid scale dissipation. Due to under-resolution of vortical dominated structures typical for LES type setups, element based high order methods suffer from stability issues caused by aliasing errors of the non-linear flux terms. A very common strategy to fight these aliasing issues (and instabilities) is so-called polynomial de-aliasing, where interpolation is exchanged with projection based on an increased number of quadrature points. In this paper, we start with this common no-model or implicit LES (iLES) DG approach with polynomial de-aliasing and Riemann solver dissipation and review its capabilities and limitations. We find that the strategy gives excellent results, but only when the resolution is such, that about 40% of the dissipation is resolved. For more realistic, coarser resolutions used in classical LES e.g. of industrial applications, the iLES DG strategy becomes quite inaccurate. We show that there is no obvious fix to this strategy, as adding for instance a sub-grid-scale models on top doesn't change much or in worst case decreases the fidelity even more. Finally, the core of this work is a novel LES strategy based on split form DG methods that are kinetic energy preserving. The scheme offers excellent stability with full control over the amount and shape of the added artificial dissipation. This premise is the main idea of the work and we will assess the LES capabilities of the novel split form DG approach when applied to shock-free, moderate Mach number turbulence. We will demonstrate that the novel DG LES strategy offers similar accuracy as the iLES methodology for well resolved cases, but strongly increases fidelity in case of more realistic coarse resolutions.
•A novel DG LES method based on kinetic energy preserving split fluxes.•Full control over sub-grid dissipation terms.•Better accuracy for coarse resolution than no-model LES.