Can explicit subgrid models enhance implicit LES simulations? A very high-order solver perspective

High-order Discontinuous Galerkin (DG) methods offer excellent accuracy for turbulent flow simulations and are increasingly attractive on modern GPU-oriented architectures, where high polynomial orders can improve arithmetic intensity for sufficiently large workloads. However, very high-order under-resolved simulations remain sensitive to the balance between numerical and modeled dissipation. Here, we investigate how explicit Vreman subgrid-scale (SGS) modeling interacts with the dissipation introduced by split-form stabilization and Riemann solvers in a DGSEM framework. Using the three-dimensional Taylor–Green vortex at Re=1600 and an inviscid case (Re → ∞), we evaluate kinetic energy dissipation, spectral accuracy, and numerical stability across well-resolved, under-resolved viscous, and strongly under-resolved regimes, comparing lower- and very high-polynomial-order configurations at comparable degrees of freedom. Our results show that the usefulness of explicit SGS modeling depends strongly on the resolution regime, polynomial order, and numerical dissipation already present in the scheme. For the well-resolved configurations considered here, adding a Vreman model does not improve accuracy because the wavenumber range where the model acts overlaps with the inherent numerical dissipation of the DG scheme. Using a similar number of degrees of freedom, we observe that lower-order simulations introduce stronger numerical damping near the smallest represented scales, whereas very high-order simulations retain more spectral content but are more prone to high-wavenumber energy accumulation when insufficient dissipation is present. In contrast, when the resolution is insufficient, a suitably weak SGS contribution can help control this high-wavenumber energy accumulation, whereas excessive SGS dissipation degrades intermediate scales. These findings identify regimes in which explicit SGS modeling is beneficial, neutral, or detrimental, and provide practical guidance for choosing dissipation mechanisms in very high-order DG turbulence simulations, which are well suited to modern GPU architectures.