38 research outputs found
On the Necessity of Superparametric Geometry Representation for Discontinuous Galerkin Methods on Domains with Curved Boundaries
We provide numerical evidence demonstrating the necessity of employing a
superparametric geometry representation in order to obtain optimal convergence
orders on two-dimensional domains with curved boundaries when solving the Euler
equations using Discontinuous Galerkin methods. However, concerning the
obtention of optimal convergence orders for the Navier-Stokes equations, we
demonstrate numerically that the use of isoparametric geometry representation
is sufficient for the case considered here.Comment: AIAA Aviation 2017 conference pape
Discretely Nonlinearly Stable Weight-Adjusted Flux Reconstruction High-Order Method for Compressible Flows on Curvilinear Grids
Provable nonlinear stability bounds the discrete approximation and ensures
that the discretization does not diverge. For high-order methods, discrete
nonlinear stability and entropy stability, have been successfully implemented
for discontinuous Galerkin (DG) and residual distribution schemes, where the
stability proofs depend on properties of L2-norms. In this paper, nonlinearly
stable flux reconstruction (NSFR) schemes are developed for three-dimensional
compressible flow in curvilinear coordinates. NSFR is derived by merging the
energy stable FR (ESFR) framework with entropy stable DG schemes. NSFR is
demonstrated to use larger time-steps than DG due to the ESFR correction
functions. NSFR differs from ESFR schemes in the literature since it
incorporates the FR correction functions on the volume terms through the use of
a modified mass matrix. We also prove that discrete kinetic energy stability
cannot be preserved to machine precision for quadrature rules where the surface
quadrature is not a subset of the volume quadrature. This paper also presents
the NSFR modified mass matrix in a weight-adjusted form. This form reduces the
computational cost in curvilinear coordinates through sum-fcatorization and
low-storage techniques. The nonlinear stability properties of the scheme are
verified on a nonsymmetric curvilinear grid for the inviscid Taylor-Green
vortex problem and the correct orders of convergence were obtained for a
manufactured solution. Lastly, we perform a computational cost comparison
between conservative DG, overintegrated DG, and our proposed entropy conserving
NSFR scheme, and find that our proposed entropy conserving NSFR scheme is
computationally competitive with the conservative DG scheme.Comment: 44 pages, 6 figure
Detached-Eddy Simulation of a Wing Tip Vortex at Dynamic Stall Conditions
The behavior of the tip vortex behind a square NACA0015 wing was numerically investigated. The problems studied include the stationary and the oscillating wings at static and dynamic stall conditions. Reynolds-averaged Navier-Stokes and detached-eddy simulation schemes were implemented. Vortex structures predicted by Reynolds-averaged Navier-Stokes were mainly diffused while detached-eddy simulation was able to produce qualitatively and quantitatively better results as compared to the experimental data. The breakup of the tip vortex, which started at the end of the upstroke and continued to the middle of the downstroke over an oscillation cycle, was observed in detached-eddy simulation data