Application of a Line-Implicit Scheme on Stretched Unstructured Grids

Eliasson, Peter; Weinerfelt, Per; Nordström, Jan

doi:10.2514/6.2009-163

Cited by 39 publications

(20 citation statements)

References 9 publications

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“…[15][16][17] Edge is based on a finite volume formulation where a median dual grid forms the control volumes with the unknowns allocated in the centres. Edge is formally second order accurate in space and has an efficient steady state solver where the explicit time integration is …”

Section: Methodsmentioning

confidence: 99%

A global time integration approach for realistic unsteady flow computations

Eliasson

Lundquist

Nordström

2016

54th AIAA Aerospace Sciences Meeting

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Section: Methodsmentioning

confidence: 99%

A global time integration approach for realistic unsteady flow computations

Eliasson

Lundquist

Nordström

2016

54th AIAA Aerospace Sciences Meeting

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“…The scheme for the semi-implicit 3-stage Runge-Kutta algorithm (Eliasson et al 2009) is presented in Eq. 10, which is only solved along the lines implicitly and explicitly everywhere else.…”

Section: Line-implicit Runge-kuttamentioning

confidence: 99%

“…The lack of efficiency of LU-SGS for RANS computations on high aspect ratio grids (Wright et al 1995) and the sucess of the line-implicit method on highly stretched meshes (Eliasson et al 2009), has motivated our most novel implementation, the line-implicit LU-SGS solver, combining the LU-SGS solver with the line-implicit method, for the first time, to our knowledge. The idea is to provide LU-SGS with a supplementary acceleration technique only when dealing with stretched meshes.…”

Section: Introductionmentioning

confidence: 99%

“…Agglomeration multigrid (MG) acceleration speeds up the convergence rate based on the Full Approximation Scheme/Storage (FAS) (Brandt 1977) for nonlinear problems. This is combined with the lineimplicit method (Venkatakrishnan 1998;Turkel et al 1999;Mavriplis 1999;Eliasson et al 2009;Langer 2013) for Reynolds-Averaged Navier-Stokes (RANS) on stretched meshes. The line-implicit or semi-implicit Runge-Kutta time stepping approach integrates implicitly in time along lines in regions where the computational grid is highly stretched.…”

Section: Introductionmentioning

confidence: 99%

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Acceleration on stretched meshes with line-implicit LU-SGS in parallel implementation

Otero

Eliasson

2015

International Journal of Computational Fluid Dynamics

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The implicit Lower-Upper Symmetric Gauss-Seidel solver is combined with the line-implicit technique to improve convergence on the very anisotropic grids necessary for resolving the boundary layers. The computational fluid dynamics code used is Edge, a Navier-Stokes flow solver for unstructured grids based on a dual grid and edge-based formulation. Multigrid acceleration is applied with the intention to accelerate the convergence to steady state. Lower-Upper Symmetric Gauss-Seidel works in parallel and gives better linear scaling with respect to the number of processors, than the explicit scheme. The ordering techniques investigated have shown that node numbering does influence the convergence and that the orderings from Delaunay and advancing front generation were among the best tested. 2D ReynoldsAveraged Navier-Stokes computations have clearly shown the strong efficiency of our novel approach line-implicit Lower-Upper Symmetric Gauss-Seidel which is four times faster than implicit Lower-Upper Symmetric Gauss-Seidel and line-implicit Runge-Kutta. Implicit Lower-Upper Symmetric Gauss-Seidel for Euler and line-implicit Lower-Upper Symmetric Gauss-Seidel for Reynolds-Averaged Navier-Stokes are at least twice faster than explicit and line-implicit Runge-Kutta, respectively, for 2D and 3D cases. For 3D Reynolds-Averaged Navier-Stokes, multigrid did not accelerate the convergence and therefore may not be needed.

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“…EDGE is a Navier-Stokes solver originating from FOI 17,18 . It solves the Euler and RANS equations on unstructured grids.…”

Section: Edge+rommentioning

confidence: 99%

Benchmarking the Prediction of Dynamic Derivatives: Wind Tunnel Tests, Validation, Acceleration Methods

Mialon¹,

Храбров²,

Ronch

et al. 2010

AIAA Atmospheric Flight Mechanics Conference

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The dynamic derivatives are widely used in linear aerodynamic models which are considered to determine the flying qualities of an aircraft: the ability to predict them reliably, quickly and sufficiently early in the design process is more and more important, in order to avoid late and costly component redesigns. This paper describes some experimental and computational activities dealing with the determination of dynamic derivatives. The work has been carried out within the FP6 European project SimSAC. Numerical and experimental results are compared for two aircraft configurations: the generic civil transport aircraft, wing-fuselage-tail configuration DLR-F12 and a generic Transonic CRuiser (TCR), which is a canard configuration. Static and dynamic wind tunnel tests have been carried out for both configurations and are briefly described. The data base generated for the DLR-F12 configuration includes force and pressure coefficients obtained during small amplitude pitch, roll and yaw oscillations while the data base for the TCR configuration includes force coefficients for small amplitude oscillations, dedicated to the determination of dynamic derivatives, and large amplitude oscillations, in order to investigate the dynamic effects on nonlinear aerodynamic characteristics. The influence of the canard has been investigated too. Dynamic derivatives have been determined on both configurations with a large panel of tools, from linear aerodynamic (Vortex Lattice Methods) to CFD (unsteady Reynolds-Averaged Navier-Stokes solvers). The study confirms that an increase in fidelity level enables dynamic derivatives to be better calculated. Linear aerodynamics (VLM) tools can give satisfactory results but are very sensitive to the geometry/mesh input data. Although all the quasi-steady CFD approaches give very comparable results (robustness) on steady dynamic derivatives, they do not allow the prediction of unsteady components of the dynamic derivatives (angular derivatives w.r.t. time): this can be done with either a fully unsteady approach (with a time-marching scheme) or with Frequency Domain solvers, both of them giving very comparable results for the DLR-F12 test case. As far as the canard configuration is concerned; strong limitations of linear aerodynamic tools are observed. A specific attention is paid to acceleration techniques in CFD methods, which allow the computational time to be dramatically reduced while keeping a satisfactory accuracy.

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Application of a Line-Implicit Scheme on Stretched Unstructured Grids

Cited by 39 publications

References 9 publications

A global time integration approach for realistic unsteady flow computations

A global time integration approach for realistic unsteady flow computations

Acceleration on stretched meshes with line-implicit LU-SGS in parallel implementation

Benchmarking the Prediction of Dynamic Derivatives: Wind Tunnel Tests, Validation, Acceleration Methods

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