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- Bauer, M., et al.
(författare)
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Accuracy in a finite volume godunov type method
- 2013
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Ingår i: New Results in Numerical and Experimental Fluid Mechanics VIII : Contributions to the 17th STAB/DGLR Symposium Berlin, Germany 2010 - Contributions to the 17th STAB/DGLR Symposium Berlin, Germany 2010. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642356797 ; 121, s. 387-394
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Konferensbidrag (refereegranskat)abstract
- The standard Godunov type method used in computational fluid dynamics shows accuracy problems for low Mach number flows and for the kinetic energy at the highest wave numbers resolvable on a given grid. Both drawbacks become visible when simulating the decay of isotropic turbulence at the low Mach numbers typical for the respective experimental investigations. A modification to cure both problems is proposed by Thornber et al. [10] with a mathematical motivation in case of a special fifth order reconstruction. The theoretical results are repeated here. Numerical results are achieved for schemes not investigated in that literature, namely AUSMDV and AUSM + -up which includes already modifications for low Mach number flows. First experiences with Thornber's modification confirm the positive influence in combination with AUSMDV even if the reconstruction is only of second order. In combination with AUSM + -up Thornber's modification provides too little damping when used without subgrid scale modelling. textcopyright 2013 Springer-Verlag Berlin Heidelberg.
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| 2. |
- Birken, P., et al.
(författare)
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Fast solvers for thermal fluid structure interaction
- 2013
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Ingår i: Computational Methods in Marine Engineering V - Proceedings of the 5th International Conference on Computational Methods in Marine Engineering, MARINE 2013. - 9788494140747 ; , s. 202-212
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Konferensbidrag (refereegranskat)abstract
- We consider thermal fluid structure interaction to model industrial gas quenching in steel forging, where hot steel Is cooled using cold high pressured gas. This allows to define properties of the finished steel part, as for example yield strength, locally at low cost and without environmental problems. For the numerical simulation, a partitioned approach via a Dirichlet-Neumann coupling and a fixed point iteration is employed. In time, previously developede fficient time adaptive higher order time integration schemes are used. The respective models are the compressible Navier-Stokes equations and the nonlinear heate quation, where the parameter functions are obtained from measurements on a specific steel. Here, the use of different vector extrapolation methods for convergence acceleration techniques of the fixed point iteration is analyzed. Inparticular, Aitkenrelaxation, mini-malpolynomial extrapolation (MPE) and reduced rank extrapolation (RRE) are consid-ered.
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| 6. |
- Birken, P.
(författare)
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Designing optimal smoothers for multigrid methods for unsteady flow problems
- 2011
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Ingår i: 20th AIAA Computational Fluid Dynamics Conference 2011. - 9781624101489
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Konferensbidrag (refereegranskat)abstract
- We consider the solution of unsteady flow problems using multigrid methods. There, the typical solver comes from a dual time stepping approach, where an existing method designed for a steady problem is used for unsteady flows. This design mismatch leads to a significant decrease in convergence speed. Here, we will use the linear advection equation as a model problem to find optimal Runge-Kutta smoothers specifically for the unsteady case, based on a Fourier analysis. This leads to a significantly improved multigrid method.
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