sunfluidh:new_numerical_methods_setup_namelist
Différences
Ci-dessous, les différences entre deux révisions de la page.
Les deux révisions précédentesRévision précédenteProchaine révision | Révision précédenteProchaine révisionLes deux révisions suivantes | ||
sunfluidh:new_numerical_methods_setup_namelist [2017/09/25 14:07] – [Namelist Numerical_Methods (new version)] yann | sunfluidh:new_numerical_methods_setup_namelist [2017/09/28 18:13] – [Simulation control] yann | ||
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===== Namelist " | ===== Namelist " | ||
+ | __** Not for the release SUNFLUIDH_EDU**__ | ||
<WRAP info> | <WRAP info> | ||
This new data setup is also devoted to the selection of the numerical methods and schemes used in order to solve the conservation equations for velocity components, temperature, | This new data setup is also devoted to the selection of the numerical methods and schemes used in order to solve the conservation equations for velocity components, temperature, | ||
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* [[HomeData_PoissonSolver_Namelist |HomeData_PoissonSolver]] for methods directly implemented in the code (" | * [[HomeData_PoissonSolver_Namelist |HomeData_PoissonSolver]] for methods directly implemented in the code (" | ||
* [[HypreData_PoissonSolver_Namelist |HypreData_PoissonSolver]] for methods provided by the HYPRE library | * [[HypreData_PoissonSolver_Namelist |HypreData_PoissonSolver]] for methods provided by the HYPRE library | ||
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</ | </ | ||
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===== Full data set of the namelist ===== | ===== Full data set of the namelist ===== | ||
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* The partial diagonalization method (Poisson_NumericalMethod = " | * The partial diagonalization method (Poisson_NumericalMethod = " | ||
* The HYPRE library solvers for solving the Poisson' | * The HYPRE library solvers for solving the Poisson' | ||
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</ | </ | ||
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----- | ----- | ||
==== NS_NumericalMethod | ==== NS_NumericalMethod | ||
- | (equivalent to " | + | (equivalent to " |
* Type: character string | * Type: character string | ||
* Selection of the numerical scheme for solving the conservation equations : | * Selection of the numerical scheme for solving the conservation equations : | ||
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==== MomentumConvection_Scheme ==== | ==== MomentumConvection_Scheme ==== | ||
- | (equivalent to " | + | (equivalent to " |
* Type : character string | * Type : character string | ||
* Selection of the 2nd order spatial discretization for the convection flux in the momentum equations. The options are : | * Selection of the 2nd order spatial discretization for the convection flux in the momentum equations. The options are : | ||
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==== Poisson_NumericalMethod ==== | ==== Poisson_NumericalMethod ==== | ||
- | (equivalent to " | + | (equivalent to " |
* Type : Character string | * Type : Character string | ||
* Selection of the numerical method for solving the Poisson equation in accordance to the projection method. The solution is the pressure time increment ($\Phi= P^{n+1}-P^{n}$, | * Selection of the numerical method for solving the Poisson equation in accordance to the projection method. The solution is the pressure time increment ($\Phi= P^{n+1}-P^{n}$, | ||
- | * __" | + | * __" |
* __" | * __" | ||
* __" | * __" | ||
- | * __" | + | * __" |
* __" | * __" | ||
* __" | * __" | ||
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+ | ==== Simulation control ===== | ||
+ | |||
+ | We here resort to a specific namelist named " | ||
+ | We specify here some parameters in order to define the numerical time step as well as stop criteria and recording rates related to backup and check files. | ||
+ | Two examples are given. | ||
+ | The first one corresponds to a simulation starting at t= 0 with a variable time step. | ||
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+ | The second example corresponds to a restart of the previous simulation with a uniform time step. | ||
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+ | For more information on this data set, [[sunfluidh: | ||
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+ | </note important> | ||
+ | Keep in mind the time step must be chosen with caution because it can generate numerical instabilities when it is too much large. The numerical stability depends on the property of the numerical methods used for solving the conservation equations It often relies on the CFL criterion which have not to exceeded a reference value. This value depends on the numerical scheme properties as well as the computational problem. | ||
+ | * For semi-implicit schemes proposed here, a maximum CFL-value about 0.5 is generally prescribed for usual computations, | ||
+ | * For explicit schemes, the CFL criterion also depends on the viscous/ | ||
+ | When the time-step value is constant, the user can verify if the CFL criterion is respected by checking regularly the file checkcalc_xxxxx.d | ||
+ | </ |
sunfluidh/new_numerical_methods_setup_namelist.txt · Dernière modification : 2018/05/29 15:06 de witko