FEM EquationFlux/it: Difference between revisions

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# After adding an Elmer solver as described [[FEM_SolverElmer#Equations|here]], select it in the [[Tree_view|tree view]].
# After adding an Elmer solver as described [[FEM_SolverElmer#Equations|here]], select it in the [[Tree_view|tree view]].
# Either use the toolbar button [[Image:FEM_EquationFlux.svg|24px]] or the menu {{MenuCommand|Solve → Flux equation}}.
# Either use the toolbar button [[Image:FEM_EquationFlux.svg|24px]] or the menu {{MenuCommand|Solve → Flux equation}}.
# Now either add a heat equation (toolbar button [[Image:FEM_EquationHeat.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationHeat|Heat equation]]}}) or an electrostatic equation (toolbar button [[Image:FEM_EquationElectrostatic.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationElectrostatic|Electrostatic equation]]}}). This is important because the flux equation needs the constraints set for these equastions.
# Now either add a heat equation (toolbar button [[Image:FEM_EquationHeat.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationHeat|Heat equation]]}}) or an electrostatic equation (toolbar button [[Image:FEM_EquationElectrostatic.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationElectrostatic|Electrostatic equation]]}}). This is important because the flux equation needs the boundary conditions set for these equations.
# When using the electrostatic equation, change the property {{PropertyData|Flux Coefficient}} to ''None''. and the property {{PropertyData|Flux Variable}} to ''Potential''.
# When using the electrostatic equation, change the property {{PropertyData|Flux Coefficient}} to ''None''. and the property {{PropertyData|Flux Variable}} to ''Potential''.
# Change the [[#Solver_Settings|equation's solver settings]] or the [[FEM_SolverElmer_SolverSettings|general solver settings]] if necessary.
# Change the [[#Solver_Settings|equation's solver settings]] or the [[FEM_SolverElmer_SolverSettings|general solver settings]] if necessary.
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The flux equation provides these special settings:
The flux equation provides these special settings:
* {{PropertyData|Average Within Materials}}: If ''true'', continuity is enforced within the same material in the discontinuous Galerkin discretization using the penalty terms of the discontinuous Galerkin formulation.
* {{PropertyData|Average Within Materials}}: If {{TRUE}}, continuity is enforced within the same material in the discontinuous Galerkin discretization using the penalty terms of the discontinuous Galerkin formulation.
* {{PropertyData|Calculate Flux}}: Calculates the flux vector.
* {{PropertyData|Calculate Flux}}: Calculates the flux vector.
* {{PropertyData|Calculate Flux Abs}}: Calculates the absolute of the flux vector. Requires that {{PropertyData|Calculate Flux}} is true.
* {{PropertyData|Calculate Flux Abs}}: Calculates the absolute of the flux vector. Requires that {{PropertyData|Calculate Flux}} is {{TRUE}}.
* {{PropertyData|Calculate Flux Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Flux}} is true.</br>Basically it is the same as {{PropertyData|Calculate Flux Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
* {{PropertyData|Calculate Flux Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Flux}} is {{TRUE}}.</br>Basically it is the same as {{PropertyData|Calculate Flux Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
* {{PropertyData|Calculate Grad}}: Calculates the gradient of the flux.
* {{PropertyData|Calculate Grad}}: Calculates the gradient of the flux.
* {{PropertyData|Calculate Grad Abs}}: Calculates the absolute flux gradient. Requires that {{PropertyData|Calculate Grad}} is true.
* {{PropertyData|Calculate Grad Abs}}: Calculates the absolute flux gradient. Requires that {{PropertyData|Calculate Grad}} is {{TRUE}}.
* {{PropertyData|Calculate Grad Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Grad}} is true.</br>Basically it is the same as {{PropertyData|Calculate Grad Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
* {{PropertyData|Calculate Grad Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Grad}} is {{TRUE}}.</br>Basically it is the same as {{PropertyData|Calculate Grad Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
* {{PropertyData|Discontinuous Galerkin}}: For discontinuous fields the standard Galerkin approximation enforces continuity which may be unphysical. As a remedy for this, set this property to ''true''. Then the result may be discontinuous and may even be visualized as such.
* {{PropertyData|Discontinuous Galerkin}}: For discontinuous fields the standard Galerkin approximation enforces continuity which may be unphysical. As a remedy for this, set this property to {{TRUE}}. Then the result may be discontinuous and may even be visualized as such.
* {{PropertyData|Enforce Positive Magnitude}}: If ''true'', the negative values of the computed magnitude fields are set to zero.
* {{PropertyData|Enforce Positive Magnitude}}: If {{TRUE}}, the negative values of the computed magnitude fields are set to zero.
* {{PropertyData|Flux Coefficient}}: Name of the proportionality coefficient to compute the flux.
* {{PropertyData|Flux Coefficient}}: Name of the proportionality coefficient to compute the flux.
* {{PropertyData|Flux Variable}}: Name of the potential variable used to compute the gradient.
* {{PropertyData|Flux Variable}}: Name of the potential variable used to compute the gradient.
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==Analysis Feature Information==
==Analysis Feature Information==


The flux equation does not have its own constraints. It takes the constraints from the [[Image:FEM_EquationHeat.svg|24px]] [[FEM_EquationHeat|Heat equation]] or the [[Image:FEM_EquationElectrostatic.svg|24px]] [[FEM_EquationElectrostatic|Electrostatic equation]].
The flux equation does not have its own boundary conditions. It takes the boundary conditions from the [[Image:FEM_EquationHeat.svg|24px]] [[FEM_EquationHeat|Heat equation]] or the [[Image:FEM_EquationElectrostatic.svg|24px]] [[FEM_EquationElectrostatic|Electrostatic equation]].


==Results==
==Results==


The available results depend on the [[#Solver_Settings|solver settings]]. If none of the {{PropertyData|Calculate *}} settings was set to ''true'', nothing is calculated. Otherwise also the corresponding results will be available.
The available results depend on the [[#Solver_Settings|solver settings]]. If none of the {{PropertyData|Calculate *}} settings was set to {{TRUE}}, nothing is calculated. Otherwise the corresponding results will also be available.


The resulting flux is either the heat flux <math>\rm W/m^2</math> (misleadingly named "temperature flux") or the potential flux in <math>\rm W/m^2</math> (<math>\rm A\cdot V/m^2</math>).
The resulting flux is either the heat flux in <math>\rm W/m^2</math> (misleadingly named "temperature flux") or the potential flux in <math>\rm W/m^2</math> (<math>\rm A\cdot V/m^2</math>).




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{{FEM Tools navi{{#translation:}}}}
{{FEM Tools navi{{#translation:}}}}
{{Userdocnavi{{#translation:}}}}
{{Userdocnavi{{#translation:}}}}
{{clear}}

Latest revision as of 13:22, 24 November 2023

Equazione fluxsolver

Posizione nel menu
Solve → Equazione fluxsolver
Ambiente
FEM
Avvio veloce
Nessuno
Introdotto nella versione
-
Vedere anche
Tutorial FEM

Da fare

For info about the math of the equation, see the Elmer models manual, section Flux Computation.

Usage

  1. After adding an Elmer solver as described here, select it in the tree view.
  2. Either use the toolbar button or the menu Solve → Flux equation.
  3. Now either add a heat equation (toolbar button or menu Solve → Heat equation) or an electrostatic equation (toolbar button or menu Solve → Electrostatic equation). This is important because the flux equation needs the boundary conditions set for these equations.
  4. When using the electrostatic equation, change the property DatiFlux Coefficient to None. and the property DatiFlux Variable to Potential.
  5. Change the equation's solver settings or the general solver settings if necessary.

Solver Settings

For the general solver settings, see the Elmer solver settings.

The flux equation provides these special settings:

  • DatiAverage Within Materials: If true, continuity is enforced within the same material in the discontinuous Galerkin discretization using the penalty terms of the discontinuous Galerkin formulation.
  • DatiCalculate Flux: Calculates the flux vector.
  • DatiCalculate Flux Abs: Calculates the absolute of the flux vector. Requires that DatiCalculate Flux is true.
  • DatiCalculate Flux Magnitude: Computes the magnitude of the vector field. Requires that DatiCalculate Flux is true.
    Basically it is the same as DatiCalculate Flux Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
  • DatiCalculate Grad: Calculates the gradient of the flux.
  • DatiCalculate Grad Abs: Calculates the absolute flux gradient. Requires that DatiCalculate Grad is true.
  • DatiCalculate Grad Magnitude: Computes the magnitude of the vector field. Requires that DatiCalculate Grad is true.
    Basically it is the same as DatiCalculate Grad Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
  • DatiDiscontinuous Galerkin: For discontinuous fields the standard Galerkin approximation enforces continuity which may be unphysical. As a remedy for this, set this property to true. Then the result may be discontinuous and may even be visualized as such.
  • DatiEnforce Positive Magnitude: If true, the negative values of the computed magnitude fields are set to zero.
  • DatiFlux Coefficient: Name of the proportionality coefficient to compute the flux.
  • DatiFlux Variable: Name of the potential variable used to compute the gradient.

Analysis Feature Information

The flux equation does not have its own boundary conditions. It takes the boundary conditions from the Heat equation or the Electrostatic equation.

Results

The available results depend on the solver settings. If none of the DatiCalculate * settings was set to true, nothing is calculated. Otherwise the corresponding results will also be available.

The resulting flux is either the heat flux in (misleadingly named "temperature flux") or the potential flux in ().