FEM Équation de flux

From FreeCAD Documentation
Revision as of 19:06, 5 October 2022 by FuzzyBot (talk | contribs) (Updating to match new version of source page)

FEM Équation d'écoulement

Emplacement du menu
Solveur → Équation d'écoulement
Ateliers
FEM
Raccourci par défaut
Aucun
Introduit dans la version
-
Voir aussi
Tutoriel FEM

A faire

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 constraints set for these equastions.
  4. When using the electrostatic equation, change the property DonnéesFlux Coefficient to None. and the property DonnéesFlux 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:

  • DonnéesAverage 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.
  • DonnéesCalculate Flux: Calculates the flux vector.
  • DonnéesCalculate Flux Abs: Calculates the absolute of the flux vector. Requires that DonnéesCalculate Flux is true.
  • DonnéesCalculate Flux Magnitude: Computes the magnitude of the vector field. Requires that DonnéesCalculate Flux is true.
    Basically it is the same as DonnéesCalculate Flux Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
  • DonnéesCalculate Grad: Calculates the gradient of the flux.
  • DonnéesCalculate Grad Abs: Calculates the absolute flux gradient. Requires that DonnéesCalculate Grad is true.
  • DonnéesCalculate Grad Magnitude: Computes the magnitude of the vector field. Requires that DonnéesCalculate Grad is true.
    Basically it is the same as DonnéesCalculate Grad Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
  • DonnéesDiscontinuous 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.
  • DonnéesEnforce Positive Magnitude: If true, the negative values of the computed magnitude fields are set to zero.
  • DonnéesFlux Coefficient: Name of the proportionality coefficient to compute the flux.
  • DonnéesFlux Variable: Name of the potential variable used to compute the gradient.

Constraint Information

The flux equation does not have own constraints. It takes the constraints from the Heat equation or the Electrostatic equation.

Results

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

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