FEM EquationFlow: Difference between revisions

From FreeCAD Documentation
(correct Convection)
(more info)
Line 45: Line 45:
* {{PropertyData|Flow Model}}: The flow model that should be used. The default ''Full'' includes convection and time derivative terms in the model. ''No convection'' switches off the convection terms and the ''Stokes'' model switches off the convection terms and the (explicit) time derivative terms.
* {{PropertyData|Flow Model}}: The flow model that should be used. The default ''Full'' includes convection and time derivative terms in the model. ''No convection'' switches off the convection terms and the ''Stokes'' model switches off the convection terms and the (explicit) time derivative terms.
* {{PropertyData|Gradp Discretization}}: If set to ''true'' pressure [https://en.wikipedia.org/wiki/Dirichlet_boundary_condition Dirichlet boundary conditions] can be used. Also the mass flux is available as a natural boundary condition.
* {{PropertyData|Gradp Discretization}}: If set to ''true'' pressure [https://en.wikipedia.org/wiki/Dirichlet_boundary_condition Dirichlet boundary conditions] can be used. Also the mass flux is available as a natural boundary condition.
* {{PropertyData|Variable}}: Change the default of ''3'' to ''2'' for simulations in 2D.
* {{PropertyData|Variable}}: Optional only for simulations in 2D: You can change the default of ''3'' to ''2''.</br>'''Note''': In this case none of the flow constraints may have a specified z-component.


Equation:
Equation:

Revision as of 01:10, 28 October 2022

This documentation is not finished. Please help and contribute documentation.

GuiCommand model explains how commands should be documented. Browse Category:UnfinishedDocu to see more incomplete pages like this one. See Category:Command Reference for all commands.

See WikiPages to learn about editing the wiki pages, and go to Help FreeCAD to learn about other ways in which you can contribute.

FEM EquationFlow

Menu location
Solve → Flow equation
Workbenches
FEM
Default shortcut
None
Introduced in version
0.19
See also
None

This equation calculate viscous fluid flows using the Navier-Stokes equations.

For info about the math of the equation, see the Elmer models manual, section Navier-Stokes Equations.

Usage

  1. After adding an Elmer solver as described here, select it in the tree view.
  2. Now either use the toolbar button or the menu Solve → Flow equation.
  3. 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 flow equation provides these special settings:

  • DataDiv Discretization: To be set to true for incompressible flow for more stable discretization when Reynolds number increases.
  • DataFlow Model: The flow model that should be used. The default Full includes convection and time derivative terms in the model. No convection switches off the convection terms and the Stokes model switches off the convection terms and the (explicit) time derivative terms.
  • DataGradp Discretization: If set to true pressure Dirichlet boundary conditions can be used. Also the mass flux is available as a natural boundary condition.
  • DataVariable: Optional only for simulations in 2D: You can change the default of 3 to 2.
    Note: In this case none of the flow constraints may have a specified z-component.

Equation:

  • DataConvection: The type of convection to be used in the Heat equation equation.
    Note: For thermal flows it must be set to Computed (the default).
  • DataMagnetic Induction: If set to true the magnetic induction equation will be solved along with the Navier-Stokes equations.

Constraint Information

The electrostatic equation takes the following constraints into account if they are set:

Note

Except for calculations in 2D, for all above constraints it is important that they act on a face or body. Constraints for 3D set to lines or vertices are not recognized by the Elmer solver.

Results

The results are the velocity in and the pressure in . If there is no Constraint initial pressure and Constraint pressure constraint given, the resulting pressure will be relative not absolute. Since a pressure must act on a face, absolute pressure results cannot be obtained in 2D simulations