FEM EquationFlow/ru
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Системное название |
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FEM EquationFlow |
Расположение в меню |
Solve → Equation flow |
Верстаки |
FEM |
Быстрые клавиши |
Нет |
Представлено в версии |
- |
См. также |
FEM tutorial |
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
- After adding an Elmer solver as described here, select it in the tree view.
- Now either use the toolbar button
or the menu Solve → Flow equation.
- 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:
- ДанныеDiv Discretization: To be set to true for incompressible flow for more stable discretization when the Reynolds number increases.
- ДанныеFlow 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.
- ДанныеGradp Discretization: If set to true pressure Dirichlet boundary conditions can be used. Also the mass flux is available as a natural boundary condition.
- ДанныеVariable: Optional only for calculations in 2D: You can change the default of 3 to 2.
Note: In this case none of the flow velocity constraints can have a specified z-component.
Equation:
- ДанныеConvection: The type of convection to be used in the
Heat equation.
Note: For thermal flows it must be set to Computed (the default). - ДанныеMagnetic Induction: If set to true the magnetic induction equation will be solved along with the Navier-Stokes equations.
Notes for Convergence
If the solver results do not converge, you can try these things (in the given order):
- Reduce the ДанныеRelaxation Factor, see the nonlinear system settings.
- Increase the value for ДанныеNonlinear Newton After Iterations, see the nonlinear system settings.
- Reduce the number of CPU cores used, see the FEM preferences.
- Increase the mesh density (make it more fine).
Constraint Information
The electrostatic equation takes the following constraints into account if they are set:
Constraint flow velocity
Constraint initial flow velocity
Constraint pressure
Constraint initial pressure (introduced in version 0.21)
Notes
- 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.
- Since
Constraint pressure can only be set to faces, pressure constraints cannot be used for calculations in 2D.
- If there is no
Constraint pressure set,
Constraint initial pressure will only be taken into account if ДанныеGradp Discretization is set to true.
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.
- Materials: Solid, Fluid, Nonlinear mechanical, Reinforced (concrete); Material editor
- Element geometry: Beam (1D), Beam rotation (1D), Shell (2D), Fluid flow (1D)
Constraints
- Electromagnetic: Electrostatic potential, Current density, Magnetization
- Geometrical: Plane rotation, Section print, Transform
- Mechanical: Fixed, Displacement, Contact, Tie, Spring, Force, Pressure, Centrif, Self weight
- Thermal: Initial temperature, Heat flux, Temperature, Body heat source
- Without solver: Fluid boundary, Bearing, Gear, Pulley
- Overwrite Constants: Constant vacuum permittivity
- Solve: CalculiX Standard, CalculiX (new framework), Elmer, Mystran, Z88; Equations: Deformation, Elasticity, Electrostatic, Electricforce, Magnetodynamic, Magnetodynamic 2D, Flow, Flux, Heat; Solver: Solver control, Solver run
- Results: Purge, Show; Postprocessing: Apply changes, Pipeline from result, Warp filter, Scalar clip filter, Function cut filter, Region clip filter, Contours filter, Line clip filter, Stress linearization plot, Data at point clip filter, Filter function plane, Filter function sphere, Filter function cylinder, Filter function box
- Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types

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