FEM EquationFlux
FEM EquationFlux |
Menu location |
---|
Solve → Flux equation |
Workbenches |
FEM |
Default shortcut |
None |
Introduced in version |
0.17 |
See also |
None |
This equation is used to calculate the fluxes resulting usually from Poisson kind of equations. These include the Heat equation and the Electrostatic equation.
For info about the math of the equation, see the Elmer models manual, section Flux Computation.
Usage
- After adding an Elmer solver as described here, select it in the tree view.
- Either use the toolbar button or the menu Solve → Flux equation.
- 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.
- When using the electrostatic equation, change the property DataFlux Coefficient to None. and the property DataFlux Variable to Potential.
- 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:
- DataAverage 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. - DataCalculate Flux: Calculates the flux vector.
- DataCalculate Flux Abs: Calculates the absolute of the flux vector. Requires that DataCalculate Flux is
true
. - DataCalculate Flux Magnitude: Computes the magnitude of the vector field. Requires that DataCalculate Flux is
true
.
Basically it is the same as DataCalculate Flux Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced. - DataCalculate Grad: Calculates the gradient of the flux.
- DataCalculate Grad Abs: Calculates the absolute flux gradient. Requires that DataCalculate Grad is
true
. - DataCalculate Grad Magnitude: Computes the magnitude of the vector field. Requires that DataCalculate Grad is
true
.
Basically it is the same as DataCalculate Grad Abs but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced. - DataDiscontinuous 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. - DataEnforce Positive Magnitude: If
true
, the negative values of the computed magnitude fields are set to zero. - DataFlux Coefficient: Name of the proportionality coefficient to compute the flux.
- DataFlux 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 DataCalculate * 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 ().
- 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
- Overwrite Constants: Constant vacuum permittivity
- Solve: CalculiX Standard, 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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