FEM EquationFlux

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Flow equation

Heat equation

FEM

FEM EquationFlux
Menu location
Solve → Flux equation
Workbenches
FEM
Default shortcut
None
Introduced in version
0.19
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

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 DataFlux Coefficient to None. and the property DataFlux 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:

• 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 {{PropertyData|Calculate Grad} is true.
• DataCalculate Grad Magnitude: Computes the magnitude of the vector field. Requires that DataCalculate Flux 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.

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 ${\rm {W/m^{2}}}$ (misleadingly named "temperature flux") or the potential flux in ${\rm {W/m^{2}}}$ (${\rm {A\cdot V/m^{2}}}$).

Flow equation

Heat equation

FEM

FEM

• FEM Analysis

• Materials: Solid, Fluid, Nonlinear mechanical, Reinforced (concrete); Material editor

• Element geometry: Beam (1D), Beam rotation (1D), Shell (2D), Fluid flow (1D)

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Constraints

• Electromagnetic: Electrostatic potential, Current density, Magnetization

• Fluid: Initial flow velocity, Initial pressure, Flow velocity

• 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

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• Mesh: Mesh Netgen, Mesh GMSH, Mesh boundary layer, Mesh region, Mesh group, Nodes set, Mesh to mesh

• Solve: CalculiX Standard, Elmer, Mystran, Z88; Equations: Deformation, Elasticity, Electrostatic, Electricforce, Magnetodynamic, Magnetodynamic 2D, Flow, Flux, Heat; Solver: Solver control, Solver run

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• Utilities: Clipping plane, Remove clipping planes, Open FEM examples; Mesh clear, Mesh display info

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• Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types

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