FEM EquationFlux: Difference between revisions

Latest revision as of 13:19, 24 November 2023

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Flow equation

Heat equation

FEM

Menu location
FEM EquationFlux
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 ${\rm {W/m^{2}}}$ (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 Analysis

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

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

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

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

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

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

User documentation

Getting started
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Hubs: User hub, Power users hub, Developer hub

@@ Line 15: / Line 15: @@
 {{GuiCommand
 |Name=FEM EquationFlux
-|MenuLocation= Solve → Flux equation
+|MenuLocation=Solve → Flux equation
 |Workbenches=[[FEM_Workbench|FEM]]
-|Version=0.19
+|Version=0.17
 |SeeAlso=
 }}
@@ Line 24: / Line 24: @@
 This equation is used to calculate the fluxes resulting usually from Poisson kind of equations. These include the [[Image:FEM_EquationHeat.svg|24px]] [[FEM_EquationHeat|Heat equation]] and the [[Image:FEM_EquationElectrostatic.svg|24px]] [[FEM_EquationElectrostatic|Electrostatic equation]].
+<!--T:10-->
 For info about the math of the equation, see the [http://www.elmerfem.org/blog/documentation/ Elmer models manual], section ''Flux Computation''.
-==Usage==
+==Usage== <!--T:11-->
+<!--T:12-->
 # After adding an Elmer solver as described [[FEM_SolverElmer#Equations|here]], select it in the [[Tree_view|tree view]].
 # Either use the toolbar button [[Image:FEM_EquationFlux.svg|24px]] or the menu {{MenuCommand|Solve → Flux equation}}.
-# Now either add a heat equation  (toolbar button [[Image:FEM_EquationHeat.svg|24px]] or menu {{MenuCommand|Solve → heat equation}}) or an electrostatic equation (toolbar button [[Image:FEM_EquationElectrostatic.svg|24px]] or menu {{MenuCommand|Solve → Electrostatic equation}}). This is important because the flux equation needs the constraints set for these equastions.
+# Now either add a heat equation  (toolbar button [[Image:FEM_EquationHeat.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationHeat|Heat equation]]}}) or an electrostatic equation (toolbar button [[Image:FEM_EquationElectrostatic.svg|24px]] or menu {{MenuCommand|Solve → [[FEM_EquationElectrostatic|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 {{PropertyData|Flux Coefficient}} to ''None''. and the property {{PropertyData|Flux Variable}} to ''Potential''.
 # Change the [[#Solver_Settings|equation's solver settings]] or the [[FEM_SolverElmer_SolverSettings|general solver settings]] if necessary.
-==Solver Settings==
+==Solver Settings== <!--T:13-->
+<!--T:14-->
 For the general solver settings, see the [[FEM_SolverElmer_SolverSettings|Elmer solver settings]].
+<!--T:15-->
 The flux equation provides these special settings:
-* {{PropertyData|Average 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.
+* {{PropertyData|Average 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.
 * {{PropertyData|Calculate Flux}}: Calculates the flux vector.
-* {{PropertyData|Calculate Flux Abs}}: Calculates the absolute of the flux vector. Requires that {{PropertyData|Calculate Flux}} is true.
+* {{PropertyData|Calculate Flux Abs}}: Calculates the absolute of the flux vector. Requires that {{PropertyData|Calculate Flux}} is {{TRUE}}.
-* {{PropertyData|Calculate Flux Magnitude}}:  Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Flux}} is true.</br>Basically it is the same as {{PropertyData|Calculate Flux Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
+* {{PropertyData|Calculate Flux Magnitude}}:  Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Flux}} is {{TRUE}}.</br>Basically it is the same as {{PropertyData|Calculate Flux Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
 * {{PropertyData|Calculate Grad}}: Calculates the gradient of the flux.
-* {{PropertyData|Calculate Grad Abs}}: Calculates the absolute flux gradient. Requires that {{PropertyData|Calculate Grad}} is true.
+* {{PropertyData|Calculate Grad Abs}}: Calculates the absolute flux gradient. Requires that {{PropertyData|Calculate Grad}} is {{TRUE}}.
-* {{PropertyData|Calculate Grad Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Grad}} is true.</br>Basically it is the same as {{PropertyData|Calculate Grad Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
+* {{PropertyData|Calculate Grad Magnitude}}: Computes the magnitude of the vector field. Requires that {{PropertyData|Calculate Grad}} is {{TRUE}}.</br>Basically it is the same as {{PropertyData|Calculate Grad Abs}} but this requires less memory because it solves the matrix equation only once. The downside is that negative values may be introduced.
-* {{PropertyData|Discontinuous 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.
+* {{PropertyData|Discontinuous 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.
-* {{PropertyData|Enforce Positive Magnitude}}: If ''true'', the negative values of the computed magnitude fields are set to zero.
+* {{PropertyData|Enforce Positive Magnitude}}: If {{TRUE}}, the negative values of the computed magnitude fields are set to zero.
 * {{PropertyData|Flux Coefficient}}: Name of the proportionality coefficient to compute the flux.
 * {{PropertyData|Flux Variable}}: Name of the potential variable used to compute the gradient.
-==Constraint Information==
+==Analysis Feature Information== <!--T:16-->
+<!--T:17-->
-The flux equation does not have own constraints. It takes the constraints from the [[Image:FEM_EquationHeat.svg|24px]] [[FEM_EquationHeat|Heat equation]] or the [[Image:FEM_EquationElectrostatic.svg|24px]] [[FEM_EquationElectrostatic|Electrostatic equation]].
+The flux equation does not have its own boundary conditions. It takes the boundary conditions from the [[Image:FEM_EquationHeat.svg|24px]] [[FEM_EquationHeat|Heat equation]] or the [[Image:FEM_EquationElectrostatic.svg|24px]] [[FEM_EquationElectrostatic|Electrostatic equation]].
-==Results==
+==Results== <!--T:18-->
+<!--T:19-->
-The available results depend on the [[#Solver_Settings|solver settings]]. If none of them was set to ''true'', nothing is calculated. Otherwise also the corresponding results will be available.
+The available results depend on the [[#Solver_Settings|solver settings]]. If none of the {{PropertyData|Calculate *}} settings was set to {{TRUE}}, nothing is calculated. Otherwise the corresponding results will also be available.
+<!--T:20-->
-The resulting flux is either the heat flux <math>\rm W/m^2</math> (misleadingly named "temperature flux") or the potential flux in <math>\rm W/m^2</math> (<math>\rm A\cdot V/m^2</math>).
+The resulting flux is either the heat flux in <math>\rm W/m^2</math> (misleadingly named "temperature flux") or the potential flux in <math>\rm W/m^2</math> (<math>\rm A\cdot V/m^2</math>).
@@ Line 75: / Line 82: @@
 {{FEM Tools navi{{#translation:}}}}
 {{Userdocnavi{{#translation:}}}}
-{{clear}}