FEM ConstraintFlowVelocity: Difference between revisions
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{{GuiCommand |
{{GuiCommand |
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|Name=FEM ConstraintFlowVelocity |
|Name=FEM ConstraintFlowVelocity |
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|MenuLocation=Model → Fluid |
|MenuLocation=Model → Fluid boundary conditions → Flow velocity boundary condition |
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|Workbenches=[[FEM_Workbench|FEM]] |
|Workbenches=[[FEM_Workbench|FEM]] |
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|SeeAlso=[[FEM_ConstraintInitialFlowVelocity| |
|SeeAlso=[[FEM_ConstraintInitialFlowVelocity|Constraint initial flow velocity]] |
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}} |
}} |
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<!--T:2--> |
<!--T:2--> |
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Applies a flow velocity as boundary condition to an edge in 2D or to a face in 3D. |
Applies a flow velocity as boundary condition to an edge in 2D or to a face in 3D. |
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</translate> |
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[[File:FEM-constraint-flow-velocity task-panel.png|400px]] |
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<translate> |
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⚫ | |||
{{Caption|Constraint flow velocity menus within the [[Task_panel|task panel]]}} |
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==Usage== <!--T:9--> |
==Usage== <!--T:9--> |
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<!--T:11--> |
<!--T:11--> |
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# Press the {{Button|[[Image:FEM_ConstraintFlowVelocity.svg|16px]] [[FEM_ConstraintFlowVelocity|Flow velocity boundary condition]]}} button or select the menu {{MenuCommand|Model → Fluid boundary conditions → [[Image:FEM_ConstraintFlowVelocity.svg|16px]] Flow velocity boundary condition}}. |
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# There are several ways to invoke the command: |
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#* Press the {{Button|[[Image:FEM_ConstraintFlowVelocity.svg|16px]] [[FEM_ConstraintFlowVelocity|FEM ConstraintFlowVelocity]]}} button. |
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#* Select the {{MenuCommand|Model → Fluid Constraints → [[Image:FEM_ConstraintFlowVelocity.svg|16px]] Constraint flow velocity}} option from the menu. |
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# The [[Task_panel|task panel]] will display menus for constraint flow velocity |
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# Select the target Edges or Faces. |
# Select the target Edges or Faces. |
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# Press the {{Button|Add}} button. |
# Press the {{Button|Add}} button. |
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# |
# Uncheck ''Unspecified'' to activate the necessary fields for edition. |
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# Set the velocity values or {{Version| |
# Set the velocity values or ({{Version|0.21}}) specify a formula. |
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==Formulas== |
==Formulas== <!--T:15--> |
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⚫ | |||
{{Version| |
{{Version|0.21}} |
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<!--T:17--> |
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It is possible to define a velocity by specifying the velocity profile as formula. In this case the solver sets the velocities at the different positions according to the profile. |
It is possible to define a velocity by specifying the velocity profile as formula. In this case the solver sets the velocities at the different positions according to the profile. |
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<!--T:18--> |
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To specify for example the velocity profile |
To specify for example the velocity profile |
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<!--T:19--> |
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<math>\quad |
<math>\quad |
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v_{x}=6\left(y-1\right)\left(2-y\right) |
v_{x} (y)=6\left(y-1\right)\left(2-y\right) |
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</math> |
</math> |
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<!--T:20--> |
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for <math>y\in[1;2]</math> (assuming that e.g. a pipe has the wall at y=1 and y=2) |
for <math>y\in[1;2]</math> (assuming that e.g. a pipe has the wall at y = 1 m and y = 2 m) |
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<!--T:21--> |
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enter this to the ''Formula'' field:</br> |
enter this to the ''Formula'' field:</br> |
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{{incode| Variable Coordinate 2; Real MATC "6*(tx-1)*(2-tx)"}} |
{{incode| Variable Coordinate 2; Real MATC "6*(tx-1)*(2-tx)"}} |
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<!--T:22--> |
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This code has the following syntax: |
This code has the following syntax: |
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* the prefix ''Variable'' specifies that the velocity is not a constant but a variable |
* the prefix ''Variable'' specifies that the velocity is not a constant but a variable |
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* the |
* the variable to calculate the velocity is ''Coordinate 2'', meaning y |
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* the velocity values are returned as ''Real'' (floating point value) |
* the velocity values are returned as ''Real'' (floating point value) |
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* ''MATC'' is the prefix for the Elmer solver that the following code is a formula |
* ''MATC'' is the prefix for the Elmer solver that the following code is a formula |
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* ''tx'' is the variable in |
* ''tx'' is always the name of the variable in ''MATC'' formulas, no matter that ''tx'' in our case is actually ''y'' |
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<!--T:23--> |
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That ''y'' will only be in the range <math>y\in[1;2]</math> is set because ''MATC'' only evaluates the ''tx'' range where the result is positive. This behavior is a bit special but has the advantage that one does not need to specify the range manually. |
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<!--T:24--> |
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It is also possible to use more than one variable. See as example the definition of rotations in the [[FEM_ConstraintDisplacement#Rotations|displacement constraint]]. |
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==Notes== <!--T:14--> |
==Notes== <!--T:14--> |
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<!--T:12--> |
<!--T:12--> |
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* For a wall with non-slip condition, set all velocity components to 0. |
* For a wall with non-slip condition, set all velocity components to 0. |
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* For a symmetry condition, set the the flow to 0, Unspecified, Unspecified) if |
* For a symmetry condition, set the the flow to (0, Unspecified, Unspecified) if '''Normal to boundary''' is checked. |
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Latest revision as of 14:00, 11 November 2023
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Menu location |
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Model → Fluid boundary conditions → Flow velocity boundary condition |
Workbenches |
FEM |
Default shortcut |
None |
Introduced in version |
- |
See also |
Constraint initial flow velocity |
Description
Applies a flow velocity as boundary condition to an edge in 2D or to a face in 3D.
Usage
- Press the
Flow velocity boundary condition button or select the menu Model → Fluid boundary conditions →
Flow velocity boundary condition.
- Select the target Edges or Faces.
- Press the Add button.
- Uncheck Unspecified to activate the necessary fields for edition.
- Set the velocity values or (introduced in version 0.21) specify a formula.
Formulas
It is possible to define a velocity by specifying the velocity profile as formula. In this case the solver sets the velocities at the different positions according to the profile.
To specify for example the velocity profile
for (assuming that e.g. a pipe has the wall at y = 1 m and y = 2 m)
enter this to the Formula field:
Variable Coordinate 2; Real MATC "6*(tx-1)*(2-tx)"
This code has the following syntax:
- the prefix Variable specifies that the velocity is not a constant but a variable
- the variable to calculate the velocity is Coordinate 2, meaning y
- the velocity values are returned as Real (floating point value)
- MATC is the prefix for the Elmer solver that the following code is a formula
- tx is always the name of the variable in MATC formulas, no matter that tx in our case is actually y
That y will only be in the range is set because MATC only evaluates the tx range where the result is positive. This behavior is a bit special but has the advantage that one does not need to specify the range manually.
It is also possible to use more than one variable. See as example the definition of rotations in the displacement constraint.
Notes
- Any vector component that should be the result of the solver must be set as Unspecified.
- If the target face or edge is not aligned with the main Cartesian coordinate system, it is possible to set the option Normal to boundary.
- If Normal to boundary is checked, the normal vector to the selected edge or face is X and it will be oriented away from the mesh domain.
- For example, if a flow of 20 mm/s of air should enter the domain, then with Normal to boundary one must input -20 mm/s in the Velocity x field.
- For a wall with non-slip condition, set all velocity components to 0.
- For a symmetry condition, set the the flow to (0, Unspecified, Unspecified) if Normal to boundary is checked.
- 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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