FEM ConstraintFlowVelocity/ru: Difference between revisions

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Устанавливает скорость потока в качестве граничного условия к ребру в 2D или к грани в 3D.
Устанавливает скорость потока в качестве граничного условия к ребру в 2D или к грани в 3D.

[[File:FEM-constraint-flow-velocity task-panel.png|400px]]
{{Caption|Constraint flow velocity menus within the [[Task_panel|task panel]]}}


<span id="Usage"></span>
<span id="Usage"></span>
==Применение==
==Применение==


# Either press the button {{Button|[[Image:FEM_ConstraintFlowVelocity.svg|16px]] '''FEM ConstraintFlowVelocity'''}} or select the menu {{MenuCommand|Model → Fluid Constraints → [[Image:FEM_ConstraintFlowVelocity.svg|16px]] Constraint flow velocity}}.
# Either press the toolbar button {{Button|[[Image:FEM_ConstraintFlowVelocity.svg|16px]] '''FEM ConstraintFlowVelocity'''}} or select the menu {{MenuCommand|Model → Fluid Constraints → [[Image:FEM_ConstraintFlowVelocity.svg|16px]] Constraint flow velocity}}.
# Select the target Edges or Faces.
# Select the target Edges or Faces.
# Press the {{Button|Add}} button.
# Press the {{Button|Add}} button.
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<math>\quad
<math>\quad
v_{x}=6\left(y-1\right)\left(2-y\right)
v_{x} (y)=6\left(y-1\right)\left(2-y\right)
</math>
</math>


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This code has the following syntax:
This code has the following syntax:
* 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
* the coordinate the velocity profile is based on is ''Coordinate 2'', meaning Y
* the variable to calculate the velocity is ''Coordinate 2'', meaning y
* the velocity values are returned as ''Real'' (floating point value)
* 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
* ''MATC'' is the prefix for the Elmer solver that the following code is a formula
* ''tx'' is the variable in the 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 <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.

It is also possible to use more than one variable. See as example the definition of rotations in the [[FEM_ConstraintDisplacement#Rotations|displacement constraint]].


<span id="Notes"></span>
<span id="Notes"></span>
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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.
* For a symmetry condition, set the the flow to 0, Unspecified, Unspecified) if '''Normal to boundary''' is checked.
* For a symmetry condition, set the the flow to (0, Unspecified, Unspecified) if '''Normal to boundary''' is checked.





Revision as of 10:51, 1 April 2023

Other languages:

FEM ConstraintFlowVelocity

Системное название
FEM ConstraintFlowVelocity
Расположение в меню
Model → Fluid constraints → Constraint flow velocity
Верстаки
FEM
Быстрые клавиши
Нет
Представлено в версии
-
См. также
FEM tutorial

Описание

Устанавливает скорость потока в качестве граничного условия к ребру в 2D или к грани в 3D.

Применение

  1. Either press the toolbar button FEM ConstraintFlowVelocity or select the menu Model → Fluid Constraints → Constraint flow velocity.
  2. Select the target Edges or Faces.
  3. Press the Add button.
  4. Uncheck Unspecified to activate the necessary fields for edition.
  5. Set the velocity values or (introduced in version 1.0) specify a formula.

Formulas

introduced in version 1.0

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.

Примечания

  • Компоненты вектора, отмеченные как не указана, будут интерполированы выбранным решателем.
    Любой вектор, который должен быть результатом решателя, должен быть помечен как не указана.
  • Если целевая грань или ребро не выровнены с основной декартовой системой координат, можно поставить галочку нормаль к границе.
    Если установлен флажок нормаль к границе, вектор нормали к выбранному ребру или грани равен X, и он будет ориентирован от области сетки.
    Например, если в домен должен поступать поток воздуха со скоростью 20 мм/с, то после отметки нормаль к границе пользователь должен будет ввести -20 мм/с в поле скорость X.
  • 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.