FEM Граничное условие скорости потока
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| 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.
The FEM flow velocity task panel
Применение
- There are several ways to invoke the command:
- Press the
Flow Velocity Boundary Condition button.
- Select the Model → Fluid Boundary Conditions →
Flow Velocity Boundary Condition option from the menu.
- Press the
- Press the Add button.
- Select the target objects. introduced in 1.1: To remove objects from the selection, press the Remove button.
- Uncheck unspecified to activate the necessary fields for editing.
- Set the velocity values or (introduced in 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.
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.
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