FEM ConstraintFlowVelocity

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Fem-constraint-flow-velocity.svg FEM ConstraintFlowVelocity

Menu location
Model → Fluid constraints → Constraint flow velocity
Default shortcut
Introduced in version
See also
FEM tutorial


Applies a flow velocity as boundary condition to an edge in 2D or to a face in 3D.


  1. Click on Fem-constraint-flow-velocity.svg or choose Model → Fluid Constraints → Fem-constraint-flow-velocity.svg Constraint flow velocity from the top menu.
  2. The task panel will display menus for constraint flow velocity
    FEM-constraint-flow-velocity task-panel.png

    Above: Constraint flow velocity menus within the task panel

  1. Select the target Edges or Faces.
  2. Click Add
  3. Deselect "unspecified" to activate the necessary fields for edition.
  4. Fill in the values in mm/s for the main Cartesian components.


  • Vector components that are ticked as "unspecified" will be interpolated by the selected solver.
    Any vector that should be the result of the solver must be ticked as "unspecified".
  • If the target face or edge is not aligned with the main cartesian coordinate system, it is possible to tick "normal to boundary".
    If "normal to boundary" is ticked, 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 must enter the domain, then after ticking "normal to boundary" the user will have to input -20 mm/s in the "velocity X" field.
  • For a Wall with non-slip condition, the flow will be (0,0,0)
  • For a Symmetry condition, the flow will be (0, Unspecified, Unspecified) if "normal to boundary" is ticked.

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