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Flow Velocity Constraint

In one sentence: Prescribe the fluid velocity on inlet, wall, and symmetry faces for Elmer Navier-Stokes analysis.

Overview

Workbench: FEM
Menu: FEM → Model → Fluid BCs → Flow Velocity Constraint

Prescribes the fluid velocity on selected faces. This is the primary inlet, outlet, and wall boundary condition for Elmer Navier-Stokes flow analysis.

Common configurations

Face type Velocity prescription
Inlet Set all velocity components (uniform or profile)
Wall (no-slip) All components = 0
Slip wall Normal component = 0, tangential components free
Outlet Often left unconstrained (natural outflow)
Symmetry plane Normal component = 0

Parameters

Parameter Description
Velocity x X-component of velocity (m/s) or free
Velocity y Y-component
Velocity z Z-component
Normalise Normalise to a unit inlet profile

Common mistakes and pitfalls

Inlet velocity must be physically consistent

For incompressible flow, the inlet flow must balance the outlet flow (continuity ∇·v = 0). An inconsistent inlet with no matching outlet BC can cause the solver to diverge.

See also