Walls

Wall conditions assigned to surfaces of a fluid region prevent flow through those surfaces. A no slip wall is created by default for all fluid flows.

The conditions that best describe the forces applied to a wall are summarized below.

Condition at the wall	Wall type	Additional information
The fluid sticks to the wall. If the wall is moving, the fluid moves with the same velocity as the wall.	No slip	Specify the Wall velocity to be stationary, rotational, or translational. For rotating and translating walls, the direction of motion must be tangential to the face.
Where the viscosity or velocity of the fluid flow means that the friction at the interface with a solid wall has a negligible impact and can be ignored.	Free slip	Components of velocity normal to a free slip wall are zero. Free-slip walls are used to: approximate the free surface of a liquid, for example where the surface of water meets air. provide a symmetry boundary by modeling an insulated free-slip wall.

If your simulation includes the heat distribution within the fluid, choose how heat transfers through the wall, via the thermal condition option that best matches your known information.