6.8.6 Slitting Face Zones

The face-zone slitting feature has two uses:

• You can slit a single boundary zone of any double-sided type (i.e., any boundary zone that has cells on both sides of it) into two distinct zones.

• You can slit a coupled wall zone into two distinct, uncoupled wall zones.

When you slit a face zone, the solver will duplicate all faces and nodes, except those nodes that are located at the ends (2D) or edges (3D) of the zone. One set of nodes and faces will belong to one of the resulting boundary zones and the other set will belong to the other zone. The only ill effect of the shared nodes at each end is that you may see some inaccuracies at those points when you graphically display solution data with a slit boundary. (Note that if you adapt the boundary after slitting, you will not be able to fuse the boundaries back together again.)

Before you can slit, you first need select the zone in the Boundary Condition task page and change the Type to wall. Upon changing the Type to wall, another shadow zone will be created (i.e., if the original zone is called rad-outlet, another zone called rad-outlet-shadow will be created). Then you can apply the mesh/modify-zones/slit-face-zone text command on either of the walls (i.e., rad-outlet or rad-outlet-shadow) to separate them into two distinct walls.

For example, the outlet of the radiator in an underhood application is typically of interior type (i.e., has cells on both sides). If you know the mass flow rate through this zone (either from other CFD models or from test data) and want to apply it as a boundary condition at the radiator outlet, you first need to slit the radiator outlet. To be able to slit it, select wall from the Type drop-down list in the Boundary Conditions task page for this outlet. It will create a wall and a shadow. Then you can use the TUI command ( mesh/modify-zones/slit-face-zone) to slit them. After it is slit, two additional walls will be created, one facing one side of the outlet and another facing the other. Then you can select the appropriate wall and change the Type to mass-flow-inlet and specify the mass flow rate using the Mass-Flow Inlet dialog box. There is no option of mass-flow-inlet without first slitting it.

You should not confuse "slitting'' a face zone with "separating'' a face zone. When you slit a face zone, additional faces and nodes are created and placed in a new zone. When you separate a face zone, a new zone will be created, but no new faces or nodes are created; the existing faces and nodes are simply redistributed among the zones.

Inputs for Slitting Face Zones

If you wish to slit a face zone, you can use the mesh/modify-zones/slit-face-zone text command.

mesh $\rightarrow$ modify-zones $\rightarrow$ slit-face-zone

You will specify the face zone's name or ID, and the solver will replace the zone with two zones:

/mesh/modify-zones> slit-face-zone

Face zone id/name [] wall-4


  zone 4 deleted
  face zone 4 created
  face zone 10 created

Remember to save a new case file (and a data file, if data exist) after slitting faces.