How to replace an interior face with actual prism layers without having to remesh

Lets say you have a planar face zone, vent-1. This face represents some vent. You are not modeling the details of the vent but are representing it by just a face. You have meshed the entire domain.

But later you found out that this vent actually have vains that direct the flow in certain known direction. In the porous jump model, which is applied on a face zone, viscous and inertial losses are only normal to the face, so we can't really use it to direction the flow. But in the porous media model, which is applied on a cell zone, since we can specify those loss coefficients in 3 different directions, we CAN use it to direction the flow.

You should have meshed the thickness of the vent, to use the porous media, but you didn't. How to insert a cell zone (prism layers) to model the vent without having to mesh the entire domain.
1. Change the vent-1 into wall type.
+ Define-->Boundary Conditions
-select vent-1 under Zone
-select wall under Type
-answer Yes to the question
-keep the same zone name
It will create vent-1-shadow.

2. Slit vent-1 and vent-shadow into two boundary walls. Use the following text user interface (TUI).

/grid/modify-zones/slit-face-zone vent-1

It will create two walls with the name "wall-##". The number ## is the default zone ID. Let say it created wall-4 and wall-7. One wall is attached to one side of the cell and the other is attached to the other side.

3. Identify which wall (wall-4 or wall-7) is facing which side.
+Display --> Grid
Display both walls with faces. Make sure color them by ID.

+Display --> Options
-turn on Outer Face Culling

You may need to display one wall at the time to determine its color. Then display both of them at one time. They are two walls overlapping. If you rotate the geometry and view both sides, you will see different colors. Since you already know which color of each wall, now you know where they are facing.

4. Extrude one of the walls to grow prisms.

Use the following text command:

/grid modify-zones extrude-face-zone-delta wall-4 .001 .001 .001 .001 () yes

The above text command will create 4 prism layers from wall-4 (you could also use the other wall). Also, wall-4 will be sharing nodes with the prism layer, and will be changed into interior type with the name interior-4. The prism is grown away from cells that are adjacent to wall-4. So the prisms will overlap the cells on the other side, which is just fine - overlapping cells can be solved in Fluent.

The extrusion will also create prism-cap (lets say wall-10) and prism-side (lets say wall-11). It will also create a cell zone (lets say fluid-9).

Now we need to connect wall-7 to wall-10. This can be done using periodic model.

5. Using periodic model to connect the cells. Use the following TUI:

/grid modify-zones make-periodic wall-7 wall-10 no yes yes

It will delete wall-10 and create a periodic zone periodic-7.

6. Apply BC and run.

Now they are connected! Now you should be able to apply porous model on fluid-9 and solve.

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