Creating surface in surface, help wanted!

  • Last Post 03 March 2020
HusseinK posted this 27 February 2020

Hello all and thank you for your help and support.

I am trying to do some analyisis on a room with air coming from the circle on top and coming out of the small slot on the lower side.

I started by sketching the room and then sketching the circle as an inlet and convert it to a face from sketch, but it is not working correctly in Mesh and analysis as it is not being able to define as an inlet.

How can I define this circle as a dependent face, I tried Boolean operation but it didn't work, I hope you understand what I mean, which is make this circle as an independent face and not related to the face that is drawn on.


Thank you a lot

Order By: Standard | Newest | Votes
peteroznewman posted this 28 February 2020

Why are you using DesignModeler? If you use SpaceClaim, then it is quick and easy. Sketch the base and pull the cube, then select a face, sketch the circle, and return to 3D. The face is automatically split, the sketch is automatically deleted. Repeat on the other face with a rectangle.

There are so many more steps in DM that it is tiresome to list them in detail.  After you have a cube...

  • Create a plane on the top
  • Create a sketch on the new plane of a circle
  • Extrude the sketch, Add Frozen, as a zero thickness surface. Extrude Symmetric so the surface will be above and below the face.
  • Under Tools, Face Split, change the method to by Surface, pick the face and pick the surface. Generate. Now you have a separate face.
  • Suppress the surface body that was the tool.
  • Repeat for the other face.


HusseinK posted this 01 March 2020

peteroznewman, Thank you for your reply, it worked, although I am not familiar with Spaceclaim, but it worked in Designmodeler.


Thank you again you can call this case closed.

HusseinK posted this 01 March 2020

If I may ask another question and I hope it can be understood clearly, so I made this cube or 3d room as a fluid domain with inlet and outlet.

later on, I want to insert a diffuser and see how the air is distributed through it, after drawing the diffuser seperatly, how can I insert it inside this cube, knowing that it would be attached to the wall from inside (opposite side of the inlet circle), what settings I have to adjust (Since it will have an outlet), so my questions are:

1- How to attach the part inside a domain I specified as Fluid.

2- How to assign the Inlet and outlet as the diffuser itself will have an outlet.


Thank you in advance. 

peteroznewman posted this 01 March 2020

Please reply with an image of the diffuser.  Are you talking about a set of surfaces that the air blows against and the surfaces send the air in a different direction?

If you have a solid model of the diffuser in a CAD system, you export that solid body from the CAD system (Parasolid preferred) and in DM, use File, Import External Geometry File and Generate, then the solid will be inside your cube of air.  Then you just do a Boolean operation and Subtract the diffuser solid from the air solid.

You probably want to name those faces to get some inflation layers during meshing, but that is a new disucssion.

HusseinK posted this 02 March 2020

So the diffuser is constructed in CATIA, and it will be imported to DM, the Idea is in DM I have the room as the attached photo of it above with inlet ( the circle ), after I import the diffuser to DM, it is supposed to be fixed directly under the circle ( inside the room of course ) ( as if you are in a room and looking up at the ceiling ).

The diffuser has a circular inlet, which will fit the diameter of the circle, and will be having an outlet, I have attached the photo for clarification.

So Now I have an air inlet which is the circle ( Originally ) and there is the diffuser part inlet and outlet, that's why I don't know what to assign inlets and outlets after I put the part in the room.

And the second question, since my domain ( the room ) is fluid, do I need to do something with the new part since its a solid part?


I know it maybe confusing so that's why I talked too much to explain LOL



peteroznewman posted this 02 March 2020

Forget about inlets and outlets on the diffuser.

There is one circular inlet on the room. Air flows out of that circle with a specified velocity.  If you put solid bodies in front of that air stream, the air velocity will diffuse as it hits the surfaces of that solid body.

But remember, a solid body in space is a cavity in the air body, because you subtract the diffuser solid from the air and leave a diffuser shaped cavity in the air. Above that is the inlet.

HusseinK posted this 02 March 2020

I understand, so when I import the diffuser into DM, should I convert it to fluid before subtracting it from the room? or should I try both cases and see the difference? 

peteroznewman posted this 03 March 2020

When you import the diffuser, it doesn't matter what it is, you will subtract it from the air and it will be gone (or you can delete it).  The air is a fluid.