Learning Forum

[emontalto]

Hi all,

I'm simulating pollutant dispersion in a street canyon and analysing the influence of solid barriers on air flow (walls, canopies, etc.). One of my configurations has 2 coffee shops on the footpaths like the one showed in this picture:

This is my 3D model, created with Space Claim: 

The coffee shops have been created using surfaces with no thickness. Everything works fine until the meshing step, but when I open FLUENT, these surfaces disappear. 

Does anybody know why this happens?

Thanks in advance,

Enrico

[peteroznewman]

Hello Enrico,

Please attach your .scdoc file or a .wbpz file to your post so I can try it out.

I found it difficult to make a zero thickness imprint into a solid in this discussion using DesignModeler. 

[Rob]

The usual trick is to make a block(s) and then label faces to suit either in SpaceClaim. This also means you can look at an average concentration/temperature/whatever in the cafe volume. 

[peteroznewman]

Okay, so create a block for each cafe and divide up the faces of the block to get two faces of "wall-canopy" and four faces of "wall-fence", then the faces in between are labeled "interior" and that allows airflow from the street into the volume under the canopy.  Each cafe block is subtracted from the street canyon solid.

[emontalto]

Thank you both for your replies. 

I've tried to create two different solids for the cafes and labelled the faces as you suggested, but I don't really understand how to set the appropriate boundary conditions on the faces of the cafes to let the airflow enter the volume under the canopy. I'm attaching my last .scdoc file to my post, that might help.

Best regards,

Enrico 

[peteroznewman]

There are two operations left to do.

1) Subtract the cafes from the canyon solid because you can't have overlapping solids.  Click on the Combine tool, click on the canyon as the Target and click on a cafe, then click on the same cafe again. This second click is to remove the cafe solid that was cut from the canyon. It is called solid in the structure.  Click on the Select tool so you can repeat that with the other cafe.  There may be a way to keep going, but I haven't looked for it.

Now you have a canyon with the cafes subtracted from it and two cafes.

2) Turn on Share Topology.  Click on the Design tab, click on the canopy-v2 file name, click on Properties and on the line called Share Topology, change it to Share.

Now there are three solids that share common faces.

Here are the three named selections of faces for the cafe on the negative x side with the cafe-air solid hidden.

  

Mesh below is deliberately coarse just to show the separate solids of air under the canopy.

[emontalto]

It works. Thank you very much for your help, I really appreciate that!

Best regards,

Enrico