Learning Forum

[fluentlearner]

Hi, I am currently studying the flow around building clusters and terrain using Fluent.

Yet, when it came to the result part, the velocity vectors are penetrating the buildings.

As my goal of the simulation is to see the flow around buildings, How can I avoid this situation? I have watched some youtube videos, they used boolean in design modeler which didn't encounter my problem. However, as the buildings in my model are not as simple as the youtube videos and the quantity is over 100, is it a must to use boolean or any other method can I use to get my desired result?

[Amine Ben Hadj Ali]

You should remove the builds in your pre processing or keep them but create the fluid volume. In DM you can just have the buildings then add an enclosure and it will create automatically the fluid volume.

[fluentlearner]

Thanks DrAmine. I have reference the YT video: https://www.youtube.com/watch?v=dJVOP1B-aSI, and I have created a simple model to make sure I got the correct concept. However, the vectors are still penetrating my building.
Would you mind teaching me how I can remove the building in pre processing? My boundary condition setting and the modelled result are shown below. Thanks!

[Amine Ben Hadj Ali]

If you have the building as cell zone UT should be a wall wall shadow if all done correct but you do not have a shadow and UT seems youvdo not have cell zone as solid so asking myself how many cell zones do you have here?

Other point ensure you do use presto! As pressure interpolation scheme.

[fluentlearner]

I have set the cell zone of the building as solid and Presto! as pressure. But the result is still penetrating the building and the contour is very odd also. Below are my settings in fluent.
I am wondering is it a must to use Boolean in Design modeller to avoid penetration in the building and are there any inputs are wrong which results in this strange outcome?
Thanks!!

[Rob]

Use Boolean and make sure you only have one cell zone at the end that has "holes" in it where the buildings should be. The above looks like you've got overlapping geometry so the solver isn't seeing the buildings.

[fluentlearner]

Thanks Rob. If my project contains building clusters with complicated structures, is it also a must to use Boolean?

[Rob]

Yes. Otherwise you won't have any structures for the air to blow around. You may need to simplify things though: if your domain is of the order of a few km across have you got sufficient compute resource to be resolving small features? Railings may become porous jumps, trees are porous media, complex facades may be flat surfaces.

[fluentlearner]

My model is around 1000m x 1000m x 500m containing 175 bodies (including 3d terrain and buildings). When I use Boolean, it pop out this error "Model size is out of range" and there are also some buildings with error "Conversion of body to DesignModeler format failed". But those buildings have very simple geometry (e.g. only a simple cube). How can I successfully use Boolean and get rid of these problems?
Thanks!

[Rob]

There's a large model support option in DM, but I can't remember where it is at present.

[Rob]

In DM, Tools-Options-Units and set Enable Large Model Support to "Yes". Do this before importing the CAD.