Guide to Importing 'Foreign' geometry (From SketchUp) for CFD / (Open Foam) analysis

Hi

I am trying to figure out if I am using the wrong search terms. My questions seems likely to be a common problem: I have a complex SketchUp model that I wish to analyse through OpenFoam. Re-drawing the geometry seems pointless, and fraught with potential for error. I am sure that bringing in foreign models like SketchUp to Rhino is something that many users of Honeybee/Ladybug/Butterfly have struggled with. And yet I can find no guidance as to how to treat the geometry when importing so as to ensure reliable analysis. I have trialled the analysis with a simplistic model from SketchUp, and I get the same error message that I get with the much more complex model (reference to there being 8 arguments in the model when only 6 are needed).

What I am trying to do is make as few changes as possible to the startup outdoor airflow example script distributed with Butterfly…To no avail… Are there geometry simplification commands I could be contemplating?

outdoor_airflow_test_2018.gh (437.1 KB)

testv8.skp (104.0 KB)

Hi @MichaelDonn,

Please make sure that in Sketchup, all the geometry that should be air tight from Energy modelling or CFD point of view, is a solid. A trick in sketchup to know if a geometry is solid is to pick one of the solid tools and hower over your geometry. It shows if the geometry is a solid or not. In almost all the cases, a solid in sketchup is an air tight geometry in Rhino.

You can import Sketchup geometry in Rhino.

Hi @MichaelDonn,

In your SketchUp file there is an extra surface which doesn’t need to be imported. For the rest of geometry I imported the .skp file in Rhino as Trimmed Surfaces.

image

Then I tried selClosedPolysrf command and it didn’t pick up the geometry. To figure out where the problem lies I used showEdges command in Rhino and clicked on Naked edges.

In this case it looked like a tolerance issue show I just exploded and joined the surfaces and it gave me a closed polysurface!

image

It’s not always this easy but most of the time you can follow the same logic. There is also a command for join edges which you can use to join the edges when appropriate.

In order to make sure that your geometries come as closed polysurfaces, please make sure they are solids in sketchup. That way you can import them and simply move on to the analysis.

Hi

Thanks.

The only reason I was persevering with the test issue was I was replicating with a very simple example the same error I was finding with a much more complex building. Your suggestions have provided inspiration. I am not very hopeful that the process necessarily will convert this building, but I can see I have only two choices: carry on with the standard desk top opinion based aerodynamics analysis that I have always done, or make this work with the complex design geometry. Copying the geometry in SketchUp is just not feasible. Thanks for taking the time.

@MichaelDonn, Is it possible for you to share the more complex model? In my previous life I used to prepare models for 3d printing and mold which is a very similar process. I want to see how complicated your model is.

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Kia ora Mostapha

I now have access to an even more detailed city model than I had in 2018 in fbx and sketchup formats. It is 3D geometrical record of a Lidar collection of data. The origin is a GIS set of files. Each 3-4 block section of the city is ~200Mb in size. There are 28 of these files!

I would love to develop a system of bringing the 3D data in and estimating the UTCI score with Open Foam and Honeybee - but then relinking those UTCI textures to this rendered version of the city. At present, the import options I am trying are not working well … I cannot share this file publicly unfortunately.