Simulation Forums

Find Simulation answers, share expertise, and connect with your peers

Simulation CFD

Revit export for third-party CFD platform

204 Views, 10 Replies
02/10/2018 4:12 PM



I'm in the business of designing ventilation and smoke extraction systems for underground parking facilities.


The biggest issue I’m seeing right now is that the 3D Revit models are not put together with the level of accuracy necessary by the structural designers to export the model to a supported file type and import into the CFD software platform.  Therefore, it's my responsibility to copy the 3D Revit models and clean-up/prepare them to the level necessary for my use.


The training team of the company we purchased the CFD software from provided me with a high level overview of the work needed to our 3D Revit model before it’s ready to be exported for use.  A quick summary of items are:

  • File size is too large with all levels present.  Each level to be analyzed should be its own separate file.
  • The surrounding structure, which makes up the volume of air inside the parking deck to be analyzed, must be drawn “watertight”:
    • Eliminate all small gaps:
      • on the side walls
      • between the floor panels
      • between the floor and walls
    • Merge individual solids into larger solids:
      • each individual floor panel

To help visualize this a bit more, I like to imagine the following:

  1. block off all entrances, exits, ramps, and any other openings to the exterior or parking levels located above or below
  2. completely submerge the parking level of interest with water from floor to ceiling
  3. any surface that is wetted by the water is the geometry I need to retain


Going back in my career some time ago, I would correlate this to an AutoCAD operation that cross-hatches an area using the “flood” option.  Except, I’m looking at this from a 3D point-of-view rather than 2D. 


I am a novice Revit-user, with my only experience so far being ‘Autodesk Revit MEP Fundamentals Online training’.  Therefore, I need to call on the experts for determining the best approach for getting where I need to go in the most efficient manner.


Is there a way to do what I’m asking or to essentially make a mold of the internal volume of the parking level, while ignoring all of the “small gaps” that exist?


Thanks for your time and I look forward to seeing a response!




Report Inappropriate Content
Message 1 of 10 ( Views: 204 )

Re: Revit export for third-party CFD platform

02/13/2018 3:49 PM

Hello Justin,


Do you want air inside the car park only or also outside?

In CFD, if you create an external volume around your model is will also fill the inside if your model is not water tight.

You would still have to clean up the Revit model if it has small gaps and sliver surfaces or imperfections.  The Revit forum might be a better place to post Revit questions.





Report Inappropriate Content
Message 2 of 10 ( Views: 174 )

Re: Revit export for third-party CFD platform

02/13/2018 8:58 PM



Let me first mention that I am truly a novice at CFD simulations.  Also, I already posted the same exact message in the Revit forum and someone mentioned I should post in this forum as well.


I'm looking to run a simulation of the air movement inside the car park only.  In real-life the car park will not be completely airtight/watertight so I'm wondering how important it really is to have the model completed in that manner.


Thanks for the reply!

Report Inappropriate Content
Message 3 of 10 ( Views: 168 )

Re: Revit export for third-party CFD platform

02/15/2018 10:49 AM

It is important.

You can use this method to locate leakage paths.


Once you have the model 100% sealed with caps over the inlets and outlets, CFD will auto-fill the model for you and it will be the volume plus the caps from Revit that make your air volume.


Does that help?

Report Inappropriate Content
Message 4 of 10 ( Views: 157 )

Re: Revit export for third-party CFD platform

07/09/2018 11:49 AM

Since I'm not using Autodesk's CFD program, I believe the solution is not the same.  I'm using a cloud-based CFD, named Simscale.


I've posted on the Revit forum and haven't had any success finding my answer.  I will try again and let you know if I have any success.


Let me summarize again what I'm looking for.  

I’m looking for a way to get the architectural model geometry exported from Revit to use in a 3rd party CFD (computational fluid dynamics) simulation program.  I need a good process for creating a “negative volume” solid extract of a Revit model.  This means essentially a “solid” mold of the air-only region inside a structure.


If I understand it correctly, Autodesk CFD will create this volume.  I however, need to create the volume first, in order to import it into the CFD program I'm using.


I've attached three different .rvt files that I've been using to try and troubleshoot the issue, even though most geometries I'll be working with on a daily basis will be much more complicated.  One file is a very simple file with the air inlets and large vehicle opening (in the exterior walls) and the air outlets (centered in the interior) as openings in the walls.  The second file is exactly the same with the openings filled in.  The third is a more complex geometry that I would expect to see on a daily basis from my structural/architectural engineering team.


Any input here would be greatly appreciated!


Thanks in advance,



Report Inappropriate Content
Message 5 of 10 ( Views: 135 )

Re: Revit export for third-party CFD platform

07/09/2018 2:06 PM

Hi @JStirlingF3H5B,


I think I can provide some help here. If you are trying to use simscale then I would save out a SAT file from Revit. You will then need to do CAD prep/geometry clean up in a a 3rd party package. I can't really speak to whether it is better to do the geometry CAD prep in Revit or another package. I have no experience with Revit, so I don't know it's strengths of weaknesses. 


I am proficient with Fusion 360, so I would use that CAD package. It has built in "create internal fluid volume" function. You could use fusion to clean up the CAD and then create an internal fluid volume. Like Jon said, if this command fails it's because the CAD is not watertight. Finally, I am sure other CAD packages have the "create internal fluid volume" functionality, but I am most experienced with fusion. 

create fluid volume.jpg


Does this help at all?



Matt Bemis

Technical Support Specialist

Report Inappropriate Content
Message 6 of 10 ( Views: 119 )

Re: Revit export for third-party CFD platform

07/09/2018 2:11 PM

It does help @matt.bemis, but I'm most concerned with trying my best to keep all of the processes in Revit before I go to Simscale.  Thanks for the input!

Report Inappropriate Content
Message 7 of 10 ( Views: 117 )

Re: Revit export for third-party CFD platform

07/09/2018 2:20 PM

@Viveka_CD, adding you to this forum post.

Report Inappropriate Content
Message 8 of 10 ( Views: 114 )

Re: Revit export for third-party CFD platform

07/10/2018 6:57 AM

I agree with Matt.

You can do the work to make the model watertight in Revit and then run through Fusion purely to create the internal volume (couple of clicks) before jumping into CFD.


I cannot think of a faster way :)

Report Inappropriate Content
Message 9 of 10 ( Views: 82 )

Re: Revit export for third-party CFD platform

07/10/2018 10:45 AM

Thank you @matt.bemis & @Jon.Wilde!!

@Viveka_CD, if you come up with something, please let us know!

Report Inappropriate Content
Message 10 of 10 ( Views: 79 )