SimScale CAE Forum

Can't Make Car Wind Tunnel Simulation Run


#1

I’m trying to set up a wind tunnel simulation that I can load a car into and test the addition and removal of different aerodynamic elements.

I think I’ve loaded the model of the car correctly, and I think I have a correctly created mesh, but whenever I try and run the simulation, I get an error and it doesn’t finish running.

I’ve tried reading various tutorials and watching video webinars for SimScale, but it seems like every video and tutorial is for a different version of the software and none of them have exactly the same information.

I also tried taking someone else’s public project and copying it, and then just adding the geometry of the car I want to test into that project, but I can’t get that to work either. I keep getting a message to review the error logs, but I can’t even find where those error logs are located.

Here’s a link to a project I copied from someone else, with my model added: https://www.simscale.com/workbench/?pid=2607533383845974773

I would greatly appreciate someone helping me figure out how to get this to work! Thanks in advance.


#2

Hi @pkeck!

Split your geometry in order to create a mesh with inflated boundary layer elements. On top of that your domain is too small and the wedge boundary condition on your car is wrong it should be a wall condition with no-slip activated. The road can be modeled using a moving wall boundary condition.

Cheers,

Jousef


#3

Thank you for the quick response! Much appreciated.

I see multiple steps:

  1. Split your geometry in order to create a mesh with inflated boundary layer elements: It sounds like this is two steps: split the geometry, then create a mesh with inflated boundary layer elements…is that correct? I don’t know how to split my geometry. I added the refinement to inflate the boundary layer, but I’m not sure what settings to put into it.

  2. your domain is too small: I assume you mean the background mesh box needs to be bigger? I saw that it should be bigger based on other projects, but I was keeping this small to just try and speed up the simulation process. If you mean something else–what do you mean? :slight_smile:

  3. wedge boundary condition on your car is wrong it should be a wall condition with no-slip activated: Done

  4. The road can be modeled using a moving wall boundary condition.: Done

Thank you again!


#4

Hi @pkeck!

  1. I would suggest that you split the geometry in the CAD program you have created your model in. @yosukegb4 might give you some good tips on how to achieve that (depending on which program you use).

  2. Start with a generous background mesh box size, anyway this will be one simulation wasted if the domain is too small and this saved time is just artificial saved time :wink: You can have a look at some of the top project to get an idea of how many lengths space there should be in the front, rear and sides.

  3. & 4. Perfect :slight_smile:

Cheers,

Jousef


#5

Hi @pkeck,

I checked your geomerty and mesh. I found 0 thickness board on the bumper of your car model as below.
Generally, a zero thickness geometry causes calculation error in many cases.

How about removing the 0 thickness wall or change it with some thickness at least 6 to 10 [mm].

Regards,
Yosuke


#6

Great, thank you for the further input!

I added an air dam to the front of the car and wanted to just make it the absolute simplest possible shape to just get a result on it, but that makes sense that it needs to have thickness. I made a super basic spoiler on the rear of the car that has the same zero-thickness issue, but have resolved that.

I’m finally getting things to work now, so thank you for the input! I made started a new version of the project here: https://www.simscale.com/workbench/?pid=7927394204939999645

Now to try and figure out how to measure downforce and drag…


#7

Hi @pkeck,

That can be done relatively easily offline in ParaView.

Follow this particular tutorial on how to deduce/visualize CL CD. You can then modify the calculator values to measure for downforce and select specific areas based on the surface selection to deduce which parts generate how much downforce etc.

Hope this helps.

Cheers.

Regards,
Barry


#8

Just realized I never replied to you! Thanks for the pointer. I followed the tutorial video and am working through how to get useful results…it’s a shame that this particular functionality isn’t natively part of Simscale. Hopefully at some point in the future!


#9

Hi @pkeck,

Well the advantage of the online post-processor is convenience. Im sure better functions can and will be added soon.

Cheers.

Regards,
Barry


#10

But not for those of us who computers that can’t run Paraview :wink: