SimScale CAE Forum

Forces coefficients are too high for simulation of rear wing

Hey,

So I changed my mesh to hex-dominant parametric and made my domain bigger. My simulation worked but i got large values for my coefficient of lift&drag

Hey this is Fillia :smiley:

Instead of the two hex dominant versions, can you try the Standard mesher algorithm? Keep in mind to check the mesh quality after the generation, for example in your project here, the quality is really low:

This means that the results you extracted are based on this representation of your model:

This guide can be helpful when it comes to assessing your mesh’s quality,

Also, how did you calculate the reference length and area here?

Section 2.4 here shows the right way:

Best regards,
Fillia

3 Likes

Hello,

So I had issues with diverging velocity in my simulation. I tried using the website around me to try and fix it but It did not work So then I had switched to hex dominant parametric and I had got good results for my drag and lift for my first run. Then a few weeks later I redo the test but with different tweaks and I get my cl and cd above 1000.

Hi again, are you working on a different project at the moment? Could you provide the link please?

https://www.simscale.com/workbench/?pid=57934978301224601&mi=spec%3Add55d516-f2ac-488c-8992-7ab98fe89d44%2Cservice%3ASIMULATION%2Cstrategy%3A26&ps=domain

I see, the mesh is still really coarse and does not represent the original model.

A correct mesh should like the CAD model you are using. Please refer to the message I sent you before in order to fix your mesh: Forces coefficients are too high for simulation of rear wing - #2 by tsite

This was the mesh that I used that diverged.

I also imported my cad geometry in one shape to try and get the reference area value which I did. But i switched it back to 1 because my values of CL and CD were too high

It seems when my simulation works when I use the hex meshing but won’t work when I use the standard mesher.I don’t know why it does this

Hey,

So I spotted the bad cells in my mesh and I changed the Small feature suppression and Gap refinement factor values to try and fix that. I also made the mesh finer(7.7). The simulation worked and nothing diverged! but i got my coefficient of drag and lift values really high again. Is there still a problem with my mesh or?

Screenshot 2021-04-08 at 22.42.54

Screenshot 2021-04-09 at 10.42.48 .

Thanks!

Hey, I just noticed that the velocity is 90 m/sec, and it is expected the maximum velocity that will be reached is even higher. I suggest you try to use the compressible analysis too.

By the way, after opening the solution fields, I noticed a very large maximum velocity value, so I assume there are some bad cells. You can inspect your mesh using this guide: