OF ESI and OF org giving different results

twnspl · July 22, 2022, 06:09

I recently shifted from OF from ESI to OF from openfoam.org and I ran one of my old wing simulation cases I found that the forces from that wing are orders of magnitude higher that what I had obtained from the ESI version. I was getting about 200N for the ESI version but I am now getting 1.4e6 N which is physically not possible. I have not changed anything in my case file. As far as I know both versions are not that different from each other is there something I am missing ?

Yann · July 22, 2022, 06:30

Hi,

It would be interesting to know which version you used on your reference case and which ESI and foundation versions you are using now.
ESI and foundation branches are slowly diverging from each others, with major changes on many aspects.

On your case, I would start by checking other quantities such as pressure and velocity fields to see if the difference lies in the force calculation or if there is something going on with the flow itself.

Yann

twnspl · July 22, 2022, 06:51

Quote:

Originally Posted by Yann

Hi,

It would be interesting to know which version you used on your reference case and which ESI and foundation versions you are using now.
ESI and foundation branches are slowly diverging from each others, with major changes on many aspects.

On your case, I would start by checking other quantities such as pressure and velocity fields to see if the difference lies in the force calculation or if there is something going on with the flow itself.

Yann

I used OF v2106 for the initial cases and now I am using OpenFOAM 9. I am trying to run the case in my friends workstation which has ESI v2206 to check.

I did not know that both versions were becoming different, that something I learnt today. Thanks !

Yann · July 22, 2022, 07:00

To be honest I am already surprised you could run your case from OpenFOAM-v2106 on OpenFOAM-9 without changing anything in the case setup!

Let us know how your tests go!

Yann

twnspl · July 23, 2022, 01:28

Quote:

Originally Posted by Yann

To be honest I am already surprised you could run your case from OpenFOAM-v2106 on OpenFOAM-9 without changing anything in the case setup!

Let us know how your tests go!

Yann

ESI v2206 gives the same result as the v2106 so I presume that the .org version doesn't like the ESI one. I think I have to switch to ESI version.

Yann · July 25, 2022, 04:49

Thanks for your feedback!
If you want to stick to the .org version, you may want to investigate on where the result difference lies. Is it only on the force calculation (it may be as simple as fixing the function object setup) or do you get a different flow?

Regards,
Yann

jan.kracik · August 8, 2024, 09:50

Hello twnspl, it may not be actual now, but I sometimes get something similar. For me, the discrepancies in results between the two branches were most of the time related to 2D simulations. I noticed that if you deal with a 2D case, the width of the case matters in regard to calculation of forces, mass flows, etc. We should always keep in mind that in general everything is 3D and transient. The 2D and steady approach are just cheat codes. Try to play around with both versions a bit and let us know how you succeed! Bless you!

July 22, 2022, 06:09	OF ESI and OF org giving different results	#1
twnspl New Member N/A Join Date: Oct 2021 Posts: 7 Rep Power: 5	I recently shifted from OF from ESI to OF from openfoam.org and I ran one of my old wing simulation cases I found that the forces from that wing are orders of magnitude higher that what I had obtained from the ESI version. I was getting about 200N for the ESI version but I am now getting 1.4e6 N which is physically not possible. I have not changed anything in my case file. As far as I know both versions are not that different from each other is there something I am missing ?

July 22, 2022, 06:30		#2
Yann Senior Member Yann Join Date: Apr 2012 Location: France Posts: 1,236 Rep Power: 29	Hi, It would be interesting to know which version you used on your reference case and which ESI and foundation versions you are using now. ESI and foundation branches are slowly diverging from each others, with major changes on many aspects. On your case, I would start by checking other quantities such as pressure and velocity fields to see if the difference lies in the force calculation or if there is something going on with the flow itself. Yann

July 22, 2022, 07:00		#4
Yann Senior Member Yann Join Date: Apr 2012 Location: France Posts: 1,236 Rep Power: 29	To be honest I am already surprised you could run your case from OpenFOAM-v2106 on OpenFOAM-9 without changing anything in the case setup! Let us know how your tests go! Yann

July 25, 2022, 04:49		#6
Yann Senior Member Yann Join Date: Apr 2012 Location: France Posts: 1,236 Rep Power: 29	Thanks for your feedback! If you want to stick to the .org version, you may want to investigate on where the result difference lies. Is it only on the force calculation (it may be as simple as fixing the function object setup) or do you get a different flow? Regards, Yann

August 8, 2024, 09:50		#7
jan.kracik New Member JK Join Date: Jun 2016 Posts: 4 Rep Power: 10	Hello twnspl, it may not be actual now, but I sometimes get something similar. For me, the discrepancies in results between the two branches were most of the time related to 2D simulations. I noticed that if you deal with a 2D case, the width of the case matters in regard to calculation of forces, mass flows, etc. We should always keep in mind that in general everything is 3D and transient. The 2D and steady approach are just cheat codes. Try to play around with both versions a bit and let us know how you succeed! Bless you!