SimScale CAE Forum

Cd calculation for a NACA0012 Airfoil


#1

Hello,

I am trying to validate Cl and Cd data for a NACA 0012 at different angles of attack. I am able to get the values for Cl but when it comes to Cd my values are off. I have been seeing other similar projects with different settings but no luck. Could someone take a look at the project and suggest what I am not setting up right? The project is: https://www.simscale.com/workbench/?pid=4806889445452025339&mi=spec%3A99bbbb49-6f9a-4a14-ba93-29f99f497f9d%2Cservice%3AMESHING%2Cstrategy%3A17&ps=geometryPrimitives%2F0&sh=20

Thanks!


#2

I am trying to get the simulation 3AoA to work


#3

Hi @dsafieh!

Having a look at it later on! Let me tag my colleagues, the @CFD-SQUAD who might jump in a bit earlier to give you some useful input here.

Cheers!

Jousef


#4

I had the same issue, here was my write up on the solution, key outcomes is velocity divergence scheme and Y+ for k-omega SST. @CFD-SQUAD please share this project whenever drag coefficient questions come up that need to be highly accurate.

Best,
Darren


#5

Hi @1318980,

Where can I find your write up? Also, I am new to the system so where can I find the divergence scheme and Y+ settings?

Best Regards,
Dsafieh


#7

I deeply apologise @dsafieh, I forgot to post a link:

https://www.simscale.com/projects/dlynch/naca0012_validation_3/

Any questions give me a shout.

Best,
Darren


#8

Hey @1318980,

I was looking at your project before, I have the same settings (Except the reference area) but for some reason I can’t get mine to work. Could you take a look at mine to see if I am missing something? (Look at Simulation 3 AoA, that’s the one I have been working in lately)

Best,
Dsafieh


#9

Heya @dsafieh, I dont think you have selected the Gauss linear upwind scheme, also, you havnt added the Y+ field in field calulations so that you can check the Y+ values of your aerofoil surface. Add these and a stable solution and I think you will be much closer to the mark.

Let me know how it goes,
Darren


#10

Hey @1318980, Thanks for that input. When you mean the Y+ is it under result control, under Field Calculation and then under Turbulence?

Bests,
DSafieh


#11

Hi @dsafieh, yep that’s the one :slight_smile: you will then be able to see the y+ as fields on your surfaces.

Best,
Darren


#12

Hey @1318980 Thanks for the help, do you think this will give me the correct data? I will get back to you when the simulation finishes

Best,
Dsafieh


#13

Hi @dsafieh, Should do, in my experience a high drag is down to the divergence scheme. You may then go too low, then it could be mesh.

Lets see :slight_smile:


#14

Hi @1318980, The simulation is 50% done and it appears that the cd has converged around 0.02 (which is 4x higher than what is expected ) what could be causing this problem?

Best,
Dsafieh


#15

Hi @1318980, The simulation was canceled because it ran out of time but the cd looked like it converged at around 0.02 and the Cl was on track to get to the desired value of 0.33. What do you think could be wrong?

Best,
Dsafieh


#16

But you’re now using Gauss upwind not gauss linear upwind, they might not sound different but linear upwind is second-order (more accurate).

Best,
Darren


#17

Hi @1318980 I changed everything to gauss linear upwind or gauss linear upwind v unlimited. I will let you know how it goes

Best,
Dsafieh


#18

Hi @1318980, It told me that Gauss Linear Upwind Unlimited was not compatible. What type of Gauss Linear Upwind are you talking about and in what settings should I apply it?