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Low Reynolds Number

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Old   September 24, 2014, 22:22
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Isaac
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Hi,
Im doing a CFD analysis on a NACA 0012 wing, with a AR of 5.0 at a Re number of 80000. I am validating it with an experimental data. Im still unsure which model I have to be using , whether to go with laminar or use turbulent BL. When I have used , laminar model, the lift coefficients matched, but the drag coefficients are far way off.
Experimental @ 5 degrees
Cl - 0.4, cd -0.12.
My analysis
Cl -0.38, cd -0.06.
Any help in helping me solve this, is deeply appreciated
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Old   September 28, 2014, 21:28
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Gabriel Boucher
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I guess you could use a low-Reynolds Turbulence model such as k-omega sst. Those are usually good for external aero purpose. That being said, in my experience I've found that it's always hard to match the drag values.
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Old   September 29, 2014, 03:30
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Iv tried that too, Iv played with the turbulence intensity and viscosity ratio too, still no avail , is there a limiting factor for Tu?
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Old   September 29, 2014, 18:50
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What does your grid look like? That's more than likely the problem.
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Old   September 29, 2014, 19:04
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Could the Turbulence Suppression model help in this problem?
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Old   October 1, 2014, 15:21
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Quote:
Originally Posted by me3840 View Post
What does your grid look like? That's more than likely the problem.

I have 300 grid points on the airfoil, and y+ = 0.8,
Regarding the grid, my only question, shd i keep dropping the y+ value, to see if my results would get any better?
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Old   October 1, 2014, 15:22
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Quote:
Originally Posted by lcarasik View Post
Could the Turbulence Suppression model help in this problem?
Yes, i have used Turbulence Suppression Model, but the answers still did not change. I am running this simulation in Star CCM+, and i used, SA model, and tried playing with turbulence viscosity ratio, the Cd value increased to 0.89, but I didnt see any major changes,
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Old   October 1, 2014, 17:45
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You're doing LES for this?
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Old   October 2, 2014, 11:29
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You're doing LES for this?
I am doing RANS for this
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Old   October 2, 2014, 13:10
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I thought the turbulent suppression model was for LES.

Anyway, can you show me the grid?
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Old   October 3, 2014, 01:27
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Quote:
Originally Posted by me3840 View Post
I thought the turbulent suppression model was for LES.

Anyway, can you show me the grid?
http://www.4shared.com/folder/prFsZuQ1/_online.html
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Old   October 4, 2014, 18:48
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Your near-wall layers seem to be really coarse. What is your wall y+?
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Old   October 4, 2014, 23:10
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I have kept it as 0.5
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Old   June 9, 2018, 06:12
Default same problem different issues
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hello Isaac
we're you able to resolve?
in my case drag coefficient is captured with minimal error of 1-3% whereas lift coefficient is way off. any help or suggestions please
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