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Old   April 11, 2012, 00:56
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Quote:
Originally Posted by robboflea View Post
http://hpce.iitm.ac.in/website/Manua...g/node1208.htm

from the 2nd result from google's when searching for "fluent reference values". What's not clear in that? Use the reference values of your profile but using the same definition of drag and lift coefficients used in the reference paper.

For what concerns your mesh for me it has some quality problems starting from the too big density step on the leading edge, the high aspect ratio of the cells far from the airfoil, the cells to big on the outlet boundary.

By the way this couldn't be the only problem to your simulation. What are your boundary conditions? What solver are you using? I read a few posts above that you were using a Euler solver? Was that a mistake or is that true?
Hello,
I'm using fluent 12.1, laminar model, AOA 0, velocity 25ms^-1, velocity inlet and pressure outlet. I got your reference values. While I used another mesh with aspect ration within 20 I had the same flow reversal problem. I used the youtube tutorials widely suggested at various posts here to mesh the 2D airfoil in ICEM CFD. Do u think this mesh will work fine

https://courses.cit.cornell.edu/flue...il/02face3.htm

Its from cornell university tutorial. I tried a similar density mesh and still got the flow reversal, may be I'm setting the problem wrong in fluent. Its a 10" chord length NACA 4412 that i'm trying to do simulation for.
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Old   April 11, 2012, 04:30
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The mesh from cornell university is certainly better than yours. Most likely is a problem of boundary conditions. What values do you use for your boundary conditions?
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Old   April 12, 2012, 00:24
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Quote:
Originally Posted by robboflea View Post
The mesh from cornell university is certainly better than yours. Most likely is a problem of boundary conditions. What values do you use for your boundary conditions?
I use a 20ms^-1 velocity inlet as told earlier, and then use a pressure outlet with a 0 Pa guage pressure. At the ICEM CFD, I set the solver as fluent v6 and in the BC set the FFINLET and FFOUTLET (see the geometry file) and set them as pressure farfield. Then at the fluent used the Boundary conditions to set them to velocity inlet and pressure outlet.
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Old   April 12, 2012, 03:40
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Just to know, how are your residuals going? What solver are you using? Pressure based or density based? On how many cells do you have reverse flow?
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Old   April 12, 2012, 09:44
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Originally Posted by robboflea View Post
Just to know, how are your residuals going? What solver are you using? Pressure based or density based? On how many cells do you have reverse flow?
Pressure based, and before that, when I imported the cornell university mesh it showed default fluid and when I imported mine it showed int-fluid. Is there a problem?
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Old   April 12, 2012, 09:59
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But from the residuals you don't have reversed flow anymore! it only happens at the beginning, and this is not a problem at all. Let the simulation run and see if it converges
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Old   April 12, 2012, 13:09
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Quote:
Originally Posted by robboflea View Post
But from the residuals you don't have reversed flow anymore! it only happens at the beginning, and this is not a problem at all. Let the simulation run and see if it converges
That part of snapshot was at a point of time, couldn't take for each and every line. I actually stopped the solver and took the snapshot
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Old   April 12, 2012, 13:17
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Does this mean that the reverse flow disappears and then appears again as iterations proceed? How many iterations do you normally do? What are the levels of the residuals? Are the lift and drag stable?
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