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kasim March 12, 2008 10:17

LES dynamics model
 
Hi guys

Is there some kind of bug in LES dynamic model. It gave me wrong results for Large Eddy Simulation of an airfoil. I cant see anything else that can be wrong with my simulation. Since Dynamic model is not bug free guaranteed, it makes him suspect.

kasim

Rogerio Fernandes Brito March 12, 2008 21:50

Re: LES dynamics model
 
i did not have good results on heat conducting problems using cfx11 with geometry (only solid ) of small size. take care of using cfx11, ok?

*please, read my text below*

Brazil, January, 25th, 2008.

Subject: CAE program for heat conducting

Which is the better CAE program to simulate the heat conducting in a block? I tried using FEMLAB 3.0a (3.0.0.228) from COMSOL, but the results had a big deviation! It happened with the CFX program too. The softwares are listed below:

FLUENT, ABAQUS v6.7,Flow3D or some another one. Thanks!

Details: I wanna simulate a sample (=cemented carbide tool) like that:

Total dimension of the sample (x, y, z): 0.0127 x 0.0127 x 0.0047 (m) = 1.27 x 1.27 x 0.47 (cm) = 12.7 x 12.7 x 4.7 (mm)

Interval of acquisition of data = 0.22 seconds

Initial temperature of the sample= 29.2 (C) = 302.35 K

Area (s) (s) for the (s) heat flow (s):

xo= 0 x=0.0104

yo= 0 y=0.0104

zo= 0.0 z=0.0

About the sample: The values of thermal properties used to calculate these temperatures are 43.1 W/m.K and 14.8 x 10^-06 m/s.

As boundary conditions, it was considered that all the faces were submitted to a constant convection heat transfer

coefficient ( h = 20 W/mK and Tinfinite = 302.35 K ).

About the results: Im making a comparison with experimental data and it had a big deviation, around 30%.


kasim March 13, 2008 11:50

Re: LES dynamics model
 
We can confirm then that Dynamic model has been displaying deviations within results. Thank you Rogerio

kasim

Rogerio Fernandes Brito March 13, 2008 15:22

Re: LES dynamics model
 
Im talking about this problem with engineers at www.esss.com.br (support in Brazil). Lets see What they will say for me.

Rogerio.

JD March 14, 2008 06:44

Re: LES dynamics model
 
If you're in the hands of the "engineers" of ESSS, I wish you very good luck!

Usman March 14, 2008 06:59

Re: LES dynamics model
 
Are they that bad JD?

Usman

JD March 14, 2008 07:18

Re: LES dynamics model
 
Pretty pictures, no physical world. Many theoretical words, few practical arguments. Many promises, few achievements. All talk, no walk! CFD shoudl be about real engineering problems, not about modern Art.

Usman March 14, 2008 08:40

Re: LES dynamics model
 
Wish you good luck Rogerio!

Usman

Rogerio Fernandes Brito March 20, 2008 12:12

Re: LES dynamics model
 
I can confirm too!

Best Regards!

Rogerio Fernandes Brito March 20, 2008 12:15

Re: LES dynamics model
 
Thanks very much! I guess I will need a lot of lucky in solving my problem...

jonathan March 25, 2008 14:22

Re: LES dynamics model
 
Hi guys

I am either here in Brazil working with CFD at PUC-RIO. I plan to work with LES combustion. Up until now I ran LES simulation on the cold flow of my burner. I should get some results soon.

Talking about LES Dynamic model (Germano) is there one of you guys who do know what kind of test filter is used to perform the calculus of the dynamic C constant?

regards


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