CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Turbulent flat plate

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 30, 2006, 11:31
Default Hi everybody, I'm new in Op
  #1
Senior Member
 
Vincent RIVOLA
Join Date: Mar 2009
Location: France
Posts: 283
Rep Power: 18
vinz is on a distinguished road
Hi everybody,

I'm new in OpenFOAM and I'm tryin to solve the flat plate case. The laminar case works fine but I've some troubles with the turbulnt case. I use the k-epsilon or the launder sharma k-eps model and try to compare my Cf with experimental results obtained by Weighardt.
However, either my results fits the laminar case(instead of being turbulent) either the flow is turbulent but the Cf obtained is to high (by a factor 1.5 to 2).
Does someone here allready try to solve a turbulent flat plate? What did you choose as tubulence model? DO you still have you results for Cf?

Thanks
Best regards

Vincent
vinz is offline   Reply With Quote

Old   October 30, 2006, 12:34
Default Are you using the lowRe k-eps
  #2
Member
 
Pierre Le Fur
Join Date: Mar 2009
Location: UK
Posts: 60
Rep Power: 17
pierre is on a distinguished road
Are you using the lowRe k-eps model?

Pierre
pierre is offline   Reply With Quote

Old   October 31, 2006, 10:24
Default I tried a lot of models: k-eps
  #3
Senior Member
 
Vincent RIVOLA
Join Date: Mar 2009
Location: France
Posts: 283
Rep Power: 18
vinz is on a distinguished road
I tried a lot of models: k-eps, Launder-Sharma k-eps, RNG k-eps. Non of them is giving good results.
I also tried to use first order or second order schemes. Second order gives obviously better results for laminar case but is still not able to cope with turbulence.
Did you allready run this case?
vinz is offline   Reply With Quote

Old   October 31, 2006, 10:48
Default How good is your mesh? What is
  #4
Senior Member
 
dmoroian's Avatar
 
Dragos
Join Date: Mar 2009
Posts: 648
Rep Power: 20
dmoroian is on a distinguished road
How good is your mesh? What is your y+?

Dragos
dmoroian is offline   Reply With Quote

Old   October 31, 2006, 11:13
Default I have two meshes. One mesh i
  #5
Senior Member
 
Vincent RIVOLA
Join Date: Mar 2009
Location: France
Posts: 283
Rep Power: 18
vinz is on a distinguished road
I have two meshes.
One mesh is realy fine with y+ of the order of 1e-2 or 1e-3. I use this one with turbulence models without wallfunctions.
The other one is a bit less refined at the wall, and is used with k-eps model using wallfunction. This one is giving the best results.
However, I tried both meshes with the different models and as I said, results are not good enough.

Vincent
vinz is offline   Reply With Quote

Old   November 3, 2006, 04:19
Default I was testing Low Re k-epsilon
  #6
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 17
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
I was testing Low Re k-epsilon (Chien, LienLeschziner, LamBremhorst, AbeNagano) compressible (inlet Ma = 0.2) turbulence models , over a flat plate with no pressure gradient.
I was checking the behaviour of turbulence quantities near the wall at the section with Rex = 1.03*10^7.
Unfortunatly I cannot post process my data now to obtain the Cf as a function of x but the skin friction coefficient on my test section seems to be consistent with the experimental data from Wieghardt: I got a mean value of 0.0028.
Hope this can help.
Cosimo
__________________
Cosimo Bianchini

Ergon Research s.r.l.
Via Panciatichi, 92
50127 Florence - ITALY
Tel: +39 055 0763716
Mob: +39 320 9460153
e-mail: cosimo.bianchini@ergonresearch.it
URL: www.ergonresearch.it
cosimobianchini is offline   Reply With Quote

Old   April 15, 2007, 07:11
Default Hi everyone which boundry c
  #7
Senior Member
 
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 17
marhamat is on a distinguished road
Hi everyone

which boundry conditions is proper for turbulent flat plate modeling?
can we use empty for front and back wall?(can we model this case in 2D ) .and symetry for upper wall?
Do anybody have experience in this field?
What is your conditions for correct result?

Best Regards
Marhamat
marhamat is offline   Reply With Quote

Old   April 15, 2007, 18:39
Default Hi Marhamat, that's exactly wh
  #8
Member
 
cosimo bianchini
Join Date: Mar 2009
Location: Florence, Tuscany, Italy
Posts: 88
Rep Power: 17
cosimobianchini is on a distinguished road
Send a message via Skype™ to cosimobianchini
Hi Marhamat, that's exactly what I did:

symmetryplane on the upper boundary,
empty for left and right boundaries,
obviously wall, inlet and outlet for the other three.

I was testing some Low-Reynolds k-epsilon compressible models in order to choose only few of them for more advanced tests.
The test with experimental data has been done properly only for kplus and epsilonplus behavior normally to the wall, with just a rough estimate for the other quantities of interest.
Aiming at catching turbulent peaks, the grid was very fine with an yplus of almost 0.1.

Hope this will help,
Best regards
Cosimo
__________________
Cosimo Bianchini

Ergon Research s.r.l.
Via Panciatichi, 92
50127 Florence - ITALY
Tel: +39 055 0763716
Mob: +39 320 9460153
e-mail: cosimo.bianchini@ergonresearch.it
URL: www.ergonresearch.it
cosimobianchini is offline   Reply With Quote

Old   April 16, 2007, 03:29
Default Hi Marhamat, I would also a
  #9
Senior Member
 
Vincent RIVOLA
Join Date: Mar 2009
Location: France
Posts: 283
Rep Power: 18
vinz is on a distinguished road
Hi Marhamat,

I would also advise a slip plate just before the wall plate to avoid singularities. But as you see, I didn't get right results for the turbulent plate. At that time, I didn't have the time to go deeply in the problem so I gave up.

Then, I waiting forward to see the results that you will obtain. It would be great if you could post your results and the parameters values that you used (k, eps, Re...).

Good luck.
Best regards,

Vincent
vinz is offline   Reply With Quote

Old   April 16, 2007, 08:22
Default Hi I thank you a lot for yo
  #10
Senior Member
 
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 17
marhamat is on a distinguished road
Hi

I thank you a lot for your answer
I'm interested in LES of this case
So if i get any right result i will inform you.

Best Regards
Marhamat
marhamat is offline   Reply With Quote

Old   April 29, 2007, 05:03
Default Anyone knows how to extract sk
  #11
felic
Guest
 
Posts: n/a
Anyone knows how to extract skin friction Cf from simpleFoam?
  Reply With Quote

Old   May 7, 2007, 04:50
Default Hello everybody I used channe
  #12
Senior Member
 
Marhamat Zeinali
Join Date: Mar 2009
Location: Tehran, Tehran, iran
Posts: 107
Rep Power: 17
marhamat is on a distinguished road
Hello everybody
I used channelOodles for this case(turbulent flat plate) with below settings.
Dimentions (1000 10 1)mm for 2D analysis with two blocks
(
hex (0 1 2 3 4 5 6 7) (20 100 1) simpleGrading (1 1000 1)
hex (1 8 9 2 5 11 10 6) (80 100 1) simpleGrading (1 1000 1)
);
In block0 bed(with L=200mm) is symmetryplane

Inlet Velocitt(U)=10m/s & nu=1e-6
So: Re=8*10e6 in the end of plate

You see distribution of U after runnig and initial perturbed condition that imposed to this case.




I don't see any turbulence structures in my case.
What is your idea about this?

Best Regards
Marhamat
marhamat is offline   Reply With Quote

Old   November 16, 2008, 17:00
Default Hi foamers! I'm having some t
  #13
Senior Member
 
Ivan Flaminio Cozza
Join Date: Mar 2009
Location: Torino, Piemonte, Italia
Posts: 210
Rep Power: 18
ivan_cozza is on a distinguished road
Send a message via MSN to ivan_cozza
Hi foamers!
I'm having some troubles with a turbulent flat plate calculation. I'm using simpleFoam with SST k-Omega model, for a Mach 0.11 and Re 5x10^5, but I can't get the correct values for k and it seems that the boundary layer is not represented, but my y+ is up to 8!
Any idea? Maybe SST is not the best model for the flat plate problem?
ivan_cozza is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Turbulent Boundary Layer on a Flat Plate Hoshang Garda FLUENT 1 November 27, 2013 11:24
Turbulent boundary layer on a flat plate seb62 OpenFOAM Running, Solving & CFD 0 January 16, 2009 10:33
Turbulent boundary layer on a flat plate seb62 OpenFOAM Running, Solving & CFD 0 January 16, 2009 10:30
flow over a flat plate-assume turbulent? Ben Akih CFX 4 May 5, 2006 04:33
Turbulent flow over flat plate Narayanan Main CFD Forum 1 May 8, 2000 08:03


All times are GMT -4. The time now is 02:40.