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• ## RE: [CFDBible] What is the Value of Y+ for Airfoil??

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• Dear Teguh, As far as I know k-w is used for modeling turbulence flow through complex geometries. Yes, controlling Y+ on wall is not easy, but again its the
Message 1 of 8 , Nov 18, 2009
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Dear Teguh,
As far as I know k-w is used for modeling turbulence flow through complex geometries. Yes, controlling Y+ on wall is not easy, but again its the only solution. If you are using some turbulence model you should try to closely match its Y+ requirements or at least the deviation from standard y+ values must not be very large, how large?, its another question.
Another Solution to your problem could be use of some other turbulence model. Like k-e or S-A. k-e has a y+ requirement of 30-300 and S-A has a y+ requirement of 0<y+<1 or 30<y+. If you could elaborate your problem a bit it would get more easy to suggest some more close and possible solution.
Regards,
Awais

To: CFDBible@yahoogroups.com
From: huget_teguh@...
Date: Mon, 16 Nov 2009 15:09:44 -0800
Subject: [CFDBible] What is the Value of Y+ for Airfoil??

Dear Awais,
Well,  I use experiment data of Sandia National Laboratories. My turbulence is k-w SST. I've read that the correct value of Y+ = 1-2. But it's hard for me to make boundary layer to get that value of Y+. Any suggestion??
Thank you
regards
Teguh Hady Ariwibowo

--- On Sat, 11/14/09, Awais Jaffari <awais_4u@hotmail. com> wrote:

From: Awais Jaffari <awais_4u@hotmail. com>
Subject: RE: [CFDBible] How to DRAW CURVE ON GAMBIT??
To: cfdbible@yahoogroup s.com
Date: Saturday, November 14, 2009, 6:42 PM

Dear Teguh,
Cd is always hard to predict with CFD, in fact its the trickiest part of CFD to match your value of Cd with that of authenticated experimental value. Firstly you need to have an authenticated data to compare your results with. In case you have the authenticated experimental data and you can't match your Cd with that, you need to check your turbulence model. Drag in CFD simulations consists of two components i.e. pressure drag and viscous drag. Its the viscous drag that is problematical if your turbulence model is not correct. I don't know which turbulence model you are using, you should try using a different turbulence model. Also keep a track of the Y+ values on the wall, there is different requirement of wall y+ for each turbulence model. But before doing all this check you solution properly for convergence and y+.

Regards,
Awais Ali

To: CFDBible@yahoogroup s.com
From: huget_teguh@ ymail.com
Date: Mon, 9 Nov 2009 05:29:26 -0800
Subject: Re: [CFDBible] How to DRAW CURVE ON GAMBIT??

Dear Mr mahdi

Thanks for your reply. I'll try ^^. I've other question for you, when i wanna simulate an airfoil GOE type. there is some thing wrong. The value of Cl is close to hand book but Cd is far to hand book. what's wrong with my simulation??
I'm looking forward to receiving your answer.
teguh
--- On Sat, 10/31/09, mahdi hosseinali <anishtain4@yahoo. com> wrote:

From: mahdi hosseinali <anishtain4@yahoo. com>
Subject: Re: [CFDBible] How to DRAW CURVE ON GAMBIT??
To: CFDBible@yahoogroup s.com
Date: Saturday, October 31, 2009, 1:26 AM

 HiSorry for late reply. you have to press and hold the key on the straight line icon on right panel and it will open, then there are all of the options for drawing lines in GAMBIT. There is another method that is used for airfoils which is by adding a lot of point and then straightly connecting them to each other, this may seems a little ugly but it is thoroughly accepted in literature even for accurate works. I guess if your curve dont be a part of circle you have to take the second way.Thank & bye--- On Tue, 9/15/09, huget_teguh@ ymail.com wrote:From: huget_teguh@ ymail.com Subject: [CFDBible] How to DRAW CURVE ON GAMBIT??To: CFDBible@yahoogroup s.comDate: Tuesday, September 15, 2009, 7:04 PMDearI'm Teguh. I'm interested in drawing n simulate fluid motion on CFD.. My final project is about redesigning water turbine (Crossflow turbine type). But I have constrained in drawing on Gambit. By the way, How to draw a curve in Gambit? The curve has no equation so i cannot draw easily. I'm lookin foward to get your reply!!! Thanks for your Attention.Teguh------------ --------- --------- ------Yahoo! Groups Links<*> To visit your group on the web, go to:    http://groups. yahoo.com/ group/CFDBible/<*> Your email settings:    Individual Email | Traditional<*> To change settings online go to:    http://groups. yahoo.com/ group/CFDBible/ join    (Yahoo! ID required)<*> To change settings via email:    mailto:CFDBible-digest@ yahoogroups. com     mailto:CFDBible-fullfeatur ed@yahoogroups. com<*> To unsubscribe from this group, send an email to:    CFDBible-unsubscrib e@yahoogroups. com<*> Your use of Yahoo! Groups is subject to:    http://docs. yahoo.com/ info/terms/

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