CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

how to get more accurate accurate coefficient of aerodynamic of subsonic airfoil

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 3, 2009, 20:57
Default how to get more accurate accurate coefficient of aerodynamic of subsonic airfoil
  #1
New Member
 
labib
Join Date: Jun 2009
Posts: 25
Rep Power: 6
nuimlabib is on a distinguished road
I donīt know what can i do to have an accurate coefficient of aerodynamic of airfoil, at a reynolds number of 3*10^6. I try to do several simulations,
with different types of turbulence models, such as spallart-allmaras, k-epsilon,
k-omega and even reynolds stress, but the outcome was not accurate enough, taking into account real wind tunnel data.
I realize that spallart-allmaras model is not the best one, due to it was designed for transonic speeds,
but i think that i using K-W model is best result with modify the turbulence intensity parameter with magnitude less than 0.1%..but i fell that the result still
not acurate enough for cd (drag coefficient). i have done the grid mesh with more number of cell..but still not accurate..
i need some suggestion what my mistake occure and what should i do to get the better result for cd that approach the experimental data..i try simulate the naca 4415 type
please help me..
nuimlabib is offline   Reply With Quote

Old   July 4, 2009, 09:07
Default
  #2
Member
 
Join Date: Mar 2009
Posts: 62
Rep Power: 7
RenardP is on a distinguished road
Hello,

what solver are you using for your simulations ?
Also do you know what was your wind tunnel turbulence intensity ?
RenardP is offline   Reply With Quote

Old   July 4, 2009, 09:56
Default
  #3
New Member
 
labib
Join Date: Jun 2009
Posts: 25
Rep Power: 6
nuimlabib is on a distinguished road
i am using pressure based solver..i follow the turbulence intensity based of the velocity...that for subsonic category turbulence intensity must less than 0.1 %...i am validated the simulation result with experimantal book in theory of wind section, by Ira and Abbot..so i don't know the value of turbulent intensity in the case...what parameters must i change...i am once change the parameter area..that the default value is 1 but i was change with more than 1. so the result is better..but still not enough accurate with experimental data in that book. what should i do ? please help me..give me more information...thaks alot of
nuimlabib is offline   Reply With Quote

Old   July 4, 2009, 10:17
Default
  #4
Member
 
Join Date: Mar 2009
Posts: 62
Rep Power: 7
RenardP is on a distinguished road
If you are using Fluent as I suspect you won't be able to obtain the correct Cd simply because Fluent doesn't take into account the transition from laminar to turbulent ( maybe if you will use Fluent 12 you will be able to use the new model of Menter ).

All the Abbott cases were done at Mach around 0.2 so you will have large zone of laminar flows on your airfoil.

You won't be able to obtain the experimental Cd unless you take into account the transition region.

However you should be able to obtain the experimental Cl with 10-15% error if you set up correctly your case.
RenardP is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Example subsonic airfoil case doug OpenFOAM Running, Solving & CFD 1 September 9, 2010 17:24
lift & drag coefficient on airfoil n. natik FLUENT 7 December 17, 2009 08:30
subsonic airfoil simulation miguel soto FLUENT 7 August 19, 2009 23:15
Automotive test case vinz OpenFOAM Running, Solving & CFD 98 October 27, 2008 09:43
Unsteady aerodynamic analysis of Airfoil Kyung-Seok, Kim FLUENT 2 August 22, 2005 15:28


All times are GMT -4. The time now is 10:41.