
[Sponsors] 
July 14, 2010, 16:37 

#21 
Senior Member
Join Date: Nov 2009
Posts: 411
Rep Power: 13 
For NACA 6 series you will find experimental data in Abbott's book or in his original NACA report 824 (if I remember correctly).
Do 

July 16, 2010, 01:40 

#22 
Member
Burak
Join Date: May 2009
Posts: 90
Rep Power: 10 
You are right, I downloaded NACA report 824 and there are expeimental results for NACA 6 series airfoils.
Thank you. 

August 9, 2010, 08:31 
naca 0012

#23 
New Member
Join Date: May 2010
Posts: 5
Rep Power: 9 
Hi all!
I'm trying to use the TransitionSST for my thesis case. I have a wind vertical asxis turbine. I'm using a NACA 0012 85.8mm for the cord, blunt. Reynolds I'm trying 360.000, so 61.3 m/s x velocity. It's quite high I suppose but it's only the first attempt. I found that there is, for alfa=0, a good corrispondence with the physics but now I would like to see if I'm modelling well the mesh. How I can see the point of transition? I have a y+ almost equal to 1 over the profile. But this is only for the first layer? I read that I have to create about 50 nodes till the number y+ reach 30, to read well the boundary layer. The question are: how to see after convergence where y+ reach 30 in the fluid? how to see where transition occurs? there are experimental data that I can compare? for example I found that cd for this case it should be 0.0079 from here http://www.cyberiad.net/library/airf...ta/n0012cd.htm there are other references? I tried to use Xfoil to know before where exactly this point is but I didn't manage it yet. I tried the other transition model... it oscillates around 0.0075, good value but it's not converging. with SST I reached 0.0078, but very slowly(16000 iterations, ok I have 109k elements but in the end I modelled the entire wind tunnel. I attach some images about the mesh near the profile. done with ICEM. please if anyone can help me I would be very grateful thank all best regards baggiovive 

September 4, 2010, 10:39 

#24 
Senior Member
Join Date: Nov 2009
Posts: 411
Rep Power: 13 
It is trivial to get the transition point in Xfoil for your problem. Just search Google for "Xfoil tutorials" and you will find a bunch of indications of how you can solve this problem.
Do 

September 4, 2010, 11:41 
long pipe study

#25 
New Member
eu
Join Date: Sep 2010
Posts: 2
Rep Power: 0 
Hi friends,
I got a question, I have to study the head loss along a 1 km 8" pipe and to do so, I would face the problem by dividing the pipe into several parts and the result of one section pipe will be the input of the next one and so on till getting the final head loss. Could anybody tell me how to take those results and use them as an input of the next section pipe? every section pipe is stored into a different file. thanks 

September 14, 2010, 12:34 

#26 
New Member
Join Date: May 2010
Posts: 5
Rep Power: 9 
Hi Do,
it's not so trivial to get the right transition point.. Xfoil works as a e^n method and the transition point depends on the number of n. N itself depends on the freestream turbulence. Likewise it's the same problem with menter. I've the sandia references for the naca 0012.. but there's no informations about the level of turbulence in the wind tunnel. I cannot explain better. I would onl know if someone has found the same difficulty to reach the theoric value of Cd. Write me soon. bye baggiovive 

September 14, 2010, 21:50 

#27 
Senior Member
Join Date: Nov 2009
Posts: 411
Rep Power: 13 
If you have an experimental Cd for an airfoil at moderate Mach and a reasonable Reynolds number you can "guess" the correct N by ... trial and error. First try with the default N=9 and see the relative error of the experimental Cd vs the calculated one and so on ...
Once you have the good Cd for a certain N (say less then 8% relative error), you can look at the transition point, you can assume the code has correctly placed the transition. Do 

July 21, 2013, 21:45 

#28  
Member
Join Date: Nov 2011
Posts: 86
Rep Power: 8 
Quote:
Thanks a lot, Best Roberto 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
flow simulation with a fixed transition point?  cfdzou  FLUENT  2  March 4, 2016 23:05 
HOW TO TELL WHERE THE TRANSITION point is?  Rif  Main CFD Forum  2  February 24, 2008 09:40 
Gmsh and samplesurface  touf  Open Source Meshers: Gmsh, Netgen, CGNS, ...  2  December 10, 2007 03:27 
CFX4.3 build analysis form  Chie Min  CFX  5  July 12, 2001 23:19 
Importance of transition point  Tim Franke  Main CFD Forum  4  January 28, 2000 12:14 