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

Drag Factors

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 8, 2000, 20:09
Default Drag Factors
  #1
Nassar Majothi
Guest
 
Posts: n/a
Dear All, I am doing a final year degree project to predict the drag factors of various simple automotive shapes, i have currently obtained results that are around 40% away from experimental results. I have tried many solvers and mesh structures, could you please help me with further suggestions on how i may further improve my results. (using Fluent 5) Cheers, Nas.
  Reply With Quote

Old   March 9, 2000, 01:59
Default Re: Drag Factors
  #2
Bob Anderson
Guest
 
Posts: n/a
Are they 40% higher, or 40% lower than experiment? My first guess would be that you are not modeling separation correctly or at all. Are these separated flows? If so, how are you modeling that separation?

Bob
  Reply With Quote

Old   March 9, 2000, 12:57
Default Re: Drag Factors
  #3
clifford bradford
Guest
 
Posts: n/a
also try asking around in the fluent forum
  Reply With Quote

Old   March 10, 2000, 06:19
Default Re: Drag Factors
  #4
Nassar Majothi
Guest
 
Posts: n/a
Thanks for the replies. My results are 40% higher than experimental values, I am modelling seperation, although as i am new to this, i may not be doing it correctly. I am using Reynolds stress equations with non equilibrium boundary conditions. What would be the best way to model seperation? Cheers, Nas.
  Reply With Quote

Old   March 13, 2000, 07:11
Default Re: Drag Factors
  #5
Ahmed Al-otaibi
Guest
 
Posts: n/a
you have to check the base drag..it has major contribution in total drag..
  Reply With Quote

Old   March 15, 2000, 03:09
Default Re: Drag Factors
  #6
ROOH-UL-AMIN KHURRAM
Guest
 
Posts: n/a
Drag estimation is perhaps most difficult field in CFD. And if you are matching it with Wind tunell results it become even more difficult because of WT errors like wall effects and sting effect. First of all you have to get a reliable WT data with corrections. i suggest you should first match the drag coefficient of a simpler shape like a 10 degree cone. By chance I am presently involved in matching the drag coeficient of 10 degree cone with WT data. but I am doing it at supersonic Mach numbers and with various turbulence models, as base drag strongly depend on the Turbulence models. I have got quite interesting results. If you are interested to repeat this study, contact me

regards

khurram R.A
  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
Pressure drag, friction drag and total drag? Cheng CFX 9 January 26, 2024 14:46
Force vectors for drag during sweeping motion aamer FLUENT 0 April 18, 2011 09:17
Drag formulation remy Main CFD Forum 0 March 10, 2002 14:05
Inviscid Drag at subsonic, subcritical Mach # Axel Rohde Main CFD Forum 1 November 19, 2001 13:19
Drag Factors Nassar Majothi FLUENT 1 March 10, 2000 15:41


All times are GMT -4. The time now is 03:34.