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

Best turbulance model for analysis

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 12, 2013, 02:25
Default Best turbulance model for analysis
  #1
New Member
 
adi
Join Date: Feb 2013
Posts: 13
Rep Power: 3
addy01 is on a distinguished road
I am doing a undergraduate research for calculating drag force and co-efficient of drag on heavy vehicle. please suggest me best turbulence model which one i should select for more realistic and accurate result. And please tell me should i scale down my model or i should perform analysis on full length model?? nd Wht should be OPTIMUM no of iteration for convergence?? I am using SOLIDWORKS FLOW & AUTODESK CFD.
addy01 is offline   Reply With Quote

Old   March 15, 2013, 16:18
Default
  #2
Senior Member
 
atmcfd's Avatar
 
ATM
Join Date: May 2009
Location: United States
Posts: 104
Rep Power: 7
atmcfd is on a distinguished road
Dear Addy,

1) There is no such thing as "best" turbulence model... but usually in these cases k-epsilon / Spalart - Allmaras models are preferred ( and well documented for external flows, so you can refer)

2) Scaling is really your choice, provided a good scaling factor exists for your problem. Else, its safer to do a full length sim. But if you want a good solution and want to observe the trailing vortices etc. from the vehicle, you might have to make the near wall mesh quite fine, and this will increase your computation time.

3) There is no such thing as the optimum no. iterations for convergence in turbulent flow simulations. you can give a reasonably low tolerance criteria for the residuals. The residuals going down is a good indication of convergence,but not the only one. You can also observe the flow statistics , like averaging of the velocity fields etc. and when you get something close to a statistically stationary/uniform field, you can say that the simulation has converged (almost)
atmcfd is offline   Reply With Quote

Old   March 16, 2013, 01:51
Post Thank you sir!!!
  #3
New Member
 
adi
Join Date: Feb 2013
Posts: 13
Rep Power: 3
addy01 is on a distinguished road
One more thing i want to ask if i scale down my model then i have to increase the velocity in same proportion. Sir can u tell me what is the maximum speed till that we can neglect the effect of compressibility?? neglect the Effect of mach number on Coefficient of drag?? Please Reply..
addy01 is offline   Reply With Quote

Old   March 16, 2013, 11:47
Default
  #4
Senior Member
 
Lefteris
Join Date: Oct 2011
Location: UK, Greece
Posts: 186
Rep Power: 4
Aeronautics El. K. is on a distinguished road
You have to adjust the velocity with respect to the characteristic length of your model in order to have the same Reynolds number.

If the flow you're studying is not dominated by viscous effects (which in your case I believe it's not) then you can approximate the flow as incompressible if the Mach number is less than 0.3 (Ma<0.3).
__________________
Lefteris

Aeronautics El. K. is offline   Reply With Quote

Old   March 31, 2013, 14:04
Default
  #5
New Member
 
mohammed mahdi
Join Date: Jan 2010
Location: Sudan, Khartoum
Posts: 6
Rep Power: 6
momahadi30 is on a distinguished road
the appropriate turbulent model for aerodynamics application according to Tinoco is K-omega SST with transiltional flow.
momahadi30 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
multiphaseInterFoam for RAS turbulence model chiven OpenFOAM Bugs 7 August 23, 2011 02:52
help for different between les model (subgrid-scale model) liuyuxuan FLUENT 1 October 2, 2009 15:25
Grid resolution for full-scale and down scaled model gravis Main CFD Forum 0 October 2, 2009 10:27
2 stage axial turbine model convergence issues sherifkadry CFX 2 September 7, 2009 20:51
multi fluid mixture model issue rystokes CFX 3 August 9, 2009 19:13


All times are GMT -4. The time now is 00:21.