CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Usefulness of Similarity theory in External Aero

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

LinkBack Thread Tools Display Modes
Old   January 10, 2007, 03:14
Default Usefulness of Similarity theory in External Aero
Amod Kumar
Posts: n/a

I am simulating external aerodynamic simulation of an automobile body. I am using symmetrical half. As per standard recommended practice, the computational domain should be 8L X 4L X 2L in longitudinal, transverse and vertical direction.

However, I have a machine limitation with mesh size restricted to < 1 million elements. It seems impossible to squeeze the number within this limit.

I resorted to use Similarity analysis to reduce the domain size. I have scaled down the computational domain by a factor of 16 and increase the inlet velocity 16 times to ensure dynamic similarity (constant Re for model and prototype).

Can anyone suggest the imlication of such simulation strategy on final result (vis-a-vis drag forces)?


Amod Kumar
  Reply With Quote

Old   January 10, 2007, 03:42
Default Re: Usefulness of Similarity theory in External Ae
Posts: n/a
Hi Amod, The problem has become interesting due to the limitations you are playing with. I have never worked on such problems, however, I am telling whatever little I know. I think you might have taken care of to check the change in Hydraulic Diameter u r using in the Re No constant. Otherwise you may end up with errouneous results. Cheers.

  Reply With Quote

Old   January 10, 2007, 05:58
Default Re: Usefulness of Similarity theory in External Ae
Posts: n/a
dear amod

i think u miss a main issue in your dimensional analysis,

note that at first u have physical spatial and temporal scales (imposed by your system behavior and phenomena under study) that are used for generation of dimensionless system.

In ur strategy, u decrease physical spatial scale by factor 16, this leads to decreasing ur mesh size (new simulation) by factor 16 for generation of previous results!!!

so u don't acquire anything, else if your solver is not dimensionless u may increase effect of ploating poits errors.

  Reply With Quote


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
CGNS Compiling Diego Main CFD Forum 17 December 21, 2014 02:40
Experiences with OpenFOAM and Automobile External Aero kyle OpenFOAM 5 October 24, 2013 06:52
Similarity Theory in External Aerodynamics Amod Kumar CFX 3 January 11, 2007 07:08
Reversed flow on external aero problem Ben FLUENT 2 August 22, 2006 10:05
External aero recommendations leo FLUENT 8 July 1, 2002 02:45

All times are GMT -4. The time now is 22:21.