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

flow across sphere at Re=10,000

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 14, 2009, 00:28
Default flow across sphere at Re=10,000
  #1
New Member
 
Raheel Rasool
Join Date: Apr 2009
Posts: 7
Rep Power: 8
raheelrasool is on a distinguished road
Good Day,

I am trying to simulate flow over a sphere(using water 998.2 kg/cubic m) at Re=10,000 (V=0.01005 m/s) using Fluent. The following is my simulational setup:
  • unsteady LES with dynamic smagorinsky model
  • PISO (pressure velocity coupling)
  • standard pressure discretization and second order upwind for momentum and energy
  • time step size is 19.9005 sec (based upon assumed St=0.2, giving 25 steps in one cycle)
The problem is that my drag convergence history is a bit offset from those calculated by other people. Its a bit high, varying between 0.5~0.4 whereas it should be in the range of 0.42~0.37
I would be greatful if somebody can guide me in this regard.
Best Regards,
Raheel
raheelrasool is offline   Reply With Quote

Old   April 14, 2009, 04:03
Default
  #2
Senior Member
 
sbaffini's Avatar
 
Paolo Lampitella
Join Date: Mar 2009
Location: Italy
Posts: 519
Blog Entries: 14
Rep Power: 17
sbaffini will become famous soon enough
Second order upwind is not a good choice when performing LES. The Bounded Central Scheme is the suggested one for LES simulations, for momentum and energy.

Also, the time step should be calculated from the Re number. Actually, when performing LES, it is assumed that time filtering is not present so the time step should be chosen following this reasoning (probably a courant number less than 1 is a safe condition). Obviously, the grid spacing should be selected in the same way.

Finally, i'd choose NITA- Fractional Step instead of PISO and the PRESTO! interpolation instead of the Standard one.
sbaffini is offline   Reply With Quote

Old   April 14, 2009, 05:11
Default turbulent pipe flow
  #3
New Member
 
fudhail
Join Date: Apr 2009
Posts: 2
Rep Power: 0
fudhail is on a distinguished road
hi all,

I want to simulate turbulent in pipe flow. Could you guys give me some references so that i can validate my data. Thanks in advanve.
fudhail is offline   Reply With Quote

Old   April 19, 2009, 22:31
Default
  #4
New Member
 
Raheel Rasool
Join Date: Apr 2009
Posts: 7
Rep Power: 8
raheelrasool is on a distinguished road
Thanx Paolo for your suggestions. I applied the suggested modifications and the results are much better now.

Thanx Again...
raheelrasool 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
Flow past a sphere Fabio FLUENT 23 December 18, 2009 16:32
Can 'shock waves' occur in viscous fluid flows? diaw Main CFD Forum 105 November 20, 2009 05:19
Modeling diffusion of cell (sphere) under flow Shel Main CFD Forum 0 August 22, 2005 15:26
3D sphere flow MH Kim Main CFD Forum 1 August 8, 2005 17:06
meshing F1 front wing Steve FLUENT 0 April 17, 2003 12:37


All times are GMT -4. The time now is 02:39.