CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

please contribute with ideas: fluent and false/numerical diffusion

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 20, 2010, 08:54
Smile please contribute with ideas: fluent and false/numerical diffusion
  #1
New Member
 
mario
Join Date: Jan 2010
Posts: 3
Rep Power: 16
mario91 is on a distinguished road
false/numerical diffusion is a quite classical problem in CFD.

However I think that each simulation case should have more important corrections to handle that.I am having extreme numerical diffusion!

Briefly my case is this:

Fully developed flow along x direction. Free Atmospheric flow between ground and 150m high plane. Ground is flat so vy and vz are zero. I use orthogonal hexaedronds with r=1.07.
I am doing dispersion with species and varying schmidt number. Sct=0.7 gives high numerical diffusion, which increases even more with lower schmidt numbers (e.g. 0.4). vx velocity=(0,43m.s-1/0.4)*ln[(z+z0)/z0]. Z0=0.1m.

I am doing a point source emission and there is concentration of the emitted species even at upwind of its release!

Thanks for your ideas on this.
mario91 is offline   Reply With Quote

Old   January 20, 2010, 10:38
Default
  #2
Senior Member
 
Bernhard
Join Date: Sep 2009
Location: Delft
Posts: 790
Rep Power: 21
Bernhard is on a distinguished road
Where (which height) is your point source located?
Bernhard is offline   Reply With Quote

Old   January 20, 2010, 11:42
Default
  #3
New Member
 
mario
Join Date: Jan 2010
Posts: 3
Rep Power: 16
mario91 is on a distinguished road
i am doing different scenarios

point source (~1m3) at 10 m high or 30 m high.

Is that relevant for Numerical diffusion?
Numerical diffusion is higher near ground (e.g 1 meter high) because wind speed is slower?!


Thanks
mario91 is offline   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



All times are GMT -4. The time now is 01:51.