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

Validity of NS-eq at low pressures

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

Reply
 
LinkBack Thread Tools Display Modes
Old   November 5, 2002, 17:17
Default Validity of NS-eq at low pressures
  #1
P.Fonteijn
Guest
 
Posts: n/a
Hi all,

I would like to know if anyone have experience in CFD calcluations at very low pressures, say 0.01 Pa. Are the Navier-Stokes equations still valid at such low pressures? Is there a limit anyway for the NS-eqs.?

Pascale
  Reply With Quote

Old   November 6, 2002, 03:23
Default Re: Validity of NS-eq at low pressures
  #2
cheetah
Guest
 
Posts: n/a
I think your problem is not well raised. And I think you should change your pressure into adimensional conditions. And at that time, it is still much lower than other parameters, the NS equations may not to be correct any longer. On another side, the pressure is too low to consider your fluid to be continuum, the NS equation is no longer accepted.
  Reply With Quote

Old   November 6, 2002, 08:12
Default Re: Validity of NS-eq at low pressures
  #3
Praveen
Guest
 
Posts: n/a
You must look at the Knudsen number (Kn), which is the ratio of the molecular mean free path to the characteristic length scale of the flow. If Kn<<1 then the continuum models are valid. If Kn=O(1), then it is not.
  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
Low Reynolds Number SST Model Josh CFX 39 February 19, 2014 09:47
Low Pressure, Low Temperature Luke CFX 0 August 4, 2006 18:36
Guage vs. Absolute pressures in Fluent. Riaan FLUENT 1 January 21, 2005 15:22
Multicomponent fluid Andrea CFX 2 October 11, 2004 05:12
CFD code for very low Re Flow Raj Main CFD Forum 2 May 31, 1999 22:06


All times are GMT -4. The time now is 23:00.