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

Strong Conservation Form

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 4, 2007, 11:26
Default Strong Conservation Form
  #1
Harish
Guest
 
Posts: n/a
What are the advantages of using the strong conservation form of the Navier-Stokes equations ? . I would like to know the advantages it offers over other forms in different areas of application.

  Reply With Quote

Old   May 4, 2007, 12:47
Default Re: Strong Conservation Form
  #2
ztdep
Guest
 
Posts: n/a
I discretize the equations by the FVM method, and the strong conservation form gives a very compact form.
  Reply With Quote

Old   May 4, 2007, 15:42
Default Re: Strong Conservation Form
  #3
Harish
Guest
 
Posts: n/a
Thanks for your answer.I'm looking at it from mathematical point of view.I'm just curious if there is any mathematical advantage in formulating in the strong conservation form.
  Reply With Quote

Old   May 5, 2007, 01:11
Default Re: Strong Conservation Form
  #4
jinwon
Guest
 
Posts: n/a
In my concerns, the conservative form is strongly encouraged to capture the shock structure exactly. If your initial conditions have discontinuities, we'd rather use the conservative form of N.S equations. That's very general and extensively mentioned comments in the community of the cfd research.

Good luck for your work.
  Reply With Quote

Old   May 7, 2007, 10:41
Default Re: Strong Conservation Form
  #5
CFDtoy
Guest
 
Posts: n/a
Conservation is required to model the process very accurately. Simply look at the convection term of NS. (rho UU )

Now given a grid

-U-C-D-

Upsteam U, C Cell , D downstream.

Across the faces rhoU (flux) conserved and discretizing the term Del. (rho UU) as such preserves conservation of momentum

i.e., rhoU U in faces between U and C = rhoU U across faces C-D

However, in non-conservation form

Del.(rhoU U ) = U.del (rhoU)

The computed Uf where f between C-D results in Uf . del (rhoU)(computed across the faces) not equal across the faces across C-U !!

Strong Conservation form is required to maintain balance of conserved quantities.

Using a non-conservation form (expanding the compact form) for easy representation in a FV method leads to incorrect computation of the fluxes leading to large errors!

As posted before, this would be critical between getting a right location of the shock and totally misjudging the position and strength of a shock front.

Similar problems are magnified in combination with other terms in the NS equations.

FVM method very well suits the Conservation property and is always preferred !

CFDtoy

  Reply With Quote

Old   May 8, 2007, 05:45
Default Re: Strong Conservation Form
  #6
Tom
Guest
 
Posts: n/a
"Using a non-conservation form (expanding the compact form) for easy representation in a FV method leads to incorrect computation of the fluxes leading to large errors!"

That's not actually true - it depends upon the problem that you are solving and the norm you calculate your error in. There's an example of this in Anderson's book where it is shown that the nonconservative form can be more accurate (pointwise) than the conservative form.
  Reply With Quote

Reply


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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solving CD Nozzle in Conservation form vovogoal Main CFD Forum 0 May 4, 2010 10:25
Conservation form? Peter_CFD Main CFD Forum 1 March 29, 2007 13:58
non-conservation vs conservation form superfool Main CFD Forum 1 September 11, 2006 06:06
strong conservation form of eulers equations Dahyalal Bhate Main CFD Forum 0 September 5, 2002 19:22
Crank-Nicolson technique for Conservation form of equations Yogesh Talekar Main CFD Forum 2 July 20, 1999 02:45


All times are GMT -4. The time now is 15:07.