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

ENO scheme asymmetry

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 21, 2004, 13:41
Default ENO scheme asymmetry
  #1
Vinod Venugopalan
Guest
 
Posts: n/a
Hi,

I am coding a 3rd order ENO scheme (F.D) to solve Euler equations for a flow in a 2D tube. I have induced a shock by adding a large source term over a small symmetric area in the center of the flow. While ENO handes the shock, the reflection and the gradients very well... the trouble is that the flow pattern being created is slightly asymmetrical.

When I zoom into the energy input area, I see that the center of the property contours has shifted by exactly one grid point in y-direction & is probably causing the asymmetry.

I've seen results from Dr Laney's Computational Gas Dynamics and also the results from my codes for simple conservation laws, eg. advection equation in pages 533-535. There is a bit of asymmetry in the results.

Is this an inherent prob with the ENO scheme? Any way of fixing this?

geometry: X:[-10 27.5] Y:[-6 6 ] Nx =250 Ny = 80. cfl =0.1 Using 3rd order R-K time integration, Lax fredrich flux splitting..

Thank you

Vinod

  Reply With Quote

Old   July 21, 2004, 17:01
Default Re: ENO scheme asymmetry
  #2
Junseok Kim
Guest
 
Posts: n/a
For an asymmetry problem, it could be generated by under resolved grid, or numerical error even if the solver is not asymmetric. You may want to solve the problem on the symmetric domain if the problem is symmetric in nature or put more grids.

  Reply With Quote

Old   July 21, 2004, 17:40
Default Re: ENO scheme asymmetry
  #3
Vinod Venugopalan
Guest
 
Posts: n/a
hi,

I tried increasing grid resolution, went from del_x &del_y of 0.15 to 0.075 .. the solution still has an asymmetry.. Again the center of the contour plots is shifted by one grid point.

I don't want to reduce grid size further because of really long run times.

  Reply With Quote

Old   July 22, 2004, 06:42
Default Re: ENO scheme asymmetry
  #4
Hrvoje Jasak
Guest
 
Posts: n/a
I have seen something like this before and the differencing scheme I use has got the same property. In my opinion, symmetry is an additional constraint which is not inherently present in ENO, so when you derive a new scheme it may or may not behave symmetrically.

I have a vague memory that some (not all?) of the TVD schemes are properly symmetrical - it may be useul to repeat your test with the van Leer scheme and see if the symmetry is preserved (I think it should be).

Hrv
  Reply With Quote

Old   July 22, 2004, 07:00
Default Re: ENO scheme asymmetry
  #5
Praveen
Guest
 
Posts: n/a
This could be related to conservation. Are you using a finite volume scheme ? If yes are you starting with cell-averaged initial conditions ?
  Reply With Quote

Old   July 22, 2004, 13:06
Default Re: ENO scheme asymmetry
  #6
Vinod Venugopalan
Guest
 
Posts: n/a
I am using a finite difference scheme..

The reason I was wondering if the asymmetry is because of the scheme is because of earlier results from solution of scalar conservation laws.. U can see them in Dr Laney's book "Computational Gas Dynamics" pages 53 -535
  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
ENO scheme (ENO-Roe) (Shu and Osher). J. K. Main CFD Forum 8 March 28, 2013 09:09
ENO Scheme in a Shock tube problem Shiv Main CFD Forum 4 January 29, 2007 16:31
ENO scheme asymmetry vinod venugopalan Main CFD Forum 7 October 7, 2004 11:21
Entropy condition and ENO scheme Question Man. Main CFD Forum 5 January 17, 2003 08:10
ENO scheme: (Shu and Osher) J. K Main CFD Forum 3 July 18, 2002 12:51


All times are GMT -4. The time now is 18:25.