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

non-reflecting boundary condition

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 18, 2005, 08:19
Default non-reflecting boundary condition
  #1
queram
Guest
 
Posts: n/a
another question is on NRBC: my comp. domain is meshed also outside the pipe = suitable far-field boundary is to be set at the far left, far-north and on a piece of upper west boundary. First, I simply put there outlet condition - that lead to nice wave reflections. Then I modified it to more proper, setting the state in external ghost cell to be the same as in the last cells of the domain, that would, imho, cause zero flux accross the boundary (at least for planar wave). result are better, but still reflecting the waves. Now I'm going through maaaaaany papers on nrbc, but: I want something really simple (no buffer zone with increased dose of artificial viscosity or modified equations). How good do you think is simple extrapolation technique? I am intending to extrapolate the state in external ghost cells from the state values in last two interior cells, enough? more? linear extrapolation? Another idea that come to my mind is to set such a state in the ghost cells that would cause a flux of the same magnitude but opposite direction (I mean ghost cell would "suck" just as the last domain cell "spits") actually, any advice is welcome
  Reply With Quote

Old   October 20, 2005, 07:27
Default Re: non-reflecting boundary condition
  #2
Alan
Guest
 
Posts: n/a
Hi queram,

just as a hint and just in case you aren't aware: There are two good references on non-reflecting boundary conditions to start with: Chapter 19 in "Numerical Computation of Internal and External Flows" Vol. 2 by C. Hirsch

And: "Numerical and Theoretical Combustion" by Poinsot and Veynante

There is also a famous paper on BC written by Lele and Poinsot: Poinsot, T. & Lele, S. 1992 "Boundary conditions for direct simulations of compressible viscous flows." J. Comp.Phys. 101, 104-129

(You probably know all these.)

I am currently involved in implementing inlfow BC for incoming boundary layers and I was looking for someone to discuss with (see my post in this forum below). Maybe we can solve our both problems togther? Are you interested?

Alan
  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
Wind turbine simulation Saturn CFX 45 February 8, 2016 05:42
Boundary Conditions Thomas P. Abraham Main CFD Forum 20 July 7, 2013 05:05
inlet velocity boundary condition murali CFX 5 August 3, 2012 08:56
how to set up a wall boundary condition according to calculated wall shear stress? gameoverli OpenFOAM Pre-Processing 1 May 21, 2009 08:28
non reflecting boundary condition? adarsh Main CFD Forum 1 May 30, 2002 10:27


All times are GMT -4. The time now is 22:13.