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

Applying boundary conditions to 1D Steady Convection Diffusion using Power Law Scheme

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 5, 2012, 20:47
Post Applying boundary conditions to 1D Steady Convection Diffusion using Power Law Scheme
  #1
New Member
 
Join Date: Jan 2012
Posts: 1
Rep Power: 0
ConvDiff is on a distinguished road
I am currently trying to solve the convection diffusion problem for Phip(centre of node) utilising the power law scheme but have come unstuck in determining the co-efficients(ae, aw, Su, Sp) at the boundaries i.e the first and last nodes. The form utilised is following the Versteeg CFD Textbook 1995, and the co-efficients are given for only the central nodes:

ap*Phip=ae*Phie+aw*Phiw+Su

ap=aw+ae-Sp

For instance for the central differencing scheme at the 1st node:

aw=0, ae=D-F/2, Sp=-(2D+F), Su=(2D+F)*Phi0.
Where D=DiffusionCoeff/dx and F=rho*u


I have written a TDMA solver in matlab that is currently working for the central differencing, upwind and hybrid schemes, this is the last one and I'm losing my mind!

Any help would be greatly appreciated! Regards Rastaman
ConvDiff is offline   Reply With Quote

Old   January 7, 2012, 17:40
Default
  #2
Senior Member
 
Join Date: Aug 2011
Posts: 251
Rep Power: 6
leflix is on a distinguished road
Quote:
Originally Posted by ConvDiff View Post
I am currently trying to solve the convection diffusion problem for Phip(centre of node) utilising the power law scheme but have come unstuck in determining the co-efficients(ae, aw, Su, Sp) at the boundaries i.e the first and last nodes. The form utilised is following the Versteeg CFD Textbook 1995, and the co-efficients are given for only the central nodes:

ap*Phip=ae*Phie+aw*Phiw+Su

ap=aw+ae-Sp

For instance for the central differencing scheme at the 1st node:

aw=0, ae=D-F/2, Sp=-(2D+F), Su=(2D+F)*Phi0.
Where D=DiffusionCoeff/dx and F=rho*u


I have written a TDMA solver in matlab that is currently working for the central differencing, upwind and hybrid schemes, this is the last one and I'm losing my mind!

Any help would be greatly appreciated! Regards Rastaman
Hi,
Once you have been able to compute all the coefficients for every nodes (I mean AP, AW, AE and SU) if your TDMA solver works for the other schemes (central, upwind and hybrid) it should work as well with powerlaw scheme.

Another point is that the BC do not depend on the discretizing scheme at least only on the way to implement them.
If the scheme you use is based on 3 points, W, P and E at most, the way you have implemented the BC for central or upwind will not change for powerlaw.
The scheme which is used only change the coefficients. That"s all.
What you have done according Versteeg seems correct..
Jah guide !
leflix is offline   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
Applying two different boundary conditions on same region shahpar73 CFX 1 October 4, 2010 19:06
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55
New topic on same subject - Flow around race car Tudor Miron CFX 15 April 2, 2004 06:18
Please help with flow around car modelling! Tudor Miron CFX 17 March 19, 2004 20:23
grid manipulation and applying boundary conditions Chetan Kadakia FLUENT 3 August 22, 2000 05:51


All times are GMT -4. The time now is 16:15.