CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

Finite differences approximation on a Orifice Plate

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

Like Tree2Likes
  • 1 Post By Gerry Kan
  • 1 Post By Matheus.Costa

LinkBack Thread Tools Search this Thread Display Modes
Old   June 25, 2020, 23:50
Default Finite differences approximation on a Orifice Plate
New Member
Join Date: Jan 2020
Posts: 9
Rep Power: 6
Matheus.Costa is on a distinguished road

I'm doing my thesis right now, which consists on the discretization of flow on steady state through an orifice plate using the central finite difference of second order applied to the Navier-Stokes equations, a also using a Poisson to calculate de pressure. I'm using Matlab for codding by the way, and using a staggered grid (Cartesian coordinates), and the SCGS( Symmetric-Coupled Gauss-Seidel) as the solving method for the equations' system. I'm having some trouble implementing the method, specially on how to deal with the boundary conditions. I would be very thankful if any of you guys could shed some light on that matter. The graphic results that I want are the velocity gradient and the pressure associated to it. Thanks for the attention.
Matheus.Costa is offline   Reply With Quote

Old   June 26, 2020, 14:30
Senior Member
Gerry Kan's Avatar
Gerry Kan
Join Date: May 2016
Posts: 350
Rep Power: 10
Gerry Kan is on a distinguished road
Dear Matheus:

If you are using finite difference method with staggered grid, your grid will have uniform spacing. How you incorporate boundary conditions into the grid will depend on the stagger arrangement. Typically (and I mean typically) velocity components will be face centered, while other scalars will be cell centered.

For the face centered variables they are relatively trivial; the boundary node are at the boundary so you simply have to write an equation there to reflect the boundary condition.

For cell centered variables, your boundary is staggered. You need an extra cell beyond each boundary, and effectively write your linearized equation so that the boundary conditions can be maintained.

Of course, I am assuming that your boundary conditions are first order accurate. You will need to pad more cells beyond the first and last cells if you need higher order interpolation.

I don't really have too much time to write out the equations, but I hope the descriptions would help you get started.

Sincerely, Gerry.
Matheus.Costa likes this.

Last edited by Gerry Kan; June 28, 2020 at 05:27.
Gerry Kan is offline   Reply With Quote

Old   June 27, 2020, 22:59
New Member
Join Date: Jan 2020
Posts: 9
Rep Power: 6
Matheus.Costa is on a distinguished road
Thank you, indeed the velocities are face centered and the pressure is cell centered, I forgot to mention it.
So I have to use an extra cell outside my control volume for the face centered variables on the boundary, that makes everything clearer!
Once more thanks for the information.
Best regards, Matheus.
Gerry Kan likes this.
Matheus.Costa is offline   Reply With Quote


finite difference method, matlab, orifice plate, presure, velocity gradients

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Drag Force Ratio for Flat Plate Rob Wilk Main CFD Forum 40 May 10, 2020 04:47
Finding Drag Force from Skin Friction Rob Wilk Main CFD Forum 0 May 8, 2020 06:04
Simulating orifice plate with Finite Differences Matheus.Costa Main CFD Forum 0 January 30, 2020 20:34
conservative finite differences and finite volumes Joachim Main CFD Forum 7 January 23, 2014 16:32
Cavitation of an Orifice Plate in Pipe System CFXuser CFX 0 April 8, 2006 09:30

All times are GMT -4. The time now is 22:48.