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

Is this the "checker board" problem?

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

LinkBack Thread Tools Display Modes
Old   April 10, 2006, 10:32
Default Is this the "checker board" problem?
Posts: n/a

I've been using my 2d fractional step FVM NS solver to solve different problems. Now, I'm solving flow past square cylinder. Everything is ok at Re=100. However, at Re=400 onwards, there is oscillation of velocity u at from left to right ie u along horizontally is varying up and down e.g. 0.95,0.9,0.925 ... 0.8,0.75,0.77... although the trend is overall decreasing. Only close to the cylinder (upstream) will it be strictly decreasing.

A closer look shows that it is due to the pressure, which is oscillating e.g 0.2 0.05 0.18 0.06 ....

Is this the so called "checker board" problem? But Rhie Chow interpolation has been incorporated in the current scheme (Ham JCP (179) 2002, pp469) so this shouldn't happen. different outlet BCs such as du/dx,dv/dx=0 and convective BCs have been used. Similarly, far stream distances are very large. p is fixed at outlet and at inlet, u=1, p is extrapolated from interior.

Some things I've noticed:

1. oscillations decreases as more cells are present in the x direction 2. the higher the Re, the more severe the oscillations, assuming the no. of the cells are equal. 3. 1st few steps are ok but as time proceeds, oscillations start...
  Reply With Quote

Old   April 16, 2006, 23:36
Default Re: Is this the "checker board" problem?
Posts: n/a
Hi, By seeing your values it looks like your problem has become unsteady vortex shedding.) so it is strugling to converge as steady state problem.
  Reply With Quote

Old   April 18, 2006, 09:38
Default Re: Is this the "checker board" problem?
Posts: n/a
hi, can you explain further what do you mean? Btw, the oscillations happen upstream of the cylinder. Moreover I've encountered this problem when solving for an airfoil like body, which should be a steady state solution....

I am wondering if it could be my discretization, central differencing....
  Reply With Quote


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
conduction problem venkataramana OpenFOAM 3 December 1, 2013 08:30
UDF compiling problem Wouter Fluent UDF and Scheme Programming 6 June 6, 2012 04:43
area does not match neighbour by ... % -- possible face ordering problem St.Pacholak OpenFOAM 9 November 22, 2011 11:02
Problem in implementing cht tilek CFX 3 May 8, 2011 08:39
Adiabatic and Rotating wall (Convection problem) ParodDav CFX 5 April 29, 2007 19:13

All times are GMT -4. The time now is 00:45.