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

Laplace Eqn. Finite Diff. Error Problem

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

LinkBack Thread Tools Display Modes
Old   April 4, 2015, 17:33
Default Laplace Eqn. Finite Diff. Error Problem
New Member
Gorkem Ocalan
Join Date: Feb 2015
Posts: 5
Rep Power: 4
gorkemocalan is on a distinguished road
Sponsored Links

I have some problems about error analysis of Laplace Eqn. in 2D. I generated coefficient matrix and right-hand side vector as Au=b format properly and solved u=A\b.

I calculated analytical solution with respect to boundary conditions which are
u(x,0)=0 ,u(x,1)=x-x^2, u(0,y)=0, u(1,y)=0.

There is a problem about error. I was expecting to observe the decrease in error by making the mesh finer. But it did not happen in that way. 41x41 mesh gave better error result than 81x81 mesh.

I also attached the code (MATLAB) for the people who are interested in.

Thanks for your concern...
Attached Files
File Type: doc problem2.doc (28.0 KB, 4 views)
gorkemocalan is offline   Reply With Quote
Sponsored Links

Old   April 4, 2015, 17:46
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,409
Rep Power: 39
FMDenaro will become famous soon enoughFMDenaro will become famous soon enough
indeed, the error must diminuish ... how do you invert A? check if A*A^-1 is the identity matrix (note that u=A^-1*b)
Check also the exact solution
FMDenaro is online now   Reply With Quote

Old   April 5, 2015, 01:06
Join Date: Jan 2014
Posts: 54
Rep Power: 5
H0T_S0UP is on a distinguished road
Be careful with MATLAB. Its matrix operations don't always work the way you'd expect.
H0T_S0UP is offline   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
Eliminating exchange energy between phase in Granular Temperature diff eqn. cfdbusiness FLUENT 0 February 2, 2010 23:30
Finite volumes vs. finite elements: applications Lionel S. Main CFD Forum 10 January 22, 2007 11:51
Laplace operator in finite element formulation Rafael Main CFD Forum 2 October 19, 2004 21:09
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 13, 2000 23:03
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 11, 2000 03:43

Sponsored Links

All times are GMT -4. The time now is 04:12.