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problem in coding FEM for 2D incompressible flow with triangle elemets |
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May 24, 2014, 14:48 |
problem in coding FEM for 2D incompressible flow with triangle elemets
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#1 |
New Member
Mahdi Salami
Join Date: Feb 2014
Posts: 6
Rep Power: 12 |
Dear all
I have written a FEM code for 2D incompressible flow, but I have encountered a problem. In my code every thing seems OK but the results are dreadful. I check everything (almost) and find nothing. I'm attaching all the functions I wrote. Please check them and let me know if there is problem or bug. It turns out to be my nightmare.... Bests Mahdi PS: just run main.m and see the results. You can check the results in TECPLOT but reading data file (fem.dat) Last edited by wyldckat; May 24, 2014 at 15:07. Reason: accidental double post |
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May 25, 2014, 12:37 |
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#2 |
Senior Member
Jonas T. Holdeman, Jr.
Join Date: Mar 2009
Location: Knoxville, Tennessee
Posts: 128
Rep Power: 18 |
It would help if you described your application and method here.
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May 25, 2014, 14:24 |
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#3 |
New Member
Mahdi Salami
Join Date: Feb 2014
Posts: 6
Rep Power: 12 |
Hi Jonas,
I used the method described in "nonlinear finite element analysis" by N.J. Reddy and it is a mixed method. I used linear triangle element for Ux and Uy and constant function for pressure (Np = 1). I'm writing this for lid driven problem to extend it for viscoelastic flow. The program is made up of five files, one main and four functions. read_data.m is reading the mesh information from node.txt, elements.txt and boundary conditions. KFlocal.m integrate local K and F using Gauss-quadrature rule. KFcalc.m calculate Kij and Fi for each integration point. I tried to write the routines as simple as possible so anyone could follow the code. If there is any question about the code... the problem is that when I try to solve the final equation set, [K]{U}={F}), MATLAB tells that [K] in badly scales or singular... |
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May 26, 2014, 17:22 |
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#4 |
New Member
Mahdi Salami
Join Date: Feb 2014
Posts: 6
Rep Power: 12 |
Do anybody have any idea about this problem?
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May 26, 2014, 21:19 |
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#5 |
Member
Join Date: Jul 2013
Posts: 56
Rep Power: 13 |
I will not debug your code, and from the information you gave, it can be various things, and no one will be able to tell you exactly what is wrong.
Here's a few idea : - Is you're mesh connectivity correct? - Are every boundary conditions properly defined? - Do you use a sufficient number of integration points? - Are the element matrix (K) and vector (F) ok? - Is the global assembly properly done? |
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fem, incompressible flow, matlab |
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