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-   -   Probable bug with laplacian steady state (http://www.cfd-online.com/Forums/openfoam/70400-probable-bug-laplacian-steady-state.html)

novyno November 23, 2009 09:53

Probable bug with laplacian steady state
 
Hi foamers...

I noticed this stange behaviour with OpenFOAM.

I've built a solver that only solve the laplacian (steady state version of laplacianFoam). I've tested this solver with the cavity geometry (icoFoam folder) where I set the boundaries value of my field in this way:

FixedWalls: zeroGradient
movingWall: fixedValue uniform 1
InternalField: fixedValue uniform 1

The analitic solution of this problem is that values of the field converged to the value 1, so in this case the initial solution correspond to the exact solution. The expected behaviour is that at first "time" step the solver of the linear system only does one (or zero) step and the convergence is achived. But, even if the correct solution is achived, the solvers needs many iterations and the initialResidual value doesn't decrese.

I've tried many experiment with different initial values and my oppinion is that ther is a converging problem to the uniform solution.

Someone can say me why?

alberto November 23, 2009 20:31

Ciao Valerio,

did you try to run the case with the original laplacianFoam? It should give you a set of lines with initial and final residuals equal to zero.

The solution to that problem is always identical to the initial condition since all the fluxes are zero (on fixedWalls by default, and due to the equal value of T on movingWall and inside the system), as a consequence the initial residual should be zero also in the unsteady case.

How did you code the steady solver?

P.S. I'm Italian too :D


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