SIMPLE algorithm not converging.
I am new to CFD and i have started to code incompressible flow between two plates (given in anderson). The thing is, the code i have developed is not converging. the p' computed as given in anderson book, from the pressure poisson equation doesnot decrease. it keeps on increasing.
The boundary conditions i have given are
inlet: u=1, v=0, p'=0
exit: u(exit)=u(exit-1), p'=0// column before exit
Also, i dont know whether the way i am implementing staggering is correct or not.
npx+2,npy+1 grid points for v-component
npx+1,npy grid points for u-component
npx,npy grid points for pressure.
i am computing u momentum at 1 to npx-1 and from 2 to npy-1
and v momentum at 1 to npx and from 2 to npy-1.
what could be the reason for p' not comverging.
thanks in advance,
npx, npy+1 for v-components
npx+1, npy for u-components
npx, npy for the pressure.
You should then compute u-momentum from 1 to npx-1 ( I assume your starting index is 0) and v-momentum from 1 to npy-1 because the nodes 0 and npx/npy will coincide with points where the velocities are known. If you are using one of the other less common staggered grids, then maybe what you have now is correct. One thing that could cause convergence is your treatment of relaxation factor in the pressure correction equation. Are you incorporating it at all?
thanks for the reply.
I am using under-relaxation factor for the pressure term as i read in Patankar's book that under-relaxation factor increases the stability of the code.
Is it right? I also want to know if there is any sample code for SIMPLE algorithm by patankar available in internet.
Thanks in advance,
"ftp://ftp.springer.de/pub/technik/peric/" - you can type the ftp directly in your browser. I think the code is based on collocated grid though but should still help somehow.
I think the velocity correction in pressure correction is just neglected.
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