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-   -   Solar Chimney doesn't converge (https://www.cfd-online.com/Forums/fluent/108818-solar-chimney-doesnt-converge.html)

 djchris November 2, 2012 03:36

Solar Chimney doesn't converge

Hi, the last 4 months I try to simulate a solar chimney which is installed in a pavilion/shed of a square. The problem is that even I tried to run 18000 iterations, the problem doesn't converge.
- I tried Bousinesq model for air, I also tried the incompressible ideal gas,
- I tried coupled solver and SIMPLE
- In solution controls, I change the density to standard, body forced weighted etc. but nothing.
- I turned off the multigrid
- changed the second order upwind to first order...

What I have to do?

The residuals are under the limits for example the energy is 4.5e-07 but doesn't converge.
Can everyone help, as I need to finish the project until 1 December, it's my M.Sc. Thesis?

 sagila November 2, 2012 05:44

Hi,

One of the solutions is increasing gravitational acceleration step by step.
Another solution is defining a good initialization (instead of increasing gravitational acceleration step by step).
Also, often you need to change under-relaxation factors.

 djchris November 2, 2012 06:06

Quote:
 Originally Posted by sagila (Post 389825) Hi, One of the solutions is increasing gravitational acceleration step by step. Another solution is defining a good initialization (instead of increasing gravitational acceleration step by step). Also, often you need to change under-relaxation factors.

Sagila thanks for the quick reply,
About the gravitational acceleration, do you mean that I have to start with, for example, 2 m/s^2 and increase it every 100 iterations by 1 point unless 9.8 m/s^2?

I use the hybrid initialization, I can't use the FMG as I use the shell-conduction option.

 sagila November 2, 2012 06:37