# Natural Convection

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 November 19, 2003, 18:30 Re: Natural Convection #2 Jim Park Guest   Posts: n/a It would help if you explain what's not working. Is the iteration procedure diverging? Or is it converging to an unrealistic solution? Are you doing a transient or steady-state simulation? Most of the big CFD codes have pretty powerful iteration controls, and the support staffs have considerable experience in using them. You might want to ask the Fluent folks for their advice as well.

 November 19, 2003, 23:40 Re: Natural Convection #3 elyyan Guest   Posts: n/a The iterations are not converging, espcially the continuity, I am using the segregated method for solving it. I have tried to start with low Ra (10^5)and increase it gradually to (10^10) but it diverges. Also, I am using the steady state scheme. and I am not using the boussinisque approximation, I have added the density as a polynomial. I hope those additional details will help. Thanks alot for your help and time.

 November 20, 2003, 16:02 Re: Natural Convection #4 Wei Guest   Posts: n/a What is your boundary condition ?

 November 20, 2003, 16:11 Re: Natural Convection #5 Elyyan Guest   Posts: n/a I am using isothermal walls, hot and cold, the temperature difference between them will range between 15-30 degrees.

 November 22, 2003, 01:10 Re: Natural Convection #6 Goicox Guest   Posts: n/a Use the following: * Simple * Upwind (first order for every solved variable) * An start with the simplest Turbulence model * If possible, turn off the radiation model at the begining. Try to set the initial values for every variable according the problem, not just 0. If it does not work, try to use the couple solver, for a small Courant number e.g. < 1.0. Try to iterate for serveral time steps (needed in the coupled solver), and then change to the segregate solver (without re - starting the values of the solved variables). If it does not work, check your problem setup, boundary conditions, etc.

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