Natural Convection
 

Hi, I am trying to simulate natural convection within enclosure using Fluent, my Ra is ~10^10 (which means it is fully turbulent), I have been trying to make it work for a while. I am using the K-e model for modeling visc flow, and I am enabling the bouyance effects option, I have tried to use different radiation models, my medium is a gas with absorbtion coeff. 0.14 cm^-1, and my enclosure height is 50 cm. I made my mesh very fine, I used a BL with the first row of 0.01 cm height with growth factor of 1.2, and I have generated 40 rows, I think this should do it. Could you please help me making this simulation work, because I have been trying to make it work for a while now. If possible could you give me advice on what turbulent model to use, and if there are any options that I need to activate. Also, what do you suggest for the radiation model, and what solution schemes should I use, first order, PRESTO ... To tell the truth I will be grateful for any information you give, and I will appreciate all the details you provide. Thanks alot in advance

Re: Natural Convection
 

That Rayleigh number isn't going to be easy. Use PRESTO and the second order upwind scheme. Try getting a solution without the radiation enabled, then re-enable it and continue the solution. Also, try increasing gravity in steps (i.e., 2 m/s^2 then 4 m/s^2 etc.) so you get a flow field set-up slowly. If all else fails, you may have to do a transient evaluation.