HI!trying to carry out natural convection in a 2d rectangular cavity (100mm X 50mm. the solution will not converge. Using Boussinesq approximation. Rayleigh num is of the order of 10^7 so flow is laminar. Left wall appplied temperature of ninety degrees and right wall at 50....Have used suggested set up as in user tutorial and have altered under relaxation values but residuals wont converge!!Any tips PLease????

try using ideal gas, lower under-relax factor.

Hi thanks for responding!im using water. Have tried lowering under-relaxation values but still wont converge. If you have any more advice please post it....need to finish this project soon

Don't use Boussinesq. Define water as having density as a function of temperature (either a polynomial or piecewise linear).