how to increase time step size?

co2

hi all,

I am solving a natural convection unsteady problem. I am getting good convergence in 20 iterations per time step for a step size of 2 sec. --- so I decide to move to 3 sec time step size -- That results in a problem -- continuity residual does not seem to go down. it hovers around 1.6e-4 yes, i have nice stringent convergence criteria for an accurate solution. Can you tell me how i can run my simulation at 3 sec time step size? what urfs do i need to bring down ? both my presure and vel urfs are at 0.1 already.

thanks, co2