buoyancy in large domain

Gea

Hi

I am now lookng for modelling a condenser in atmosphere. To do that, I placed it in a large cylinder (25meters radius and 50meters high). I created a gravity in the fluid, but I have a problem with the boundary condition of the cylinder of atmosphere : I must place an opening, in which I have to precise the pressure. But Pressure is not constant, it is function of altitude. So I created a function for the pressure : -Density*9,81[m s-2]*(Z Coordinate).

But the system does not want to converge easily, very hard to have better than 10-2. To you have any solution for this kind of problem ? Are there a special functiun dedicated to this issue ?

Thanks a lot and have a good day !