Non-isothermal flow problem

Hi there,

I am trying to create a model that is similar to the cold water glass model found within the comsol model library. However, I want to have a temperature governed by a step function at the bottom (which I have) and a cold temperature at the top that I just define in the initial values.

However, when I try to compute the model, an error appears that says that the time-dep solution is not converging, could I get some help with this please!

Thanks

Ross