Ansys Employee
Diffusion of zero should fail as it'll divide by zero somewhere, 1e-10 is about right for liquids. User Scalars tend to be more sensitvie to mesh etc than the Fluent ones (energy, species etc) as the solver maths is different. Setting dS = 0 is fairly common. Try turning the scalars off and putting the same equation into UDM and see what values it's giving. That should cause the solver to fail and will give you some idea what's going on. n