Hello everyone I want to model particle nucleation and growth in Fluent. particles are formed by a reaction. I used population balance method with UDFs for nucleation and growth rate. Mass transfer in phase interaction was done based on population balance method. But, when calculation was performed, there is no mass transfer between phases. I used constant rates for nucleation and growth rates, but it didn't work. what should I do? should I introduce special boundary condition for population balance method? please help me.