Particle growth
 

Im am currently attempting a project in which i have a particle rotating downwards in a cylindrical vessel towards the bottom. Firstly i wish to impose a temperature difference between the top and bottom of the vessel. I then want input some equations which will allow the particle to grow with a drop in temperature. I Am honestly lost and have been going around in circles with all my attempts. If anyone knows anyway in which i could do this it would be unbelievable! any help ir guidlines at all would be greatly appreciated. Thanks a million