Problems In The Mathematical Description Of Flow Processes In The Free Forming Glass

The basic physical equations and boundary conditions for a free surface are such that their solution is very difficult for any particular problems. Even for isothermal processes involving the forming of glasses at typical viscosities but including a free surface, solutions are rarely possible. However, for some simple cases such as the elongation of a viscous cylinder, direct solutions can be obtained. The simplifications of the basic equations and boundary conditions permissible in such cases are considered and their generalisation investigated.