[Ishant]

Can anyone help me with some issue :

I am trying to of a simple problem : A mixture of hot gases flowing at 11m/s through a 20 cm hole inside a cylinder of refractory lining inside of 3 cm diameter and length surrounded by a steel casing of thickness 10 cm.

Problem is : How to give inlet velocity needs that needs to be multiplied to a smoothly increasing function like 'step' so that the software can begin to solve from a 0 value and then reach a solution for unsteady state problem ?