How Do You Calculate Air Flow Velocity Between Two Tanks?

[supernova1387]

This might be simple but I can't remember how to do it.

problem: we have 2 tanks. One filled with atmospheric air at 1 bar and the other is vacuum. The two tanks are connected by a rigid pipe which has a valve. I open the valve and air flows to the vacuum tank. How do I calculate the air velocity?

P.s: I don't think Bernoulli is valid here because the flow isn't steady I guess. Please state your assumptions clearly.

Thanks in advance

 

[Baluncore]

Flow velocity depends on the thickness and length of the pipe, and on the temperature of the air.

 

[SteamKing]

Instead of 'thickness' of the pipe, the term 'internal diameter' would be more apt.

 

[boneh3ad]

Also pay attention to the pressures. The flow is going to start off choked but will eventually un-choke as the pressures equalize.