# Calculate the flow velocity

by supernova1387
Tags: bernoulli, fluid, velocity
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 P: 30 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
 Sci Advisor Thanks P: 1,716 Flow velocity depends on the thickness and length of the pipe, and on the temperature of the air.
 Emeritus Sci Advisor HW Helper Thanks PF Gold P: 6,265 Instead of 'thickness' of the pipe, the term 'internal diameter' would be more apt.
 PF Gold P: 1,487 Calculate the flow velocity Also pay attention to the pressures. The flow is going to start off choked but will eventually un-choke as the pressures equalize.

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