Calculate the flow velocity

  1. 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
  2. jcsd
  3. Baluncore

    Baluncore 2,516
    Science Advisor

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

    SteamKing 8,599
    Staff Emeritus
    Science Advisor
    Homework Helper

    Instead of 'thickness' of the pipe, the term 'internal diameter' would be more apt.
  5. boneh3ad

    boneh3ad 1,642
    Gold Member

    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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