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Nozzle flow

  1. Aug 14, 2008 #1
    suppose air is flowing throught the nozzle
    with the inlet conditions
    static pressure = .2 MPa
    static temperature = 350 K
    velocty of air at the inlet = 150 m/s

    speed of sound for ideal gas is given by c = sqrt (k * R * T)

    suppose if i want to calculate the speed of sound at the inlet do i have to consider the static temperature or the stagnation temperature?
  2. jcsd
  3. Aug 15, 2008 #2
    i mean suppose if we want to calculate the mach number at the inlet, then which sonic velocity has to be used? is it the sonic velocity based on static temperature or the stagnation temperature?
  4. Aug 16, 2008 #3
    you are talking about De Laval nozzle , at the inlet the speed of air is not sonic it is sub-sonic and when it enters at the tightest point in nozzle where the flow is choked and then the velocity incease at the end of the nozzle which is divergeant

    velocit calculated at outlet is :

    Ve = Exhaust velocity at nozzle exit, m/s
    T = absolute temperature of inlet gas, K
    R = Universal gas law constant = 8314.5 J/(kmolĀ·K)
    M = the gas molecular mass, kg/kmol (also known as the molecular weight)
    k = cp/cv = isentropic expansion factor
    cp = specific heat of the gas at constant pressure
    cv = specific heat of the gas at constant volume
    Pe = absolute pressure of exhaust gas at nozzle exit, Pa
    P = absolute pressure of inlet gas, Pa

  5. Aug 18, 2008 #4


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    Science Advisor

    That equation references the static temperature.
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