|MadSci Network: Physics|
I don't understand: According to Bernouilli uncompressible (sonic) : P1-P2 = (rV2^2-rV1^2)/2 where P1 and V1 are the pressure and speed of air (fluid) before a restriction and P2 & V2 after, and r the density. If V2 >> V2 (small restriction), we get: P1-P2 = rV2^2/2, which gives for V2=Mac/3=100m/s and r=29g/22.4L=1300g/m3 : P1-P2 = 6.5 MPa So it should be impossible to get ultrasonic conditions (higher speed) with P1=1 atm and P2=Vacuum because P1-P2 < 0.1MPa (1 atm) The fact is that experiments proves it is easy to get ultrasonic condition with vacuum (flow does not increase anymore even vacuum rate (P1-P2) increases) Conclusion: I am for sure missing something... Thanks for your help !
Re: how come it is easy to get ultrasonic air flow under vacuum ?
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