Velocity of liquid from bottom pinhole of closed container

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SUMMARY

The discussion centers on the application of Bernoulli's equation and Torricelli's law to determine the velocity of liquid exiting a closed container through a pinhole. The velocity is expressed as v2 = √(2p1/ρ + 2gh), where p1 is the pressure at the top of the liquid, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the height of the liquid column. The discussion emphasizes the need to account for changing pressures in the headspace as the liquid level decreases, particularly under isothermal conditions. The conversation also touches on the implications of a closed system and the potential for vacuum formation as the liquid drains.

PREREQUISITES
  • Understanding of Bernoulli's equation
  • Familiarity with Torricelli's law
  • Knowledge of fluid dynamics concepts, including pressure and density
  • Basic calculus for differential equations
NEXT STEPS
  • Research the derivation of Bernoulli's equation in closed systems
  • Study the implications of isothermal expansion in fluid dynamics
  • Learn about the effects of pressure changes in fluid systems
  • Explore the concept of vacuum formation in liquid containers
USEFUL FOR

Fluid dynamics engineers, physicists, and anyone involved in the study of liquid flow in closed systems will benefit from this discussion. It is particularly relevant for those analyzing pressure dynamics and flow rates in engineering applications.

  • #31
Ravi Singh choudhary said:
I was searching for this since afternoon. Let me see it again.
My favorite version is with a playing card under an upside down glass of water so that you hold the glass upside down in mid-air with the water inside without supporting the playing card. It is fairly easy to do.
 
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  • #32
What I read;

Case 1: if you do this experiment in vacuum; cover plate will fall down (avoid other effect like boiling).
Case 2: Now in normal atmospheric condition; air need to go inside so that cover would fall; but if you have good sealing, it would never happen.

Now when I come to case 2 it appears very non-intuitive to me; what if there is only small of water in it.

Can you please elaborate.
 
  • #33
Ravi Singh choudhary said:
Case 1: if you do this experiment in vacuum; cover plate will fall down (avoid other effect like boiling).
Case 2: Now in normal atmospheric condition; air need to go inside so that cover would fall; but if you have good sealing, it would never happen.

Now when I come to case 2 it appears very non-intuitive to me; what if there is only small of water in it.
Physics is an experimental science. I highly recommend that you do the experiment.
 
  • #34
jbriggs444 said:
Physics is an experimental science. I highly recommend that you do the experiment.
Ok let me try this
 

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