Thrust of an underpressure tank of air

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Discussion Overview

The discussion revolves around calculating the thrust produced by an underpressure tank of air when the valve is released. Participants explore various interpretations of "underpressure," the conditions under which thrust is generated, and the parameters necessary for calculation, including mass flow rate and velocity of escaping air.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks a detailed explanation for calculating thrust from an underpressure tank of air.
  • Several participants question the term "underpressure," with differing interpretations regarding whether it refers to pressure less than or greater than ambient pressure.
  • Another participant clarifies that the original poster likely refers to thrust from a cylinder of compressed air.
  • There is a suggestion that measuring mass flow rate and velocity of the escaping air could lead to calculating net thrust.
  • One participant proposes that thrust could be calculated simply as the product of pressure in the tank and the area of the orifice, questioning if this leads to a straightforward result.
  • Another participant challenges this approach, indicating that the thrust is influenced by additional variables beyond just pressure and area.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definition of "underpressure" or the appropriate method for calculating thrust. Multiple competing views on the interpretation of terms and calculation methods remain evident.

Contextual Notes

Some participants express confusion over terminology, particularly the distinction between "underpressure" and other terms. There is also uncertainty regarding whether certain parameters can be calculated or must be experimentally measured.

Who May Find This Useful

This discussion may be of interest to individuals exploring fluid dynamics, thrust calculations, or those involved in engineering applications related to pressurized systems.

Raresss
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How can I calculate the thrust of an underpressure tank of air when the valve is released? If you can, please, explain in detail. Thank you!
 
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"Underpressure?" Less than ambient?
 
Bystander said:
"Underpressure?" Less than ambient?
More than the ambient pressure
 
Raresss said:
More than the ambient pressure
Pressure "under" what? Do you mean when it's running out?
 
The OP just means the thrust produced by air escaping from a cylinder of compressed air.

Most people in my country understand "under" to mean "due to". As in "The bridge failed under the weight of traffic".
 
CWatters said:
The OP just means the thrust produced by air escaping from a cylinder of compressed air.

Most people in my country understand "under" to mean "due to". As in "The bridge failed under the weight of traffic".
I can see that now. In English, underpressure and "underweight" (compound words) have different meanings from when the two words are separated by a space; hence my confusion. If this were a German forum, things might be different. . . :smile:
 
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Can the mass flow rate and the velocity of the exhausted gas be calculated or those can only be measured in an experiment ?
 
Raresss said:
Can the mass flow rate and the velocity of the exhausted gas be calculated or those can only be measured in an experiment ?

Bernoulli should be a good approximation.

sophiecentaur said:
If this were a German forum, things might be different. . . :smile:

Not really. "Unterdruck" instead of "unter Druck" would result in the same confusion.
 
  • #10
Would it not just be the pressure in the tank x the area of the orifice?
I.E. If the pressure is 1 Mpa (above ambient) and the orifice is 12mm then the thrust should be 1 Newton, right?
 
  • #11
mrspeedybob said:
Would it not just be the pressure in the tank x the area of the orifice?
I.E. If the pressure is 1 Mpa (above ambient) and the orifice is 12mm then the thrust should be 1 Newton, right?
Your force is the normal force, and your pressure is the surface pressure. We can't use those in my problem. The thrust is based on other variables . Check out this link to find out more : https://en.wikipedia.org/wiki/Thrust
 

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