Understanding the Components of Energy in Fluid Mechanics

AI Thread Summary
Emec is defined as the mechanical energy per unit mass, represented by the equation Emec = P/ρ + v²/2 + gz, where P is pressure, ρ is density, v is velocity, and g is gravitational acceleration. The resulting units of m²/s² indicate energy per unit mass, which is consistent with the concept of specific energy. The confusion arises from the expectation that energy should be measured in Joules, but in this context, Emec is specifically a measure of energy per unit mass. The equation effectively divides each term by mass, leading to the interpretation of Emec as energy per unit mass rather than total energy. Understanding this distinction clarifies the relationship between pressure, velocity, and gravitational potential energy in fluid mechanics.
custer
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Why does Emec= P/\rho + v^2/2 + gz ?
The units resulting from the three expressions are m^2/s^2
but unit for energy is supposed to be Joules? where does the mass go? If the three expressions were already divided by the mass then why Emec still remains as Emec?
 
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Hi custer! :smile:

(have a rho: ρ :wink:)
custer said:
Why does Emec= P/\rho + v^2/2 + gz ?

Which book did you get that equation from? :confused:

The LHS should be the mechanical energy per unit mass.

(Compare it with ε, the internal energy per unit mass, or "specific internal energy").

See the PF Library on pressure and Bernoulli's equation :wink:
 
got it from a slide in my lecture note.. no wonder ;P
thank you :)
 

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