What Sets Kinetic Energy Apart from Flow Work?

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SUMMARY

Kinetic energy and flow work are distinct concepts in fluid dynamics, as established by the work-energy principle. Kinetic energy pertains to the energy of an object in motion, while flow work specifically relates to the energy required to move fluids. Internal energy changes, temperature variations, and viscous forces complicate the relationship between these two forms of energy, necessitating a detailed energy analysis. The power input to a control volume is defined by the equation Power = Force - Internal Energy, highlighting the separate contributions of flow work and kinetic energy.

PREREQUISITES
  • Understanding of the work-energy principle
  • Familiarity with fluid dynamics concepts
  • Knowledge of internal energy changes in fluids
  • Basic mechanics, particularly power calculations
NEXT STEPS
  • Study the work-energy principle in detail
  • Explore the fundamentals of fluid dynamics
  • Investigate the effects of temperature and viscosity on fluid motion
  • Review the provided reference on compressible flow fundamentals
USEFUL FOR

Students and professionals in mechanical engineering, fluid dynamics researchers, and anyone interested in the principles of energy analysis in fluid systems.

Mohankpvk
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As per work energy principle, the energy spent in moving an object is stored as kinetic energy.Flow work is done to make the fluid move.Why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered separately?
 
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Mohankpvk said:
Why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered separately?

the flow of liquids are a bit complicated due to internal energy changes , may be temperature change, viscous forces as well as the

molecular motions, i think a detail energy analysis is required. and one can not simply equate the work done to the K.E. of the flow.

The forces that act on the surface of a control volume do work on the fluid in the control volume and therefore contribute to the energy

balance. The power (energy per second) put into the fluid within the control volume is given by the classical relation from mechanics P ower input to the control volume = F - U

there is an interesting analysis in the following reference-

<https://web.stanford.edu/~cantwell/AA210A_Course_Material/AA210A_Course_Notes/AA210_Fundamentals_of_Compressible_Flow_Ch_01_BJ_Cantwell.pdf>
 

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