Energy of an axisymmetric fluid jet

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Discussion Overview

The discussion revolves around calculating the energy associated with an axisymmetric fluid jet, focusing on the complexities of quantifying energy generated by shear in the flow field. Participants explore various aspects of fluid dynamics related to this topic, including flow velocity, mass flow rate, and turbulent energy in the context of both theoretical and practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests guidance on calculating the energy of an axisymmetric jet, providing a schematic for reference.
  • Another participant questions the formulation of the problem, suggesting that while flow velocity and mass flow rate can be calculated, translating these into a definitive measure of energy is problematic.
  • A subsequent reply elaborates that the jet induces shear in the flow field, and the participant is interested in quantifying the energy generated by this shear, particularly in relation to particle fluid interaction.
  • Another participant acknowledges the complexity of the problem, noting that while kinetic energy can be estimated, measuring the turbulent energy in the free shear layer poses significant challenges and may lack an analytical solution.
  • It is suggested that one could estimate the change in kinetic energy at a specific location in the jet to gauge energy loss to the surroundings, though this method is acknowledged as imperfect.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of calculating energy associated with the jet, with some focusing on kinetic energy while others highlight the challenges of measuring turbulent energy. The discussion remains unresolved regarding the best approach to quantify the energy generated by the jet.

Contextual Notes

Participants note limitations in the problem formulation, including the dependence on specific definitions and the lack of analytical solutions for certain aspects of turbulent energy measurement.

neyganesh
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Can someone give me an go ahead of how I can calculate the energy associated with an axis symmetric jet? I have included the schematic of the flow as an attachment.
 

Attachments

  • jet.PNG
    jet.PNG
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I'm not sure that's a well-posed problem. At least, I can calculate the (steady state) flow velocity, mass flow rate, and (say) the reaction force on a nozzle, but I don't see how to turn any of those into *the* energy- power, maybe.
 
Thank you for the reply.
Let me give more details then. A jet similar to the one shown in the figure introduces a shear in a flow field. If we have particle fluid interaction along the edge, I am interested in quantifying the energy generated by the shear of the jet.
 
Well that is a difficult problem. I at first assumed you wanted kinetic energy, which could be accomplished, but to measure the turbulent energy induced in the free shear layer is much more difficult. To my knowledge there isn't an analytical solution to that.

I suppose you could look at [itex]\Delta KE[/itex] at a given x-location in the jet to get an estimate of how much has been lost to the surroundings, but this certainly isn't perfect.
 

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