Jet Spread Rate K Values- Momentum diffusement

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SUMMARY

The discussion focuses on calculating the rate of momentum diffusement in a jet entering a nozzle, specifically comparing the inlet velocity (ui) to the ambient fluid velocity (ue). Empirical K-values are highlighted, with ~0.1 for turbulent flow and ~0.4 for laminar flow, indicating the relationship between momentum diffusement and shear forces. The conversation explores whether momentum diffusement can be directly calculated from the difference between ui and ue, and the implications of K-values less than 1 on velocity gradients. Additionally, the initial region length of 5 diameters is questioned in relation to a K-value of 0.2.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with K-values in momentum diffusement
  • Knowledge of Reynolds number and its significance
  • Basic concepts of shear forces in fluid flow
NEXT STEPS
  • Research the relationship between K-values and flow regimes in fluid dynamics
  • Explore the calculation of momentum diffusement using empirical formulas
  • Study the effects of viscosity on momentum transfer in fluids
  • Investigate the design and function of underwater pressure nozzles and Venturi systems
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Fluid dynamics engineers, mechanical engineers, and researchers focusing on jet flow characteristics and momentum transfer in various fluid systems.

Tom79Tom
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The Problem Statement
I have a jet entering leaving a nozzle at ui into an ambient fluid with ue = 0
I am trying to equate the rate of momentum diffusement (or spread) to the shear forces caused by ue -ui

I understand that the rate momentum diffusement is are equated by empirical K- values (~0.1 for turbulent flow ~0.4 for laminar flow)

The Question

Is there any way to calculate the rate of momentum diffusement or spread directly from ui -ue
I am trying to understand what would happen as the flow develops from ui=0, ue = 0
Would the momentum diffusement always equal the rate of flow development or does K values < 1 indicate that a the momentum diffusement is inadequate to prevent a velocity gradient.
Attempt at a solution
I am thinking that it does as there is a length to the initial region where this occurs.
A K-value of 1 would indicate an immediate dispersal of any additional increase in ui so no shear forces could ever develop.[/sub] and therefore no motive to cause a diffusement . A cyclical argument.
I think the K value must factor the viscosity of the fluid and its Reynolds number

Edit : sorry one other question, the initial region length is described as 5 diameters in length . Is that representative of a k value of 0.2
$$\frac{1D}{0.2}=5D$$
 

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I'm sorry I don't have an answer for you but I was wondering if you could help me. Do you know of an underwater pressure nozzle that can increase the pressure and volume of the fluid mass by pulling in fluid from the surrounding areas of fluid around the exterior of the nozzle possibly with a Venturi or jet pump type opening before the nozzle's release?
 

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