How Does Bulk Velocity Relate to Maximum Velocity in Turbulent Tube Flow?

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SUMMARY

The discussion focuses on deriving the relationship between average velocity (bulk velocity) and maximum velocity in turbulent flow within a smooth, circular tube at a Reynolds number of approximately 10^5. The velocity profile is defined by the equation Vx = Vxmax * [(R-r)/R]^(1/7), where R is the tube radius and r is the radial distance from the center. Participants emphasize the need to integrate this equation to find the average velocity, defined as = Q/A, where Q represents the volumetric flow rate and A is the cross-sectional area. The integration can be simplified using the substitution z = R - r.

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  • Understanding of fluid dynamics principles, particularly turbulent flow.
  • Familiarity with Reynolds number and its significance in flow characterization.
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  • Experience with volumetric flow rate calculations.
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  • Study the derivation of average velocity in turbulent flow using integration techniques.
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Homework Statement


For turbulent flow in a smooth, circular tube with a radius R, the velocity profile varies according to the following expression at a Reynolds number of about 10^5.

Vx= Vxmax * [(R-r)/R)]^(1/7)

where r is the radial distance from the center and Vmax the maximum velocity at the center. Derive equation relating the average velocity ( bulk velocity ) Vav to Vmax for an incompressible fluid.
( Hint: The integration can be simplified by substitution z for R-r )


Homework Equations





The Attempt at a Solution


i don't know which equation i should integrate and how?
 
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I guess the average speed is defined as <v>=\frac{Q}{A} where Q is the volume of fluid passing through the cross section of area A in 1 second. How do you find Q? :wink:
 
hikaru1221 said:
I guess the average speed is defined as <v>=\frac{Q}{A} where Q is the volume of fluid passing through the cross section of area A in 1 second. How do you find Q? :wink:
i think working with volume rate is useless
 
Okay, why and what do you think of the solution?
 

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