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Homework Help: Von Karman and Prandtl laws

  1. Apr 26, 2016 #1
    1. The problem statement, all variables and given/known data
    there are 2 formula of vont karman and prandit laws to find the friction factorfor rough pipe and smooth pipe , which formula should i use for this question?
    d1kMTSw.png .
    P/ s : I'm asked to find the friction factor using the vont karman and prandit laws.
    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Apr 26, 2016 #2
    it didnt stated whether it's smooth or rough pipe , which formula should we use?
  4. Apr 26, 2016 #3


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    I was going to propose you do both (assuming some reasonable ##e## for galvanized ion pipe ) and compare ... :smile:

    On the other hand, you do have the data to calculate Re so I certainly wouldn't leave out that one...
  5. Apr 27, 2016 #4
    well , i have found that the f for rough pipe is 0.017 , nut i am not sure how to find f for smooth pipe using von karman and Prandlt laws ... for smooth pipe , i have 1 / ( surd f ) = 2 log [(3.72 x 10^5) (surd f ) / 2.51 ]

    P/ s: by using scientific calculator , i get the f for smooth pipe is 0.014 , which value should i choose ? f= 0.017 or 0.014 ?
  6. Apr 27, 2016 #5


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    Edit : Duplicate information removed .
    Last edited: Apr 27, 2016
  7. Apr 27, 2016 #6
    so , do you have any comment on this question / which is correct ?
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