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Homework Statement
what is the meaning of number of diameter N ? why the author make L = ND ? and then divide it by D ?
Homework Equations
The Attempt at a Solution
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can you explain about what is ND / D ? i am confusedThis is a practical way to do it: you get an equivalent length for fittings, elbows etc. that you can add to the sum of lengths of straight sections and use in friction factor formulas (e.g. Darcy).
Head loss is a function of ##L\over D## .
Didactically the sheet you show is indeed rather ready for improvement. I find it confusing.
why L = ND ? i dont understand itND is L so ND / D is L/D. That is the factor that appears in the friction factor equations such as Darcy and Fanning (*). The approach exploits the observed similarity in flow properties between a flow in a pipe of 100 m and 1 m diameter and a flow in a pipe of 10 m with a diameter of 10 cm.
(*)
And I would almost wish one of the two never existed . Now you have to be really careful if you divide 16 or 64 by Re for laminar flow.....
That's what has been observed to be the case .why they will have the same pressure drop
ok , how does the case that you mentioned relate yo number of diameter ?Allright, L/D = 100 .
That's what has been observed to be the case .
'Apparently' ##\Delta p## is a function of L/D, something that probably also comes out of similarity considerations.
Something with ##{\rm Re} = {\rho v D\over \mu}##