In my text book it's written that head losses in elbows is produced by secondary flows..
I have looked for the meaning of secondary flow, and I found that :
The primary flow is parallel to the main direction of fluid motion and the secondary flow is perpendicular to this..
But I didn't find why does it occur.. Can you help me?
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1 Answer
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Secondary flow can result from obstacles, viscosity effects and because of changes in the size and orientation of the cross section. In general these causes lead to nonvanishing convective terms in the Navier-Stokes equation whicht lead to more complex flow patterns because of nonlinear effects.
