railway RRB JE (CBT I + CBT II) Mock Test 2024 Fluid Mechanics Flow Through Pipes Friction Loss (Darcy Weisbach Equation)
For steady, fully developed flow inside a straight pipe of diameter D, neglecting gravity effects, the pressure drop Δp over a length L and the wall shear stress τw are related by
1
\({\tau _w} = \frac{{{\rm{\Delta }}pD}}{{4L}}\)
2
\({\tau _w} = \frac{\Delta p{D^2}}{4{L^2}}\)
3
\({\tau _w} = \frac{{{\rm{\Delta }}pD}}{{2L}}\)
4
\({\tau _w} = \frac{{4{\rm{\Delta }}pL}}{D}\)