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The velocity profile of a fully developed laminar flow in a straight circular pipe, as shown in the figure, is given by the expression
u(r) = − R² ∂p 1 − r² 4μ ∂x R²
where ∂p/∂x is a constant
The average velocity of fluid in the pipe is
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− R² ∂p 8μ ∂x -
− R² ∂p 4μ ∂x -
− R² ∂p 2μ ∂x -
− R² ∂p μ ∂x
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Correct Option: A
u = − | ![]() | − | ![]() | ![]() | 1 − | ![]() | |||
4μ | dx | R |
dQ =u (2πrdr)

Solving, we get
Q = − | ![]() | − | ![]() | ||
8μ | dx |
Now Q = Area ´ average velocity
∴ uav = | = | ||
Area | πR2 |
or uav = | ![]() | ![]() | ||
8μ | dx |