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Fluid Mechanics and Hydraulic Machinery Miscellaneous

Fluid Mechanics and Hydraulic Machinery

  1. 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) = −
    ∂p
    1 −
    ∂x

    where ∂p/∂x is a constant
    The average velocity of fluid in the pipe is
    1. ∂p
      ∂x
    2. ∂p
      ∂x
    3. ∂p
      ∂x
    4. ∂p
      μ∂x
Correct Option: A


u = −
dp
1 −
dxR

dQ =u (2πrdr)

Solving, we get
Q = −
πR²
dp
dx

Now Q = Area ´ average velocity
∴  uav =
Q
=
Q
Area πR2

or   uav =
dp
dx



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