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Homework Help: Fluid mechanics

  1. May 10, 2010 #1
    1. The problem statement, all variables and given/known data
    fluid is flowing upward through a 1cm diameter pipe at 0.15m/s find the necessary power per unit length to drive the flow through the pipe.

    2. Relevant equations
    tau= (viscosity)dU/dy
    flux of momentum out - flux of momentum in= forces acting on the CV (tau( downward) and F_y( upward))
    force x velocity = power.

    3. The attempt at a solution
    I found all the forces acting on the CV:
    shear stress
    and F subscript y
    I ignored the weight as it might already be contained in the Force y which pushes the flow upward and also because I have no idea what the mass of the water would be here.

    in this case mom in= mom out => tau( shear stress)*A=F_y
    tau= 0.03006 Pa
    tau*A=7.85*10^-5N= F_y
    => F_y*U( velocity)=1.17809*10^-5 J/S
  2. jcsd
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