Consider two pipes of same length and diameter through which water is passed at the same velocity. The friction factor for rough pipe is f1 and that for smooth pipe is f2. Pick out the correct statement ?

Related Mcqs:

1. Friction factor for a hydraulically smooth pipe at NRe = 2100 is f1. If the pipe is further smoothened (i.e., roughness is reduced), the friction factor at the same value of NRe, will_______________?

   A. Increase
   B. Decrease
   C. Remain unchanged
   D. Increase or decrease depending on the pipe material

2. In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of___________________?

   A. Relative roughness
   B. Absolute roughness
   C. Friction co-efficient for flows at equal Reynold number
   D. All A., B. & C.

3. A pipe of I.D. 4 m is bifurcated into two pipes of I.D. 2 m each. If the average velocity of water flowing through the main pipe is 5 m/sec, the average velocity through the bifurcated pipes is__________________?

   A. 20 m/sec
   B. 10 m/sec
   C. 5 √2 m/sec
   D. 5 m/sec

4. In turbulent flow, a rough pipe has the same friction factor as a smooth pipe____________________?

   A. In the zone of complete turbulence
   B. When the roughness projections are much smaller than the thickness of the laminar film
   C. Everywhere in the transition zone
   D. When the friction factor is independent of the Reynold’s number

5. For turbulent flow in smooth circular pipe, the velocity distribution is a function of the distance ‘d’ measured from the wall of the pipe and the friction velocity ‘v’, and it follows a _____________ relationship?

   A. Logarithmic
   B. Linear
   C. Hyperbolic
   D. Parabolic

6. A centrifugal pump is used to pump water through a horizontal distance of 150 m, and then raised to an overhead tank 10 m above. The pipe is smooth with an I.D of 50 mm. What head (m of water) must the pump generate at its exit E. to deliver water at a flow rate of 0.001 m3/s? The Fanning friction factor, f is 0.0062 ?

   A. 10 m
   B. 11 m
   C. 11.8 m
   D. 30 m

7. A pipe has a porous section of length L as shown in the figure. Velocity at the start of this section of V0. If fluid leaks into the pipe through the porous section at a volumetric rate per unit area q(x/L)2, what will be axial velocity in the pipe at any „x‟? Assume incompressible one dimensional flow i.e., no gradients in the radial direction ?

   A. VX = V0 + q (x3/L2D)
   B. VX = V0 + ⅓q (x3/L2)
   C. VX = V0 + 2q (x2/LD)
   D. VX = V0 + (4/3) q (x3/L2D)

8. If three pipes of different diameters, lengths & friction factors are connected in parallel, then (where, Q = flow rate, V= fluid velocity f = friction factor). ?

   A. Q = Q1 + Q2 + Q3
   B. V1 = V2 = V3
   C. Q1 = Q2 = Q3
   D. f = f1 + f2 + f3

9. Transition length for turbulent flow in smooth pipe is equal to _____________ times the pipe diameter?

   A. 0.5
   B. 5
   C. 50
   D. 500

10. The pressure drop per unit length of pipe incurred by a fluid ‘X’ flowing through pipe is Δp. If another fluid ‘Y’ having both the specific gravity & density just double of that of fluid ‘X’, flows through the same pipe at the same flow rate/average velocity, then the pressure drop in this case will be__________________?

    A. Δp
    B. 2Δp
    C. Δp2
    D. Δp/2