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
Related Mcqs:
- 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 - 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 ?
A. f1 = f2
B. f1 < f2
C. f1 > f2
D. Data not sufficient to relate f1 & f2 - 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 - 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. - The friction factor for turbulent flow in a hydraulically smooth pipe______________?
A. Depends only on Reynolds number
B. Does not depend on Reynolds number
C. Depends on the roughness
D. None of these - Transition length for turbulent flow in smooth pipe is equal to _____________ times the pipe diameter?
A. 0.5
B. 5
C. 50
D. 500 - 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 - What is the value of Fanning friction factor f ‘ for smooth pipe at NRe = 106 approximately ?
A. 0.003
B. 0.01
C. 0.1
D. 0.3 - For a given Reynolds number, in a hydraulically smooth pipe, further smoothening ____________ the friction factor?
A. Brings about no further reduction of
B. Increases
C. Decreases
D. None of these - Colebrook equation for friction factor in turbulent flow is given by, f-0.5 = -4 loge [(ε/D) + (1.26/NRe √F). It reduces to Nikuradse equation for a value of (ϵ/D) equal to __________________?
A. 0
B. 1
C. ∞
D. 0.5
