The value of critical Reynolds number for pipe flow is_________________?

Related Mcqs:

1. 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.

2. 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

3. 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)

4. For turbulent flow of an incompressible fluid through a pipe, the flow rate „Q‟ is proportional to (Δ P)n, where ΔP is the pressure drop. The value of exponent ‘n’ is_________________?

   A. 1
   B. 0
   C. < 1
   D. > 1

5. A fluid (μ/ρ) = 0.01 cm2/sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is _______________ cm/sec?

   A. 7
   B. 700
   C. 7000
   D. 630

6. Reynolds number for flow of water at room temperature through 2 cm dia pipe at an average velocity of 5 cm/sec is around________________?

   A. 2000
   B. 10
   C. 100
   D. 1000

7. Reynolds number for water flow through a tube of I.D. 5 cm is 1500. If a liquid of 5 centipoise viscosity and 0.8 specific gravity flows in the same pipe at the same velocity, then the pressure drop will______________________?

   A. Increase
   B. Decrease
   C. Remain same
   D. Data insufficient to predict pressure drop

8. What is the ratio of the velocity at the axis of the pipe to the mean velocity of flow in case of pipe flow under viscous condition ?

   A. 0.5
   B. 0.67
   C. 1
   D. 2

9. As the velocity V and thus the Reynolds number of a flow past a sphere increases from very low value, the drag force for Re << 1 ?

   A. Increases linearly with V
   B. Decreases linearly with V
   C. Decreases as V2
   D. None of these

10. 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