Which of the following equations as suggested by Colebrook and White gives the increase in roughness of a new surface (ε0) with age/time (t) (where, ε = roughness of the surface after time’t’. α = a co-efficient to be experimentally determined) ?

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. 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

3. A rectangular surface 3′ × 4′, has the lower 3 edge horizontal and 6′ below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is (where, y = specific weight of water) ?

   A. 39.6y
   B. 48y
   C. 49.2y
   D. 58y

4. Co-efficient of discharge (Cd) is defined as actual discharge/theoretical discharge and is equal to Cc . Cv; where Cc = Co-efficient of contraction and Cv = co-efficient of velocity. Cd of an orifice is usually about__________________?

   A. 0.42
   B. 0.62
   C. 0.82
   D. 0.98

5. Cd, Cc and Cv are related (for flow through an orifice) as (where, Cd = discharge co-efficient, Cc = co-efficient of contraction = (area of jet at vena-contracta/area of opening), Cv = co-efficient of velocity = (actual velocity at vena-contracta/theoretical velocity)?

   A. Cd = Cc/Cv
   B. Cd = Cc.Cv
   C. Cd = Cv/ Cc
   D. None of these

6. 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

7. Which of the following equations is valid for laminar flow of a fluid through packed bed ?

   A. Fanning equation
   B. Kozeny – Karman equation
   C. Hagen-Poiseuille equation
   D. Blake-Plummer equation

8. Which of the following equations applies to the fluid flow through a packed bed for very large Reynolds number ?

   A. Fanning equation
   B. Blake-Plummer equation
   C. Hagen-Poiseuille equation
   D. Kozeny-Carman equation

9. The location of centre of pressure, which defines the point of application of the total pressure force on the surface, can be calculated by applying the principle of moments according to which “sum of the moment of the resultant force about an axis is equal to the sum of the components about the same axis”. The centre of pressure of a rectangular surface (of width ‘w’) immersed vertically in a static mass of fluid is at a depth of (where, y = depth of the liquid) ?

   A. 1/(y/3)
   B. 2y/3
   C. 1/(y/4)
   D. 3y/4

10. The drag co-efficient for a bacterium moving in water at 1 mm/s, will be of the following order of magnitude (assume size of the bacterium to be 1 micron and kinematic viscosity of water to be 10-6m2/s) ?

    A. 24000
    B. 24
    C. 0.24
    D. 0.44