**76. The discharge of a liquid of kinematic viscosity 4 cm2/sec through a 8 cm dia-meter pipe is 3200n cm7sec. The type of flow expected is**

a) laminar flow

b) transition flow

c) turbulent flow

d) not predictable from the given data

**Ans: a**

**77. The Prartdtl mixing length is**

a) zero at the pipe wall

b) maximum at the pipe wall

c) independent of shear stress

d) none of the above

**Ans: a**

**78. The velocity distribution for laminar flow through a circular tube**

a) is constant over the cross-section

b) varies linearly from zero at walls to maximum at centre

c) varies parabolically with maximum at the centre

d) none of the above

**Ans: c**

**79. A fluid of kinematic viscosity 0.4 cm2/sec flows through a 8 cm diameter pipe. The maximum velocity for laminar flow will be**

a) less than 1 m/sec

b) 1 m/sec

c) 1.5 m/sec

d) 2 m/sec

**Ans: b**

**80. The losses are more in**

a) laminar flow

b) transition flow

c) turbulent flow

d) critical flow

**Ans: c**

**81. The wake**

a) always occurs before a separation point

b) always occurs after a separation point

c) is a region of high pressure intensity

d) none of the above

**Ans: b**

**82. The maximum thickness of boundary layer in a pipe of radius r is**

a) 0

b) r/2

c) r

d) 2r

**Ans: c**

**83. The hydraulic grade line is**

a) always above the centre line of pipe

b) never above the energy grade line

c) always sloping downward in the direction of flow

d) all of the above

**Ans: b**

**84. Two pipe systems are said to be equivalent when**

a) head loss and discharge are same in two systems

b) length of pipe and discharge are same in two systems

c) friction factor and length are same in two systems

d) length and diameter are same in two systems

**Ans: a**

**85. In series-pipe problems**

a) the head loss is same through each pipe

b) the discharge is same through each pipe

c) a trial solution is not necessary

d) the discharge through each pipe is added to obtain total discharge

**Ans: b**

**86. Select the correct statement.**

a) The absolute roughness of a pipe de-creases with time.

b) A pipe becomes smooth after using for long time.

c) The friction factor decreases with time.

d) The absolute roughness increases with time.

**Ans: d**

**87. A valve is suddenly closed in a water main in wl.ich the velocity is 1 m/sec and velocity of pressure wave is 981 m/ sec. The inertia head at the valve will be**

a) 1 m

b) 10m

c) 100m

d) none of the above

**Ans: c**

**88. The speed of a pressure wave through a pipe depends upon**

a) the length of pipe

b) the viscosity of fluid

c) the bulk modulus for the fluid

d) the original head

**Ans: c**

**89. When time of closure tc = L/v0 (where L is length of pipe and v0 is speed of pressure wave), the portion of pipe length subjected to maximum head is**

a) L/4

b) L/3

c) L/2

d) L

**Ans: a**

**90. If the elevation of hydraulic grade line at the junction of three pipes is above the elevation of reservoirs B and C and below reservoir A, then the direction of flow will be**

a) from reservoir A to reservoirs B and C

b) from reservoir B to reservoirs C and A

c) from reservoir C to reservoirs A and B

d) unpredictable

**Ans: c**

**91. The length of a pipe is 1 km and its diameter is 20 cm. If the diameter of an equivalent pipe is 40 cm, then its length is**

a) 32 km

b) 20 km

c) 8 km

d) 4 km

**Ans: a**

**92. Two pipes of same length and diameters d and 2d respectively are connected in series. The diameter of an equivalent pipe of same length is**

a) less than d

b) between d and 1.5 d

c) between 1.5 d and 2d

d) greater than 2d

**Ans: a**

**93. The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is**

a) 1/3

b) 1/4

c) 1/2

d) 2/3

**Ans: a**

**94. The boundary layer thickness at a distance of l m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is O.l cm. The velocity outside the boundary layer is 25 ml sec.****The boundary layer thickness at a distance of 4 m is**

a) 0.40 cm

b) 0.20 cm

c) 0.10 cm

d) 0.05 cm

Assume that boundary layer is entirely laminar.

**Ans: b**

**95. Drag force is a function of**

i) projected area of the body

ii) mass density of the fluid

iii) velocity of the body

The correct answer is

a) (i) and (ii)

b) (i) and (iii)

c) (ii) and (iii)

d) (i), (ii) and (iii)

**Ans: d**

**96. The correct relationship among displacement thickness d, momentum thickness m and energy thickness e is**

a) d > m > e

b) d > e > m

c) e > m > d

d) e > d > m

**Ans: d**

**97. For laminar flow in circular pipes, the Darcy’s friction factor f is equal to**

a) 16/Re

b) 32/ Re

c) 64/ Re

d) none of the above

where R,, is Reynolds number.

**Ans: c**

**98. Surge wave in a rectangular channel is an example of**

i) steady flow

ii) unsteady flow

iii) uniform flow

iv) non-uniform flow

The correct answer is

a) (i) and (iii)

b) (ii) and (iii)

c) (i) and (:v)

d) (ii) and (iv)

**Ans: d**

**99. In case of an airfoil, the separation of flow occurs**

a) at the extreme rear of body

b) at the extreme front of body

c) midway between rear and front of body

d) any where between rear and front of body depending upon Reynolds number

**Ans: a**

**100. When an ideal fluid flows past a sphere,**

a) highest intensity of pressure occurs around the circumference at right angles to flow

b) lowest pressure intensity occurs at front stagnation point

c) lowest pressure intensity occurs at rear stagnation point

d) total drag is zero

**Ans: d**