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# Fluid Mechanics (101-120)

Updated: Apr 18, 2020

10l. A fluid of kinematic viscosity 0.4 cm²/sec flows through a 8 cm diameter pipe. The maximum velocity for laminar flow will be I m/sec

102. The losses are more in turbulent flow

103. The wake always occurs after a separation point

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

105. The hydraulic grade line is never above the energy grade line

106. Two pipe systems are said to be equivalent when head loss and discharge are same in two systems

I07. In series-pipe problems the discharge is same through each pipe

108. Select the correct statement The absolute roughness increases

with time.

109. A valve is suddenly closed in a water main in which the velocity is l m/sec and

velocity of pressure wave is 981 m/ sec. The inertia head at the valve will be 100m

110. The speed of a pressure wave through a pipe depends upon the bulk modulus for the fluid

111. If the speed of pressure wave is v and pipe length is L, rapid closure occurs when time of closure is less than 2l/v₀

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

L/2

113. 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 from reservoir A to reservoirs B and C

114. If there are n pipes of same diameter d laid in parallel in place of a single pipe of diameter D, then

I15. 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 32 km

116. 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 less than d

117. The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is 1/3

118. The boundary layer thickness at a distance of 1 m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is 0.1 cm. The velocity outside the boundary layer is 25 m/ sec. The boundary layer thickness at a distance 0.20 cm

119. Drag force is a function of

i) projected area of the body

ii) mass density of the fluid

iii) velocity of the body

120. The correct relationship among displacement thickness d, momentum thickness m and energy thickness e is e>d>m