Fluid Mechanics (181-200)

Updated: Apr 21, 2020

181.The condition for complete similarity to exist between model and prototype, where both gravity and viscous forces are important, is





where μᵣ is kinematic viscosity ratio and L is length scale ratio

182. A ship's model of scale 1 : 100 had a wave resistance of 1 kg at its design

speed. The corresponding wave resistance in prototype will be

1000000 kg

183. In which of the following situations, the inertia force would be unimportant ?

flow through a long capillary tube

184. For the resistance to motion of a ship's model through water, the basic similitude criteria is Reynolds Law,Froude's Law

185. The causes of cavitation are high suction lift and high pump speed

186. The cavitation parameter is given by






where p is the absolute pressure of the point of consideration, p is atmosphere

pressure, p is vapour pressure of liquid, ρ is the density of the liquid and V is the

velocity.

187. An impulse turbine operates by initial complete conversion to kinetic energy

188. Water turbines may be put in the decreasing order of specific speeds as

propeller turbine, reaction turbine, impulse turbine

189. At a rated capacity of 44 cumecs, a centrifugal pump develops 36 m of head

when operating at 1450 rpm. Its specific speed is 654

190. A Francis turbine under a head of 25 m produces 2000 KW at a speed of 250 rpm. Its specific speed is 200


191. Two geometrically similar units are homologous if they have similar streamlines

192. A reaction type turbine discharges 10 cumecs under a head of 8 m and with an overall efficiency of 85 percent. The power developed is 667 kW

193 ) An impulse turbine is ideal for high head development.

ii) Speed ratio of a reaction turbine is in the range of 0.6 to 0.9

194.i) A reciprocating pump does not need priming,

ii) A centrifugal pump can run at high speed



195. Pumps may be put in the increasing order of specific speeds as centrifugal pumps, mixed flow pumps, axial flow pumps

196. The specific speed of a turbine is defined as the speed of a unit of such a size that it produces unit power for unit head

197. Water enters a turbine steadily at the rate of 100 litres per second with a pressure of 3 x lO N/m² and a velocity of 100 m/s. It leaves the turbine with a pressure of 10 N/m² and a velocity of 50 m/sec. If no losses occur, the power produced by the 395 KW


198. An isentropic process is always frictionless and adiabatic

199. Which of the following equations are used momentum and continuity

200. critical pressure ratio 0.528

critical temperature ratio 0.833

critical density 0.634

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