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Fluid Mechanics (241-260)

Updated: Apr 22, 2020

241.Given that K = a coefficient, v velocity, f= Darcy-Weisbach

factor and D = diameter of the pipe, if the head loss in a pipe bend is given by h =

Kv²/2g, then the equivalent length of the pipe is KD/f


242.When no external energy is imposed, which of the following statements would be true?

Energy line always falls in the direction of flow

Hydraulic gradient line never rises in the direction of flow


243.The specific energy 'E' in a critical flow at depth y𝒸 occurring in a triangular

channel is given by E=1.25y𝒸


244. In a gradually varied flow, if dy/dx is positive, then dE/dy will be positive if y>y𝒸


245.Which one of the following is the correct representation of the sequence of surface profiles if the channel slope changes from mild to steep ? M,s


246.An irrigation canal has a steady discharge Q at a section where a cross- regulation (gated) is provided for control purposes. If the gate of the regulator, which is normally fully open, is suddenly lowered down to a half open position, then a rapidly varied unsteady flow results. In such a case, it would take the form of a +ve surge moving u/s and a -ve surge moving d/s


247. A 10 cm high rocket containing liquid fuel of specific gravity 1.2 lifts off at an

acceleration of 5 g. The pressure on the bottom plate of the rocket, at lift-off is

7.2 kg/cm²


248.Stream lines-Tracing of motion of different fluid particles Streak lines-Identification of location number of fluid particle Path lines-Tracing of motion of any one fluid particle Equipotential lines-Location of equal piezometric heads


249.As the depth of immersion of a vertical plane surface increases, the location of

pressure -comes closer to the centre of gravity of the area


250. If the discharge is Q, in a pipe fitted with an end-cap nozzle discharging a jet of water with velocity V and hitting normally a plate which is moving with a velocity V/2 towards the nozzle, then the jet would hit the plate with a discharge of 1.5 Q


251. Consider the following parameters related to fluid flow. Among these, those which exist both in rotational flows and irrotational flows would include

Vorticity,Stream function


252. The flow of water in a wash hand basin when it is being emptied through a central opening, is an example of free vortex


253. In a fluid flow, the time of constant piezometric head passes through two

points which have the same velocity potential


254.Mach Number-Launching of rockets Thoma Number-Cavitation phenomenon Reynolds Number-Motion of a submarine Weber Number-Capillary flow in soil


255. An error of 0.5% in the measurement of head in a V-notch causes an error of

1.25% in the discharge


256. A sphere of certain diameter, when towed submerged under water, experiences a drag force of 4 Newtons at a velocity of 1.5 m/s. If another sphere of twice the diameter of the sphere referred to above, is towed with the same velocity in water, the drag force experienced by this sphere

will be 16 N


257. Which of the following conditions would entail a greater energy dissipation in

turbulent flow ? Smaller eddy size,Large intensity of turbulence


258. Shear velocity is a fictitious quantity


259. Three reservoirs A,B and C are interconnected by pipes as shown in Fig.

Water surface elevations in the reservoirs and the piezometric level at the

junction D are also indicated in the figure

Q + Q = Q


260. Consider the following statements:

A horizontal pipe reduces from 10 cm to 5 cm in diameter. If the pressure head at 10 cm section is 10 metres and velocity head is 1 metre, then the datum head at all sections is constant Of these statements

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