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# Fluid Mechanics (221-240)

Updated: Apr 22, 2020

221.An open rectangular wagon 5 m long is filled with water to a level 0.5 m below

the open top. The maximum acceleration (in m/s²) at which it can be speeded up

without spilling the water is nearly 1.96

222. Which of the following rules are used in choosing the repeating variables in

dimensional analysis ?

Repeating variables should contain all primary units used in describing the

variables in the problem

Repeating variables should not contain the dependent variables.

223. A harbour model has a horizontal scale of 1/150 and a vertical scale of 1/60. The

interval between successive high tides in the model will be nearly 40 min

224.In a laminar flow through a circular pipe of diameter 20 cm, the maximum velocity is found to be 1 m/s. The velocity at a radial distance of 5 cm from the axis of the pipe will be 0.75 m/s

225. If a multijet Pelton turbine has 'n' number of jets, then its specific speed is directly proportional to n¹/²

226. An aeroplane having a wing span of 16 m and chord of 2.5 m weighs 11 tonnes. If it gets airborne at a velocity of 300 kmph, then the coefficient of lift is nearly 0.6

227. The Hardy Cross method of hydraulic analysis of pipe networks, besides

satisfying the continuity and energy principles, must also satisfy the condition

that the algebraic sum of the head losses around any closed loop is zero

228. A liquid of density p and bulk modulus K flows with a mean velocity V in a long rigid pipe of diameter D. A sudden closure. of a valve at the end of the pipe produces a maximum water hammer head h𝓌 which is equal to 229. Given that,

S = slope of the channel bottom,

S = slope of the energy line,

F = Froude number,

the equation of gradually varied flow is expressed as 230. Match List I with List II and select the correct answer using the codes

given below the lists: (y = Normal depth, y𝒸 = critical depth and y = 231. A discharge of 3.0 m³/s flows in a canal, 2 m wide, at a depth of 1.2 m. If the width of the canal is reduced to 1.5 m by a canal transition, then neglecting losses, the depth of flow after the contraction will be 1.12 m

232. If u and v are the components of velocity in the x and y directions of a flow given by u = ax + by; v = ex + dy, then the condition to be satisfied is

a + d = 0

233. At a point on a streamline, the velocity is 3 m/s and the radius of curvature is 9 m. If the rate of increase of velocity along the streamline at this point is 1/3 m/s/m, then the total acceleration at this point would be 2 m/s²

234. Match List I with List II and select the correct answer using the codes given

below the lists:

A. Rotational flow - Flow near a curved solid boundary B. Vortex flow -A fluid motion in which stream lines are concentric circles C. Free vortex - The fluid particles moving in concentric circles may not rotate about their mass centre D. Forced vortex - The fluid particles moving in concentric circles may rotate

235. In a Sutro weir, the rate of flow for all flows above the rectangular base of width W and depth 'a' is proportional to the head

above a datum a/3 above the crest

236. A model of reservoir is emptied in 10 minutes. If the model scale is 1:25, the

time taken by the prototype to empty itself, would be 50 minutes

237.The relationship is valid for Uniform flow

238.Which of the following statements are correct in respect of steady laminar flow through a circular pipe ?

Shear stress is zero at the centre,Velocity is maximum at the centre,Hydraulic gradient varies directly with the velocity

239.Boundary layer thickness-Distance from the boundary where velocity is 99% of uniform velocity Displacement thickness-Distance from the boundary by which the main flow can be assumed to be shifted Laminar boundary layer-Region near the boundary where viscous stress is also present Turbulent boundary layer-Distance from the boundary wherefrom the flow ceases to be laminar

240.In a compressible flow, the area of flow, the velocity of flow and the mass density are denoted by a, v and m respectively. At a particular section, the differential form of the continuity equation is given by 