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# Fluid Mechanics (281-300)

Updated: Apr 22, 2020

281 conditions will be satisfied by steady irrotational flow ? 282 Ranges of specific speeds in MKS units

A.Francis 60-300 B. Kaplan 300-1000 C. Pelton with one jet 10-35 D. Pelton with two jets 35-60

283. The surface tension of water at 20°C is 75 x 10⁻³N/m. The difference in the water surfaces within and outside an open ended capillary tube of 1mm internal bore, inserted at the water surface, would nearly be 15mm

284. A symmetrical right circular cone of wood floats in fresh water with axis vertical and the apex downmost. The axial height of the cone is /. The submerged portion has a height h, measured upwards from the apex. What would be the height of the centre of buoyancy from the apex ? (3/4)h

285. A rectangular open channel carries a discharge of 15 m³/s when the depth of

flow is 1.5 m and the bed slope is 1:1440. What will be the discharge through the

channel at the same depth if the slope would have been 1:1000 ?

18 m³/s

286. In steady flow of a compressible fluid through a pipe, the density, area and

another section the density and area are kg/m³, 0.5 m² and 3 m/s, respectively. At

another section the density and area are 0.75 kg/m³ and 1.0 m² respectively. What

is the velocity at this section ? 3.0 m/s

287. The coefficient of velocity for an orifice is given by (using usual notations) 288. The velocity potential Φ at any point for a two-dimensional steady, irrotational flow in polar coordinates, is given by (with usual notations) doublet

289. A cylindrical vessel of radius 42.31cm and height 1 m is open at the top. It holds water to half its depth. Which one of the following values approximates the speed at which the cylinder is to be rotated about the vertical axis, so as to make the apex of the paraboloid just reach the centre of the bottom of the vessel

100 rpm

290.

A. Hotwire anemometer - Turbulence

B. Orifice meter - Discharge

C. Pitottube - Mean velocity

D.Preston tube- Boundary Shear Stress

291. Water having kinematic viscosity of 0.01 stoke flows at a velocity of 2m/sec in a

pipe of 15 cm diameter. For dynamic similarity, the velocity of oil of kinematic

viscosity 0.03 stoke in a pipe of same diameter will be 6m/s

292. In the model of a highway bridge constructed to a scale of 1:25, the force of

water on the pier was measured to be 0.5 kg. The force on the prototype pier will be 7812.5 kg

293. In the stokes experiment of falling sphere, it is found that a sphere of 5 mm diameter falls in a liquid with terminal velocity 20 mm/s giving a drag coefficient of 240. The ratio of specific gravities is 2.85. Which one of the following is the

kinematic viscosity of the liquid in stokes ? 10.0

294. A ping-pong ball, having a diameter o 3.6 cm and weighing 2.4 g, is served with a horizontal velocity of 10 m/sec and a spin that gives rise to a coefficient of lift of 0.2. Assuming the density of air to be 0.00129 gf/cc, the lift experienced by the ball is nearly 0.13 gf

295.The friction factor(f), in terms of boundary shear stress (Τ0), is given by (p =mass density, v = mean velocity) 296. The loss of head at various pipe fittings is given by the expression Kv²/2g If values of K were 0.40, 0.90, 1.5 and 2.2, then these would correspond respectively to 45° elbow, 90° elbow, foot value of pump and close return bend

297.A pipe network consists of a pipe of 60 cm diameter and branches out at a point F into two branches, one of 30 cm diameter and the other of 45 cm diameter. These branch pipes rejoin at a point B. The velocity in the first branch (of 45 cm diameter) is 1.5 m/sec. Which one of the following statements is true ?

The potential drop between F and B in both branches is the same.

298.Are true in relation to water hammer phenomenon?

The pressure rise is given by ρCU for sudden closure of valve.

The volume modulus of fluid is the relevant fluid property

299. Which one of the following pairs is not correctly matched ? (b = bottom width, y = depth of flow, θ = side slope with vertical)

For critical flow v = gy through rectangular canal

300. A-Ideal

B-Non Newtonian

C-Ideal Plastic

D-Thyxotropic