Fluid Mechanics (361-380)

Updated: Apr 22, 2020

361.The shear stress in a fluid may be expressed as

where μ is the viscosity, dv/dy is the velocity gradient

and n is constant. The n-values for Newtonian and non-Newtonian fluids will

be respectively

n = 1 and n ≠ 1


362Consider the following statements relating to the stability of floating as well as

submerged bodies:

1. A submerged body is stable when the centre of gravity is below the centre

of buoyancy.

2. A floating body is stable when the centre of gravity is below the metacentre.

3. A submerged body is in stable equilibrium when the centre of

gravity coincides with the centre of buoyancy.



Continuity equation -Law of conservation of mass Momentum equation -Newtons second law of motion Energy equation -Law of conservation of energy Free Vortex -Concentric circular streamlines


364.following statements relating to fluid dynamics :

1. Momentum equation contains only vector quantities.

2. Energy equation involves scalar quantities only.

3. In uniform flow, there is no variation of velocity, at a given time, with

respect to distance


365.Figure 1.8 shows the flow net for two dimensional contraction. The size of mesh square at O is 7 mm, and at point A, the mesh size is 3.5 mm

The dimensionless pressure at A,is equal to




Venturi meter-Flow Rate Current meter-Flow velocity Piezometer-Flow Pressure


367. With V variables and 'm' fundamental dimensions in a system, which one of the following statements relating to the application of the. Buckingham's pi

Theorem is incorrect ?

Buckingham's pi theorem yields dimensionless pi terms given by the

difference between the number of variables and the number of fundamental dimensions.


368. A hydraulic model of a spillway is constructed with a scale 1:16. If the

prototype discharge is 2048 cumec, then the corresponding discharge for which the model should be tested is 2 cumec


369. Consider the following statements relating to hydraulic gradient line and

energy gradient line:

1. The line joining the points representing piezometric heads is known as hydraulic gradient.

2. In the case of ideal fluid, energy gradient line is always horizontal.

3. Hydraulic gradient line has a downward slope in the case of flow through pipes


370. Figure 1.9 shows gradually varied flow in an open channel with a break in bed slope.

Types of water surface profiles occurring from left torightare



371. A hollow cylinder made of wood (sp. gr. = 0.8) has an external diameter of 1.0 m and an internal diameter of 0.6 m. It floats in water with its axis vertical and is in stable equilibrium. This is possible only when the length of the cylinder is equal to or less than 1.03 m


372. In a horizontally held injection syringe, the piston of 0.2 cm2 cross-sectional area is pushed at a constant speed of 1.0 cm/s to eject water into the atmosphere through a hypodermic needle of 0.07 mm2 cross sectional area while rinsing. Neglecting losses, the force required to move the piston is nearly 6 Kg


373. If a sluice gate produces a change in the depth of water from 3.0 m to 0.6 m, then the force on the gate is about 38.0 KN/m


374. Consider the following types of weirs:

1. Proportional weir

2. Cipolletti weir

3. Rectangular weir


4. Parabolic weir

All these weirs have varying values exponent in the formula Q = KH. The

correct sequence of these weirs in increasing order of the value of V is


375.A velocity field with no components in the y and z directions is given by

The acceleration along the x-direction at a point (3,1,2) at time 2, is

36 units


376.set of parameters of identical dimensions ?

Velocity potential, stream function, vorticity


377. Vorticity in the z-direction is given by


378.Given that g = acceleration due to gravity and R = hydraulic mean depth, the Darcy Weisbach friction factor is related to Manning's rugosity coefficient V as


379. A surge tank is provided in a hydro power scheme to

reduce the pressures under transient conditions


380 Considering that

expresses an isentropic process, which one of the following is not a representation of speed of a sound wave? (Symbols have the usual meaning)


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