Fluid Mechanics Sheet 22

Given that, as flow takes place between two parallel static plates, the velocity midway between the plates is 2 m/s, the Reynolds number is 1200 and the distance between the plates is 10 cm. Whiich of the following statements are true ?

1. The velocity at the boundary is 1 m/s.
2. The rate of flow is $0.1$ $m^3/s/metre$ width.
3. The flow is turbulent.
4. The energy correction factor is 2.0.

Select the correct answer using the codes given below.

Codes :

Which one of the following pressure units represents the least pressure?

The correct sequence, in the direction of the flow of water for installations in a hydro-power plant is

A turbine works at 20 m head and 500 rpm speed. Its 1:2 scale model to be tested at a head of 20 m should have a rotational speed of nearly

Before passage of a surge, the depth and velocity of flow at a section are 1.8 m and 3.72 m/s and, after passage, they are 0.6 m and 7.56 m/s respectively. The speed of the surge is 

For laminar flow between parallel plates separated by a distance 2h, head loss varies

In steady laminar flow of a liquid through a circular pipe of internal diameter D, carrying a constant discharge, the hydraulic gradient is inversely proportional to

A model of a weir made to a horizontal scale of 1/40 and vertical scale of 1/9 discharges 1 litre/sec. Then the discharge in the prototype is estimated as

Consider the following statesments:

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

1. total head at any point is 11 metres
2. pressure head at the 5 cm section is negative
3. discharge varies proportionate to the diameter
4. datum head at all sections is constant

Of these statements

Which of the following conditions would entail a greater energy dissipation in turbulent flow?

a. Smaller eddy size

b. Lower viscosity

c. Large intensity of turbulence

Select the correct answer using the codes given below.

Codes:

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

Considere the following parameters related to fluid flow.

1. Velocity
2. Velocity potential
3. Stream function

Among these, those which exist both in rotational flows and irrotational flows would include

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

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

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

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

1. Energy line always falls in the direction of flow.
2. Hydraulic gradient line never rises in the direction of flow.
3. specific energy may increase or decrease in the direction of flow.
4. Energy line and hydraulic gradient line can cross each other.

Select the correct answer using the codes given below.

Codes:

Given that K= a coefficient, v= mean velocity, f= Darcy-Weisbach friction factor and D= diameter of the pipe, if the head loss in a pipe bend is given by $h_L$ = $K{v}^2/2g$, then the equivalent length of the pipe is

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 contuity equation is given by

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

1. Shear stress is zero at the centre.
2. Discharge varies directly with viscosity of the fluid flowing.
3. Velocity is maximum at the centre.
4. Hydraulic gradient varies directly with the velocity

Select the correct answer using the codes given below.

Codes:

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