A compound pipe is required to be replaced by a new pipe. The two pipes are said to be equivalent, if
When is Bernoulli’s equation applicable between any two points in aflow fields?
Ans. (d) The assumptions made for Bernoulli’s equation.
(i) The liquid is ideal (viscosity, surface tension is zero and incompressible)
(ii) The flow is steady and continuous
(iii) The flow is along the streamline (it is one-dimensional)
(iv) The velocity is uniform over the section and is equal to the mean velocity.
(v) The only forces acting on the fluid are the gravity force and the pressure force
The assumptions NOT made for Bernoulli’s equation
(i) The flow is uniform
(ii) The flow is irrotational
Which of the following assumptions are made for deriving Bernoulli'sequation?
1. Flow is steady and incompressible
2. Flow is unsteady and compressible
3. Effect of friction is neglected and flow is along a stream line.
4. Effect of friction is taken into consideration and flow is along astream line.
Select the correct answer using the codes given below:
Which one of the following statements is correct? While using boundarylayer equations, Bernoulli’s equation
Assertion (A): After the fluid has re-established its flow pattern down stream of an orifice plate, it will return to same pressure that it had upstream of the orifice plate.
Reason (R): Bernoulli’s equation when applied between two points having the same elevation and same velocity gives the same pressure at these points.
Ans. (d) There is a loss of energy due to eddy formation and turbulence. This is the
reason for that pressure is less than that it had upstream of the orifice plate.
A tank containing water has two orifices of the same size at depths of 40 cm and 90 cm below the free surface of water. The ratio of discharges through these orifices is:
The instrument preferred in the measurement of highly fluctuating velocities in air flow is:
If a calibration chart is prepared for a hot-wire anemometer formeasuring the mean velocities, the highest level of accuracy can be:
Ans. (d) Hot wire anemometer is more accurate than Pitot tube, rotanmeter, or
Which one of the following is measured by a Rotameter?
In a rotameter as the flow rate increase, the float
A glass tube with a 90° bend is open at both the ends. It is inserted into a flowing stream of oil, S = 0.90, so that one opening is directed up stream and the other is directed upward. Oil inside the tube is 50mm higher than the surface of flowing oil. The velocity measured by the tube is, nearly,
The speed of the air emerging from the blades of a running table fan is intended to be measured as a function of time. The point of measurement is very close to the blade and the time period of the speed fluctuation is four times the time taken by the blade to complete onerevolution. The appropriate method of measurement would involve the use of
Ans. (b) A Pitot tube is used for measuring speed in closed duct or pipe. Hot wire
anemometer is used for measuring fluctuation of speed. High speed photography may by useful to measure blade speed but not of air.
Which one of the statements is correct for a forced vortex?
Ans. (c) Forced vortex flow: Forced vortex flow is one in which the fluid mass is made to rotate by means of some external agency. Where (v) = ω × r As ω is constant linear velocity (v) is directly proportional to the radius (r).
For a real fluid moving with uniform velocity, the pressure
Ans. (d) In case of a real fluid moving with uniform velocity, the velocity head and pressure head are dependent on each other and their total sum remains constant. The pressure is thus independent of both depth and orientation, but in case of fluids under static condition, the pressure would depend on depth.
In a pipe flow, the head lost due to friction is 6 m. If the power transmitted through the pipe has to be the maximum then the total head at the inlet of the pipe will have to be maintained at
Ans. (d) Head lost due to friction is 6 m. Power transmitted is maximum when friction head is 1/3 of the supply head.
∴ Supply head should be 18 m.
Assertion (A): Energy grade line lies above the hydraulic grade line andis always parallel to it.
Reason (R): The vertical difference between energy grade line andhydraulic grade line is equal to the velocity head.
Which phenomenon will occur when the value at the discharge end of apipe connected to a reservoir is suddenly closed?
Water hammer in pipe lines takes place when
Ans. (c) Water hammer in pipe lines takes place when flowing fluid is suddenly brought to rest by closing a valve. When the water flowing in a long pipe is suddenly brought to rest by closing the value or by any similar cause, there will be sudden rise in pressure due to the momentum or the moving water being destroyed. This causes a wave of high pressure to be transmitted along the pipe which creates noise known as knocking. This phenomenon of sudden rise in pressure in the pipe is known as water hammer or hammer blow.
Assertion (A): The power transmitted through a pipe is maximum when the loss of head due to friction is equal to one-third of total head at theinlet.
Reason (R): Velocity is maximum when the friction loss is one-third ofthe total head at the inlet.
Ans. (c) Velocity is optimum when the friction loss is one-third of the total head at
Which one of the following statements is appropriate for the free surface, the hydraulic gradient line and energy gradient line in anopen channel flow?