Fluids Viva Questions
Fluids Viva Questions, Viva Questions on Fluids, Short Questions, and Answers on Fluids, Engineering Viva Questions, Basic Mechanical Engineering Viva Questions,
Short Questions and Answers
Q.1. When a fluid is said to be Newtonian?
Ans. When the shear stress is directly proportional to the velocity gradient.
Q.2. What are Newtonian fluids?
Ans. Fluids which follow the relation: absolute viscosity \mu =\frac{\tau }{dv/dy}
Where \tau = shear stress and \frac{\mathrm{d} v}{\mathrm{d} x} = gradient of velocity with distance between fixed plate and moving plate (at velocity V).
Q.3. Explain differences among fluid pressure, gauge pressure, the difference in pressure, bar pressure, and pressure head.
Ans. Fluid pressure is transmitted with equal intensity in all directions and acts normal to any plane.
Gauge pressure represents pressure above atmospheric pressure. It is equal to the unit weight of the liquid (Pg) multiplied by the height of the desired point above the free surface.
The difference in pressure between any two points at different levels in a liquid = unit ωt of liquid x difference in elevation.
Bar Pressure: Gauge pressure in the bar is obtained by dividing gauge pressure in pascal by 105.
Pressure Head: Pressure head ‘h‘ represents the height of a column of homogeneous fluid that will produce a given intensity of pressure \left ( h=\frac{1}{P_{g}} \right ).
Q.4. On what factors the efficiency of the pump depends?
Ans. The efficiency of a pump (centrifugal) depends on the size, speed, and proportions of the impeller and casing.
Q.5. What are the losses in the centrifugal pumps?
Ans. The losses in the centrifugal pump are:
Friction losses due to eddies inflow, leakage, friction loss due to rotation of the impeller in the chamber of water, gland, and bearing power losses.
Q.6. What is the order of efficiency of centrifugal and reciprocating pumps?
Ans. The efficiency of a centrifugal pump is of the order of 45% whereas of reciprocating pump is around 80%.
Q.7. Enumerate the advantages of (a) centrifugal pumps, (b) reciprocating pumps.
Ans. The advantage of centrifugal pumps are:
- Higher speed resulting in lower size and cost.
- Continuous delivery free from pressure fluctuations.
- It can operate on minimum flow without exceeding a predetermined pressure, maximum flow without exceeding a predetermined demand, be designed to meet several duties.
- Absence of vibration and simpler foundation.
The advantages of reciprocating pumps are:
- Higher efficiency than centrifugal pumps.
- Applicable to variable pressures without adjustment of speed.
- Self priming.
- Capable of utilising kinetic energy of rotation to give peak pressure.
- Confined to low quantity and high pressure.
Q.8. How the positive displacement is obtained in the rotary pump?
Ans. Positive displacement in rotary pumps is achieved in two ways:
- A rotor carries radially adjustable vanes, the outer tips of which are constrained by a circular casing, whose centre is remote from that of the rotor.
- Various combinations of gears, lobes, helices etc. within a casing arranged so that lobes or teeth attached to each rotor pass in sequence through the some pumping space.
Q.9. What is the difference between spillway and siphon spillway?
Ans. The spillway is an essential part of a large dam and provides an efficient and safe means of releasing floodwater that exceeds the design capacity of the reservoir. Siphon Spillway is a spillway designed to discharge water in a closed conduit under negative pressure.
Q.10. The clearance volume of a reciprocating compressor is 100 mL and the volume of the cylinder at the dead center is 1.0 liter. What is the clearance ratio of the compressor?
Ans. Clearance ratio = \frac{Clearance volume}{Swept volume}
=\frac{100}{1000-100}=\frac{1}{9}