# Fluid Mechanics Questions and Answers – Flow of Compressible Fluid through Orifices and Nozzles

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This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Flow of Compressible Fluid through Orifices and Nozzles”.

1. What is the Mach number at room temperature?
a) 310 m/s
b) 320 m/s
c) 330 m/s
d) 340 m/s

Explanation: Mach number is defined as the ratio of the speed of an object to the speed of sound. Mach number is denoted by ‘M’. Mach number ranges from zero to infinity. It falls into several flow regimes. It is 340 m/s at room temperature.

2. In a one-dimensional flow, the gas flows through one spatial dimension, namely its length.
a) True
b) False

Explanation: One dimensional flow refers to the flow of gas through a duct or channel in which the flow parameters are assumed to change significantly along a particular dimension. In this case, it’s about its duct length.

3. The compressible flow is assumed to be _____________
a) Isentropic
c) Polytropic

Explanation: Compressible flow is a branch of fluid mechanics that deals with different types of flow. Its main significance lies on the change in fluid density. It deals with gas dynamics. Flow is assumed to be isentropic.

4. Ratio of duct length to width length in a compressible flow is_______
a) More than 5
b) Less than 5
c) More than or equal to 5
d) Less than or equal to 5

Explanation: In a compressible flow, the flow is usually in a single dimension. One dimensional flow refers to the flow of gas through a duct or channel in which the flow parameters are assumed to change significantly. Thus, it is less than or equal to 5.

5. The fluid speed through the nozzle is altered with________
a) Acceleration
b) Deceleration
c) Constant speed
d) Zero

Explanation: The fluid speed through the nozzle is altered as the speed accelerates from subsonic speed to supersonic speed in a regime. It alters a nozzle and a diffuser.

6. What happens to velocity in the converging duct?
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. With the presence of a converging duct, the velocity increases. At this point, the area of the duct is less than zero.

7. What happens to velocity in the diverging duct?
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. With the presence of a converging duct, the velocity decreases. At this point, the area of the duct is more than zero.

8. The area of the duct is either maximum or minimum when the_________
a) Mach number = 1
b) Mach > 1
c) Mach = 0
d) Mach < 0

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. The area of the duct is either maximum or minimum when the Mach number of the fluid flow is exactly one.

9. Which among the following is an assumption of the compressible flow?
a) Resistance to flow of object
b) No-slip condition
c) Known mass flow rate
d) Resistance to flow of heat

Explanation: The related assumption of a compressible fluid flow is No-slip condition. It is assumed that the flow velocity at the solid surface is equal to the velocity of the surface itself. It is in direct consequence of the continuum flow.

10. Which among the following is an example of a converging-diverging nozzle?
a) De Laval nozzle
b) High velocity nozzle
c) Magnetic nozzle
d) Vacuum nozzle

Explanation: De-Laval nozzle is an example of a converging diverging nozzle. It a tube that is pinched in the mid marking with a particular balance. It is used to accelerate, hot pressurized gases that pass through a higher supersonic speed in the axial thrust.

11. Maximum achievable velocity of a gas is directly proportional to__________
a) Specific heat
b) Deceleration
c) Velocity
d) Pressure

Explanation: Maximum achievable velocity of a gas is directly proportional to the specific heat of gas. It is based on the energy content. It is derived in accordance with the law of conservation of energy.

12. How much pressure ratio makes one Mach number?
a) 0
b) 1
c) 2
d) 3

Explanation: The overall pressure ratio is given by Pb/Pt. The overall pressure ratio must be approximately 2 to attain the Mach number of one. It is because of the changes in the downstream and upstream of flow in the nozzle.

13. Normal shock waves are_______ to the local flow.
a) Parallel
b) Perpendicular
c) Same
d) Independent

Explanation: Normal shock waves are perpendicular to the local flow direction. The shock waves occur when the pressure builds up into an extremely thin shockwave that converts energy into heat. The waves thus take over one another.

14. Oblique shock waves are ______ to the local flow.
a) Parallel
b) Perpendicular
c) Less than 90 degrees
d) Independent

Explanation: Oblique shock waves have an angle less than 90 degrees with respect to its local flow. They are similar to the normal shock waves. When there is any disturbance to the fluid flow at a non-zero angle oblique shock is formed.

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