Isentropic Flows: Master the Fundamentals of Compressible Fluid Dynamics

Question 1

What is the defining characteristic of an isentropic flow process?

Accepted Answer

Constant entropy

Answer

Constant temperature

Answer

Constant pressure

Answer

Constant velocity

Question 2

Consider an isentropic flow of an ideal gas with a specific heat ratio of γ. What is the relationship between the Mach number (M) and the cross-sectional area (A) along a streamline?

Accepted Answer

M ∝ A^(γ-1)

Answer

M ∝ A^(-γ)

Answer

M ∝ A^(γ)

Answer

M ∝ A^(-γ+1)

Question 3

At which point along a converging-diverging nozzle does the flow reach sonic conditions?

Accepted Answer

At the throat

Answer

At the inlet

Answer

At the exit

Answer

At a point where the area is maximum

Question 4

In an isentropic nozzle, the fluid undergoes what transformation?

Accepted Answer

Acceleration and expansion

Answer

Deceleration and expansion

Answer

Acceleration and compression

Answer

Deceleration and compression

Question 5

What is the critical pressure ratio for an isentropic flow in a converging duct?

Accepted Answer

The pressure ratio at which choking occurs

Answer

The pressure ratio at which the flow becomes supersonic

Answer

The pressure ratio at which the flow becomes subsonic

Answer

The pressure ratio at which the flow becomes isothermal

Question 6

The Mach number is defined as the ratio of:

Accepted Answer

Flow velocity to speed of sound

Answer

Pressure to density

Answer

Temperature to specific heat

Answer

Density to viscosity

Question 7

The Prandtl-Meyer expansion fan is associated with:

Accepted Answer

Supersonic flow turning

Answer

Subsonic flow turning

Answer

Isentropic flow compression

Answer

Isothermal flow expansion

Question 8

The constant entropy in an isentropic flow is a consequence of:

Accepted Answer

Reversible processes

Answer

Adiabatic conditions

Answer

Viscous dissipation

Answer

Heat transfer

Question 9

Which dimensionless parameter is used to characterize the flow conditions in an isentropic nozzle?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Prandtl number

Answer

Nusselt number

Question 10

In an isentropic nozzle, the acceleration of the fluid along the nozzle's length is primarily attributed to:

Accepted Answer

The decrease in pressure along the nozzle length

Answer

The decrease in temperature along the nozzle length

Answer

The increase in density along the nozzle length

Answer

The increase in entropy along the nozzle length

Question 11

Which of the following assumptions is NOT made in the analysis of isentropic flows?

Accepted Answer

Inviscid flow

Answer

Adiabatic flow

Answer

Reversible flow

Answer

Negligible body forces

Question 12

Which of the following is an inherent limitation of isentropic flow analysis?

Accepted Answer

Ignores the presence and effects of shock waves

Answer

Assumes a constant specific heat ratio throughout the flow

Answer

Requires detailed knowledge of the flow geometry

Answer

Cannot predict the occurrence of flow separation

Question 13

In an isentropic diffuser, the pressure of the fluid:

Accepted Answer

Increases along the diffuser length

Answer

Decreases along the diffuser length

Answer

Remains constant along the diffuser length

Answer

Increases initially and then decreases

Question 14

Which of the following dimensionless parameters is primarily used to characterize isentropic flows?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Froude number

Answer

Grashof number

Question 15

Which of the following flow scenarios can be effectively analyzed using isentropic flow theory?

Accepted Answer

Flow through a convergent-divergent nozzle

Answer

Flow through a shock tube

Answer

Flow around an airfoil

Answer

Flow in a turbulent boundary layer

Question 16

Which of the following statements correctly describes a key characteristic of isentropic flows?

Accepted Answer

Entropy remains constant throughout the flow

Answer

The flow is always reversible

Answer

The flow is always adiabatic

Answer

The flow is always incompressible

Question 17

What is the mathematical expression that relates the Mach number (M) to the flow velocity (V) and the speed of sound (a) for isentropic flow?

Accepted Answer

M = V/a

Answer

M = V/2a

Answer

M = a/V

Answer

M = 2a/V

Question 18

Which of the following equations represents the isentropic relation for pressure (P)?

Accepted Answer

P = P0*(1-((γ-1)/2)*M^2)^((γ)/(γ-1))

Answer

P = P0*(1-((γ-1)/2)*M^2)^((γ-1)/γ)

Answer

P = P0*(1+((γ-1)/2)*M^2)^((γ)/(γ-1))

Answer

P = P0*(1+((γ-1)/2)*M^2)^((-γ-1)/γ)

Question 19

Which of the following is NOT a practical application of the principles of isentropic flow?

Accepted Answer

Incompressible fluid dynamics

Answer

Rocket propulsion systems

Answer

Supersonic wind tunnels

Answer

Gas turbine engines

Question 20

How does friction impact isentropic flow?

Accepted Answer

Increases entropy and decreases pressure

Answer

Decreases entropy and increases pressure

Answer

Has no effect

Answer

Depends on the flow velocity

Question 21

Which of the following parameters is crucial for characterizing the flow conditions in isentropic flow?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Froude number

Answer

Weber number

Question 22

What is the relationship between stagnation temperature (T0) and static temperature (T) in an isentropic flow?

Accepted Answer

T0 > T

Answer

T0 = T

Answer

T0 < T

Answer

T0 = 2T

Question 23

Which of the following is the governing equation for one-dimensional isentropic flow?

Accepted Answer

Energy equation

Answer

Continuity equation

Answer

Momentum equation

Answer

Poisson's equation

Question 24

The Mach number (M) in an isentropic flow is defined as the ratio of:

Accepted Answer

Flow velocity to speed of sound

Answer

Pressure to density

Answer

Temperature to flow velocity

Answer

Flow velocity to stagnation speed

Question 25

What type of flow is characterized by constant entropy and reversible processes?

Accepted Answer

Isentropic flow

Answer

Adiabatic flow

Answer

Isothermal flow

Answer

Irrotational flow

Question 26

The critical pressure ratio for an isentropic flow in a converging nozzle is:

Accepted Answer

1.893

Answer

0.5

Answer

1.0

Answer

2.0

Question 27

The Prandtl-Meyer expansion fan is a region of:

Accepted Answer

Supersonic flow

Answer

Subsonic flow

Answer

Laminar flow

Answer

Turbulent flow

Question 28

In an isentropic flow through a nozzle, what is the trend of velocity as the flow progresses?

Accepted Answer

It increases.

Answer

It decreases.

Answer

It remains constant.

Answer

It depends on the shape of the nozzle.

Question 29

What is the maximum Mach number attainable in an isentropic flow?

Accepted Answer

1

Answer

2

Answer

3

Answer

∞

Question 30

Which of the following is NOT a fundamental assumption of isentropic flow?

Accepted Answer

Flow is incompressible

Answer

Flow is adiabatic

Answer

Flow is reversible

Answer

Flow is inviscid

Question 31

The Mach number of a flow is defined as the ratio of:

Accepted Answer

Flow velocity to speed of sound

Answer

Speed of sound to flow velocity

Answer

Flow area to throat area

Answer

Flow density to stagnation density

Question 32

In a converging-diverging nozzle, where will the flow choke?

Accepted Answer

Throat

Answer

Converging section

Answer

Diverging section

Answer

Inlet

Question 33

Which of the following statements about stagnation enthalpy in isentropic flow is correct?

Accepted Answer

It is equal to the sum of kinetic and internal enthalpies.

Answer

It is equal to the sum of kinetic and potential enthalpies.

Answer

It is equal to the sum of potential and internal enthalpies.

Answer

It is equal to the kinetic enthalpy only.

Question 34

The Prandtl-Meyer expansion fan is characterized by:

Accepted Answer

Supersonic flow turning without shock waves

Answer

Subsonic flow turning with shock waves

Answer

Isentropic flow turning with shock waves

Answer

Inviscid flow turning with shock waves

Question 35

For a perfect gas undergoing isentropic flow, the entropy change is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Dependent on the specific heat ratio

Question 36

The normal shock wave relations can be derived using the principles of conservation of:

Accepted Answer

Mass, momentum, and energy

Answer

Mass and momentum

Answer

Momentum and energy

Answer

Mass only

Question 37

In an isentropic flow, the entropy of the fluid remains constant.

Accepted Answer

True

Answer

False

Question 38

The Mach number represents the ratio of flow velocity to the speed of sound.

Accepted Answer

True

Answer

False

Question 39

In a supersonic flow, the Mach number is greater than 1.

Accepted Answer

True

Answer

False

Question 40

The Rankine-Hugoniot equations can be used to calculate the pressure ratio across a normal shock wave.

Accepted Answer

True

Answer

False

Question 41

The total pressure in an isentropic flow is greater than the static pressure.

Accepted Answer

True

Answer

False

Question 42

The critical pressure ratio for a flow with a specific heat ratio of 1.4 is 0.528.

Accepted Answer

True

Answer

False

Question 43

How does the stagnation pressure relate to the static pressure in isentropic flow?

Accepted Answer

Stagnation pressure is always greater than static pressure

Answer

Static pressure is always greater than stagnation pressure

Answer

They are always equal

Answer

They are inversely proportional

Question 44

What is the entropy change in an isentropic flow?

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Indeterminate

Question 45

What is the critical pressure ratio for a nozzle?

Accepted Answer

The pressure ratio at which the flow becomes choked

Answer

The pressure ratio at which the Mach number reaches unity

Answer

The pressure ratio at which the flow becomes supersonic

Answer

The pressure ratio at which the flow becomes subsonic

Question 46

What is the Prandtl-Meyer expansion fan?

Accepted Answer

A region of supersonic flow where the Mach number increases

Answer

A region of subsonic flow where the Mach number decreases

Answer

A region of flow where the pressure is constant

Answer

A region of flow where the temperature is constant

Question 47

For an ideal gas undergoing an isentropic process, the ratio of specific heats (γ) can be expressed as:

Accepted Answer

Cₚ / Cᵥ

Answer

Cᵥ / Cₚ

Answer

Cₚ - Cᵥ

Answer

(Cₚ - Cᵥ) / Cᵥ

Question 48

A prominent application of isentropic flow analysis is:

Accepted Answer

Design of nozzles and diffusers

Answer

Analysis of heat transfer

Answer

Modelling of fluid-structure interaction

Answer

Design of wind turbines

Question 49

In a converging-diverging nozzle operating at supersonic conditions, the Mach number at the throat is:

Accepted Answer

Equal to 1

Answer

Less than 1

Answer

Greater than 1

Answer

Dependent on back pressure

Question 50

Which of the following statements accurately describes supersonic flows?

Accepted Answer

Flow is characterized by expansion waves

Answer

Mach number is less than 1

Answer

Flow is always isentropic

Answer

Flow undergoes a gradual change in properties

Question 51

The Prandtl-Meyer expansion fan is associated with:

Accepted Answer

Supersonic flows

Answer

Subsonic flows

Answer

Isentropic flows

Answer

Non-isentropic flows

Question 52

Which of the following conditions must be satisfied for a flow to be deemed isentropic?

Accepted Answer

Adiabatic and reversible

Answer

Isothermal and adiabatic

Answer

Adiabatic and isobaric

Answer

Isothermal and reversible

Question 53

During an isentropic flow, the entropy change is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Dependent on flow conditions

Question 54

In a converging-diverging nozzle, the flow becomes supersonic in the:

Accepted Answer

Diverging section

Answer

Converging section

Answer

Throat

Answer

Inlet

Question 55

The critical pressure ratio for an isentropic flow is defined as the ratio of:

Accepted Answer

Inlet pressure to outlet pressure at sonic conditions

Answer

Outlet pressure to inlet pressure at sonic conditions

Answer

Inlet pressure to stagnation pressure

Answer

Outlet pressure to stagnation pressure

Question 56

In isentropic flow, the Mach number is defined as:

Accepted Answer

Flow velocity divided by the local speed of sound

Answer

Local speed of sound divided by the flow velocity

Answer

Flow velocity divided by the sonic velocity

Answer

Sonic velocity divided by the flow velocity

Question 57

The isentropic efficiency of a compressor measures the ratio of:

Accepted Answer

Actual work input to ideal work input

Answer

Actual pressure rise to ideal pressure rise

Answer

Ideal temperature rise to actual temperature rise

Answer

Actual mass flow rate to ideal mass flow rate

Question 58

To determine flow properties at the throat of a converging-diverging nozzle, which method is employed?

Accepted Answer

Mass conservation equation

Answer

Method of characteristics

Answer

Energy equation

Answer

Boundary layer analysis

Question 59

Which of the following is not a potential application of isentropic flow analysis?

Accepted Answer

Weather pattern prediction

Answer

Aircraft engine design

Answer

Supersonic wind tunnel analysis

Answer

Modelling fluid flow in turbomachinery

Question 60

The Prandtl-Meyer expansion fan is a type of:

Accepted Answer

Isentropic expansion wave

Answer

Shock wave

Answer

Boundary layer

Answer

Turbulent flow

Question 61

Which of the following properties does NOT apply to isentropic flows?

Accepted Answer

Frictional

Answer

Reversible

Answer

Adiabatic

Answer

Inviscid

Question 62

The governing equation for one-dimensional, steady, isentropic flow is:

Accepted Answer

du/dx = -c^2 dp/dx

Answer

dp/dx = -ρu du/dx

Answer

ρ du/dt + dp/dx = 0

Answer

dp/dx = ρc^2 du/dx

Question 63

In a convergent-divergent nozzle, the Mach number at the throat is:

Accepted Answer

1

Answer

Less than 1

Answer

Greater than 1

Answer

Dependent on the nozzle geometry

Question 64

An example of an expansion wave in isentropic flow is the:

Accepted Answer

Prandtl-Meyer expansion fan

Answer

Shock wave

Answer

Contact discontinuity

Answer

Detonation wave