Compressible Flow: Master the Dynamics of Compressible Fluids

Question 1

In a converging-diverging nozzle, when does an ideal gas experience choking?

Accepted Answer

When the back pressure equals the critical pressure of the gas

Answer

When the back pressure is lower than the critical pressure of the gas

Answer

When the back pressure is higher than the critical pressure of the gas

Answer

When the back pressure is zero

Question 2

In a converging-diverging nozzle, what flow characteristic occurs?

Accepted Answer

Subsonic flow at the entrance and supersonic flow at the exit

Answer

Subsonic flow throughout the nozzle

Answer

Supersonic flow throughout the nozzle

Answer

Supersonic flow at the entrance and subsonic flow at the exit

Question 3

In compressible flow, which key characteristic is observed?

Accepted Answer

Significant changes in fluid density occur along the flow path.

Answer

Compressible flow is limited to supersonic velocities.

Answer

Viscosity plays a negligible role in compressible flow behavior.

Answer

Compressible flow is inherently turbulent.

Question 4

What is a defining characteristic of a supersonic nozzle?

Accepted Answer

Convergent-divergent shape

Answer

Subsonic flow at the exit

Answer

Shock waves at the nozzle entrance

Answer

Constant cross-sectional area throughout the nozzle

Question 5

In a converging-diverging nozzle, which shape is used for the exit section to transition supersonic flow to subsonic flow?

Accepted Answer

Diverging

Answer

Converging

Answer

Rectangular

Answer

Parabolic

Question 6

In a converging-diverging nozzle with a normal shock wave, how does increasing the back pressure impact the shock wave's position within the nozzle?

Accepted Answer

Moves downstream, away from the nozzle throat

Answer

Becomes stronger, with a higher pressure jump

Answer

Disappears, allowing the flow to become fully supersonic

Answer

Moves upstream slightly towards the nozzle throat

Question 7

Which characteristic defines a supersonic flow?

Accepted Answer

Flow velocity exceeds the local speed of sound.

Answer

Flow is adiabatic and reversible.

Answer

Flow is incompressible.

Answer

Flow is turbulent.

Question 8

In a supersonic nozzle, what is the flow velocity at the throat?

Accepted Answer

Equal to the speed of sound

Answer

Less than the speed of sound

Answer

Greater than the speed of sound

Answer

Zero

Question 9

Which characteristic distinguishes supersonic flow from subsonic flow?

Accepted Answer

Flow velocity in supersonic flow exceeds the local speed of sound.

Answer

Flow velocity in subsonic flow exceeds the speed of sound.

Answer

Subsonic flow is always laminar, while supersonic flow is always turbulent.

Answer

There are no significant differences between subsonic and supersonic flow.

Question 10

In a steady, one-dimensional, compressible flow along a streamline, which property remains constant?

Accepted Answer

Mach Number

Answer

Velocity

Answer

Temperature

Answer

Pressure

Question 11

In a converging-diverging nozzle, the throat is the point where the flow Mach number reaches unity. What flow regime exists downstream of the throat?

Accepted Answer

Supersonic Flow

Answer

Subsonic Flow

Answer

Laminar Flow

Answer

Turbulent Flow

Question 12

In a converging-diverging nozzle, what is the critical pressure ratio needed to achieve supersonic flow at the exit?

Accepted Answer

Approximately 1.89

Answer

Less than 1.0

Answer

Equal to 1.0

Answer

Greater than 2.5

Question 13

What happens to the flow in a converging-diverging nozzle when it passes through a normal shock wave?

Accepted Answer

The flow becomes subsonic and is no longer isentropic.

Answer

The flow becomes subsonic and remains isentropic.

Answer

The flow stays supersonic and remains isentropic.

Question 14

In a converging-diverging nozzle with fixed stagnation pressure and temperature, how does increasing the back pressure affect the mass flow rate through the nozzle?

Accepted Answer

Decreases

Answer

Increases

Answer

Remains constant

Answer

Causes choking

Question 15

In compressible flow, which dimensionless parameter represents the ratio of flow velocity to the local speed of sound?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Froude number

Answer

Weber number

Question 16

In a converging-diverging nozzle, a normal shock wave is most likely to occur when the downstream pressure is:

Accepted Answer

Higher than the critical pressure

Answer

Equal to the critical pressure

Answer

Lower than the critical pressure

Question 17

When the flow velocity surpasses the speed of sound, it is classified as:

Accepted Answer

Supersonic

Answer

Subsonic

Answer

Transonic

Answer

Hypersonic

Question 18

In a converging-diverging nozzle, where does choking occur?

Accepted Answer

At the throat (minimum area)

Answer

At the inlet (maximum velocity)

Answer

At the outlet (maximum area)

Answer

When the flow becomes supersonic

Question 19

In adiabatic flow of an ideal gas, which quantity remains constant along a streamline?

Accepted Answer

Entropy

Answer

Density

Answer

Velocity

Question 20

In adiabatic flow of an ideal gas through a converging nozzle, what happens to the stagnation temperature (T0) and stagnation pressure (P0)?

Accepted Answer

T0 remains constant, and P0 increases.

Answer

Both T0 and P0 increase.

Answer

Both T0 and P0 decrease.

Question 21

In the analysis of compressible flow, which dimensionless quantity is primarily used to evaluate the departure from incompressible flow characteristics?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Nusselt number

Question 22

In a converging nozzle, the flow area decreases as the fluid flows through it. Initially, the fluid is at rest. As the fluid accelerates through the nozzle, what happens to its pressure?

Accepted Answer

Decreases due to the increase in fluid velocity

Answer

Increases due to the decrease in flow area

Answer

Remains constant as the fluid accelerates

Answer

May increase or decrease depending on the initial conditions of the fluid

Question 23

In a converging-diverging nozzle, when will a normal shock wave occur within the nozzle?

Accepted Answer

Back pressure above critical pressure but below stagnation pressure

Answer

Back pressure below critical pressure

Answer

Back pressure at critical pressure

Answer

Back pressure at stagnation pressure

Question 24

Which characteristic differentiates compressible flow from incompressible flow?

Accepted Answer

Pressure waves travel at supersonic speeds

Answer

Density remains constant

Answer

Velocity of sound is constant

Answer

Temperature remains constant

Question 25

The Mach number is defined as the ratio of:

Accepted Answer

Fluid velocity to critical velocity

Answer

Fluid density to critical density

Answer

Fluid pressure to critical pressure

Answer

Fluid temperature to critical temperature

Question 26

A shock wave is characterized by:

Accepted Answer

An abrupt increase in pressure and density

Answer

A gradual increase in pressure and density

Answer

A decrease in fluid velocity

Answer

Constant fluid temperature

Question 27

The isentropic flow equation establishes a relationship between:

Accepted Answer

Pressure and density

Answer

Velocity and Mach number

Answer

Temperature and entropy

Answer

Density and velocity

Question 28

Which type of nozzle is not used in compressible flow applications?

Accepted Answer

Venturi

Answer

Convergent

Answer

Divergent

Answer

Constant-area

Question 29

The Prandtl-Meyer expansion fan is used to analyze:

Accepted Answer

Supersonic flow turning

Answer

Subsonic flow turning

Answer

Compressible flow over an airfoil

Answer

Shock wave interactions

Question 30

Which dimensionless parameter is specifically used to characterize compressible flow?

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Prandtl number

Answer

Nusselt number

Question 31

In a supersonic nozzle, where does the transition from subsonic to supersonic flow take place?

Accepted Answer

Downstream of the throat, where the area increases

Answer

At the throat of the nozzle

Answer

At the exit of the nozzle

Answer

At the point of maximum cross-sectional area

Question 32

In the design of a supersonic nozzle, which of the following assumptions is most likely to result in significant errors in predicting the nozzle's performance?

Accepted Answer

Ignoring non-ideal gas effects

Answer

Neglecting the effect of viscosity

Answer

Assuming isentropic flow

Question 33

What is the primary purpose of the Prandtl-Meyer expansion formula?

Accepted Answer

Calculating flow properties through a supersonic nozzle

Answer

Determining the angle of a shock wave

Answer

Estimating the pressure drop in a pipe

Answer

Analyzing viscous flow in a boundary layer

Question 34

In choked flow, what is the relationship between the Mach number and the critical Mach number?

Accepted Answer

Mach number = Critical Mach number

Answer

Mach number > Critical Mach number

Answer

Mach number < Critical Mach number

Answer

No relationship exists

Question 35

What is the primary function of a Laval nozzle?

Accepted Answer

Accelerating flow to supersonic speeds

Answer

Decelerating flow to subsonic speeds

Answer

Creating a shock wave

Answer

Controlling flow direction

Question 36

Which characteristic distinguishes compressible flow from incompressible flow?

Accepted Answer

Significant density changes

Answer

Negligible density changes

Answer

Laminar flow in incompressible fluids

Answer

Turbulent flow in compressible fluids

Question 37

The Mach number primarily quantifies:

Accepted Answer

Compressibility effects

Answer

Viscosity effects

Answer

Surface roughness effects

Answer

Gravitational effects

Question 38

In isentropic flow, what is the relationship between pressure (p), density (ρ), and velocity (v)?

Accepted Answer

p/ρ = constant

Answer

ρ/v = constant

Answer

v/p = constant

Answer

ρv = constant

Question 39

Which of the following is NOT a type of expansion wave?

Accepted Answer

shock wave

Answer

Prandtl-Meyer expansion

Answer

isentropic expansion

Answer

rarefaction wave

Question 40

In a shock wave, entropy increase is primarily attributed to:

Accepted Answer

Irreversibility

Answer

Viscosity

Answer

Heat transfer

Answer

Compression

Question 41

Which of the following is a commonly used method for measuring Mach number in supersonic flow?

Accepted Answer

Pitot-static tube

Answer

Schlieren photography

Answer

Laser Doppler anemometry

Answer

Hot-wire anemometry

Question 42

When designing supersonic nozzles for spacecraft applications, which unique challenge arises due to miniaturization?

Accepted Answer

Fabrication constraints and the need for high-precision manufacturing

Answer

Increased heat transfer resulting from miniaturization effects

Answer

Reduced Reynolds number effects influencing boundary layer development

Answer

Enhanced shock wave formation due to elevated flow velocities

Question 43

How does boundary layer behavior in a supersonic nozzle affect its performance, including mass flow rate, efficiency, and shock wave formation?

Accepted Answer

Boundary layer growth reduces mass flow rate, efficiency, and promotes shock formation.

Answer

Boundary layer growth increases mass flow rate, efficiency, and inhibits shock formation.

Answer

Boundary layer behavior has no significant impact on the nozzle's performance.

Question 44

How does the operating altitude of a supersonic nozzle influence its design parameters?

Accepted Answer

It affects both the nozzle's throat area and expansion ratio.

Answer

It solely affects the nozzle's expansion ratio.

Answer

It solely affects the nozzle's throat area.

Question 45

Which of the following statements about the relationship between Mach number and flow behavior in compressible fluids is correct?

Accepted Answer

Flow behavior becomes more complex and unpredictable with increasing Mach number.

Answer

Flow behavior remains unchanged with increasing Mach number.

Answer

Flow behavior becomes more predictable and laminar with increasing Mach number.

Answer

Flow behavior becomes more inviscid and frictionless with increasing Mach number.

Question 46

Shock waves in compressible flow are characterized by:

Accepted Answer

Sudden and discontinuous change in flow properties

Answer

Gradual and continuous change in flow properties

Answer

Formation of vortices and recirculation zones

Answer

Zero pressure gradient across the wave

Question 47

The Rankine-Hugoniot relations for a normal shock wave relate:

Accepted Answer

Upstream and downstream flow properties

Answer

Upstream and downstream pressure gradients

Answer

Upstream and downstream velocity profiles

Answer

Upstream and downstream temperature gradients

Question 48

Which of the following applications employs the principles of compressible flow?

Accepted Answer

Design of jet engines

Answer

Analysis of wind tunnel experiments

Answer

Operation of hydraulic pumps

Answer

Modeling of laminar boundary layers

Question 49

The non-dimensional parameter that quantifies the ratio of inertia forces to pressure forces in a compressible flow is:

Accepted Answer

Mach number

Answer

Reynolds number

Answer

Froude number

Answer

Weber number

Question 50

Which flow regime is characterized by the formation of shock waves?

Accepted Answer

Supersonic

Answer

Subsonic

Answer

Sonic

Answer

Laminar

Question 51

Which of the following statements accurately describes the influence of compressibility on fluid velocity?

Accepted Answer

Compressibility decreases the fluid velocity in subsonic flows and increases it in supersonic flows.

Answer

Compressibility has no effect on the fluid velocity in either subsonic or supersonic flows.

Answer

Compressibility increases the fluid velocity in subsonic flows and decreases it in supersonic flows.

Question 52

Which of the following is a fundamental dimensionless parameter used to characterize the compressibility effects in fluid flow?

Accepted Answer

Mach number

Answer

Grashof number

Answer

Reynolds number

Answer

Prandtl number

Question 53

What is the relationship between the Prandtl-Meyer expansion fan and the Mach number?

Accepted Answer

The expansion fan angle increases with increasing Mach number.

Answer

The expansion fan angle is independent of the Mach number.

Answer

The expansion fan angle decreases with increasing Mach number.

Question 54

Which dimensionless parameter characterizes the effects of compressibility in fluid flow?

Accepted Answer

Mach number

Answer

Stanton number

Answer

Prandtl number

Answer

Reynolds number

Question 55

Which governing equation is suitable for analyzing one-dimensional compressible flow?

Accepted Answer

Euler equation

Answer

Hagen-Poiseuille equation

Answer

Darcy-Weisbach equation

Answer

Stokes equation

Question 56

Which flow regime is associated with the presence of shock waves?

Accepted Answer

Supersonic flow

Answer

Transonic flow

Answer

Laminar flow

Answer

Subsonic flow

Question 57

How does a shock wave affect the flow properties?

Accepted Answer

It increases temperature, pressure, and density.

Answer

It increases only temperature and pressure.

Answer

It has no impact on flow properties.

Answer

It decreases temperature, pressure, and density.

Question 58

Which method is commonly used to analyze the behavior of flow across a shock wave?

Accepted Answer

Rankine-Hugoniot equations

Answer

Navier-Stokes equations

Answer

Bernoulli equation

Answer

Hagen-Poiseuille equation

Question 59

Which factor primarily influences the strength of a shock wave?

Accepted Answer

Mach number

Answer

Grashof number

Answer

Prandtl number

Answer

Reynolds number

Question 60

What is the fundamental difference between an isentropic and a normal shock wave?

Accepted Answer

Entropy change

Answer

Density change

Answer

Pressure change

Answer

Temperature change

Question 61

The Mach number is a dimensionless parameter used to describe:

Accepted Answer

The ratio of flow velocity to the speed of sound

Answer

The ratio of flow area to the speed of sound

Answer

The ratio of pressure to the speed of sound

Answer

The ratio of fluid density to the speed of sound

Question 62

When the Mach number is greater than 1, the flow is considered:

Accepted Answer

Supersonic

Answer

Transonic

Answer

Subsonic

Answer

Hypersonic

Question 63

Which of the following is a characteristic of shock waves?

Accepted Answer

Abrupt changes in fluid properties

Answer

No change in fluid properties

Answer

Adiabatic behavior

Answer

Gradual changes in fluid properties

Question 64

The isentropic flow equations assume:

Accepted Answer

Adiabatic and frictionless flow

Answer

Isothermal and viscous flow

Answer

Non-isentropic and turbulent flow

Answer

Isobaric and compressible flow