Supersonic Flight

Question 1

What is the equation of continuity?

Answer 1

rhoAV = constant

Question 2

What is Bernoulli’s equation?

Answer 2

P + 0.5rhoV^2 = Constant

Question 3

If density is constant (as assumed with subsonic flow), what is the velocity of the fluid proportional to?

Answer 3

The cross sectional area of the duct

Question 4

For subsonic flow in a convergent duct, what occurs when cross sectional area decreases, what happens to the flow velocity and the static pressure?

Answer 4

Velocity increases and static pressure will decrease

Question 5

For subsonic flow in a divergent duct, what occurs when cross sectional area increases?

Answer 5

Flow velocity decreases and static pressure increases.

Question 6

For supersonic flow in a divergent duct, what is the assumption about the flow at the throat?

Answer 6

It is at least Mach 1.0

Question 7

What occurs to supersonic flow as it moves into the expanding area of a divergent duct?

Answer 7

1) The flow will momentarily maintain a constant True Air Speed (TAS) due to inertia
2) Due to constant TAS and area increasing, density and temperature will decrease as air must expand to fill the space.
3) Pressure is reduced as flow density decreases, resulting in an acceleration of the flow.
4) Temperature reduction results in a reduction in the speed of sound resulting in an increase in Mach number.

Question 8

What occurs to supersonic flow in a convergent duct?

Answer 8

1) Due to inertia, velocity of flow remains constant initially
2) If TAS remains constant while area decreases, the density must increase as the air is compressed to fill the space
3) As density increases so does the temperature and pressure
4) Adverse pressure gradient results in a reduction in TAS
5) Increase temperature results in a higher speed of sound and Mach number will decrease.

Question 9

What occurs for pressure, density and velocity for subsonic flow for divergent and convergent ducts?

Answer 9

Divergent: Pressure, density increases, velocity decreases
Convergent: Pressure, density decreases, velocity increases

Question 10

What occurs for pressure, density , temperature and velocity for supersonic flow for divergent and convergent ducts?

Answer 10

Divergent: Pressure, density decreases, temperature deceases, velocity increases
Convergent: Pressure, density increases, temperature increases, velocity decreases.

Question 11

What occurs to supersonic flow around expansive corners?

Answer 11

Supersonic flow around an expansive corner will accelerate and decrease pressure.

Question 12

What is a Mach line?

Answer 12

Flow near the surface senses the change in the surface whilst the flow further away senses the change fractionally later, this discontinuity forms a Mach line.

Question 13

What is an expansion fan?

Answer 13

An infinite number of Mach lines which form a fan type effect.

Question 14

Is a mach line/expansion fan a shock wave?

Answer 14

No, as it doesn’t undergo compression

Question 15

Is the Mach number downstream of a expansion corner greater than original Mach number?

Answer 15

Yes

Question 16

What occurs to supersonic flow on a compressive corner?

Answer 16

The flow will slow and increase pressure as it passes through the shockwave associated with the compressive corner.

Question 17

Are shockwaves formed around compressive corners?

Answer 17

Yes they are

Question 18

Does the normal bow shockwave of a compressive corner become more oblique as speed increases?

Answer 18

Yes

Question 19

What occurs to velocity, mach number, pressure, density and temperature through a shockwave?

Answer 19

• Velocity and Mach number decrease

- Pressure, density and temperature increase.

Question 20

What are the two types of shockwaves?

Answer 20

• Normal

- Oblique

Question 21

How is a normal shockwave oriented to the surface?

Answer 21

Always oriented perpendicular to the direction of flow and remains detached from the source.

Question 22

Does the direction of the flow change through a normal shockwave?

Answer 22

No it doesn’t

Question 23

Are there large energy losses through normal shockwaves? What does this manifest itself as on the aircraft?

Answer 23

Yes, causes larges amount of drag on the aircraft.

Question 24

What is an oblique shockwave?

Answer 24

Oriented at an angle other than 90 degrees to the direction of flow

Question 25

What factors influence the angle of the oblique shockwave?

Answer 25

1) The speed of the flow

2) The shape/angle of the obstruction

Question 26

Is the flow ahead of an oblique shockwave always supersonic? Can flow decrease to either supersonic of subsonic?

Answer 26

Yes it is, can decrease to either supersonic or subsonic.

Question 27

Are the effects on the air through an oblique shockwave lesser than those of a normal shockwave?

Answer 27

Yes

Question 28

What occurs to the X and Y components of airflow through an oblique shockwave?

Answer 28

X component decreases

Y component remains the same.

Question 29

What is a bow wave?

Answer 29

A normal shockwave that occurs ahead of the object.

Question 30

Is there significant heat buildup between the bow wave and the leading edge of the wing?

Answer 30

Yes, very significant, mucho heato.