CH4: Waves in Supersonic Flow

Question 1

The ratios of the static thermodynamic variables across an oblique shockwave depend only on the ____________ of velocity.

Answer 1

Normal component.

Elements of Gas Dynamics, L&A, Pg. 86

Question 2

What is the maximum value that the shock deflection angle can be?

Answer 2

pi/2 or 90 degrees

Note: Do not confuse this with the flow deflection angle

Elements of Gas Dynamics, L&A, Pg. 86

Question 3

In the strong shock solution, the flow becomes ________.

Answer 3

Subsonic

Elements of Gas Dynamics, L&A, Pg. 88

Question 4

In non-viscous flow, any streamline may be replaced by a _____________.

Answer 4

Solid boundary.

Elements of Gas Dynamics, L&A, Pg. 88

Question 5

True or False
Consider the following statement in relation to oblique shockwaves. If the shockwaves are attached to the nose, the upper and lower surfaces are independent, because there is no influence on the flow upstream of the waves.

Answer 5

True.

Elements of Gas Dynamics, L&A, Pg. 89

Question 6

True or False
For a weak oblique shock, the strength of the wave is directly proportional to the deflection angle.

Answer 6

True.

Elements of Gas Dynamics, L&A, Pg. 92

Question 7

For a weak oblique shock, the change in entropy is proportional to _________.

Answer 7

The deflection angle to the third power.

Elements of Gas Dynamics, L&A, Pg. 92

Question 8

True or False
A compression through a very smooth turn can be considered isentropic if the flow is inviscid.

Answer 8

True.

Elements of Gas Dynamics, L&A, Pg. 94

Question 9

For a reflected shockwave, what is required to turn the flow back parallel to the incoming stream?

Answer 9

A Prandtl-Meyer expansion

Lecture 4 PP, Slide 49

Question 10

If an oblique shock impinges a pressure boundary condition (shear layer), the reflected wave must adjust _________ to match ___________.

Answer 10

flow pressure
boundary pressure

Lecture 4 PP, Slide 53

Question 11

With respect to the reflection of oblique shockwaves, a pressure rise will lead to a ______ and the flow will be ________.

Answer 11

Compression
Turned Back on itself (another oblique shortwave will form)

Lecture 4 PP, Slide 53

Question 12

With respect to the reflection of oblique shockwaves, a pressure drop will lead to an ________, and the flow will be ________.

Answer 12

Expansion fan
Opened up (turned away from itself)

Lecture 4 PP, Slide 53

Question 13

When expansion fans are reflected off a flat surface, what is the resulting waveform?

Answer 13

Another expansion fan.

Lecture 4 PP, Slide 54

Question 14

What is the definition of a “non-simple” region of interacting waves?

Answer 14

A region where two different families of opposite waves interact.

Lecture 4 PP, Slide 55

Question 15

What feature is introduced when considering the interaction of oblique shocks of opposite family compared to the same family?

Answer 15

The slip line is introduced.

Lecture 4 PP, Slide 57

Question 16

In the case where an oblique shockwave is generated then farther down the surface an expansion fan is generated, what will be the behavior of the oblique shock due to the expansion fan?

Answer 16

They will reflect off the bottom of the oblique shockwave. This causes the oblique shockwave to curve toward the surface over large distances.

Lecture 4 PP, Slide 59