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Compressible Flow > Chapter 9 > Flashcards

Chapter 9 Flashcards

(44 cards)

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1
Q

In general, a shock wave will make an ____ angle with respect to the upstream flow.

A

Oblique

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2
Q

Supersonic flows are also characterized by oblique expansion waves where the pressure _______ across the wave.

A

pressure decreases continuously

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3
Q

Whenever a shockwave is “turned into itself” as shown in Fig 9.2a in the textbook, an _____ will occur.

A

Oblique Shock Wave

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4
Q

How do pressure, temperature, density, and Mach number change across an oblique shockwave.

A

Mach number decreases

All other properties increase

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5
Q

Whenever a supersonic flow is “turned away from itself” as shown in Figure 9.2b in the textbook ______ will occur.

A

An expansion wave will occur.

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6
Q

Describe how Mach number, temperature, pressure, and density change as a particle travels through an expansion wave.

A

Mach Number increases

Pressure, temp, and density decrease

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7
Q

Describe the physical mechanisms that create shockwaves.

A

If the upstream flow is supersonic, the disturbances caused by the body in motion cannot work their way upstream; rather, at some finite distance from the body, the disturbance waves pile up and coalesce. This forms a standing wave in front of the body.

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8
Q

Is total temperature still constant across an oblique shockwave?

A

Yes.

Pg. 622

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9
Q

Changes across an oblique shockwave are governed only by the component of velocity _____.

A

Normal to the wave.

Pg 623

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10
Q

Changes across an OSW are dependant on what two parameters?

A

The upstream Mach number and the shock angle (beta).

Pg. 624

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11
Q

If theta is greater than theta max for a particular match number, does a solution exist for a straight OSW?

A

No

Pg. 624

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12
Q

If theta is greater than theta max what two physical phenomena will take place?

A

The shockwave will be detached and curved.

Pg. 624

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13
Q

Between the weak and strong shock solutions, which contains the higher M_n1 and the larger pressure ratio (p2/p1) ?

A

The strong shock.

Pg. 628

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14
Q

In nature, which shock solution is usually found?

A

The weak solution.

Pg. 628

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15
Q

For the strong shock solution, the downstream Mach number is always _____.

A

Subsonic.

Pg. 628

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16
Q

For the weak shock wave (except for cases where theta is close to the maximum value) the downstream Mach number is _____.

A

Supersonic.

Pg. 628

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17
Q

Normal shockwaves belong to the family of ____ shock solutions.

A

Strong.

Pg. 628

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18
Q

As the upstream Mach number increases the shock angle beta ____.

Study These Flashcards
A

Decreases.

Pg. 628

19
Q

The p2/p1 ratio will be higher or smaller for a larger upstream Mach number?

Study These Flashcards
A

Higher

Pg. 629

20
Q

In general, for attached shocks with a fixed upstream Mach number, as the deflection angle increases, the wave angle beta ____ and the shock becomes _____.

Study These Flashcards
A

Increases
Stronger

Pg. 630

21
Q

Can the theory developed in section 9.2 for general OSW’s be used to evaluate supersonic flow over wedges without any simplifying assumptions?

22
Q

Supersonic flow over a wedge is characterized by ____.

Study These Flashcards
A

An attached, straight, oblique shock wave from the noise, a uniform flow downstream of the shock with streamlines parallel to the wedge surface, and a surface pressure equal to the static pressure behind the oblique shock p2.

Pg. 634 and 635

23
Q

True or False

Wedge flow is two-dimensional.

24
Q

True or False
On a conical body moving through a supersonic flow, a consequence of the three-dimensional relieving effect is that the shock wave on the cone is weaker than on the wedge.

25
True or False | A conical body has a small wave angle than a wedge body.
True Pg. 635
26
Streamlines behind an OSW on a conical body are ____.
Curved Pg. 625
27
The surface pressure on a cone is ____ than the surface pressure on a wedge.
Less than Pg. 635
28
The cone surface Mach number is ____ than that of a wedge.
Greater Pg. 636
29
State the main three differences between supersonic flow over a cone and wedge.
1. Shock wave on the cone is weaker 2. The cone surface pressure is lower 2. The streamlines above the cone surface are curved rather than straight. Pg. 636
30
True or False | The strength of a reflected shock wave is stronger than the incident shock.
False The reflected shock is weaker than the incident. Pg. 640
31
Describe what properties are the same across a slip line.
1. Pressure is constant. 2. Direction (but not necessarily the magnitude) of the velocity is the same. All other properties (most notably entropy) are different. Pg. 641
32
On a bow shock, away from the center point of the wave, the shock wave gradually becomes ___ and ____.
Curved and weaker. Pg. 645
33
True or False | The oblique shock can produce no momentum change parallel to the plane in which it lies.
True, this is how the oblique shock relations can be deduced from the normal shock relations. Ref: Carscallen Book Pg. 135
34
For a bow shock, directly in front of the nose of the body in motion, the shockwave can be considered ____.
A normal shock wave. Ref: Pg 645
35
For a bow shock, away from the leading point, the shock waves gradually become ____ and ____. Eventually devolving into a ___ at large distances from the body.
curved and weaker mach wave Ref: Pg 645
36
How is an expansion wave formed?
When supersonic flow is turned away from itself. Ref: Pg 648
37
An expansion wave can be thought of as composing of an _____.
An infinite number of Mach waves. Ref: Pg 649
38
Why can an expansion wave be considered isentropic?
Because they are composed of an infinite number of Mach waves and by definition, the change in entropy across a single Mach wave is zero. Ref: Pg 649
39
What happens to Mach number across an expansion wave?
It increases Ref: Lecture Slides
40
How do pressure temperature and density change across an expansion wave?
They all decrease Ref: Lecture Slides
41
How does the Mach number vary across an Oblique Shock wave?
It decreases Ref: Lecture Slides
42
How do pressure, temperature, and density change across an oblique shock wave?
They all go up. Ref: Lecture Slides
43
With regard to a reflected shockwave, if the Mach number and deflection angle behind the incident shock are in such a condition that no oblique shock solution exists what occurs?
A single normal shock wave is formed on the reflecting wall. This is commonly referred to as a Mach reflection. Ref: Lecture Slides
44
For a compression curve, the deflection angle theta is positive or negative?
Negative Ref: Lecture Slides

Compressible Flow (7 decks)

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