Deck 17: Compressible Flow

Question 1

A bullet is moving in still air at 15°C at a velocity of 1200 m/s. The air temperature at the nose of the bullet where stagnation occurs is

A)15°C
B)716°C
C)1448°C
D)386°C
E)731°C

Answer 1

731°C

Question 2

Air is flowing in a wind tunnel at 25°C, 80 kPa, and 180 m/s. The stagnation pressure at a probe inserted into the flow stream is

A)80 kPa
B)457 kPa
C)115 kPa
D)96 kPa
E)91 kPa

Answer 2

96 kPa

Question 3

An aircraft is reported to be cruising in still air at 5°C and 68 kPa at a Mach number of 0.82. The velocity of the aircraft is

A)92 m/s
B)55 m/s
C)37 m/s
D)274 m/s
E)408 m/s

Answer 3

274 m/s

Question 4

Air is flowing in a wind tunnel at 8°C and 86 kPa at a velocity of 235 m/s. The Mach number of the flow is

A)0.54
B)0.87
C)2.1
D)1.4
E)0.70

Question 5

Consider a converging nozzle with a low velocity at the inlet and sonic velocity at the exit plane. Now the nozzle exit diameter is reduced by half while the nozzle inlet temperature and pressure are maintained the same. The pressure at nozzle exit will

A)remain the same.
B)double.
C)quadruple.
D)go down by half.
E)go down to one-fourth.

Question 6

Air is approaching a converging-diverging nozzle with a low velocity at 20°C and 85 kPa, and it leaves the nozzle at a supersonic velocity. The velocity of air at the throat of the nozzle is

A)82 m/s
B)98 m/s
C)313 m/s
D)343 m/s
E)408 m/s

Question 7

Argon gas is approaching a converging-diverging nozzle with a low velocity at 20°C and 120 kPa, and it leaves the nozzle at a supersonic velocity. If the cross-sectional area of the throat is 0.225 m², the mass flow rate of argon through the nozzle is

A)21 kg/s
B)122 kg/s
C)79 kg/s
D)17 kg/s
E)53 kg/s

Question 8

Carbon dioxide enters a converging-diverging nozzle at 50 m/s, 600°C, and 450 kPa, and it leaves the nozzle at a supersonic velocity. The velocity of carbon dioxide at the throat of the nozzle is

A)50 m/s
B)186 m/s
C)323 m/s
D)431 m/s
E)461 m/s

Question 9

Consider gas flow through a converging-diverging nozzle. Of the five statements below, select the one that is incorrect:

A)The fluid velocity at the throat must be at or below the speed of sound.
B)If the fluid velocity at the throat is below the speed of sound, the diverging section can still accelerate the fluid to sepersonic velocities.
C)If the fluid enters the diverging section with a Mach number greater than one and no shock occurs, the flow at the nozzle exit will be supersonic.
D)There will be no flow through the nozzle if the back pressure equals the stagnation pressure.
E)The fluid velocity decreases, the entropy increases, and stagnation enthalpy remains constant during flow through a normal shock.

Question 10

Combustion gases with k = 1.34 enter a converging nozzle at stagnation temperature and pressure of 460°C and 780 kPa, and are discharged into the atmospheric air at 20°C and 100 kPa. The lowest pressure that will occur within the nozzle is

A)27 kPa
B)100 kPa
C)321 kPa
D)420 kPa
E)780 kPa