### Thermodynamics (Compressible Flow)

1. All real fluids are
(a) incompressible
(b) compressible to some extent
(c) compressible to any extent
(d) none of the above.

2. A change in the state of a system at constant volume is called
(a) isobaric process
(b) isochoric process
(c) isothermal process

3. A process during which no heat is transferred to or from the gas is called an
(a) isochoric process
(b) isobaric process
(d) isothermal process.

4. The sonic velocity is largest in which of the following ?
(a) Water
(b) Steel
(c) Kerosene
(d) Air.

5. An isentropic flow is one which is
(a) isothermal

6. Indica upto what Mach number can a fluid flow be considered incompressible ?
(a) 0.1
(b) 0.3
(c) 0.8
(d) 1.0.

7. Which of the following is the basic equation of compressible fluid flow ?
(a) Continuity equation
(b) Momentum equation
(c) Energy equation
(d) Equation of state
(e) All of the above.

8. The velocity of disturbance in case of fluids is ...... the velocity of the disturbance in solids.
(a) less than
(b) equal to
(c) more than
(d) none of the above.

9. Sonic velocity (C) for adiabatic process is given as
(a) C = γRT3
(b) C = γRT
(c) C = γ 2RT
(d) C = γRT.
where γ = ratio of specific heats, R = gas constant, T = temperature.

10. The flow is said to be subsonic when Mach number is
(a) equal to unity
(b) less than unity
(c) greater than unity
(d) none of the above.

11. The region outside the Mach cone is called
(a) zone of action
(b) zone of silence
(c) control volume
(d) none of the above.

12. A stagnation point is the point on the immersed body where the magnitude of velocity is
(a) small
(b) large
(c) zero
(d) none of the above.

13. A convergent-divergent nozzle is used when the discharge pressure is
(a) less than the critical pressure
(b) equal to the critical pressure
(c) more than the critical pressure
(d) none of the above.

14. At critical pressure ratio, the velocity at the throat of a nozzle is
(a) equal to the sonic speed
(b) less than the sonic speed
(c) more than the sonic speed
(d) none of the above.

15. Laval nozzle is a
(a) convergent nozzle
(b) divergent nozzle
(c) convergent-divergent nozzle
(d) any of the above.

16. A shock wave is produced when
(a) a subsonic flow changes to sonic flow
(b) a sonic flow changes to supersonic flow
(c) a supersonic flow changes to subsonic flow
(d) none of the above.

17. The sonic velocity in a fluid medium is directly proportional to
(a) Mach number
(b) pressure
(c) square root of temperature
(d) none of the above.

18. The stagnation pressure (ps) and temperature (Ts) are
(a) less than their ambient counterparts
(b) more than their ambient counterparts
(c) the same as in ambient flow
(d) none of the above.

19. Across a normal shock
(a) the entropy remains constant
(b) the pressure and temperature rise
(c) the velocity and pressure decrease
(d) the density and temperature decrease.

20. A normal shock wave
(a) is reversible
(b) is irreversible
(c) is isentropic
(d) occurs when approaching flow is supersonic.

21. The sonic speed in an ideal gas varies
(a) inversely as bulk modulus
(b) directly as the absolute pressure
(c) inversely as the absolute temperature
(d) none of the above.

22. In a supersonic flow, a diffuser is a conduit having
(b) converging-diverging passage
(c) constant area throughout its length
(d) none of the above.

23. Choking of a nozzle fitted to a pressure tank containing gas implies
(a) sonic velocity at the throat
(b) increase of the mass flow rate
(c) obstruction of flow
(d) all of the above.

24. A shock wave which occurs in a supersonic flow represents a region in which
(a) a zone of silence exists
(b) there is no change in pressure, temperature and density
(c) there is sudden change in pressure, temperature and density
(d) velocity is zero.

25. Which of the following statements regarding a normal shock is correct ?
(a) It occurs when an abrupt change takes place from supersonic into subsonic flow condition
(b) It causes a disruption and reversal of flow pattern
(c) It may occur in sonic or supersonic flow
(d) None of the above.

26. Which of the following statements is incorrect ?

(a) A shock wave occurs in divergent section of a nozzle when the compressible flow changes abruptly
from supersonic to subsonic state
(b) A plane moving at supersonic state is not heard by the stationary observer on the ground until it passes
him because zone of disturbance in Mach cone trails behind the plane
(c) A divergent section is added to a convergent nozzle to obtain supersonic velocity at the throat
(d) none of the above.

1. (b) 2. (b) 3. (c) 4. (b) 5. (d) 6. (b) 7. (e) 8. (a) 9. (b) 10. (b) 11. (b) 12. (c) 13. (a) 14. (a) 15. (c) 16. (c) 17. (c) 18. (b) 19. (b) 20. (d) 21. (d) 22. (a) 23. (d) 24. (c) 25. (a)  26. (c)

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