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Unit 4: Flow in constant area duct - Practice Quiz

ASE204 — Aerodynamics-Ii 60 Questions
0 Correct 0 Wrong 60 Left
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1 Which condition best describes Fanno flow?

Fanno flow Easy
A. Isothermal flow without wall friction
B. Adiabatic flow with wall friction
C. Isentropic flow with heat addition
D. Adiabatic flow with changing area

2 Which duct geometry is assumed in the Fanno flow model?

Fanno flow Easy
A. Abruptly changing area
B. Gradually decreasing area
C. Constant cross-sectional area
D. Gradually increasing area

3 Which stagnation property remains constant in adiabatic Fanno flow?

Fanno flow Easy
A. Stagnation entropy
B. Stagnation pressure
C. Stagnation temperature
D. Stagnation density

4 In the common Fanno parameter , what does represent?

Fanno flow equations and solutions Easy
A. Density ratio
B. Dynamic pressure
C. Hydraulic diameter
D. Diffusion coefficient

5 What does the star symbol indicate in Fanno flow relations, such as ?

Fanno flow equations and solutions Easy
A. An ambient reference state
B. A sonic reference state
C. An inlet reference state
D. A vacuum reference state

6 How does entropy vary along a Fanno duct in the direction of flow?

Variation of flow properties Easy
A. It becomes zero at exit
B. It decreases due to friction
C. It increases due to friction
D. It remains exactly constant

7 What happens to stagnation pressure along a Fanno duct?

Variation of flow properties Easy
A. It decreases along the duct
B. It remains constant throughout
C. It increases along the duct
D. It becomes equal to static pressure

8 What happens to the Mach number of an initially subsonic Fanno flow as duct length increases?

Variation of Mach number with duct length Easy
A. It increases toward unity
B. It changes directly to supersonic
C. It remains at its inlet value
D. It decreases toward zero

9 What happens to the Mach number of an initially supersonic Fanno flow as duct length increases?

Variation of Mach number with duct length Easy
A. It decreases toward unity
B. It increases without limit
C. It remains at its inlet value
D. It immediately becomes zero

10 What is the limiting Mach number reached in a sufficiently long Fanno duct?

Variation of Mach number with duct length Easy
A.
B.
C.
D.

11 Fanno tables commonly list flow properties as functions of which variable?

Tables and charts for Fanno flow Easy
A. Prandtl number
B. Mach number
C. Reynolds number
D. Nusselt number

12 Which quantity can be obtained from a Fanno table to estimate the remaining length before choking?

Tables and charts for Fanno flow Easy
A.
B.
C.
D.

13 Which physical effect is central to the Rayleigh flow model?

Rayleigh line Easy
A. Wall friction
B. Shaft rotation
C. Heat transfer
D. Area variation

14 Which effect is neglected in the ideal Rayleigh flow model?

Rayleigh line Easy
A. Wall friction
B. Heat transfer
C. Mass flow
D. Compressibility

15 Which expression is constant according to the one-dimensional momentum equation for Rayleigh flow?

Rayleigh flow equations Easy
A.
B.
C.
D.

16 Which property generally changes when heat is transferred in Rayleigh flow?

Rayleigh flow equations Easy
A. Wall roughness
B. Duct cross-sectional area
C. Hydraulic diameter
D. Stagnation temperature

17 What happens to the Mach number when heat is added to a subsonic Rayleigh flow?

Variation of flow properties in Rayleigh flow Easy
A. It becomes negative
B. It remains exactly constant
C. It increases toward unity
D. It decreases toward zero

18 What happens to the Mach number when heat is added to a supersonic Rayleigh flow?

Variation of flow properties in Rayleigh flow Easy
A. It increases without limit
B. It remains exactly constant
C. It decreases toward zero
D. It decreases toward unity

19 In Rayleigh tables, starred properties refer to which condition?

Tables and charts for Rayleigh flow Easy
A. The inlet condition
B. The vacuum condition
C. The sonic condition
D. The ambient condition

20 Which ratio is typically available in Rayleigh flow tables?

Tables and charts for Rayleigh flow Easy
A.
B.
C.
D.

21 Which set of assumptions best describes ideal Fanno flow in a duct?

Fanno flow Medium
A. Unsteady, adiabatic flow through a variable-area nozzle
B. Steady, adiabatic flow with wall friction in a constant-area duct
C. Steady, isothermal flow without friction in a constant-area duct
D. Steady, frictionless flow with heating in a constant-area duct

22 For a perfect gas in Fanno flow, which stagnation property remains constant along the duct?

Fanno flow equations and solutions Medium
A. Stagnation pressure
B. Static pressure
C. Stagnation temperature
D. Static temperature

23 What happens to a subsonic stream as friction acts along a Fanno duct?

Variation of flow properties Medium
A. Mach number falls, while static pressure and temperature fall
B. Mach number falls, while static pressure and temperature rise
C. Mach number rises, while static pressure and temperature fall
D. Mach number rises, while static pressure and temperature rise

24 A subsonic Fanno duct is extended beyond the maximum length corresponding to its specified inlet state. What is the expected result?

Variation of Mach number with duct length Medium
A. The mass flow increases while the inlet state remains unchanged
B. The specified inlet state cannot persist because the flow becomes choked
C. The flow passes smoothly through and becomes supersonic
D. The additional length has no effect after the sonic condition

25 A Fanno table gives at . If the local static temperature is , what is the sonic-reference temperature ?

Tables and charts for Fanno flow Medium
A.
B.
C.
D.

26 For air with , the Fanno parameter from to the sonic state is , where is the Fanning friction factor. If and , what is ?

Fanno flow equations and solutions Medium
A.
B.
C.
D.

27 Which property variation occurs in a supersonic Fanno flow as duct length increases?

Variation of flow properties Medium
A. Mach number decreases, while static pressure and temperature decrease
B. Mach number decreases, while static pressure and temperature increase
C. Mach number increases, while static pressure and temperature decrease
D. Mach number increases, while static pressure and temperature increase

28 Two subsonic Fanno ducts have identical diameter and friction factor but inlet Mach numbers of and . Which inlet condition permits the greater duct length before choking?

Variation of Mach number with duct length Medium
A. The inlet condition
B. Neither condition can become choked
C. The inlet condition
D. Both permit the same length

29 For air, a Fanno table lists at and at . Starting at , a duct uses . What is the approximate outlet Mach number?

Tables and charts for Fanno flow Medium
A.
B.
C.
D.

30 At which condition is entropy maximum on a given Fanno line?

Fanno flow Medium
A. At the sonic state
B. At the stagnation state
C. At the lowest static temperature
D. At the highest supersonic Mach number

31 Which relation represents the Rayleigh line for one-dimensional constant-area flow with mass flux and specific volume ?

Rayleigh line Medium
A.
B.
C.
D.

32 Air enters a Rayleigh-flow duct with and leaves with . Taking , how much heat is added per unit mass?

Rayleigh flow equations Medium
A.
B.
C.
D.

33 How does heat addition affect the Mach number on the two branches of Rayleigh flow?

Variation of flow properties in Rayleigh flow Medium
A. It raises subsonic and lowers supersonic
B. It raises on both branches
C. It lowers subsonic and raises supersonic
D. It lowers on both branches

34 For air at , a Rayleigh table gives . If the local static pressure is , what is ?

Tables and charts for Rayleigh flow Medium
A.
B.
C.
D.

35 For a perfect gas in Rayleigh flow, the static-temperature ratio is For air with at , what is ?

Rayleigh flow equations Medium
A.
B.
C.
D.

36 For air with , at what Mach number does the static temperature reach its maximum on a Rayleigh line?

Variation of flow properties in Rayleigh flow Medium
A.
B.
C.
D.

37 On a pressure-specific-volume diagram, what is the slope of a Rayleigh line for constant mass flux ?

Rayleigh line Medium
A.
B.
C.
D.

38 A Rayleigh table gives for an inlet state. If the inlet stagnation temperature is , approximately how much can increase before thermal choking?

Tables and charts for Rayleigh flow Medium
A.
B.
C.
D.

39 A supersonic stream receives heat in a constant-area Rayleigh-flow duct. Which combination of changes occurs as the stream approaches choking?

Variation of flow properties in Rayleigh flow Medium
A. Mach number decreases, while static pressure and temperature increase
B. Mach number increases, while static pressure and temperature decrease
C. Mach number increases, while static pressure and temperature increase
D. Mach number decreases, while static pressure and temperature decrease

40 A Rayleigh chart shows two Mach numbers, one subsonic and one supersonic, for the same value . What explains this result?

Tables and charts for Rayleigh flow Medium
A. remains constant throughout every Rayleigh-flow process
B. Static temperature reaches its minimum at the sonic condition
C. reaches a maximum at and decreases on either side
D. Stagnation pressure has identical values at all Mach numbers

41 A calorically perfect gas flows through a constant-area, adiabatic duct with wall friction. Which statement correctly describes the limiting state reached from either an initially subsonic or initially supersonic condition?

Fanno flow Hard
A. The flow approaches , where static temperature is maximum
B. The flow approaches , where entropy is maximum on the Fanno line
C. The flow approaches , where stagnation pressure is minimum
D. The flow approaches , where stagnation temperature is minimum

42 For air with , the Fanno function is and . Air enters a duct at and leaves at . If the Fanning friction factor is and , what is the duct length?

Fanno flow equations and solutions Hard
A.
B.
C.
D.

43 Air enters a constant-area adiabatic duct at . For , the remaining Fanno parameter to choking is . If and the Fanning friction factor is , what is the maximum duct length before choking?

Variation of Mach number with duct length Hard
A.
B.
C.
D.

44 Which set of downstream trends is correct for initially supersonic Fanno flow as friction drives the state toward choking?

Variation of flow properties Hard
A. , , , , and
B. , , , , and
C. , , , , and
D. , , , , and

45 A Fanno table for air gives , , , , and . Subsonic flow enters at , and the duct has . What is the exit Mach number?

Tables and charts for Fanno flow Hard
A.
B.
C.
D.

46 Supersonic air enters a Fanno duct at , where . The duct parameter is , so . Although the equation has subsonic and supersonic mathematical roots, which exit state is physically admissible without a shock?

Fanno flow equations and solutions Hard
A. The subsonic root near
B. The sonic root exactly at
C. The supersonic root near
D. Either root, depending only on stagnation temperature

47 For Fanno flow of air, the static-pressure ratio is . What is at for ?

Variation of flow properties Hard
A.
B.
C.
D.

48 A proposed smooth Fanno solution starts at , reaches partway through a uniform duct, and then continues to farther downstream. Why is this solution inadmissible?

Variation of Mach number with duct length Hard
A. The constant-area condition prohibits every supersonic state regardless of inlet conditions
B. The sonic state exhausts the available Fanno length and cannot be crossed continuously
C. The adiabatic condition requires Mach number to remain constant after reaching unity
D. The friction force reverses direction exactly at the sonic section of the duct

49 For one-dimensional constant-area Rayleigh flow with mass flux , which equation and geometric interpretation are correct in the - plane, where ?

Rayleigh line Hard
A. , a straight line of slope
B. , a straight line of slope
C. , a parabola of slope
D. , a rectangular hyperbola

50 For air, . Air initially has and . With and , how much heat per unit mass is required to reach choking?

Rayleigh flow equations Hard
A.
B.
C.
D.

51 At what Mach number does the static temperature attain its maximum value along a Rayleigh line for a perfect gas?

Variation of flow properties in Rayleigh flow Hard
A.
B.
C.
D.

52 For , Rayleigh relations give and . Which pair applies at ?

Tables and charts for Rayleigh flow Hard
A. and
B. and
C. and
D. and

53 Heat is added to initially supersonic Rayleigh flow without reaching choking. Which downstream trends are correct?

Variation of flow properties in Rayleigh flow Hard
A. , , , , and
B. , , , , and
C. , , , , and
D. , , , , and

54 Subsonic air on a Rayleigh line changes from to the sonic state through heat addition. Using with , what is ?

Rayleigh flow equations Hard
A.
B.
C.
D.

55 A subsonic Rayleigh flow has . If and , what is the maximum heat addition possible before thermal choking?

Variation of flow properties in Rayleigh flow Hard
A.
B.
C.
D.

56 A Rayleigh table is used to infer Mach number from a measured value . Why is this ratio alone generally insufficient to determine a unique Mach number?

Tables and charts for Rayleigh flow Hard
A. The ratio normally corresponds to one subsonic root and one supersonic root
B. The ratio is independent of Mach number for a calorically perfect gas
C. The ratio depends on duct diameter as well as on the local Mach number
D. The ratio identifies Mach number only when wall friction is also specified

57 Which statement correctly compares entropy behavior in Fanno and Rayleigh flows for states approaching along their physically admissible branches?

Rayleigh line Hard
A. Entropy is constant in Fanno flow but increases in Rayleigh flow
B. Entropy decreases toward a minimum at the sonic state in both flows
C. Entropy increases in Fanno flow but remains constant in Rayleigh flow
D. Entropy increases toward a maximum at the sonic state in both flows

58 A Fanno table for air gives at and at . If a duct changes the Mach number from to , what is the stagnation-pressure ratio ?

Tables and charts for Fanno flow Hard
A.
B.
C.
D.

59 Heat is removed from a Rayleigh flow. How does the Mach number respond on the two branches?

Variation of flow properties in Rayleigh flow Hard
A. It decreases on both the subsonic and supersonic branches
B. It increases on both the subsonic and supersonic branches
C. It increases if subsonic and decreases if supersonic
D. It decreases if subsonic and increases if supersonic

60 Which comparison between subsonic Fanno flow and subsonic Rayleigh flow with heat addition is correct as each approaches choking?

Fanno flow Hard
A. Both have and constant ; only Fanno flow has
B. Both have and ; only Rayleigh flow has
C. Both have and ; only Fanno flow has
D. Both have and ; only Rayleigh flow has
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