8/12/2019 MECH448 Mid-Terms Samples 2013

1/6

MECH448Compressible Fluid Flow

MID-TERM TESTNovember, 2011

OPEN BOOK TEST (All aids allowed)ANSWER ALL QUESTIONS

Marks Assigned to each question are shown at the end of the questions.Test is marked out of 50.

COMPUTERS AND COMMUNICATING CALCULATORS ARE NOTPERMITTED

NOTE: Make and clearly state any assumptions that you considernecessary. If information appears to be missing make an assumption

about the missing information and clearly state what you have assumed.

Sample Mid-Term

QUESTION 1.Air is isentropically expanded from a large reservoir in whichthe pressure and temperature are 1350kPa and 85oCrespectively through a variable area duct until the pressure hasdropped to 70kPa. A normal shock wave occurs at this point inthe flow. Find the pressure, temperature and air velocity in theflow immediately downstream of (i.e., after) the shock wave.Also find the stagnation pressures and temperatures before andafter the shock wave. State the assumptions that you have madein arriving at your answer.

( 8 Marks)

Sample Mid-Term

QUESTION 2.A normal shock wave is propagating down a duct into still air inwhich the pressure and temperature are 75kPa and 15Crespectively. The pressure ratio across the shock is 1.35. Find thevelocity of the shock wave and the air velocity, pressure andtemperature behind the shock wave. This moving shock wavestrikes the closed end of the duct. Find the pressure acting on thisclosed end after the shock wave reflection.

( 12 Marks)

Sample Mid-Term

QUESTION 3.Air is flowing down a plane walled duct at a Mach number of 2.5and at a pressure of 60kPa. The air-stream passes over a wedgewhich turns the flow through an angle of 5 leading to thegeneration of an oblique shock wave. This oblique shock wave isreflected off the flat wall of the duct that is parallel to the initialflow direction. Find the pressure and Mach number after thereflection. Assume steady, two-dimensional flow.

( 10 Marks)

Sample Mid-Term

QUESTION 4.Consider the flow of air over the double wedge body shown inthe following figure. If the Mach number and pressure in theuniform air flow ahead of the body are 2.3 and 50 kParespectively, find the pressures acting the surfaces 1, 2, and 3indicated in the figure.

( 11 Marks)

4o3o

5o

1

2

3

M=2.3, p = 50kPa

Sample Mid-Term

QUESTION 5.(i) Explain what are meant by the terms Compressibility,Sound Wave and Mach Wave.(ii) Discuss the differences between subsonic flow, transonicflow, supersonic flow, and hypersonic flow.

(iii) Air is flowing down a parallel walled duct at a Machnumber of 2.5 and a pressure of 70kPa. The upper wall of theduct turns upward through an angle of 6 o leading to thegeneration of an expansion wave. This expansion wave isreflected off the flat lower wall of the duct. Find the Machnumber and pressure immediately downstream (i.e., after) thereflected wave.

( 9 Marks)

Sample Mid-Term

8/12/2019 MECH448 Mid-Terms Samples 2013

2/6

Mech448 Mech448

Mech448 Mech448

Mech448 Mech448

8/12/2019 MECH448 Mid-Terms Samples 2013

3/6

Mech448 Mech448

Mech448 Mech448

Mech448 Mech448

8/12/2019 MECH448 Mid-Terms Samples 2013

4/6

Mech448 Mech448

Mech448

8/12/2019 MECH448 Mid-Terms Samples 2013

5/6

8/12/2019 MECH448 Mid-Terms Samples 2013

6/6