THE UNIVERSITY OF ADELAIDE AUSTRALIA SUB CRUCE LUMEN Examination for the Degree of Bachelor of Engineering Semester 2, 2009 MECH ENG 3101 COURSE ID: 104414 APPLIED AERODYNAMICS Official Reading Time: 10 mins Writing Time: 180 mins Total Duration: 190 mins Parts A B Questions Answer all questions Answer all questions Instructions for Candidates Time 90 mins (Recommended) 90 marks 90 mins (Recommended) 90 marks Marks 180 Total · This is an Open Book examination (refer to Permitted Materials). · Answer all questions in the answer books. · Examination materials must not be removed from the examination room. · The marks for each question are indicated. · State all assumptions. Permitted Materials · Two Blue books · Any materials are permitted. · Calculator without alphanumeric memory or remote communications capability permitted. · English language dictionaries are permitted. DO NOT COMMENCE WRITING UNTIL INSTRUCTED TO DO SO.
Course ID: MECH ENG 104414 Page 2 of 12 Part A (Total 90 marks) Answer all these questions in a blue answer book. Clearly indicate "Part A" on the front of the answer book. Q1. [30 marks] An aircraft cruises at a steady state speed of 270 km/h, at low altitude where the air has a density of 1.20 kg/m3 and a dynamic viscosity (u) of 1.80 x 10-5 N.s/m2. The aeroplane's wing is thin, rectangular and unswept, with an aspect ratio of 8 and a plan area of 32 m2. The wing has a mean surface roughness of ¿ = 0.4 mm. The lift produced by the wing is 20,000 N. a) Find the chord length of the wing. [3 marks] b) Estimate the power required to overcome the skin friction drag on the wing. [12 marks] c) Estimate the thickness (8) of the boundary layer at the trailing edge of the wing and comment on the validity of this estimation. [5 marks] d) Estimate the power required to overcome the induced drag of the wing. [7 marks] e) What power saving (in watt or kilowatt) would be possible if the boundary layer could be maintained in a laminar state over the entire wing? [3 marks] PLEASE SEE NEXT PAGE
Course ID: MECH ENG 104414 Page 3 of 12 Q2. [30 marks] (a) With the aid of diagrams, explain how "downwash" is generated by three-dimensional wings. [4 marks] (b) An aircraft with a wing span 6 metres flies at constant height and a speed of 50 m/s. The lift produced by the wing is 10 kN and the air density is 1.20 kg/m3. Estimate the downwash velocity generated by the wings. [3 marks] (c) Is induced drag larger for an aircraft at take-off speed, or at cruising speed? Explain your answer. Describe four ways in which induced drag on an aircraft can be reduced. [7 marks] (d) A strong wind can blow a golf ball off a tee by pivoting it about point 1 as shown in Figure 1 below. Determine the wind speed necessary to do this. [16 marks] The drag coefficient of