ME 471 - Midterm Exam 1 Solutions

# ME 471 - Midterm Exam 1 Solutions - ME 471.3 Introduction...

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ME 471.3 Introduction to Aerodynamics Department of Mechanical Engineering Winter 2014 Instructor Rajat Chakravarty Midterm Examination This closed-book exam has 16 pages. Some equations and other information are provided with the exam. You may use your own scientific calculator. No cell phones or any other electronic devices are permitted. If you are using a continuous memory calculator, you are responsible for erasing any stored programs or information prior to the exam. No other aids are permitted. Answers are to be written on the exam question sheets in the spaces provided. No additional paper will be provided. Please ensure that your answers are clear and legible. Please put a box around, or underline, your final answers (where appropriate). This exam has 3 sections worth a total of 100 marks. Attempt all questions in Section 1 (10 questions X 1 mark each = 10 marks) and Section 2 (10 questions X 5 marks each = 50 marks). In Section 3 (2 questions X 20 marks each = 40 marks), attempt any two questions. Name: _______________________________________________________ Student No.: _______________________________________________________ Signature: _______________________________________________________ Section Grade 1 /10 2 /50 3 /40 Total /100

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Section 1: Objective-Type Questions (10 questions X 1 mark each = 10 marks) Fill in the blanks: 1) For an aerofoil, the direction of the lift force is normal / perpendicular to the freestream, and the direction of the drag force is parallel / tangential to the freestream. 2) The aerodynamic centre is defined as the point on the aerofoil about which the moment does not change with α. 3) Flow on the upper surface of a finite wing is deflected toward the root . 4) A streamline is defined to be a line which is everywhere parallel / tangential to the local velocity vector. 5) If the vorticity vector is zero at every point in a flow, the flow is said to be irrotational . 6) “Leading - edge stall” is a characteristic of relatively thin aerofoils. 7) In Part 1 of the laboratory experiments, a Pitot-static probe mounted on the side wall of the wind tunnel test section was used to measure the freesteam static / dynamic pressure . 8) For a finite wing, the three main contributions to the total drag force are skin friction drag (profile drag) , pressure drag (form drag) , and induced drag . 9) The frequency measured in the wake of a cylinder is caused by vortex shedding . 10) The locus of fluid elements which have earlier passed through a prescribed point is called a streakline .
Section 2: Short Answer Questions (10 questions X 5 marks each = 50 marks) 1) The angle of attack of an airfoil is 12 degrees. The lift curve slope is 5.8 per radian. Zero- lift angle of attack is -2 degrees. Find the lift coefficient.

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