ME 471 - Midterm Exam 1 Solutions

10 on a single clearly labeled graph sketch the lift

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Unformatted text preview: beled graph, sketch the lift curves (cl vs. α) for two aerofoils, one that exhibits trailing edge (TE) stall and one that exhibits leading edge (LE) stall. Which types of aerofoils exhibit LE stall, and which types of aerofoils exhibit TE stall? LE stall – thinner airfoils; TE stall – thicker airfoils Section 3: Long Answer Questions (Attempt any 2 questions X 20 marks each = 40 marks) 1) The shock waves on a vehicle in supersonic flight cause a component of drag called supersonic wave drag . Define the wave-drag coefficient as / , where is a suitable reference area for the body. In supersonic flight, the flow is governed in part by its thermodynamic properties, given by the specific heats at constant pressure and at constant volume . Define the ratio Pi theorem, show that . Using the Buckingham . Neglect the influence of friction. Number of physical variables : ( ) Number of fundamental dimensions : By Buckingham Pi theorem, number of dimensionless products Where the respective products are as follows: ( ( ) ( For ) ) , we have: Equating the powers of each fundamental dimension to get a dimensionless coefficient, we have: Mass: Length: Time: Temperature: Solving this system, we get: , , and Similarly, for we have: Equating the powers of each fundamental dimension to get a dimensionless coefficient, we have: Mass: Length: Time: Temperature: Solving this system, we get: For , , and , we have: Equating the powers of each fundamental dimension to get a dimensionless coefficient, we have: Mass: Length: Time: Temperature: Solving this system, we get: , , ( and ) 2) Consider the flow over an infinitely long rectangular prism of chord, , and thickness, , at an angle of attack, . A schematic is shown in the figure below. The pressures o...
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