Unformatted text preview: ASE320 Homework set # 9 Due: April 28, 2011 1.) A disc 15cm in diameter is placed in a wind tunnel at right angles to the incoming flow (perpendicular to the flow). The drag of the disk is found to be 3.2N when the air velocity is 20m/s and the air temperature is 25oC. Using this information, estimate the drag of a disk 40cm in diameter in a water flow having a velocity of 5m/s at a temperature of 15oC. 2.) Find the terminal velocity of a parachutist, assuming that the parachute can be modeled as a semicircular cup of diameter 6m. Use standard atmosphere properties of air corresponding to an altitude of 3000m. The total mass of the person and parachute is 90kg. 3.) A bracing wire used on a biplane to strengthen the wing assembly is found to vibrate at 5000Hz. a. Estimate the speed of the airplane if the wire has a diameter of 1.2mm. b. If the natural frequency of the wire is 500Hz, at what speed will the wire vibration frequency resonate? 4.) Assuming that the velocity profile in a laminar boundary layer of thickness δ is given by u/U =2(y/δ) – (y/δ)3 where u is the velocity at distance y from the surface and U is the freestream velocity. Demonstrate that θ/δ = 31/420. θ is the momentum thickness, τw is the viscous stress at the wall, Cf is the local skin friction coefficient at a distance x from the leading edge of the plate, ρ is the fluid density, and ν is the kinematic viscosity. ∞ ∞ ...
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 Spring '10
 GOLDSTEIN
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