ME 471 - Midterm Exam 1 Solutions

4 a streamline is defined to be a line which is

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Unformatted text preview: amline 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. Zerolift angle of attack is -2 degrees. Find the lift coefficient. For small angles of attack, we have a linear variation of with (in radians) as: Converting radians to degrees we have: ( ) 2) With the help of neat labelled diagrams, explain the airfoil-flap-slat configuration during (a) takeoff, and (b) landing. - Partially deployed high-lift devices - Fully deployed high-lift devices - No gap between slat/flap and airfoil. - Gap between slat and flaps - Slat increases stalling angle - Flap increases (a) takeoff (b) landing 3) An aircraft flies at a velocity , where the pressure and th the temperature is . A model of 1/10 scale is to be tested in a high-speed wind tunnel. Calculate the pressure of the tunnel stream necessary to give dynamic similarity, if the wind tunnel temperature is to be maintained at . It may be assumed that t...
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