Exam_2_2004_key

# Exam_2_2004_key - EAS 4101 Aerodynamics Spring 2004 Exam#2...

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EAS 4101 - Aerodynamics – Spring 2004 4/19/04, Exam #2 Name: _____________key___________ 1 Questions:(40 points total, 4 points each, unless otherwise marked) 1. When is flow in a boundary layer considered to be irrotational? Never 2. What does the Reynolds number represent the ratio of in terms of typical forces? The ratio of viscous to inertial forces 3. What are the normal/streamwise velocity boundary conditions for a viscous flow over a moving solid body? 0 V = r 4. Explain the assumption of “fully developed” in terms of flow physics for a flow in the z- direction. 0 dV dz = r 5. Physically, what is true about the ratio of the viscous and inertial forces in a boundary layer? They are of the same order

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EAS 4101 - Aerodynamics – Spring 2004 4/19/04, Exam #2 Name: _____________key___________ 2 Questions continued: (40 points total, 4 points each, unless otherwise marked) 6. Compared to ideal flow, what are four specific effects of viscosity on the flow over a wing? Viscous drag, separation, unsteadiness, and turbulence. 7. Draw a representative vs. L C α for a thin, cambered finite wing and compare it to a vs. L eff C for a thin, infinite cambered airfoil , please specifically comment about the differences in angle of attack intercept and lift slope for 2-D vs. 3-D bodies (8 points). For a given angle of attack, the lift is reduced for a finite wing. The lift slope is reduced due to induced drag. The zero-lift angle of attack remains the same, because lift is required to generate induced drag.
EAS 4101 - Aerodynamics – Spring 2004 4/19/04, Exam #2 Name: _____________key___________ 3 8. Draw a representative vs. L C α for a thin, infinite cambered airfoil that displays leading edge stall and compare it to the vs. L C for a thin, infinite cambered airfoil that displays trailing edge stall (8 points) Leading edge stall occurs at higher angles of attack than trailing edge stall, but the change to the lift curve is far more dramatic. The separation quickly leads to complete separation over the airfoil. With trailing edge stall, while it occurs earlier, there is a gradual transition to total wing stall.

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Exam_2_2004_key - EAS 4101 Aerodynamics Spring 2004 Exam#2...

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