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Unformatted text preview: AOE 3104 Homework #7 Solutions Problem 1. Wind tunnel tests yield the following data for lift coefficient and pitch moment coefficient about the half chord line of a given wing: (deg) C L C m 1 / 24.00.257 0.1492.0 0.030 0.084 0.0 0.194 0.062 2.0 0.210 0.020 4.0 0.5400.033 6.0 0.7520.066 Using the software of your choice (e.g., Matlab or Excel), determine C L ( ) and C m 1 / 2 ( ) using a linear least squares fit. Plot the data and the curve fits. Determine h ac and C m ac .42 2 4 6 8 100.5 0.5 1 1.5 C L42 2 4 6 8 100.20.1 0.1 0.2 (deg) C m Figure 1: Least squares fits for C L ( ) and C m ( ) versus . Solution. Using Matlabs polyfit and polyval functions, one may obtain the plots shown in Figure 1. The data fits suggest that C L ( ) = 0 . 136 + 0 . 093 (1) C m 1 / 2 ( ) = 0 . 0582 . 0197 . (2) The neutral point can be found by differentiating the identity C m 1 / 2 = C m ac + C L ( h 1 / 2 h ac ) with respect to...
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This document was uploaded on 02/05/2012.
 Fall '09

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