Prediction of the Pitch-Damping Coefficients Using Sacks' Relations

Report No. ARL-TR-3231
Authors: Paul Weinacht and James E. Danberg
Date/Pages: June 2004; 40 pages
Abstract: Throughout its development, slender body theory has been generalized to predict a large variety of aerodynamic coefficients for a wide class of flight bodies. For most applications, slender body theory provides only a qualitative predictive capability. There is, however, a set of slender body relationships which has been previously derived by Sacks that allows the individual pitchdamping coefficients and the pitch-damping coefficient sums to be related to each other. Until recently, it has been difficult to assess the accuracy of these relationships due to the lack of high-quality pitch-damping data or the lack of a higher order theory. The current work applies a recently developed computational fluid dynamics capability for predicting all three pitch-damping coefficients. From this analysis, the accuracy of these relationships has been assessed and their engineering significance demonstrated. One important result is that the pitch-damping relations developed by Sacks allow the individual pitch-damping coefficients to be determined from the pitch-damping coefficient sum with a high degree of accuracy.
Distribution: Approved for public release
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Last Update / Reviewed: June 1, 2004