Navier-Stokes Predictions of the Individual Components of the Pitch-Damping Coefficient Sum

Report No. ARL-TR-3169
Authors: Paul Weinacht
Date/Pages: April 2004; 44 pages
Abstract: An approach for predicting the two individual aerodynamic damping coefficients that form the pitch-damping coefficient sum is presented. The coefficients are obtained using prescribed or forced motions that independently excite the two different angular rates that are associated with the two damping coefficients. A key feature of the approach is that steady flow fields are produced by the selected motions. Steady flow computational fluid dynamics approaches can be applied, allowing results to be obtained in a computationally efficient manner. Application of the technique is made to an axisymmetric projectile configuration. The predicted pitch-damping coefficient sum obtained by adding the individually determined coefficients is in excellent agreement with previous predictions of the pitch-damping coefficient sum and with experimental data. Additional validation of the approach is obtained through comparisons with prior results from numerical solutions of the nonlinear unsteady potential equation. The individual coefficients are also compared with slender body theory, and the results show similar trends though the slender body theory appears to underpredict the various coefficients.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2004