Navier-Stokes Predictions of Dynamic Stability Derivatives: Evaluation of Steady-State Methods

Report No. ARL-TR-4605
Authors: James DeSpirito; Sidra I. Silton; Paul Weinacht
Date/Pages: September 2008; 44 pages
Abstract: The prediction of the dynamic stability derivatives-roll-damping, Magnus, and pitch-damping moments-were evaluated for three spin-stabilized projectiles using steady-state computational fluid dynamic (CFD) calculations. Roll-damping CFD predictions were found to be very good across the Mach number range investigated. Magnus moment predictions were very good in the supersonic flight regime; however, the accuracy varied in the subsonic and transonic flight regime. The best Magnus moment prediction in the subsonic flight regime was for the square-base projectile that did not exhibit highly nonlinear Magnus moments. A primary contribution of this report is the demonstration that the pitch-damping moment can be adequately predicted via steady-state methods rather than resorting to unsteady techniques. The predicted pitch-damping moment compared very well to experimental data for the three projectiles investigated. For one configuration, the pitch-damping moment was predicted by several CFD codes, two different steady-state methods, and a time-accurate planar pitching motion method. All methods compared very well to each other and to the experimental data.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2008