Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)September 2006 ARL-RP-131 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTESA reprint from the AIAA Atmospheric Flight Mechanics Conference and Exhibit, 16-19 August 2004, Providence, RI. ABSTRACTComputational fluid dynamic simulations (CFD) were used to predict the aerodynamic coefficients and flow field over a spinstabilized, 25-mm, sub-caliber training projectile. The primary objective of the investigation was to determine the CFD parameters necessary for the accurate prediction of the Magnus moment and roll damping of a spin-stabilized projectile. Archival experimental data was used to validate the numerical calculations. The Mach number range investigated was from 0.4 to 4.5. Steady state CFD calculations predicted the drag, normal force, pitching moment, and normal force center of pressure very well-to within 10% of the experimental data. Time-accurate, detached-eddy simulations were found necessary to predict the Magnus moment in the subsonic and transonic flow regimes. Steady state CFD was found adequate to calculate the roll damping, which was predicted to within 15% of the experimental data in both steady state and time accurate calculations. SUBJECT TERMS CFD Computation of Magnus Moment and Roll Damping Moment of a Spinning ProjectileJames DeSpirito * and Karen R. Heavey † U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005-5066Computational fluid dynamic simulations (CFD) were used to predict the aerodynamic coefficients and flow field over a spin-stabilized, 25-mm, sub-caliber training projectile. The primary objective of the investigation was to determine the CFD parameters necessary for the accurate prediction of the Magnus moment and roll damping of a spin-stabilized projectile. Archival experimental data was used to validate the numerical calculations. The Mach number range investigated was from 0.4 to 4.5. Steady state CFD calculations predicted the drag, normal force, pitching m...

Approved for public release; distribution is unlimited.ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)September 2008 ARL-TR-4605 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTThe 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. iii

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