Aerodynamics of the 120-mm M831A1 Projectile: Analysis of Free Flight Experimental Data
Aerodynamics of the 120-mm M831A1 Projectile: Analysis of Free Flight Experimental Data

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Published: 2000

Total Pages: 0

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The 120-mm M831A1 projectile is a low-cost training projectile used by U.S. armor troops. For the last several years, program managers have received feedback from the users that in some cases, M831A1 impact performance did not appear consistent with the current M831A1 computer correction factor. Based on this information, a low-scale but in-depth experimental analysis of the projectile was conducted to assess its aero-ballistic qualities and hopefully identify any potential issues that could affect accuracy performance. The work was conducted by the U.S. Army Research Laboratory at the Transonic Experimental Facility. Although the projectile has undergone fairly extensive target impact dispersion (TID), radar, and wind tunnel testing, this study presents the first spark range data and detailed free-flight aero-ballistic analysis for the M831A1. Roll data were measured via roll pins for the computation of roll-related coefficients. All rounds exhibited very little roll over the measured trajectory, mostly because of a very small roll moment. Yaw magnitudes displayed variability, and several shots had at least moderate levels. The source of the yaw levels imparted to the projectiles was the launch dynamics, and a detailed study of in-bore dynamics is in progress. Most shots exhibited a 'stepping', motion in plots of total yaw versus range. This phenomenon is the result of trim, which is believed to be caused by an aerodynamic asymmetry. A source of the trim has not been isolated. Accurate free-flight drag and pitching moment coefficients were computed on the basis of the measured trajectories. Pitch-damping characteristics were marginal. Although the M831A1 currently performs within acceptable TID standards, further experimental work is recommended, as well as a study of possible stabilizer design modifications.

Comparison of the 120-MM M831A1 Projectile's Experimental Launch Dynamic Data with Hydrocode Gun-Projectile Dynamic Simulations
Comparison of the 120-MM M831A1 Projectile's Experimental Launch Dynamic Data with Hydrocode Gun-Projectile Dynamic Simulations

Author: K. P. Soencksen

Publisher:

Published: 2001

Total Pages: 13

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This paper documents experimental validation for numerical simulations using the U.S. Army Research Laboratory's (ARL) gun-projectile dynamic simulation codes. The experimental program was conducted at ARL's Transonic Range Experimental Facility on the M831A1 high-explosive antitank (HEAT) training projectile for the M256 gun system. The experimental program consisted of the M831A1 HEAT training projectile fired for the measurement of aerodynamic characteristics. Measured first maximum yaw levels are compared to simulated data for the same system. The effect of damage tubes to help explain occasional launch anomalies is also shown.

Design for Control of Projectile Flight Characteristics
Design for Control of Projectile Flight Characteristics

Author: United States. Army Materiel Command

Publisher:

Published: 1966

Total Pages: 290

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This handbook presents a general survey of the principal factors affecting the flight of projectiles, and describes the methods commonly used for predicting and influencing the flight performance. The coefficients which characterize the aerodynamic forces and moments of a moving body are identified, methods for determining the coefficients applicable to a projectile having a given shape and center of gravity location are described, and the coefficients of a number of projectiles and projectile shapes are given. The use of aerodynamic coefficients in predicting stability, range and accuracy is described. The effects of variations in projectile shape and center of gravity location on range, accuracy and lethality are discussed. Some material on prototype testing and the effects of round-to-round variations in production lots is presented.

Static Aerodynamics CFD Analysis for 120-mm Hypersonic KE Projectile Design
Static Aerodynamics CFD Analysis for 120-mm Hypersonic KE Projectile Design

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Published: 1994

Total Pages: 44

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Computational fluid dynamics (CFD) predictions of static aerodynamic coefficients for large caliber (120-mm) M829-like cone-cylinder-flare kinetic energy (KE) projectile shapes are presented. Zero-yaw drag and static pitch- plane aerodynamic coefficients are presented for velocities in the range 1.5 to 3.0 km/sec for several flare angles. The aerodynamic coefficients are required to assess the velocity retardation and static stability of candidate configurations that use the M829 projectile as a basis for design. Comparisons of the aerodynamic coefficients are made with those of the fielded M829 projectile, and a preliminary evaluation is made of the performance of these shapes in hypersonic flight. Computational fluid dynamics, Supersonic flow, Kinetic energy projectiles, Aerodynamics.

Prediction of Projectile Performance, Stability, and Free-flight Motion Using Computational Fluid Dynamics
Prediction of Projectile Performance, Stability, and Free-flight Motion Using Computational Fluid Dynamics

Author: P. Weinacht

Publisher:

Published: 2003

Total Pages: 26

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With the recent development of capabilities for predicting the damping derivatives, it is now possible to predict the stability characteristics and free-flight motion for projectiles using data that are derived solely from computational fluid dynamics (CFD). As a demonstration of the capability, this report presents results for a family of axisymmetric projectiles in supersonic flight. The particular configuration selected for this computational study has been extensively tested in aeroballistic ranges, and high-quality experimental data have been obtained. Thin-layer Navier-Stokes techniques have been applied to compute the attached viscous flow over the forebody of the projectile and the separated flow in the projectile base region. Using the predicted aerodynamics coefficients, parameters that characterize the in-flight motion are subsequently evaluated, including the gyroscopic and dynamic stability factors, and the projectile's fast and slow mode frequencies and damping coefficients. These parameters are then used to predict the free-flight motion of the projectile. In each case, the computational approach is validated by comparison with experimental data, and very good agreement between computation and experiment is found. It is believed that this demonstration represents the first known instance of a viscous CFD approach being applied to predict all the necessary data for performance of linear aerodynamics stability and trajectory analyses.

Time-Accurate Calculations of Free-Flight Aerodynamics of Maneuvering Projectiles
Time-Accurate Calculations of Free-Flight Aerodynamics of Maneuvering Projectiles

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Published: 2007

Total Pages: 6

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This paper describes a multidisciplinary computational study undertaken to model the flight trajectories and the free-flight aerodynamics of finned projectiles both with and without control maneuvers. Advanced computational capabilities both in computational fluid dynamics (CFD) and rigid body dynamics (RBD) have been successfully fully coupled on high performance computing (HPC) platforms for "Virtual Fly-Outs" of munitions similar to actual free flight tests in the aerodynamic experimental facilities. Time-accurate Navier-Stokes computations have been performed to compute the unsteady aerodynamics associated with the free flight of a finned projectile at a supersonic speed using an advanced scalable unstructured flow solver on a highly parallel Linux Cluster. Some results relating to the portability and the performance of the flow solver on the Linux clusters are also addressed Computed positions and orientations of the projectile along the flight trajectory have been compared with actual data measured from free flight tests and are found to be generally in good agreement. Computed results obtained for another complex finned configuration with canard-control pitch-up maneuver in a virtual fly-out show the potential of these techniques for providing the actual time-dependent response of the flight vehicle and the resulting unsteady aerodynamics for maneuvering projectiles.

Experimental and Computational Results of a Maneuverable Power-Law Elliptic Cross-Section Projectile at Supersonic Speeds
Experimental and Computational Results of a Maneuverable Power-Law Elliptic Cross-Section Projectile at Supersonic Speeds

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Published: 2001

Total Pages: 77

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This report documents the results of an experimental and computational investigation of a power-law elliptic cross-section projectile for increased maneuverability. Surface-pressure measurements and force-and-moment measurements have been conducted in the Tri-Sonic Wind-Tunnel (TWT) at the Aerodynamic Research Center (ARC) at the U.S. Air Force Academy. Flow visualization data were also obtained in the form of Schlieren photographs and surface oil-flow patterns during these test programs. Data were obtained at a Mach number of 4.2% over a range of Reynolds numbers (based on the free-stream conditions and the model length) of 12.47 million to 19.96 million over an angle-of-attack range from -11 to +11 degrees. The data from these wind-tunnel tests were compared with computations generated using the Cobalt code, which was run on the Beowulf cluster at the High-Performance Computing Facility (HPCF) at the ARC. It should be noted that the experimental and the computational parts of this investigation were conducted concurrently in a double-blind fashion. That is, the results from the experimental effort were not used to influence the way in which the results from the CFD effort were produced and vice versa. Free flight investigations were carried out at the U.S. Air Force Research Laboratory Munitions Directorate Aeroballistic Research Facility and were conducted at Mach numbers ranging from 3.0 to 5.0. The free flight experimental data consisted of nine free-flight projectiles launched within an instrumented facility. Additional computational work was again carried out via the Cobalt code at the flight conditions of the experimental facility. The results indicate good agreement between the experimental and computational data determined in this effort, as well as, with engineering level predictions. The free-flight data was limited to small angles of attack therefore high fidelity determination of the aerodynamic stability coefficients and derivatives was not possib7.