Wind tunnel and CFD investigation of aerodynamic interactions during sabot separation

Abstract

A series of supersonic wind tunnel tests was performed in the DREV 0.6 m x 0.6 m indraft facility in order to obtain experimental data on snrface static pressure distribution and aerodynamic coefficients for projectiles during sabot separation. Two model variants were used: a full scale model of the C-76 ArmourPiercing Fin-Stabilized Discarding-Sabot (AFFSDS) projectile and a generic APFSDS model. Relative attitudes and locations of the sabot/projectile system were frozen in test section providing twelve configurations of each variant The results were obtained atMach 3.5 and 4. They indicated mat the generic variant gave results very similar to those of the C-76 variant In addition to wind tunnel experiments, Computational Fluid Dynamics (CFD) calculations were performed on the generic configurations using a 3D Navier-Stofces code (TASCflowTM *). The predicted results showed good agreement with the wind tunnel measurements. An analysis of the expected trajectory deviation of the projectile due to the aerodynamic interference of sabot separation was performed. It indicated that the magnitude of the aerodynamic interference measured in the wind tunnel would generate a trajectory deviation similar to that observed hi firing trials. Introduction Modem Armour-Piercing Fin-Stabilized DiscardingSabot (APFSDS) ammunition is only effective if delivered accurately to the target One important factor affecting the launch and flight of such projectiles is the sabot separation. In order to develop a capability to assess sabot designs, DREV conducted a wind tunnel experiment and carried out CFD calculations for a series of configurations. A wind tunnel experiment on the aerodynamics of sabot separation interaction was carried out in 1980 by BRL. This experiment included only pressure distributions on a generic configuration. This was not considered sufficient to fulfill the objective of the project since the effects involved with a real Copyright O 1995 by Defence Research Establishment Valcartier. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. * TASCflow is a registered Canadian trademark of ASC Ltd. sabot/projectile configuration were not investigated. A new experiment was therefore designed taking into consideration the BRL experiment. It included wind tunnel tests with a full scale model of the C-76 projectile, and with a model of a generic cone/cylinder projectile and cone/cylinder sabot petals. An approach with a generic configuration represented many advantages such as a simplified meshing for CFD modelling and the potential use as a calibration model for wind tunnel experiments, but the study of a real configuration was also a matter of great practical interest For that purpose, the C-76 105 nun projectile and its 3 petal sabot was identified as me candidate f or wind tunnel testing. This wind tunnel experiment was conducted in the DREV 0.6 m x 0.6 m indraft facility. In addition to the wind tunnel experiment, CFD calculations were performed on the generic configurations for the experimental conditions. The more elaborate calculations for the C-76 configurations have not been performed yet Finally, a simple analysis of the effect of the aerodynamic interaction of sabot separation on projectile trajectory deviation is also included. Wind Tunnel Experiment The experiment was carried out in the DREV trisonic facility which is an intermittent indraft type with a 0.6 m x 0.6 m test section. Flow conditions for these tests are presented in Table 1. Table 1 Wind Tunnel Test Conditions