COUPLED FLUID-STRUCTURE CALCULATIONS TO PREDICT THE ROLL INDUCED BY FLEXIBLE FINS ON 155 MM PILOTED GUIDED AMMUNITION

KATANA® is a 155 mm long-range, high-accuracy, precision-guided artillery projectile. Guiding ammunition requires controlling roll in flight. To achieve this, the geometry of the fins in flight is an essential factor but is mainly the result of several loads occurring successively from the manufacturing stage to the interior, intermediate and exterior ballistics phases. Modeling was carried out for all these stages, including coupled fluid-structure interaction and the effect on induced roll was assessed. This model provides a better understanding of each physical phenomenon, their impact on the final geometry of the fin and the consequences on flight. It enables quicker and more efficient analysis of incidents, optimization of design and prediction of performances. Experimental trajectories were modeled, considering measured data as projectile mass and measured muzzle velocity of each round, and compared with firing radar and telemetry records. Each stage of the modeling and validation is explained and illustrated.