An experimental and theoretical investigation of shot cloud ballistics
This thesis is concerned with an investigation of the evolution in time and space of shot clouds. The shot cloud is produced by launching a number of spherical projectiles from a shotgun barrel. With limited detailed information on the distribution of pellets within a shot cloud generated from previous studies, a considerable part of the investigation is dedicated to the design and implementation of a measurement facility to acquire accurate experimental data. Opto- and acousto-electronics were employed to meet contractual and research requirements in generating timing and positional information on the distribution of pellets in a shot cloud travelling, typically, at transonic velocities. The nature of the measurement facility also allows three-dimensional graphical reconstruction of shot cloud outlines. From the experimental data statistical analysis on the distribution of pellets within shot cloud was performed. Theoretical models are introduced which describe the dispersion of pellets within a shot cloud as it develops in flight. The preliminary work involved the motion of a single sphere in free flight and with the experimental data the deceleration characteristics of pellets were determined. U sing this information a model was developed which predicted the development of the shot clouds from the point where the pellets become independent of one another. Finally, a stochastic model was developed to describe the behaviour of a shot cloud. The equation of motion of a single sphere was perturbed by the addition of a random force term, and the width and length of the cloud were determined by performing ensemble averages. The prediction of these theoretical models were then compared to the experimental data to assess their validity.