Evaluation and quantification of randomness in free-fall trajectories of instrumented cylinders

As part of a field experiment designed to contribute to the Navy´s effort to improve its capability to model and predict depth of burial of anti-ship mines in mud seafloors, the trajectory, velocity and orientation of a 1,100-kg cylinder were observed during 21 free-fall trials in a field setting. Extreme values and distribution of linear and angular velocity components as well as orientation throughout the water column and, in particular, on impact with the sediment are described. The findings indicate that a critical depth (of about 4 m, for the cylinder configuration tested) appears to exist beyond which the influence of the release conditions is insignificant. All the different nose shapes tested resulted in similar mean values of velocities and orientations. Cylinders with chamfered noses appear to possess the highest variability in these parameters, complicating the mine burial modeling effort. Periodic nature in the variation of several parameters was observed and its changes with cylinder geometry presented. Overall implications on the impact burial prediction analysis of heavy, cylindrical shapes are discussed.