Deterministic and Stochastic Predictions of Motion Dynamics of Cylindrical Mines Falling Through Water

Abstract

A physics-based computational model has been developed that is capable of reliably predicting the motion of a 3-D mine-shaped object impacting the water surface from the air, and subsequently, dropping through the water toward the sea bottom. This deterministic model [mine's six-degree-of-freedom dynamics (MINE6D)] accounts for six-degree-of-freedom motions of the body including unsteady hydrodynamic interaction effects. MINE6D allows for physics-based modeling of other hydrodynamic effects due to water impact, viscous drag associated with flow separation and vortex shedding, air entrainment, and realistic flow environments. To demonstrate the efficacy of the model, we compare deterministic MINE6D predictions with tank drops tests and field measurements. MINE6D captures the myriad of complex 3-D motions of cylindrical mines observed in field and laboratory experiments. For relatively simple straight motions, it obtains quantitative comparisons with the field measurements for the kinematics of mines freely dropping in the water including water impact and air cavity effects. In practical applications, the environments are often quite irregular, and the releasing conditions are also with uncertainties. To provide some guidance in understanding and interpreting statistical characterizations of mine motions in practical environments, we perform Monte Carlo simulation using MINE6D. These statistical results are not only the essential input for stochastic bottom impact and burial predictions of mines but also useful for the design of mines.