Optimal design of cylindrical shells for enhanced buckling stability: Application to supercavitating underwater vehicles

The static and dynamic stability of supercavitating vehicles is investigated. The vehicles are modeled as thick shells, using nine-node iso-parametric shell elements. The model allows the prediction of the behavior of shells of non-uniform thickness, and it is formulated to account for the presence of circumferential stiffeners. The considered buckling loads include compressive forces corresponding to propulsion and drag at the nose of the vehicle, and a concentrated axial force corresponding to the drag experienced by the vehicle on its afterbody. The latter is modeled as a time-dependent force, varying harmonically in time.The stability performance of plain shells is compared to those of tapered and stiffened shells. The tapered and stiffened configurations are then optimized to enhance the overall stability characteristics of the vehicle, while minimizing the required added weight. The considered stability study highlights operating limits for the considered class of vehicles and suggests simple design solutions for their extension.