Minimizing Buoyancy Factor of Metallic Pressure-Hull Subjected to Hydrostatic Pressure

Abstract

To increase the payload, reduce energy consumption, improve work efficiency and therefore must accordingly reduce the total hull weight of the submersible. This paper introduces a design optimization process for the pressurehull of submarines under uniform external hydrostatic pressure using both finite element analysis (FEA) and optimization tools. A comprehensive study about the optimum design of the pressure hull, to minimize the weight and increase the volume, to reach minimum buoyancy factor and maximum operating depth minimizing the buoyancy factor (B.F) is taken as an objective function with constraints of plate and frame yielding, general instability and deflection. The optimization process contains many design variables such as pressure-hull plate thickness, unsupported spacing, dimensions of long and ring beams and finally the elliptical submersible pressure-hull diameters. The optimization process was conducted using ANSYS parametric design language (APDL) and ISIGHT. The Multi-Island Genetic Algorithm (G.A) is considered to conduct the optimization process. Additionally, parametric analysis is done on the pressure hull to examine the effect of different design variables on the pressure-hull design. As a result, the B.F of the proposed optimal model is reduced by an average of 31.78% compared with Reference Model (RM). Maximum von Mises stress is reduced by 27% as well. These results can be helpful for submarine pressure-hull designers.