Chapter 6 - Other shell and plate geometries

Abstract

Recent developments in the structure of submersibles have led to consideration of pressure hull geometries other than spherical. The prolate spheroid offers, in certain circumstances, some advantages over the sphere, in particular ease of arrangement of interior systems, improved hydrodynamic characteristics, and reduced susceptibility to initial geometric imperfections. The chapter provides a rational analysis of instability of a prolate spheroidal shell, which employs the coordinate system for the shell and considered the buckling mode to consists of a single isolated indentation. Toroidal shells may serve to store compressed gas within a submersible. The toroidal configuration can, in certain circumstances, offer an attractive utilization of space not found for more conventional shapes such as cylindrical or spherical. Toroidal shells may be of circular or non-circular cross-section, constant or variable wall thickness. Circular plates, usually with a concentric circular hole, are often found in submersibles. They serve to strengthen a cylindrical pressure hull and offer a point of attachment for various optical or electronic or electric sub-systems carried inside the vehicle. The hydrostatic loading on the cylindrical hull is transmitted to the circular plate by means of compressive radial forces acting at the outer boundary of the plate and directed toward the longitudinal axis of the cylinder, and bending moments acting on the outer circular edge of the plate representing interaction between the flat plate and the cylindrical shell.