Tourist submersibles are a new class of underwater vehicles where new materials and innovative structural concepts are used. Because of the lack of experience with these innovative vessels, prescribed rules of classification societies are not directly applicable in their structural design. Thus, a novel design-by-analysis approach, as given in the Boiler and Pressure Vessel Code of ASME, is employed for dimensioning structural components. Design-by-analysis stands for a consistent set of loads, boundary conditions, modelling principles, failure modes, and safety factors if the finite element analysis is performed instead of using rule formulas. The approach has been used until now in the structural design and optimization of unconventional pressure vessels, while in this paper it is for the first time employed in structural design of the underwater vehicle. This study can serve as guidance for future applications of design-by-analysis in the development of the innovative structures exposed predominantly to the pressure loading.

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We present an algorithm for the fully automatic generation of a class-compliant mesh for ship structural analysis. Our algorithm is implemented as an end-to-end solution. It starts from a description of a geometry and produces a class conforming surface mesh as a result. The algorithm consists of two parts, the automatic geometry refinement and the preconditioned Delaunay frontal quad dominant mesh generator. A geometry is described by a dictionary of elements and it contains points, rods, plates, and openings. A dictionary can contain modeling errors such as unintended overlaps or an unintended loss of connectivity between elements. The main contribution of the paper is the automatic geometry refinement algorithm and the virtual stiffener procedure designed to control the local mesh orientation of a marching front meshing algorithm. The geometry refinement algorithm guarantees that the output dictionary will be such that intersections of the boundary edges of plates are guaranteed to be nodes of any mesh generated by tessellating such geometry. The algorithm is implemented in Python, using the open-source Gmsh system together with the Open CASCADE kernel which is used to implement the automatic geometry refinement. We present several benchmark models from an engineering practice to illustrate our claims as well as to benchmark the efficiency of the various stages of the processing pipeline.

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