Parametric design of ship hull forms with a complex multiple domain surface topology

This thesis aims at contributing to the field of ship design by introducing a new design methodology of ship hull forms with a complex multiple domain surface topology. In practice, the general ship hull geometry with a parallel midbody and bow and stern bulbs contains various types of complex surface topology with regular, irregular and hybrid meshes, particularly in the bow and stern part, and hence a single domain surface representation is not sufficient. To alleviate this problem, we suggest the use of multiple domain surface representations and introduce a new method for representing complex ship hull forms by multiple domain B-spline surfaces accounting for their topological arrangement, where all subdomains are fully defined in terms of form parameters, e. g., positional, differential and integral descriptors. Form parameters for the curve and surface design constitute the input to the geometrical modeling process that is viewed as an optimization problem in which fairness criteria are employed as measures of merit and additional geometrical information, e. g., interpolating offset points as well as form parameters are treated as design constraints. B-spline curves and surfaces are chosen for all mathematical representations and form the output, and therefore the B-spline control points are the unknown free variables to be computed. Fairness criteria and form parameters can be exibly selected to best-suit a particular modeling problem. A complex ship hull geometry is decomposed into free-form elementary models and blending surfaces which are symmetric to the center plane. Free-form elementary models in this thesis are forebody, afterbody and bulbs, and are generated by skinning based on parametric design. To generate skinning surfaces with at regions and closed sections, we have developed new B-spline approximation methods based on an optimization technique. For the construction of complex hull forms, these free-form elementary models are united by Boolean operation and blending surfaces in compliance with the sectional area curve (SAC) of the whole ship. In this thesis this new design process is called Sectional Area Curve-Balanced Parametric Design (SAC-BPD). In principle, it is based on the balance of volumes and volume-moments of free-form elementary models and blending surfaces to design the envisioned ship hull form. All modeling techniques are described in detail. To prove their applicability to complex ship hull design, we show three demonstration examples, featuring a container carrier Ville de Mercure, a KRISO-container ship and a KRISO-tanker.