Parametric design of an unmaned hull with triangular lift surface

An unmanned hull with triangular lift surface featured in good seakeeping and high speed is distinguished from conventional V-shaped planing hull in its unique hull form. Well-designed hull form is of vital significance to the hydrodynamic performance of planing hull, which requires an efficient and effective design procedures including modeling and modifying the hull surface. In this paper, a systematic uniform modeling method is established for an unmanned hull, which integrates the generation and modification of the hull with parametric representation technique. The hull is mainly divided into two parts by the chine. The lower part under the chine is unique in its triangular lift surface with sharp deadrise angle and a step afterward. While the upper part above the chine features in flared wavepiecing from stem to stern. Each part can be modeled by decomposing the surface geometry into control curves including the boundary lines as well as significant contour lines. These control curves can be produced by B-spline curves and surfaces defined with constraints and control parameters. For a typical wave-piecing planing hull, these control curves are the center, deck, bow, shoulder, triangular bottom and stern lines. Typical constraint characteristics are the position, slope, enclosed volume and centroid. The control parameters can manipulate the shape of the ship hull not only in principle dimension including length, beam and height but also local dimension such as the bilge radius, dead rise angle and bow size, which adds to the physical implications from the design point of view. Given the displacement and dimension constraints, a series of parametric hull designs are generated through parametric variation of NURBS, which provides the necessary geometry inputs for further performance optimization of the hull.