A T-splines-based parametric modeller for computer-aided ship design

We present a T-splines-based parametric modeller (TshipPM) for complex ship forms, capable to provide smooth geometries at a low cost in comparison with parametric modellers (PM) employing the standard NURBS representation. For a given set of design parameters, we measure complexity via the number of degrees of freedom needed, i.e., the number of control points for representing the geometry of each instance. TshipPM, presented here, is an improved version of that in [1], enabling more flexibility for representing challenging areas of the ship-hull geometry, such as bow, stern and the transition areas from mid-ship towards forward and afterward perpendiculars. In this connection, the associated control-cage construction process, which maps the user-defined parameters to the control points of the T-splines representation, is described in detail for the forward transition part of the hull. Furthermore, TshipPM delivers instances lying in the proximity of a parent hull, with deviation measured in terms of moments (volume, volume centroid, moment of inertia) and sectional area curve (SAC) distribution, which are used in ship design. Finally, TshipPM is compared against a commercial PM, CAESES®, opting for its NURBS functionality, with both PMs’ outputs compared against a parent container-ship hull already used in the literature for CAD and CFD benchmarking purposes. The employed comparison criteria include the common external parameters, the previously mentioned moments, the sectional area curve, Gaussian and sectional curvatures for assessing surface and curve fairness, respectively, and the Hausdorff distance for measuring the geometric distance between two hulls.