Section: New Results

Geometric model for shape deformation

Participants : Elisa Berrini, Bernard Mourrain.

In [13], we describe a new parametric modeller for an automatic shape optimization loop. The modeller enables the generation of shapes by selecting a set of design parameters that controls a twofold parameterization: geometrical – based on a skeleton approach – and architectural – based on the experience of practitioners, to impact the system performance. The resulting forms are relevant and effective, thanks to a smoothing procedure that ensures the consistency of the shapes produced.

The skeleton consists of a set of B-Spline curves composed of a generating curve and section curves. The deformation of the shape is performed by changing explicit parameters of the representation or implicit parameters such as architectural parameters. The new shape is obtained by minimizing a distance function between the current parameters and the target parameters in combination with a smoothing term to ensure shape consistency. Finally, a 3D surface is reconstructed around the skeleton with an iterative method handling multi-patches and boundary constraints.

Thanks to this approach, architects can directly use a CAD-model based on NURBS representations in the modeller tool that allows a straightforward modification of the initial design to improve performance. The methodology developed can be applied to any shape that can be described by a skeleton, e.g. hulls, foils, bulbous bows, but also wind turbines, airships, etc.

As application, we consider the optimization of the shape of a bulbous bow. The modeller is linked to the RANSE-CFD solver FINE/Marine. The aim is to reduce the total drag of the hull with variation of its bulbous bow shape.