Filippo Cucinotta

Sail Plan Parametric CAD Model for an A-Class Catamaran Numerical Optimization Procedure Using Open Source Tools

A geometric tool for a catamarans sail plan and appendages optimization procedure is descripted. The method integrates a parametric CAD model, an automatic computational domain generator and a Velocity Prediction Program (VPP) based on a combination of sail RANS computations and analytical models. The boat performance is obtained, in an iterative process, solving the forces and moment equilibrium system of equations. Hull and appendages forces are modelled by analytical formulations. The closure of the equilibrium system is provided by the CFD solution of the sail plan. The procedure permits to find the combination of appendages configuration, rudders setting, sail planform, shape and trim that maximize the VMG (Velocity Made Good). A significant effort was addressed to the selection and evaluation of open-source tools to be adopted in the implementation of the method. The geometric parametric model, which is the core of the procedure, was object of particular attention. The FreeCAD geometric modeller was selected for this task. The sail shapes candidates are automatically generated, within the optimization procedure, by Python scripts that drive FreeCAD to update the geometry according to the variables combination. A very flexible model, able to offer a very wide space of variables, was implemented. This paper describes the implemented geometric model and the environment in which is included.

A preliminary method for the numerical prediction of the behavior of air bubbles in the design of Air Cavity Ships

Air-cavity ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel’s hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship’s bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, considering as parameters the critical mass of air, the rising speed and aspect ratio of the bubble. Then it is evaluated the interaction bubble-flat plate in order to obtain a reliable prediction of the behavior of air bubbles under the hull.

A comparative Life Cycle Assessment of utility poles manufactured with different materials and dimensions

In the production of utility poles, used for transmission, telephony, telecommunications or lighting support, for many years, the steel has almost entirely replaced wood. In recent years, however, new composite materials are a great alternative to steel. The questions are: is the production of composite better in terms of environmental impact? Is the lifecycle of composite pole more eco-sustainable than lifecycle of steel pole? Where is the peak of pollution inside the lifecycle of both of technologies? In the last years, in order to deal with new European polices in environmental field, a new approach for the impact assessment has been developed: the Life Cycle Assessment. It involves a cradle-to-grave consideration of all stages of a product system. Stages include the extraction of raw material, the provision of energy for transportation and process, material processing and fabrication, product manufacture and distribution, use, recycling and disposal of the wastes and the product itself. A great potentiality of the Life Cycle assessment approach is to compare two different technologies designed for the same purpose, with the same functional unit, for understanding which of these two is better in terms of environmental impact. In this study, the goal is to evaluate the difference in environmental terms between two different technologies used for the production of poles for illumination support.

Optical measurements and experimental investigations in repeated low-energy impacts in powerboat sandwich composites:

In the world of powerboats competition, the high-performance sandwich-structured composites have completely replaced traditional materials. During the competition, the structure of this kind of ships is subjected to repeated impacts. It is then fundamental to understand the damage evolution in order to select the most appropriate materials and increase safety issues. The present study is aimed at analysing the behaviour of sandwich-structured composites undergoing repeated low-energy impacts. Three different materials have been analysed. Two are sandwich-structured composites used for the cockpit of offshore powerboats and differing only by the core cell thickness. The third material is composed only by the skin of the same sandwich structures, without the core. Impacts were made at three different energy levels: 15, 17.5 and 20 J. In addition to the parameters typically used for the assessment of the impact damage, a new damage assessment has been carried out by means of three-dimensional optical measurements of the imprinted volumes resulting from the impact events. This approach has allowed the definition of a correlation between the imprinted volumes and the number of impacts, until the complete perforation, for each single specimen. Finally, thanks to usual indexes and the imprinted volumes, some considerations are developed about the influence of the core cell thickness in powerboats design.