KITE FOIL MAST VENTILATION STUDY

Considering the evolution of the racing sailing yacht in the last decade, we have seen the increasingly extensive use of hydrofoil systems able to support and fly boats over the free surface. The great advantage of these systems is to increase comfort in navigation and to reduce drag. Unfortunately, these systems, in addition to the great advantages in terms of efficiency, bring with them problems linked above all to their functioning between two fluids, air and water. In fact, the hydrofoils systems are subjected to natural ventilation and cavitation. In particular, the phenomenon of ventilation is typically present when there is a surface piercing strut that includes air and water in particular conditions of use; the geometry and physical conditions allow the creation of a region with a lower pressure than the atmospheric one, which then causes a cavity connected to the external environment. Ventilation is therefore an important phenomenon to be taken into consideration when designing hydrofoil appendages for racing boats and understanding the phenomena is fundamental for the success of the project. Using the numerical simulation, in this case CFD, it is possible to investigate the favorable conditions of formation of the ventilated cavity for the conditions of use of a foil appendage. In order to use CFD as a forecasting and design tool, it was necessary to carry out a validation campaign using a reference benchmark; the results of the investigation made it possible to fine-tune the CFD tool to be able to predict the phenomenon of ventilation in a robust manner. By applying the method developed on a kite foil surface piercing strut case, it was possible to estimate the performance differences of 2D sections and planform shapes to understand the ventilation tolerance of new candidate designs for construction. Furthermore, it was possible to visualize the ventilation trend by means of numerical indices able to visually show the behavior of one design compared to another. These methods could be used together with low fidelity methods (VLM, panel code, lifting line) to build response surfaces or surrogate models to be used in performances prediction..