engleski

Analysis of the Ventilated Flow on a Surface-Piercing Hydrofoil

Ventilation is a multi – phase flow characterized by the suction of gas or a mixture of gases, most commonly the air from the free surface, within the fluid flowing around the fully or partially immersed hydrofoil. Uncontrolled or unexpected formation of a ventilation cave can have very harmful effects on the performance of the vessel. Ventilation can lead to large and sudden changes in the force acting on the body. This leads to dynamic instability in navigation and structural problems on the vessel itself, since such events occur regularly under unexpected loads. In some cases, a change in lift force at high speeds was observed. Any sudden change in the lift force could cause swinging or overturning the vessel. Numeca FineMarine Computational Fluid Dynamics – CFD software dedicated to naval purposes, numerically analyzed the phenomenon. In the first step, the procedure and the key variables for the CFD analysis have been defined, after conducting the investigation, CFD simulations provided the results to an extent that is consistent with the experimental results. Thereafter, a series of simulations were performed for different velocities and angles of attack, whereby the different influencing parameters determined in the first step were varied. The aim of the work was to analyze the occurrence of ventilation inception on surface – piercing hydrofoil on a fast ship and to propose a modified form of hydrofoil with fences that would reduce the possibility of ventilation for the designed speed.

high-speed craft, hydrofoil, CFD, multi-phase flow, ventilation

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