THE HYDRODYNAMIC IMPACT OF INTERCEPTORS AND BOW FENDER ON A HIGH SPEED DISPLACEMENT VESSEL

Substantial financial resources are dedicated to the design and research of new series of vessels, ensuring compliance with increasingly stringent emission regulations imposed every 5 years. With each design iteration, the final product becomes more energy efficient with a better hull shape, better fuel consumption and improved adaptability for a wide range of applications. For existing vessels, the challenge of increasing energy efficiency is constrained due to lower market demand for vessel modification, limited flexibility in comparison to new projects and budget limitations. In the present paper, the objective is set to analyse and improve the hydrodynamic flow for a small high speed displacement vessel, with the implementation of solutions that bring small changes in vessel design. Among the available options, active interceptors were chosen for further investigation. Mounted in the transom, this control system deploys a plate as an extension of the transom, generating a pressure area that creates a vertical force, thereby assisting in the correction of the trim angle. The investigation used Computational Fluid Dynamics (CFD) method, due to the speed and cost-effectiveness, when compared to an experimental method. To capture the viscous flow development around the hull, the Reynolds-averaged Navier-Stokes (RANS) equations were solved, and the free surface was discretized based on the volume of fluid. To establish a baseline for comparing the impact of the interceptor, a set of seven numerical simulations was conducted for the bare hull of a high-speed displacement pilot boat. Subsequently, the initial results revealed that, within the range of Froude number between 0.19 and 0.74 corresponding to the ship speed regime, the hull has a trim by the stern, generating a significant bow wave and causing a spray effect on the fore. Based on these first results, several solutions were modeled to improve the flow at the bow at a higher speed. With an average improvement of 1.3% in total resistance and reduced spray effect, the selected configuration, comprising a pipe and a fender, was further considered in the analysis. For the hull with the proposed bow configuration, in the transom area, the interceptor blade was extended across the entire transom edge. The effect on the flow was systematically investigated for different interceptor heights, which led in changes of trim angle and total resistance.