Investigating the effect of underlying angle, width, and number of spray rails on the performance of planing hull and their optimization using the Taguchi method

Resistance reduction is one of the main goals in designing high-speed vessels to achieve higher speeds. The wetted surface caused by water spray is one of the main parts of the hydrodynamic resistance in high-speed vessels. In this research, the geometrical characteristics of the spray rail, including the underlying angle, width, and number of spray rails were changed to evaluate their effects on the hydrodynamic behavior of the vessel using computational fluid dynamics (CFD). Validation of the numerical simulation has been done with the performed tests in the NIMALA towing tank. The Taguchi method is used to optimize the geometry of the spray rail by specifying 18 different models each of them containing two modes (the the direction of chine and parallel with keel) to be simulated according to its design of experiment method. The results show that the underlying angle and the number of spray rails have a direct relationship with the increase in the Froude number of the vessel. Also the width of the spray rail has an inverse relationship with the increase in the Froude number. Also, it has been found that the spray rails parallel to the keel have a more constructive effect on hydrodynamic performance and longitudinal stability of the vessel compared to the spray rails in the direction of the chine.