Numerical Study of the Effect of Angle and Location of the First and Second Steps on the Performance of Planing Hull and Their Optimization Using the Taguchi Statistical Method

Providing steps at the bottom of a high-speed craft could decrease the resistance and enhance the longitudinal stability by dividing a single pressure hump into several ones and extending the hydrodynamic pressure towards aft of the vessel. In the present paper, the effects of the fore and aft steps’ locations and angles on double-stepped hulls are investigated systematically via a numerical approach. The parent model investigated in this study is a model of a high-speed recreational craft called Cougar, with a 1 : 5 scale. The three-dimensional analysis of the model is conducted via the finite volume method, and the free surface is tracked using the volume of the fluid technique. The computational domain is discretized by the overset technique, and the calculations are validated via experimental data. Overall, 27 numerical tests designed by the Taguchi experiment design method are simulated, and the resistance, trim, and rise-up values are calculated at 8 to 10 m/s speeds. The findings support the notion that the resistance increases by increasing the distance between the fore step and vessel stern. In addition, increasing the distance between the aft step and vessel stern and the increase of the angle of the fore step leads to reducing the vessel resistance. However, the results showed that finding a sensible relationship between the angle of the aft step and resistance requires more investigation. The findings revealed that the interactional effects between the angles of the aft and fore steps are the most considerable among all studied interactional effects. Among the all studied configurations, the lowest resistance was experienced by the model with an aft step at 25% of the vessel’s length to the stern, having an angle of 150°, and a fore step at 40% of the vessel’s length to the stern, having an angle of 180°.