An Introduction to Retro Bulb Concept

The idea for the Retro Bulb concept presented on this paper it’s originated from a linear approximation to obtain the roll motion damping coefficients from the decay test of high block coefficient vessels with bilge keels using Keulegan-Carpenter number (KC). Hence, from this analysis it is possible to understand that, the damping that’s rules the roll motion of high block coefficient vessels with appendages its more effective at lower oscillations amplitudes (roll decay test latest cycles), its mean at lower KC numbers (KC<) were the laminar flow regime is predominant and the GMT has a linear variation in the stability curve, which however didn’t occur for larger oscillation amplitudes (roll decay test initial cycles) were highest KC numbers (KC>) are relevant and therefore the appendages effectiveness such as bilge keels are neglected as results of the turbulence derived from the back and forth oscillating flow, being the main source for the energy dissipation the hull geometry. Therefore, taking into account this factors, from the Submerge Trimaran (STR) hull concept which proposes a modification to the submerge hull geometry by considering the flow produced by the roll motion (oscillatory flux measure by KC numbers) like a free surface effect to be contained by making a draft variation at the same displacement, in order to generate a potential damping increment (energy dissipation) to reduce the angle of list (roll motion amplitudes) and from which the Retro Bulb concept arise by doing a geometrical projection from a conventional vessel bulbous bow to the STR hull extended draft to obtain an additional mass increment into the systrem to reduce the angle of list (roll motion amplitudes) within the stability curve in which GMT varies linearly for a broad range of sea estate which allow navigate ocean routes more efficiently with energy savings and decarbonization.