An Introduction to Nautilus System Stabilizers FSE Concept

The Nautilus System (NTLS) concept (stabilizers for motions and currents) presented on this paper is based on a 2 sides linear approximation using Keulegan-Carpenter number (KC) to obtain the roll motion damping coefficients from the decay test of high block coefficient vessels with bilge keels and from which,  it´s possible to understand that, the damping that’s rules the roll motion of high block coefficient vessels with appendages is more efficient at lower oscillations amplitudes (roll decay test latest cycles), it´s mean at lower KC numbers (KC<) were the steady state 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 (drag forces), meaning the action of appendages such as bilge keels is less effective in reducing roll amplitudes, as results of the turbulence derived from the  back and forth oscillating   flow being the main source for the energy dissipation the hull form capability to generate waves. Therefore, the Nautilus System (NTLS) is a proposal for a roll motion control and directional stabilizer appendages with neutral or positive buoyancy capability and with the hydrodynamics properties to improve the transversal stability and directional stabilization (weathervane) from a perspective of lower KC numbers regimes by contributing with an amount of additional mass into the hull hydrodynamics system to increase  the vessel resistance to roll and therefore, extending the transversal stability linear GM_T variation assumption for a broad range of sea states as more external excitation energy, it´s require to  achieve the same roll amplitudes as before the modification, being the Free Surface Effect (FSE) concept a NTLS variation conceive from the perspective of considering the oscillation flow associated with roll motion like a free surface effect to be suppressed by adding at the hull base longitudinal NTLS devices distributed through the breadth (vertical keels), allowing floating system such as FPSO and high block coefficients vessels to improve the transversal stability and directional stabilization and therefore expanding the operational sea state field scenarios safety margin with energy savings and decarbonization.