Abstract

The idea for the Submerge Trimaran hull concept (STR) presented on this paper it’s originated from the Nautilus System (NTLS) stabilizers for motions and currents, which is based on a 2 sides linear approximation using Keulegan-Carpenter number (KC) to obtain the roll motion damping coefficients from the roll 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 significant 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 GM_T 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 that, 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 vessel hull form capability to generate waves. Therefore, the Submerge Trimaran hull (STR) is a NTLS variation to be applied in conventional vessels with advance velocity to obtain a reduction to the roll amplitudes by increasing the potential damping while restricting the transversal oscillation flow by doing a hull modification from a perspective that considers as a base a hull immerse in a steady state flow regime (lower KC numbers) that´s has the effect of varying the natural roll period, extending the GM_T (STR) linear variation in the transverse stability envelope for a broader range of sea state, as more external excitation energy it´s require to obtain the same conventional hull roll amplitude, as part of the main motivation for the STR hull concept development idea, which is to achieve an overall improvement to a vessel sea keeping performance to cross ocean routes efficiently with energy savings and decabornization.

Keywords: Nautilus System (NTLS); Submerge Trimaran Hull (STR); Roll Motion Control

References

1. Antonio C Fernandes and Sergio AB Kroff. “Nonlinear Rolling of an FPSO with Larger-Than-Usual Bilge Keels”. Offshore Mechanics and Arctic Engineering (OMAE) (1998a).
2. Antonio C Fernandes and Sergio AB Kroff. “Ad hoc Dinghy for Transverse Balance Control of FPSO-type Production Systems”. Congress of the Brazilian Society of Naval Engineering (Sobena), Rio de Janeiro (Portuguese) (1998b).
3. Antonio C Fernandes and Sergio AB Kroff. “Ad hoc Bowline for Transverse Balance Control of FPSO-type Production Systems”. Ibero-American Congress of Naval Engineering (Portuguese) (1998c).
4. Bearman PW., et al. “Forces on Cylinders in Viscous Oscillatory Flow at Low Keulegan Carpenter Numbers”. Journal of Fluid Mechanics Vol. 154m (1985) pp337.
5. Faltinsen OM. “Sea Loads on Ships and Offshore Structures”. Cambridge. Press, UK (1990).
6. Blagoveshchensky SN. “Theory of ship motions”. Iowa Institute of Hydraulic Research (1962).
7. Principles of Naval Architecture (PNA) Vol III. SNAME.
8. Lloyd ARJM. “Sea keeping Ship Behavior in Rough Weather”. Ellis Horwood Limited (1989).
9. Martin A Abkowitz. “Stability and Motion Control of Ocean Vehicles”. MIT press (1969).
10. RED Bishop. The dynamics of marine vehicles and structures in waves (1975).
11. JN Newman. “Marine Hydrodynamics”. MIT Press (1977).
12. Program SCORES - Ship Structural Response in Waves User Manual.
13. Sergio AB Kroff. “Nautilus System (NTLS) concept Introduction”. Note Book 1 (2020).
14. Sergio AB Kroff. “NTLS Submerge Trimaran Hull (STR) concept” Note Book 4 (2021).

Citation

Sergio AB Kroff. “An Introduction to STR Hull Concept". Clareus Scientific Science and Engineering 2.1 (2025): 08-22.

Copyright

© 2025 Sergio AB Kroff. Licensee Clareus Scientific Publications. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.