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Metacentric height

About: Metacentric height is a(n) research topic. Over the lifetime, 219 publication(s) have been published within this topic receiving 1505 citation(s).
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11 Jul 2006-
Abstract: A wind energy conversion system optimized for offshore application. Each wind turbine includes a semi-submersible hull with ballast weight that is moveable to increase the system's stability. Each wind turbine has an array of rotors distributed on a tower to distribute weight and loads and to improve power production performance where windshear is high. As much of the equipment associated with each rotor as possible is located at the base of the tower to lower the metacentric height. The equipment that may be emplaced at the bottom of the tower could include a power electronic converter, a DC to AC converter, or the entire generator with a mechanical linkage transmitting power from each rotor to the base of the tower. Rather than transmitting electrical power back to shore, it is contemplated to create energy intensive hydrogen-based products at the base of the wind turbine. Alternatively, there could be a central factory ship that utilizes the power produced by a plurality of wind turbines to create a hydrogen-based fuel. The hydrogen based fuel is transported to land and sold into existing markets as a value-added "green" product.

93 citations

Journal ArticleDOI
B.J. Koo1, Moo-Hyun Kim1, Robert E. Randall1Institutions (1)
01 Dec 2004-Ocean Engineering
Abstract: Mathieu instability for a spar platform arises when there is a harmonic variation in the pitch restoring coefficients caused by large heave motion and the period of the heave motion is half of the pitch natural period. The pitch restoring coefficient can be represented by a function of the displaced volume and the metacentric height of spar hull. Due to heave motion, the displaced volume and the metacentric height of the spar platform change in time and this heave/pitch coupling can be represented by Mathieu’s equation. The objective of this study is to evaluate damping effects and hull/mooring/riser coupled effects on the principal instability. In the simulation, the heave/pitch coupling of the spar platform is considered using the modified Mathieu equation. The wave elevation effect on Mathieu instability is also investigated. The Mathieu instability of a practical spar platform is carefully checked by a series of systematic simulations and comparisons of many different scenarios. When heave resonance occurs at the heave natural period equal to half of the pitch natural period, Mathieu instability, a kind of lock-in phenomenon, actually arises to increase the pitch motion significantly. The available damping is found to be important in suppressing the instability. The results also show that the additional pitch restoring force from buoyancy-cans plays an important role in the spar Mathieu instability.

86 citations

01 Jan 1967-
Abstract: Linking Ship Stability and Ship Motions: Forces and Moments Centroids and the centre of gravity Density and specific gravity Laws of flotation Effect of density on draft and displacement Transverse statical stability Effect of free surface of liquids on stability TPC and displacement curves Form coefficients Simpsons Rules for areas and centroids Second moments of areas Calculating KB, BM and Metacentric Diagrams Final KG twenty reasons for a rise in G Angle of List Moments of statical stability Trim or longitudinal stability Stability and hydrostatic curves Increase in draft due to list Water pressure Combined list and trim Calculating the effect of free surface of liquids (FSE) Bilging and permeability Dynamical stability Effect of beam and freeboard on stability Effects of side winds on stability Icing allowances - effects on trim and stability Floodable and Permissible length curves Tabular and assigned Freeboard Marks Timber ship Freeboard marks IMO Grain Rules and angle of list Angle of Loll True mean draft The Inclining Experiment or Stability Test Effect of trim on tank soundings Drydocking and grounding Liquid pressure and thrust - Centres of pressure Ship squat Interaction Heel due to turning Rolling, pitching and heaving motions Synchronous rolling and Parametric rolling of ships List due to bilging side compartments Effect of change of density on draft and trim List with zero metacentric height The Deadweight Scale The Trim and Stability book The Calibration book soundings and ullages Simplified stability information A trim and stability pro-forma sheet Linking Ship Stability and Ship Strength: Bending of beams Bending of ships Strength curves for ships Bending and shear stresses

85 citations

Journal Article
Abstract: This paper describes latest collaborative researches between Japan and the UK on parametric roll resonance of a container ship in following and head seas with realistic modelling of restoring moment as a nonlinear function of wave steepness in experimental, geometrical and analytical approaches. Firstly, captive model experiments were conducted, and demonstrated that the Froude-Krylov prediction could overestimate the amplitude of its variation. Secondly, Poincare mapping technique applied to the numerical model with measured time-varying restoring moment was used for tracing stable steady states, and revealed symmetry-breaking, period-doubling, chaos and capsizing associated with parametric roll resonance. Thirdly, an averaging method was applied to the same numerical model, and confirmed good agreement with the Poincare mapping as well as subcritical bifurcation. Finally, by utilising the present numerical model and methodology, it is shown that a requirement of higher metacentric height does not always improve safety for capsizing associated with parametric roll resonance.

63 citations

Journal ArticleDOI
01 Jul 2003-Ocean Engineering
Abstract: The prediction of ship stability during the early stages of design is very important from the point of vessel’s safety. Out of the six motions of a ship, the critical motion leading to capsize of a vessel is the rolling motion. In the present study, particular attention is paid to the performance of a ship in beam sea. The linear ship response in waves is evaluated using strip theory. Critical condition in the rolling motion of a ship is when it is subjected to synchronous beam waves. In this paper, a nonlinear approach has been tried to predict the roll response of a vessel. Various representations of damping and restoring terms found in the literature are investigated. A parametric investigation is undertaken to identify the effect of a number of key parameters like wave amplitude, wave frequency, metacentric height, etc.

52 citations

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No. of papers in the topic in previous years

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Topic's top 5 most impactful authors

Yonghwan Kim

6 papers, 35 citations

Adrian Biran

5 papers, 10 citations

Mogens Blanke

4 papers, 95 citations

Naoya Umeda

4 papers, 80 citations

Hezhen Yang

4 papers, 18 citations