Metacentric height

About: Metacentric height is a research topic. Over the lifetime, 219 publications have been published within this topic receiving 1505 citations.

Roll of a Ship in Astern Seas—Metacentric Height Spectra

Abstract: Unstable roll motions can be a problem in astern seas because of fluctuation in the metacentric height. A formulation for the fluctuations in metacentric height is derived in terms of the distribution of instantaneous wave elevations and wave elevation accelerations along the ship's hull. This formulation is manipulated to derive an equation relating the spectrum of metacentric height fluctuations to the point spectrum of a long-crested, astern sea. Numerical simulations are performed to demonstrate the validity of the method. The singular behavior of the metacentric height spectrum at a frequency of g/4U has implications with respect to the safe operating speeds of a ship in random astern seas.

Roll of a ship in astern seas: response to GM fluctuations

Abstract: An effect of astern seas on a ship is to produce fluctuations in the metacentric height (GM) of the ship. GM fluctuations are shown to produce an effect analogous to a reduction in the roll damping. Roll damping reductions are predicted for two extreme types of random GM fluctuations: wide-band and narrow-band random processes. Numerical simulations of the roll motion of a ship with realistic random GM fluctuations are used to compare with the predictions of damping reduction. Good agreement is found. Implications of a reduced roll damping are discussed.

Satellite separator platform (ssp)

Abstract: A floating platform with motion characteristics for offshore deepwater developments with vertical axial symmetry and decoupling of hydrodynamic design features. A motion-damping skirt (120) is provided around the base of the hull (1), which is configured to provide ease of installation for various umbilicals and risers. A retractable center assembly (300) is used in a lowered position to adjust the center of gravity and metacentric height, reducing wind loads and moments on the structure, providing lateral areas for damping and volume for added mass for roll resistance. The center assembly (300) is used to tune system response in conjunction with the hull damping skirt (120) and fins (121). The center assembly (300) also includes separators (350) below the floating platform deck which serve to add stability to the floating structure by shifting the center of gravity downward, the separators (350) capable of being raised and lowered vertical separators alone or as a unit.

Eight man rowing shell

Abstract: Eight man rowing shells in lightweight and super heavyweight configurations have an elongated hull with a bow and stern and a smoothly tapered hull surface therebetween. The hull surfaces have particular cross-sections below the waterline at stations spaced along the hull waterline. Other parameters for both super heavyweight and lightweight hulls are provided such as waterline length, entry and exit angles, maximum beam, maximum draft, and metacentric height. In both configurations, the hull itself may be made of a laminate of a fiber composite skin over a core, such as a carbon fiber/honeycomb laminate, or of natural materials such as wood.

Practical maneuvering simulation method of ships considering the roll-coupling effect

Abstract: In this study, a practical maneuvering simulation method is presented considering the roll-coupling effect by extending an ordinal simulation model (3D-MMG model) proposed by Yasukawa and Yoshimura (J Mar Sci Technol 20:37–52, 2015), and adding the motion equation of roll. The roll moment acting on the hull is estimated by multiplying the hull lateral force with the vertical acting point. With respect to the surge force, lateral force, and yaw moment, the derivative expression model is employed. Subsequently, hydrodynamic derivatives with the exception of the roll-related terms are obtained by a captive model test based on the 3D-MMG model. The roll-related derivatives and the vertical acting point of the hull lateral force are estimated by simple formulae constructed based on the experimental data of four ship models. To validate the proposed simulation method, turning simulations are conducted for a pure car carrier model with variations in the metacentric height $${\overline{\mathrm{GM}}}$$ and are compared with free-running model test results. The simulation method exhibits sufficient accuracy with respect to its practical use and is useful to conventionally predict turning motions by considering the roll-coupling effect.