EXPERIMENTAL INVESTIGATION OF MOONPOOL SHAPES ON A SHIP WITH FORWARD SPEED

Sharanabasappa C.Sajjan 1, S.Surendran 2

1KLE Inst of Tech Hubli, Karnataka, India

2Indian Institute of Technology, Madras Chennai, TN, India

DOI: DOI: 10.1515/aon-2019-0015

ABSTRACT

A moonpool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch. A floating platform with a moonpool is subjected to different forces due to sloshing and movement of the entrapped fluid in it, while the body is subjected to environmental loads like waves, winds, currents etc.,. Inside a moonpool considerable relative motions may occur, depending on shape and depth of the moonpool and the frequency range of the waves to which it is exposed. The vessel responses are entirely different in zero and non-zero Froude numbers. Later situation is paid attention in this study. There will be different water column elevations in the moonpool depending on the shapes. Two modes of responses are possible based on the shape of the moonpool viz., piston mode for square and sloshing mode for rectangular shape. An aspect ratio of 1:1 for square, 1:1.5 and 1:2 in case of rectangular shapes is considered during experimentation. Circular shaped moonpool is also tested for finding the response. The vessel is initially tested in a towing tank with different drafts and speeds based on Froude scaling. The different modes of oscillations of water column are measured using wave gauge and the vessel resistance is also studied, with and without moonpool. The water column elevation in moonpool may provide better insight to the designer to consider operational and safety parameters.

KEYWORDS

Drillship, Underwater exploration, sloshing, frequency range, Froude number

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