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Heave added mass and damping of a suction can in proximity to the sea floor
Citation
Roe, T and MacFarlane, GJ and Drobyshevski, Y, Heave added mass and damping of a suction can in proximity to the sea floor, Proceedings of 27th International Conference on Offshore Mechanics and Arctic Engineering, 15 - 20 June 2008, Esroril Portugal, pp. [OMAE2008-57172].. (2008) [Refereed Conference Paper]
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Copyright Statement
Copyright © 2008 by ASME
Official URL: http://www.asme.org/
Abstract
Suction cans are usually deployed by the crane of a
construction vessel, which must have adequate capacity to
withstand the dynamic hook loads generated by motions of the
vessel and heave response of the suction can. Before the
structure is placed on the sea floor, it must be positioned above
the target location; in this phase the suction can is manoeuvred
into position being suspended in proximity to the sea floor.
Hydrodynamic properties of the structure in the positioning
phase are different from those experienced during the decent,
due to the effect of the bottom proximity. As a result, the
dynamic hook loads experienced in this phase may be also
different from the deep water condition.
The objective of this study is to quantify these effects; in
particular the impact of the bottom proximity on the heave
added mass and hydrodynamic damping. The added mass and
damping of a 6-metre diameter suction can, of dimensions
typical for Australian North West Shelf conditions, have been
determined by testing a I: 10 model in the 4.2 m deep water
tank of the Australian Maritime College. Free decay tests were
conducted at several heave frequencies, and the heave added
mass and damping determined. Four clearances of the model
from the sea floor were investigated ranging from 1.20 to 0.20
of the can height. For each clearance, several sizes of open
hatches were examined, by testing the model with 3 pairs of
hatches of various diameters, with up to 4.8% of the relative
area open.
Model tests demonstrate that the heave added mass and
damping increase as the suction can approaches the sea floor.
Increase in added mass is found to be within 20% of its deep
water value, and is made less pronounced by opening hatches of larger area. Linear (proportional to velocity) hydrodynamic
damping also increases moderately as the under-bottom
clearance reduces. Quadratic (proportional to velocity squared)
damping is strongly affected, especially at very small
clearances, with drag coefficient reaching unusually high
values; this is attributed to substantial constraining effect of the
bottom, which causes increasing flow velocities past the lower
edge of the can. Results of the tests are presented, and their
application for the installation lift analysis is discussed
Item Details
Item Type: | Refereed Conference Paper |
---|---|
Research Division: | Engineering |
Research Group: | Maritime engineering |
Research Field: | Marine engineering |
Objective Division: | Transport |
Objective Group: | Water transport |
Objective Field: | International sea freight transport (excl. live animals, food products and liquefied gas) |
UTAS Author: | MacFarlane, GJ (Associate Professor Gregor MacFarlane) |
ID Code: | 53988 |
Year Published: | 2008 |
Deposited By: | NC Maritime Engineering and Hydrodynamics |
Deposited On: | 2009-02-04 |
Last Modified: | 2012-03-21 |
Downloads: | 4 View Download Statistics |
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