2 Answers

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answered May 23, 2015 by gagonza (3,020 points)

In order to determine the viscous damping due to the bilge keels, the results of numerous tests performed for the past 25+ years from Maritime Research Institute Netherlands (MARIN) have been used to provide a formula relating the variance of the roll velocity, the bilge keel dimensions, the main particulars of the vessel and the loading conditions to the amount of additional damping.

The formula to determine the additional linearized viscous roll damping based on the Root Mean Square of the roll velocity is given by:

0 votes
answered May 23, 2015 by gagonza (3,020 points)
In order to determine the amount of additional roll damping in a given sea condition, an iteractive procedure has to be followed until the damping and the variance of the roll velocity are in mutual correspondence.

Although common practice is to determine the viscous damping for all wave directions based on the governing beam sea, this may lead to non-conservative added damping for the other wave directions. Therefore, in order to assess the amount of additional roll damping due to the bilge keels for every on-site loading condition, the iterative procedure was applied to each wave energy spectrum and wave heading giving the maximum roll significant single amplitude for each environmental conditions.
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