The paper presents an assessment of the use of porous plates as motion damping devices. The first part sets the concept in the context of the work of other investigators studying the characteristics of porous devices and of those researching the use of bilge keels. The idea of porous bilge keels is then discussed in relation to the performance that might be expected of them on the basis ofvortex based theoretical predictions. The second part of the paper presents the results of an experimental study into the use of porous bilge keels as damping devices. One set of experiments was carried out in a wave basin on a turret-moored tanker and a deep wall-sided barge of square water plane area similar to that of the BARBOX concept The tanker was tested with a set of solid and a set of porous bilge keels. The barge was tested with four sets of keels, two of them solid and two of them precious. The programme included natural decay tests and tests in regular waves and in random seas. A further set of tests, carried out as part of an ongoing project, were conducted on porous plates in an oscillating U-tube water tunnel The behaviour of porous plates is shown to be consistent with predictions and they are demonstrated to be more effective damping devices than solid ones in specified flow regimes.
There is a long history of the use of flat plates in controlling the motion of bodies immersed in fluids, or the motion of fluids in containers. Obvious examples are the use of bilge keels to reduce roll motions and of baffles to moderate the effects of liquid sloshing.
