Damping effect of bilge keels with different aspect ratios

Jukka Pajala

Research output: Contribution to journalArticleProfessional

Abstract

The main goal of this research project was to improve the accuracy of numerical seakeeping analysis. Better estimation methods make the evaluation procedures for new vessels more useful. All ship responses are non-linear to some extent, but in many cases when non linearities are small a linear theory yields good predictions. Linear potential theory estimates of motion damping are generally adequate, and reasonable motion predictions are usually obtained. Rolling is an exception to this general rule: roll motions are large, and viscous damping is important. The bilge keel produces additional damping due to normal force on the keel plus pressure variation on the hull surface caused by the presence of the bilge keel. The additional damping caused by bilge keels seemed to be directly proportional to the area of the appendages. A bilge keel of higher aspect ratio was more effective than one with a lower aspect ratio.
Original languageEnglish
Article number7
JournalMaritime Research news
Volume21
Issue number1
Publication statusPublished - 2006
MoE publication typeD1 Article in a trade journal

Fingerprint

Aspect ratio
Damping
Seakeeping
Ships

Keywords

  • ship hydrodynamics
  • sea keeping
  • rolling motion

Cite this

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title = "Damping effect of bilge keels with different aspect ratios",
abstract = "The main goal of this research project was to improve the accuracy of numerical seakeeping analysis. Better estimation methods make the evaluation procedures for new vessels more useful. All ship responses are non-linear to some extent, but in many cases when non linearities are small a linear theory yields good predictions. Linear potential theory estimates of motion damping are generally adequate, and reasonable motion predictions are usually obtained. Rolling is an exception to this general rule: roll motions are large, and viscous damping is important. The bilge keel produces additional damping due to normal force on the keel plus pressure variation on the hull surface caused by the presence of the bilge keel. The additional damping caused by bilge keels seemed to be directly proportional to the area of the appendages. A bilge keel of higher aspect ratio was more effective than one with a lower aspect ratio.",
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language = "English",
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Damping effect of bilge keels with different aspect ratios. / Pajala, Jukka.

In: Maritime Research news, Vol. 21, No. 1, 7, 2006.

Research output: Contribution to journalArticleProfessional

TY - JOUR

T1 - Damping effect of bilge keels with different aspect ratios

AU - Pajala, Jukka

PY - 2006

Y1 - 2006

N2 - The main goal of this research project was to improve the accuracy of numerical seakeeping analysis. Better estimation methods make the evaluation procedures for new vessels more useful. All ship responses are non-linear to some extent, but in many cases when non linearities are small a linear theory yields good predictions. Linear potential theory estimates of motion damping are generally adequate, and reasonable motion predictions are usually obtained. Rolling is an exception to this general rule: roll motions are large, and viscous damping is important. The bilge keel produces additional damping due to normal force on the keel plus pressure variation on the hull surface caused by the presence of the bilge keel. The additional damping caused by bilge keels seemed to be directly proportional to the area of the appendages. A bilge keel of higher aspect ratio was more effective than one with a lower aspect ratio.

AB - The main goal of this research project was to improve the accuracy of numerical seakeeping analysis. Better estimation methods make the evaluation procedures for new vessels more useful. All ship responses are non-linear to some extent, but in many cases when non linearities are small a linear theory yields good predictions. Linear potential theory estimates of motion damping are generally adequate, and reasonable motion predictions are usually obtained. Rolling is an exception to this general rule: roll motions are large, and viscous damping is important. The bilge keel produces additional damping due to normal force on the keel plus pressure variation on the hull surface caused by the presence of the bilge keel. The additional damping caused by bilge keels seemed to be directly proportional to the area of the appendages. A bilge keel of higher aspect ratio was more effective than one with a lower aspect ratio.

KW - ship hydrodynamics

KW - sea keeping

KW - rolling motion

M3 - Article

VL - 21

JO - Maritime Research news

JF - Maritime Research news

SN - 0784-6010

IS - 1

M1 - 7

ER -