HYDRODYNAMIC INERTIA AND DAMPING OF SHIP HULL VIBRATIONS

The entrained water plays an important role in ship hull vibrations. The classic Lewis method for calculation of hydrodynamic added mass has some inherent shortcomings that can result in insufficient accuracy, particularly for higher order modes. This is essentially due to the fact that the Lewis method uses a diagonal mass matrix that is dependent on the mode of vibration, while the physical reality is more accurately represented by a mode-independent, full mass matrix. Such full mass matrices can be calculated with Finite Volume or Source-Sink methods, which, however, require extensive computer calculations with detailed input data. A method is presented with which the Lewis transform can be used to determine a full mass matrix and gives very good agreement with Finite Volume calculations for a test case on a small ship. The Finite Volume calculations have also been used to study damping due to sound radiation. These calculations indicate that the hydrodynamic damping due to this mechanism contributes a significant part of the total modal damping.

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  • Supplemental Notes:
    • Transactions paper
  • Authors:
    • Sunnersjo, S
    • Janson, C
  • Publication Date: 1988

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  • Accession Number: 00658520
  • Record Type: Publication
  • Source Agency: Maritime Technical Information Facility
  • Files: TRIS
  • Created Date: Jul 21 1994 12:00AM