Hydrodynamic inertia and damping of ship hull vibrations

Artikel i vetenskaplig tidskrift, 1988

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 …