Damping Forces in Vibrations of a Ship

Boundary element methods in the prediction of the acoustic damping of ship whipping vibrations

Damping of ship whipping vibrations following a slam due to wave impact is traditionally assumed to be primarily of material or structural origin. However, several mechanisms of energy dissipation to the surrounding water exist, including gravity and acoustic waves. Neither transports much energy for the lowest frequency modes, in which the acoustic wavelength may be an order or magnitude great...

Ship roll damping control

The technical feasibility of roll motion control devices has been amply demonstrated for over 100 years. Performance, however, can still fall short of expectations because of difficulties associated with control system designs, which have proven to be far from trivial due to fundamental performance limitations and large variations of the spectral characteristics of wave-induced roll motion. Thi...

Power Electronic Devices for Damping Torsional Vibrations

Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or ...

Analysis of Rotor Forces in a Ship Airwake

Glass-specific behavior in the damping of acousticlike vibrations.

High frequency sound is observed in lithium diborate glass, Li2O-2B2O3, using Brillouin scattering of light and x rays. The sound attenuation exhibits a nontrivial dependence on the wave vector, with a remarkably rapid increase towards a Ioffe-Regel crossover as the frequency approaches the boson peak from below. An analysis of literature results reveals that the boson-peak frequency is closely...