| Noise and Vibration |
Services tailored to your needsStrong noise and vibration in working and living spaces can be the origin of reduced crew performance and passenger discomfort. Moreover, excessive vibration might cause damage at the structure, machinery and equipment. GL assists to avoid noise problems during all phases of a ship's life, beginning from the early design stage, during building and commissioning or if unexpected noises or vibrations occur during operation. Global Structural Vibration Analysis
This analysis comprises several steps. After preparation of the finite element model of the ship, the mass distributions being typical for the individual ship's service are applied. Then the ship's natural vibrations are computed to identify critical resonance conditions. Subsequently, the expected vibration level distribution over the whole ship is computed for the relevant power conditions. Through extensive post processing a clear idea is gained how to counteract vibration most effectively. For this, knowledge of the strength and frequencies of the vibration sources is of utmost importance. Excitations from engines, propellers, vortex shedding and the sea way can be considered. Finally, the predicted levels are compared to the target values and it is assessed whether design modifications are advisable. Stringent automation of the analysis process enables us to investigate the effect of design variants in very short time.
Contact: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Local Structural Vibration Analysis
Local structures close to the propeller, main engine or thrusters might vibrate excessively. To avoid such resonant vibration, it must be ensured that the natural frequency of the structure does not coincide with the respective exciting frequency. Typically, strong local vibration occurs at stiffened panel structures (deck panels, tank walls) or as a coupled vibration of a subsystem and its foundations. The subsystem can be either a structure itself (mast, rudder, shaft bracket etc.) or a machinery and equipment part (gear box, fin stabiliser, generator etc.). The natural frequencies of regular panel structures can be calculated quickly by estimation formulae but for the analysis of coupled vibration phenomenon the finite element method is called for.
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The propulsion shafting of ships is exposed to fluctuating propeller forces, imbalances and torque fluctuations induced by the main engine. Torsional, lateral or axial shaft vibration might occur. If becoming excessive, increased bearing and sealing wear and enhanced fatigue stresses will be created. Moreover, shaft vibration might be transferred to the ship structure and thus form the origin of increased noise and vibration levels. The choice of the applicable analysis method and the suitable extent of the simulation model depend on the individual case. E.g., whirling vibration must often be analysed in combination with shaft alignment and axial vibrations can be computed reliably only, if thrust bearing flexibility is considered. We will help you to define a work scope tailored to your individual need.
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