Early Prediction of Vibrations on Ships
Shipyards primarily build one-of-a-kind vessels, which is why they lack the opportunity to refine their products using physical prototypes. Early and efficient computer-aided prediction of the vibroacoustic behavior of ship designs can therefore help identify acoustic anomalies, optimize the ship design, and avoid costly rework following sea trials.
At Fraunhofer LBF, a methodological approach based on parametric, modular, and hierarchical modeling was developed. The focus was on ease of interchangeability as well as quick and straightforward initialization of the individual submodels. Thanks to the chosen approach, the overall model can be used throughout the entire design process, as the initially very simple submodels can be replaced with more detailed descriptions as the design progresses, or feasibility studies can be conducted using different components. Furthermore, it is possible to determine the influence of sensitive parameters of a component through parameter variations.
Parametric Models and Efficient Simulation
To simulate the transmission of noise and vibrations into ship structures, scientists at Fraunhofer LBF numerically modeled the relevant structure-borne noise sources. Main engines and pumps were examined as application examples; models were developed and validated using measurement data.
The proposed simulation approach was validated using a scaled torsional vibration test rig consisting of an internal combustion engine, a rotor, and an eddy current brake. Extensive comparative measurements were conducted regarding source modeling to calibrate the powertrain models. Subsequently, a numerical model for the internal combustion engine was developed, and steady-state operating conditions as well as transient events—such as misfires and engine ramp-ups—were simulated at the system level using MATLAB/Simulink.
Easy to Use Thanks to a Custom Software Toolkit
The numerical models presented are a part of a software toolkit currently under development for the efficient prediction of a ship’s vibroacoustic behavior. One of the goals of this toolkit is to identify acoustic excitation mechanisms early in the design phase and also throughout the development process. Thanks to the modular structure of the numerical models, it is easy to swap out individual submodels to evaluate and derive the effects of appropriate measures for reducing vibrations and noise. Furthermore, the methods are being further developed at Fraunhofer LBF, making them suitable for applications beyond shipbuilding in the future.
Project Partners and Funding:
BMWi, Grant Number 03SX305, Partners: System Reliability and Machine Acoustics research group at the Technical University of Darmstadt, Flensburger Schiffbau-Gesellschaft mbH & Co. KG, Fr. Lürssen Werft GmbH & Co., Novicos GmbH, Technische Universität Berlin, Hamburg University of Technology (TUHH), Howaldtswerke-Deutsche-Werft GmbH, and TKMS Blohm + Voss Nordseewerke GmbH
