Pressure and Noise Induced by a Cavitating Marine Screw Propeller PDF Download
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Author: Jerzy Matusiak
Publisher:
ISBN:
Category : Cavitation
Languages : de
Pages : 48
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Book Description
Author: Jerzy Matusiak
Publisher:
ISBN:
Category : Cavitation
Languages : de
Pages : 48
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Book Description
Author: Seungnam Kim
Publisher:
ISBN:
Category :
Languages : en
Pages : 520
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Book Description
In this work, a systematic procedure of analyzing marine propeller performance and its underwater acoustics is delineated. The main focus is laid on the numerical prediction of hull pressure fluctuations and far-field acoustics induced by marine propellers via frequency- or time-domain approaches. As the first step, a hydrodynamic boundary element method (BEM) is implemented to analyze the comprehensive marine propeller performance in open water and ship-behind conditions. An elaborate numerical scheme modeling developed tip vortex cavitation is proposed for cavitating propellers. In the frequency domain approach, a potential-based panel method (or pressure-BEM) solving for the diffraction potential on the ship hull is coupled with the hydrodynamic BEM to predict the propeller-induced hull pressure fluctuations. Infinite speed of sound is assumed in the near-field, neglecting the time travel of acoustic waves to reduce the Helmholtz equation to the Laplace equation, which can be solved by a standard BEM solver. Far-field underwater noise is investigated in the time domain using the Ffowcs Williams-Hawkings (FW-H) formulation. The model propeller is mounted on the ship with an infinite plane assumed at the design draft to consider the pressure release or solid wall boundary conditions. Time-dependent surface quantities from the hydrodynamic analysis are taken as the known noise sources to the FW-H equation given in the form proposed by Farassat. The complex hull geometry and its disturbance to the medium are considered by solving the boundary integral equations. A half-space domain is modeled by modifying standard full-space Green's function to consider the image model beyond the infinite plane. The propeller-induced noise, its reflections from the hull, and their sums as the total noise will be investigated in full-space or half-space domains. Numerical predictions, including the time history of acoustic pressures and noise spectra, under various operating conditions are compared with experimental measurements, observations, and results from finite volume methods to validate the feasibility and accuracy of the present method
Author: John Carlton
Publisher: Butterworth-Heinemann
ISBN: 0080971237
Category : Technology & Engineering
Languages : en
Pages : 539
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Book Description
The early development of the screw propeller. Propeller geometry. The propeller environment. The ship wake field, propeller performance characteristics.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 484
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Book Description
Author: Duncan McIntyre
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Noise pollution threatens marine ecosystems, where animals rely heavily on sound for navigation and communication. The largest source of underwater noise from human activity is shipping, and propeller-induced cavitation is the dominant source of noise from ships. Mitigation strategies require accurate methods for predicting cavitation-induced noise, which remains challenging. The present thesis explores prediction and modelling strategies for cavitation-induced noise from marine propellers, and provides insight into models that can be used both during propeller design and to generate intelligent vessel control strategies. I examined three distinct approaches to predicting cavitation-induced noise, each of which is discussed in one of the three main chapters of this thesis: a high-fidelity computational fluid dynamics scheme, a parametric mapping procedure, and the use of field measurements. Each of these three chapters presents different insight into the acoustic behaviour of cavitating marine propellers, as well both real and potential strategies for mitigating this critical environmental emission. A combined experimental and numerical study of noise from a cavitating propeller, focused on both the fundamental importance of experimental findings and the effectiveness of the numerical modelling strategy used, is detailed in the first main chapter of this thesis. The experimental results highlighted that loud cavitation noise is not necessarily associated with high-power or high-speed propeller operation, affirming the need for intelligent vessel operation strategies to mitigate underwater noise pollution. Comparison of the experimental measurements and simulations revealed that the simulation strategy resulted in an over-prediction of sound levels from cavitation. Analysis of the numerical results and experiments strongly suggested that the cavitation model implemented in the simulations, a model commonly used for marine propeller simulations, was responsible for the over-prediction of sound levels. Ships are powered primarily by combustion engines, for which it is possible to generate "maps" relating the emission of pollutants to the engine's speed and torque; the second main chapter of this thesis presents the methodology I developed for generating similar "maps" relating the level of cavitation-induced noise to the speed and torque of a ship's propeller. A proof-of-concept of the method that used the model propeller from the first main chapter is presented. To generate the maps, I used a low-order simulation technique to predict the cavitation induced by the propeller at a range of different speed and torque combinations. A pair of semi-empirical models found in the literature were combined to provide the framework for predicting noise based on cavitation patterns. The proof-of-concept map shows a clear optimal operating regime for the propeller. The final main chapter of this thesis presents an analysis of field noise measurements of coastal ferries in commercial operation, the data for which were provided by an industrial partner. The key finding was the identification of cavitation regime changes with variation in vessel speed by their acoustic signatures. The results provide a basis for remotely determining which vessels produce less noise pollution when subject to speed limits, which have been implement in critical marine habitats, and which vessels produce less noise at a specific optimum speed.
Author: Sverre Steen
Publisher: MDPI
ISBN: 3038972029
Category : Technology & Engineering
Languages : en
Pages : 355
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Book Description
This book is a printed edition of the Special Issue "Marine Propulsors" that was published in JMSE
Author: John S. Carlton
Publisher: Butterworth-Heinemann
ISBN:
Category : Science
Languages : en
Pages : 518
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Book Description
Author: Isaac McKim Chase
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 324
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Book Description
Author: Michael B. Wilson
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 66
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Book Description
Author: Donald Ross
Publisher: Elsevier
ISBN: 1483160467
Category : Science
Languages : en
Pages : 390
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Book Description
Mechanics of Underwater Noise elucidates the basic mechanisms by which noise is generated, transmitted by structures and radiated into the sea. Organized into 10 chapters, this book begins with a description of noise, decibels and levels, significance of spectra, and passive sonar equation. Subsequent chapters discuss sound waves in liquids; acoustic radiation fundamentals; wind-generated ocean ambient noise; vibration isolation and structural damping; and radiation by plate flexural vibrations. Other chapters address cavitation, propeller cavitation noise, radiation by fluctuating-force (dipole) sources, and mechanical noise sources. This book will be helpful as a self-education text and as a reference for workers in the field.
