Practical Methods for Predicting Periodic Propeller Loads PDF Download
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Author: Robert J. Boswell
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 52
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Book Description
Author: Robert J. Boswell
Publisher:
ISBN:
Category : Propellers
Languages : en
Pages : 52
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Book Description
Author: R. J. Boswell
Publisher:
ISBN:
Category :
Languages : en
Pages : 46
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Book Description
A variety of procedures for predicting periodic bearing (shaft) loads and single-blade loads on propellers operating in circumferentially nonuniform flow are systematically evaluated. These procedures include the following: 1. a simple quasi-steady procedure that uses the open water characteristics of the propeller; 2. a simple stripwise two-dimensional unsteady procedure; 3. an unsteady lifting line procedure; and 4. four different numerical procedures based on unsteady lifting surface theory. The ranges of applicability and limitations of the evaluated procedures are assessed. The assessments of applicability are based on comparisons with: 1. model experimental periodic bearing loads over systematic ranges of propeller parameter in idealized wake patterns; 2. model experimental single-blade loads in idealized wake patterns; and 3. model experimental single-blade loads simulating the effects of waves and ship motions. Tradeoffs between accuracy of predictions versus ease and simplicity of the computational procedures for practical applications are discussed. The results show that unsteady lifting surface procedures give the best prediction of periodic bearing loads over practical ranges of propeller parameters. However, quasi-steady and empirical methods are adequate for estimating single blade loads for most practical applications.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: H. J. J. van den Boom
Publisher: Elsevier Publishing Company
ISBN:
Category : Science
Languages : en
Pages : 784
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Book Description
The topics reviewed in this volume explore the role of 'Computations, Model Tests and Reality' in design, engineering and operation of ships and offshore platforms. Divided into four different sections the subject areas cover: Advanced Vessels; Station Keeping; Propulsor Hull Interactions; and Nautical Simulators. The present work contains 79 workshop papers and summaries as well as keynote addresses on the above topics. The contributions will prove indispensable for all those interested in the latest technologies involved in arriving at cost effective, acceptable, efficient, safe ships and offshore structures.
Author: Society of Naval Architects and Marine Engineers (U.S.)
Publisher:
ISBN:
Category : Marine engineering
Languages : en
Pages : 402
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Author:
Publisher: Elsevier Publishing Company
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 200
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Book Description
The highly competitive markets of the present require extraordinary ingenuity and skill to develop and construct proper ships and structures. In order to be successful a broad spectrum of knowledge is a necessity. Consequently, the role of information centres such as MARIN are becoming increasingly important. Only the most progressive and cost effective designs can meet the challenges facing the maritime industry. Ever higher standards are required to meet the demanding environment of economic pressure and the forces of nature. The contributions in this volume provide the latest insights on the various technologies involved in arriving at a cost effective, acceptable, efficient, safe ships and offshore structures.
Author: Anthony F. Molland
Publisher: Cambridge University Press
ISBN: 0521760526
Category : Science
Languages : en
Pages : 569
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Book Description
Written by experts in the ship design field, this book provides a comprehensive approach to evaluating ship resistance and propulsion.
Author: Julia Cole
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A new higher-order free-wake (HOFW) method has been developed to enable conceptual design space explorations of propeller-wing systems. The method uses higher order vorticity elements to represent the wings and propeller blades as lifting surfaces. The higher order elements allow for better force resolution and more intrinsically computationally stable wakes than a comparable vortex-lattice method, while retaining the relative ease of geometric representation inherent to such methods. The propeller and wing surfaces and wakes are modeled within the same flow field, thus accounting for mutual interaction without the need for empirical models. The method was shown to be accurate through comparisons with other methods and experimental data. To ensure the method is capable of capturing an unsteady lift response, it was compared with a Kussner function approximation of the change in two-dimensional lift due to a sharp-edged gust. This study showed excellent agreement with an average error in the HOFW lift response of less than 3% from 0 to 10 semi-chords, but required high time and space resolution. The time-accurate lift response of a propeller-wing system as predicted with the HOFW method was then compared with with fully unsteady CFD. These results showed that the HOFW method can identify the peak frequency and general amplitude of the lift oscillations at high resolution. Due to the high resolution requirements, this mode of analysis is not recommended for use in design studies. Time-averaged results found using the HOFW method were compared with experimental propeller, proprotor, and propeller-wing system data, along with two semi-empirical methods. The method matched experimental propeller efficiencies to within 4% for lightly loaded conditions. Increases in lift coefficient due to interaction with a propeller for a series of wings as analyzed with the HOFW method matched the average of those predicted with two semi-empirical methods with an average of 6.5% error for a lightly loaded propeller case. A comparison of HOFW predictions of lift for a more non-conventional propeller-wing system with experimental results over a range of angles of attack showed an average difference of 0.04 in lift coefficient. For this system, predictions in thrust and torque also matched experimental results within 5% over a small angle of attack range (+/- 5 degrees). The method was less successful at predicting the magnitude of drag in comparison with experimental results, but was capable of qualitatively matching trends in drag, both with changes in angle of attack and for variations in design.Finally, two design studies were conducted to show the practical utility of the method: an investigation of the twist distribution on a large civil tiltrotor wing and an investigation into propeller rotation direction and vertical location on a distributed electric propulsion vehicle. The studies showed that the method is capable, fast, accurate, and robust for performance prediction of propeller-wing systems, and thus appropriate for use in design-space exploration.
Author:
Publisher:
ISBN:
Category : Naval architecture
Languages : en
Pages : 368
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Book Description
Author: M. H. Dunn
Publisher:
ISBN:
Category : Propellers, Aerial
Languages : en
Pages : 52
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Book Description
