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Experimental studies of noise/vibration damping for undersea warfare applications /Cahill, John J. January 2002 (has links) (PDF)
Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s):Young S. Shin. Includes bibliographical references (p. 57). Also available online.
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Vibration of finite coupled structures, with applications to ship structures /Lin, Tian Ran. January 2005 (has links)
Thesis (Ph.D.)--University of Western Australia, 2006.
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Comparison of added mass modelling for shipsYang, James January 1990 (has links)
This thesis presents a comparison of added mass modeling techniques that may be used to determine the the vibration response characteristics of ships in water. The mathematical treatment of added mass is reviewed, and a number of numerical approaches are discussed. Experiments to determine the natural frequencies of a ship model in air and in water were performed and were compared with the results obtained from the numerical approaches. It will be shown in this thesis that the use of modal analysis to predict ship vibration responses in water is a satisfactory and less time consuming alternative to a full eigenvalue solution. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate
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Identification of structural parameters and hydrodynamic effects for forced and free vibrationKruchoski, Brian L. (Brian Louis) 10 August 1992 (has links)
Statistically-based estimation techniques are presented
in this study. These techniques incorporate structural test
data to improve finite element models used for dynamic
analysis.
Methods are developed to identify optimum values of the
parameters of finite element models describing structures.
The parameters which may be identified are : element area,
mass density, and moment of inertia; lumped mass and stiffness;
and the Rayleigh damping coefficients. A technique is
described for incorporating hydrodynamic effects on small
bodies by identifying equivalent structure mass, stiffness,
and damping properties. Procedures are presented for both
the free vibration problem and for forced response in the
time domain.
The equations for parameter identification are formulated
in terms of measured response, calculated response,
the prior estimate of the parameters, and a weighting
matrix. The form of the weighting matrix is presented for
three identification schemes : Least Squares, Weighted Least
Squares, and Bayesian. The weighting matrix is shown to be
a function of a sensitivity matrix relating structural
response to the parameters of the finite element model.
Sensitivities for the forced vibration problem are derived
from the Wilson Theta equations, and are presented for the
free vibration problem.
The algorithm used for parameter identification is
presented, and its implementation in a computer program is
described.
Numerical examples are included to demonstrate the
solution technique and the validity and capability of the
identification method. All three estimation schemes are
found to provide efficient and reliable parameter identification
for many modeling situations. / Graduation date: 1993
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Vibration response of the polar supply and research vessel the S. A. Agulhas II in Antarctica and the Southern oceanSoal, Keith Ian 12 1900 (has links)
Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Full scale measurements were conducted on the polar supply and research vessel
the S.A. Agulhas II during a 78 day voyage from Cape Town to Antarctica in
2013/2014. Investigations were conducted into the effect of vibration on human
comfort and the structural dynamic response of the vessel. Vibration measured
in the bridge of the vessel is found to have little effect on human comfort for a
standing person and is classified as not uncomfortable according to BS ISO 2631-1.
Structural fatigue as a result of vibration is found to reach levels where damage
is possible in the stern and where damage is probable in the bow during open
water navigation, according to ship vibration guidelines by Germanischer Lloyd.
Multivariate statistical analyses are performed to investigate the relationships between
multiple predictor variables and vibration response. Factor analysis revealed
data structure from which specific physical phenomena could be identified. Multivariable
linear regression models are developed to predict vibration response and
are found to provide more accurate predictions in open water than in ice. The
2-node, 3-node and 4-node normal bending modes of the structure are identified
using operational modal analysis while the vessel was moored in the harbour. The
natural frequencies, damping ratios and mode shapes are estimated and compared
using LMS Operational PolyMAX and ARTeMIS CCSSI. A comparison of operational
modal analysis results to the STX Finland finite element model show that
the vessel’s modes occur at lower frequencies than numerically predicted. Clear
potential is identified to further investigate structural vibration and operational
modal analysis algorithm development in future research. / AFRIKAANSE OPSOMMING: Volskaal metings was op die poolvoorsienings en navorsingskip die S.A. Agulhas
II uitgevoer tydens ’n 78 dae reis van Kaapstad tot Antarktika in 2013/2014.
Ondersoeke is uitgevoer met betrekking tot die effek van vibrasie op menslike gemak
en die strukturele dinamiese reaksie van die vaartuig. Vibrasie wat in die brug
van die skip gemeet is, het min invloed op menslike gemak vir ’n staande persoon
en word geklassifiseer as nie ongemaklik volgens BS ISO 2631-1. Strukturele vermoeidheid
as gevolg van vibrasie bereik vlakke waar skade moontlik is in die spieël
en waar skade waarskynlik is in die boog tydens navigasie in oop water, volgens
skip vibrasie riglyne deur Germanischer Lloyd. Meerveranderlike statistiese ontledings
is uitgevoer om die verhoudings tussen verskeie voorspellerveranderlikes
en vibrasieterugvoer te ondersoek. Faktorontleding het data struktuur openbaar
waaruit spesifieke fisiese verskynsels geïdentifiseer kan word. Multi-veranderlike lineêre
regressiemodelle was ontwikkel om vibrasie reaksie te voorspel en lewer meer
akkurate voorspellings in oop water as in ys. Die 2-nodus, 3-nodus en 4-nodus normale
buig modes van die struktuur is geïdentifiseer met behulp van operasionele
modale analise terwyl die skip vasgemeer in die hawe is. Die natuurlike frekwensie,
demping verhoudings en mode vorms is beraam en vergelyk met behulp van
LMS operasionele Polymax en ARTeMIS CCSSI. ’n vergelyking van operasionele
modale analise resultate en ’n STX Finland eindige element model toon dat die
vaartuig se modusse voorkom by laer frekwensies as wat numeries voorspel word.
Duidelike potensiaal is geïdentifiseer om strukturele vibrasie en die ontwikkeling
van operasionele modale analise algoritmes te ondersoek in toekomstige navorsing.
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Whole-body vibration comfort measurement aboard the S. A. Agulhas II and just noticeable difference threshold testing in the laboratoryMcMahon, Kim J. 12 1900 (has links)
Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: A continuous comfort analysis of the whole-body vibration level aboard the
S.A. Agulhas II during the 2013-2014 Antarctic voyage was conducted ac-
cording BS ISO 2631-1:1997, assuming a standing posture. Just noticeable
difference in magnitude testing was conducted on nine subject in the standing
posture on a man-rated shaker in the laboratory environment. Two stimuli,
a 5 Hz sinusoidal stimulus with a magnitude of 0,5 m.s-2 and a slamming
event recoded during the voyage with a magnitude of 0,2 m.s-2 where selected
as the stimuli on which to investigate the just noticeable difference thresh-old. The study shows that the vibration level for the duration of the voyage
can be considered to be not uncomfortable. The results of the just notice-able difference threshold obtained for the sinusoidal stimulus concur with that
found in literature for seated subjects. The just noticeable difference threshold
obtained for the ship stimulus does not correlate with the results for the sinu-soidal vibration, implying that there may be an error in the vertical weighting filter provided by the standard or that Webers law does not hold for the just
noticeable difference threshold of standing subjects. / AFRIKAANSE OPSOMMING: 'n Deurloopnede gemakanalise van volliggaam vibrasievlakke aanboord die
S.A. Agulhas II is uitgevoer. Die analise tydens die 2013-2014 Antarktiese
reis is gedoen volgens BS ISO 2631-1 : 1997 vir 'n staande postuur. 'n Net-opmerkbare-verskildrempel toets is uitgevoer op nege vrywillers in 'n staande postuur deur vibrasieherkonstruksie op 'n platform in die laboratorium. Twee stumuli, 'n 5 Hz sinusvorminge stimulus (0,5 m.s-2 r.m.s.) en 'n branderim-pak stimulus (wat tydens die reis opgeneem is, 0,2 m.s-2 r.m.s. is gebruik)
om die net-opmerkbare-verskildrempel to ondersoek. Die studie toon dat die
vibrasievlakke gedeurende die reis as `nie ongemaklik' geklassifiseer kan word.
Die resulte van die net-opmerkbare-verskildrempel verkry vir die sinusvormige
stimulus stem saam met bevindinge vir sittende vrywilligers uit die literatuur.
Die net-opmerkbare-verskildrempel verkry vir die skip stimulus stem egter nie
'n moonlike onakkuraatheid weegfunksie is wat deur die standard is aanbeveel
word of datWeber se wet nie toepaslik is vir die net-opmerkbare-verskildrempel van staande vreywilligers nie.
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A study of the transmission of vibration in structures characteristic of naval ships / Yan Tso.Tso, Y. (Yan) January 1996 (has links)
Bibliography: leaves 159-169. / xii, 170 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis is concerned with the transmission and distribution of vibratory power in built-up structures, and in particular, structures characteristic of naval ships. The study consists of a detailed investigation of the wave transmission properties of structural junctions, followed by an analysis of the wave propagation through plates with periodic stiffeners. The results are used to develop Statistical Energy Analysis (SEA) models for the prediction of vibration levels in structures characteristic of naval ships. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996
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Analysis of ship hull and plate vibrations caused by wave forcesUnknown Date (has links)
In the present dissertation, the hydrodynamic and hydro-elastic characteristics of ship hull and plate vibrations are analyzed using theoretical and numerical methods. The wave forces are determined using a suite of methods which include the Froude-Krylov method for incident wave forces, Wagner's method and ABS rules for the slamming wave force, and numerical methods for nonlinear wave radiation forces. Finite difference methods are developed to determine the wave forced vibrations of ship hull plates which are modeled using a range of plate theories including nonlinear plate theory with and without material damping and orthotropic plate theory for stiffened hull plates. For small amplitude deformation of thin plates, a semi-theoretical superposition method is used to determine the free and forced vibrations. The transient ship hull vibration due to whipping is also analyzed using the finite difference method. Results, in the form of deformations and stress distributions, are obtained for a range of scantling and wave parameters to identify key parameters to consider in ship structural design. / by Fnu Lakitosh. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.
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Comportamento dinamico de riser rigido em catenaria devido a vibração induzida por vortices em aguas profundas / Dynamic behavior of steel catenary riser due to vortex induced vibration in dreepwaterTsukada, Raphael Issamu, 1983- 13 August 2018 (has links)
Orientador: Celso Kazuyuki Morooka / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-13T09:48:02Z (GMT). No. of bitstreams: 1
Tsukada_RaphaelIssamu_M.pdf: 4706299 bytes, checksum: b217ddb6687b4f89959018a445ff1dee (MD5)
Previous issue date: 2009 / Resumo: O presente trabalho tem como objetivo principal caracterizar o comportamento dinâmico de risers em configuração catenária (SCR) sob os efeitos do fenômeno da vibração induzida por vórtices (VIV). Estes estudos foram realizados através de experimentos e simulações numéricas. O experimento foi realizado com modelo de SCR em escala reduzida em um tanque de provas sob várias condições simuladas do ambiente, variando a velocidade do carro dinamométrico, a amplitude dos movimentos impostos no topo do modelo, amplitudes e períodos de ondas. As simulações numéricas foram realizadas usando um modelo de VIV criado para a avaliação de risers rígidos verticais. Modificações para o modelo foram implementadas de forma a considerar a inclinação do riser em relação ao escoamento e os movimentos apresentados pela SCR. Os resultados experimentais e numéricos apresentaram algumas características de comportamento semelhantes aos dos risers utilizados para grandes lâminas da água, verificados por outros pesquisadores, tais como: os altos harmônicos da freqüência de desprendimento de vórtices e o comportamento misto de standing e travelling waves. Uma boa concordância foi observada comparação entre os resultados experimentais e numéricos. / Abstract: The primary objective of this work is to characterize the dynamic behavior of steel catenary risers (SCR) under the effects of the Vortex-Induced Vibration (VIV) phenomenon. This study was conducted applying both experimental and numerical approaches. A SCR model test was performed in a towing tank under several simulated environment condition combinations such as; varying the towing speed, riser top forced oscillation amplitudes and surface wave characteristics. Numerical simulations were computed using an empirical VIV model created for the evaluation of top tensioned vertical rigid risers. Modifications to the model were implemented to allow consideration for the inclination of the riser relative to the fluid flow and the movement of the SCR. The experimental e numerical results present some dynamic behavior characteristics similar to that of deep sea risers found by others researcher mainly high harmonics of the vortex shedding frequency and a mix of standing and traveling wave behavior. Results from the comparison of experimental and numerical results have shown a good agreement. / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo
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Modelagem de esforços de VIV em risers em catenária / Modeling of VIV forces in a catenary riserTsukada, Raphael Issamu, 1983- 24 August 2018 (has links)
Orientador: Celso Kazuyuki Morooka / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-24T00:38:15Z (GMT). No. of bitstreams: 1
Tsukada_RaphaelIssamu_D.pdf: 8094235 bytes, checksum: 003f9b0a99d7b57efcd8ccf12ba266fd (MD5)
Previous issue date: 2013 / Resumo: Durante os últimos anos, as Vibrações Induzidas por Vórtices (VIV) foram intensamente estudadas a partir de experimentos com cilindros retos instalados verticalmente ou horizontalmente, que diferem significativamente das tubulações curvas em forma de catenária, encontradas nos risers em catenária. Desta forma, as VIVs para esta configuração de riser ainda são pouco compreendidas. Nesse sentido, neste trabalho é proposto um procedimento para o cálculo das VIVs em riser em catenária no domínio do tempo, utilizando as hipóteses do princípio da independência, que considera que apenas a componente normal da velocidade de correnteza em relação ao eixo do riser é significativa para as VIVs. Uma abordagem semi-empírica é adotada para calcular as forças transversais das VIVs, com base em coeficientes hidrodinâmicos encontrados a partir de experimentos com cilindros rígidos oscilando transversalmente ao escoamento. A frequência das forças de VIV é calculada através da mudança da frequência natural do riser devido à variação da massa adicional com a velocidade reduzida. Uma vez que respostas multi-modais podem ocorrer, um procedimento com base nas observações experimentais de células de desprendimento de vórtices e regiões de power-in são adotadas para determinar os modos de vibração excitados pelas VIVs. Dois experimentos com modelos flexíveis foram analisados. A partir do primeiro experimento verificou-se a validade das considerações do princípio da independência para tubos flexíveis. Já o segundo experimento teve a finalidade de entender o comportamento dinâmico de risers em catenária devido às VIVs, que demonstrou grande influência do comportamento das traveling waves na resposta da estrutura às VIVs. Por fim, o procedimento de cálculo das VIVs foi comparado com resultados experimentais para diferentes configurações e apresentou uma boa concordância. / Abstract: During the last years, the Vortex Induced Vibrations (VIV) were intensively studied from experiments with straight cylinders installed vertically or horizontally, which differ significantly from curved cylinders in catenary shape, found in catenary risers. Thus, for this riser configuration, VIVs are still poorly understood. Accordingly, this thesis proposes a procedure for the calculation of VIVs in catenary riser in the time domain, using the assumptions of the principle of independence, under which only the normal component of the flow velocity relative to the riser axis is significant to VIV. A semiempirical approach is adopted to calculate the transverse forces of VIV based on hydrodynamic coefficients found from experiments with rigid cylinders oscillating transversely to the flow. The frequency of the VIV forces is calculated by changing the natural frequency of the riser due to the variation of added mass in relation to the reduced velocity. Since multi-modal responses can occur, a procedure based on experimental observations of vortex shedding cells and power-in regions are adopted to determine the vibration modes excited by VIV. Two experiments with flexible models were analyzed. From the first experiment, the validity of the considerations of the principle of independence for flexible pipes is verified. The second experiment aimed to understand the dynamic behavior of catenary risers due to VIV, which showed a great influence of traveling wave's behavior in the response of the structure to VIV. Finally, the procedure of calculating VIV was compared with experimental results for different configurations and showed good agreement. / Doutorado / Explotação / Doutor em Ciências e Engenharia de Petróleo
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