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Milandri, Giovanni Sergio. "Seakeeping control of HYSUCATs." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2993.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006.This thesis investigates practical methods of modelling and control of the vertical motions of a hydrofoil assisted catamaran, the HYSUCAT. The aim of the control application is to reduce the motions, and consequently the motion sickness of the passengers. First, a potential flowcommercial program, POWERSEA,was used to model the system. This uses 2-D strip methods to model the planing hull-form of the vessel, and the Peter du Cane hydrofoil theory for modelling of the foils. These simulations are compared to experimental towing tank results, with fair agreement at lower speeds, but limited applicability at high speeds. Thus for the control design the agreement was insufficient. As an alternative, a simple coupled 2 degree-of-freedom spring - mass - damper model is proposed, for which the equations of motion are derived. This has 9 unknown parameters; three of these aremeasured directly, two are modelled, and the remaining four were identified using an experimental parameter estimation technique. Representative parameter values were calculated frommultiple experiments for application in the control design. The design of a control system was based on the above model. First, an output-weighted Linear Quadratic Regulator (LQR) was designed to obtain the full state feedback gains. A non-linear ’bang-bang’ control design was then implemented to try and speed up the response of the system. These control strategies, as well as no control, were applied in the towing tank in regular waves, with good results at low and medium frequencies. At the design point, 32% and 65% reductions in rms motions were achieved for pitch and heave, respectively. At high frequencies, though, not much improvement was achieved due to the bandwidth limitation of the control system. The LQR results were better overall (reduced motions) across the frequency range than the bang-bang controller, as well as having a lower added resistance in waves. The control design of the output-weighted LQR was then revised to be based on alternative outputs, as a possible improvement. However, a further two controller designs did not yield any noticeable improvement and were not developed further.
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Peffers, Stephen B. "Seakeeping aspects of SLICE hulls." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA294545.
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Claudel, Remi. "Seakeeping enhancement bylengthening a ship." Thesis, KTH, Marina system, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234835.
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In this study, a tentative assessment of a passive solution for pitch decrease, namely the increase in length of the studied ship, is made. The hull form of the lengthened version of the ship is derived from the reference hull form after utilization of Lackenby’s sectional area curve transformation through a prismatic coefficient change (Reference [3]), and utilization of a sectional area curve “swinging” induced by a change of longitudinal position of the centre of buoyancy. Following this, and after a complementary mass estimate of the lengthened version, seakeeping calculations are made and show a significant decrease in pitch, from almost 35% for low sea states to 20% for relatively high sea states. To conclude this study, operability for classic NATO frigate missions have been calculated and the decrease in pitch induces a slight gain in operability for the lengthened version.
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Farstad, Thomas Henning. "Transient seakeeping analysis using generalized modes." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42611.
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Lagemann, Benjamin. "Efficient seakeeping performance predictions with CFD." Thesis, KTH, Marina system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261772.
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With steadily increasing computational power, computational fluid dynamics (CFD) can be applied to unsteady problems such as seakeeping simulations. Therefore, a good balance between accuracy and computational speed is required. This thesis investigates the application of CFD to seakeeping performance predictions and aims to propose a best-practice procedure for efficient seakeeping simulations. The widely used KVLCC2 research vessel serves as a test case for this thesis and FINEŠ/Marine software package is used for CFD computations. In order to validate the simulations, results are compared to recent experimental data from SSPA as well as predictions with potential ˛ow code SHIPFLOW® Motions. As for the calm water simulations, both inviscid and viscous ˛ow computations are performed in combination with three mesh refinement levels. Seakeeping simulations with regular head waves of different wavelengths are set-up correspondingly. Furthermore, different strategies for time discretization are investigated. With the given computational resources, it is not feasible to complete seakeeping simulations with a ˝ne mesh. However, already the coarse meshes give good agreement to experiments and SHIPFLOW® Motions' predictions. Viscous ˛ow simulations turn out to be more robust than Euler ˛ow computations and thus should be preferred. Regarding the time discretization, a fixed time discretization of 150 steps per wave period has shown the best balance between accuracy and speed. Based on these findings, a best-practice procedure for seakeeping performance predictions in FINEŠ/Marine is established. Taking the most efficient settings obtained from head wave simulations, the vessel is subjected to oblique waves with 160° encounter angle. Under similar wave conditions, CFD predictions of a similar thesis show close agreement in terms of added wave resistance. Compared to the previous head wave conditions of this study, added resistance in 160° oblique waves is found to be significantly higher. This underlines that oblique bow quartering waves represent a relevant case for determining the maximum required power of a ship. CFD and potential ˛ow show similar accuracy with respect to ship motions and added wave resistance, albeit potential ˛ow outperforms CFD in terms of computational speed. Hence, CFD should be applied in cases where viscous effects are known to have large influence on a vessel's seakeeping behavior. This can be the case if motion control and damping devices are to be evaluated, for instance.Tack vare den stadigt ökande beräkningskraften kan beräkningsuiddynamik (CFD) idag användas på beräkningsintensiva problem som sjöegenskapssimulationer. Den här rapporten undersöker användning av CFD på sjöegenskapsprestanda och syftar till att foreslå ett best-practice förfaringssätt för effektiv sjöegenskapssimulationer. Forskningsskrovet KVLCC2 fungerar som ett testfall för denna rapport och FINE/Marine-mjukvarupaketet används för CFD-beräkningar. Viktiga parametrar, såsom ödestyp, beräkningsnät och tidssteg varierars systematiskt. Resultaten jämförs med experiment gjorda vid SSPA. Baserat på resultaten förelås en best-practice. Den föreslagna best-practice användas vidare för berökningar av sjöegenskaper i sneda vågor. Jämförelse av resultaten med liknande studier visar god överensstämmelse. Genom att använda det föreslagna förfarandet för best-practice kan CFD-sjöegenskapssimulationer användas på fall där viskösa krafter måste beaktas, till exempel rörelseregleringsanordningar.
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Yaakob, Omar bin. "Incorporating seakeeping in the design of fishing boats." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287812.
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Rollings, Sarah E. "Seakeeping analysis of small displacement high-speed vessels." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FRollings.pdf.
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Mesbahi, Ana Paula Moura Esteves. "Preliminary design tools for seakeeping of high-speed craft." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445568.
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Wright, Peter N. H. "The preliminary design of catamarans for seakeeping and resistance." Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401840.
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Pons, Roser Aina. "Parametric Hull Form Variation and Assessment of Seakeeping Performance." Thesis, KTH, Marina system, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232812.
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This Master Thesis is about the assessment of the seakeeping performance of different ships subjected to hull parametric variations. The latest version of the potential flow CFD software Shipflow in combination with a CAD platform (CAESES) have been used to carry out the evaluations. Two ships are studied: a simple one that can be mathematically defined, the Wigley hull, and the KVLCC2, a realistic oil tanker. The software is validated, comparing it to experimental results and other CFD solvers, showing a good agreement with the rest of the data; the mesh dependence studies also show only small variations between the used meshes and finer ones. Then, first the performance in calm water is evaluated for both ships by looking at the wave resistance. With the results of the original hulls as a reference, they are parametrically modified in different ways and evaluated as well to see which trends lead to an improved resistance. With the parametrization applied in the Wigley hull big changes can be appreciated, as the variation in wave resistance due to different parametric modifications ranges between -6% and 14%. For the KVLCC2, two different parametrizations are tested. The first one, focusing mainly on the bulb, produces changes that are generally smaller than for the Wigley hull, especially the ones due to bulb modifications; and the negative effects over the wave resistance due to variations affecting the general shape of the hull are larger than the positive effects. The second parametrization mimics the one used for the Wigley hull, focusing on the general forebody: the results obtained with this approach are very similar to the ones of the Wigley hull, also reaching wave resistance reductions of about a 6%. After that, the evaluation is moved to the ships in regular head waves, where the added resistance due to waves is studied; in a range of wavelengths going from 30% to a 200% of the length of the ship for the Wigley hull, while the study of the KVLCC2 is focused around the wavelength where the resistance is higher, at a 120% of the ship’s length and extending to 100% and 140%. Here the differences of the effect a same parametric variation has over the resistance in calm water and waves are assessed. The results of the Wigley hull show many interesting facts: some of the parametrically modified designs that performed worse in calm water have a consistent better behaviour at the wavelengths analysed; while the best designs in calm water exhibit both large positive and negative added resistance variations depending on the wavelength observed. The first KVLCC2 parametrization approach presents again smaller deviations in resistance, frequently even minor than in calm water; despite that, most of the parametric variations that worked well in calm water display also a reduction of added resistance in waves. On the other hand, the results obtained with the second parametrization of the KVLCC2 show the same trends and behaviour as for the Wigley hull.
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Kurultay, Aziz Alper. "Sensitivity analysis of the seakeeping behavior of trimaran ships." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FKurultay.pdf.
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Rollings, Sarah E. "Rudko, David D.:." Thesis, Monterey, California. Naval Postgraduate School, 2003.
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In developing designs for high speed vessels, the engineer must account for the response of the ship in the environment while operating at mission essential speeds. This thesis presents a seakeeping analysis of David Taylor Model Basin's Series 64 models scaled to a 2500-ton displacement using the SHIPMO and MATLAB software. It also discusses the current technology associated with high speed vessels (HSV's) and the relation to the US Navy. Series 64 models provided the benchmark for resistance data. To expand upon this well known series, this research develops seakeeping data trends for scaled-up models. SHIPMO allows the user to specify the ship's characteristics and the environmental conditions such as wave specifications and spectrum. Using the output files from SHIPMO, the MATLAB program designed during this thesis, produced contour plots for the models' response in pitch and heave. Seakeeping trends were observed based on the plots and further compared to calculations of the seakeeping rank, R, a formula originally developed by Nathan Bales. The results of the research can be used by engineers in application to the design of small displacement, high speed ships, both monohulls and multi-hulls.http://hdl.handle.net/10945/1070
US Navy (USN) author.
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Johnson, Michael Charles. "Improvements in the conduct and interpretation of ship seakeeping trials." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409610.
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Xing-Kaeding, Yan. "Unified approach to ship seakeeping and maneuvering by a RANSE method." Hamburg Arbeitsbereiche Schiffbau, Techn. Univ. Hamburg-Harburg, 2006. http://doku.b.tu-harburg.de/volltexte/2006/303/.
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Hedderly, James W. "A seakeeping study on the autonomous sustainment cargo container delivery system." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://bosun.nps.edu/uhtbin/hyperion-image.exe/08Mar%5FHedderly.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2008.Thesis Advisor(s): Papoulias, Fotis. "March 2008." Description based on title screen as viewed on May 2, 2008. Includes bibliographical references (p. 61-62). Also available in print.
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Gillespy, Andrew J. "Integrating seakeeping in the design of semi-displacement and displacement monohulls." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/10945/24329.
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CIVINSEarly stage ship design and assessment continues to be a challenge for naval architects and ocean engineers. Furthermore, seakeeping at high speeds cannot be reliably calculated by traditional methods such as strip theory due to the hydrodynamic effects that occur in the semidisplacement region. Traditional methods have a vessels' response in seas calculated after most initial design decision have been cemented, making changes in design for improved seakeeping difficult at best. This paper puts forth a method for narrowing the design space for semidisplacement and displacement patrol craft operating at Froude numbers up to Fn= 1.0 and incorporating the vessels' response in seas into early stage design. Optimization of the design is done through the use of response surface methodology. Using a systems approach, a Patrol Craft Assessment Tool (PCAT) was created and tested to aide designers in the initial design and assessment of patrol craft of less than 90 m. PCAT is an MATLAB code that interfaces with Surface Wave Analysis (SWAN2) to incorporate resistance, engine selection, structures, seakeeping, and mission profiles into one design program to aide a designer.
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Okan, Orhan Barbaros. "A design procedure for seakeeping analysis of close proximity ship towing." Thesis, Monterey, Calif. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/6039.
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Approved for Public Release; Distribution is Unlimited.The purpose of this thesis is to develop an efficient analysis and design procedure for assessing the seakeeping behavior of surface ships in close proximity towing. The problem is formulated by using the heave and pitch equations of motion in regular waves. The vertical plane relative motions between the trailing and the leading ships are matched through the speed-resistance characteristics of the trailing ship. A sea state degradation factor is introduced. This factor characterizes the expected seakeeping performance penalty resulting from the connection. A series of parametric studies is conducted for various geometric properties and environmental characteristics. The results can be used to evaluate the response of the system and provide insight into parameter selection for motion minimization.
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Lesh, Donald B. "Seakeeping characteristics of SLICE hulls : a motion study in six degrees of freedom /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA304157.
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Li, Lin. "Numerical seakeeping predictions of shallow water effect on two ship interactions in waves." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63481.pdf.
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Ha, Taebum. "A three dimensional prediction of the seakeeping performance of high speed marine vehicles." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366898.
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Ahmed, Tamer M. "Three-dimensional frequency-domain singularity distribution methods for seakeeping predictions : deficiencies and remedies." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405530.
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Taunton, Dominic John. "Methods for assessing the seakeeping performance of high speed displacement monohulls and catamarans." Thesis, University of Southampton, 2001. https://eprints.soton.ac.uk/426726/.
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The research programme has investigated methods for assessing the seakeeping performance of high speed vessels. This has included a review and assessment of seakeeping attributes, the development of a suitable database of motion characteristics using experimental and numerical techniques and proposals for assessing the seakeeping characteristics of alternative vessels. An experimental test programme was carried out in regular head and oblique waves as well as irregular open seas on two different hull forms of fast displacement catamarans. The results of the experiments in oblique waves are extended to beam and foUowing headings using the transfer functions &om a 3D pulsating source code at headings from head to following seaa in regular waves. This effectively provides a meajis of generating 3D transfer functions. The methodology used to compare and assess the seakeeping performance of vessels at an early design stage is discussed. The use of short crested seas as opposed to long crested is assessed and the differences compared. This leads to the use of spreading relationships to generate 3D transfer functions from the database of transfer functions in regular head waves. This allows the motion prediction method to be greatly enhanced by ciHowing any heading to be assessed. The proposed attributes and criteria suitable for assessing the seakeeping performance of high speed vessels are summarised.
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Erselcan, Ilkay Ozer. "A frequency domain strip theory applied to the seakeeping of the Zumwalt-Class destroyer." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61868.
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Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 87-88).
Seakeeping analysis of the Zumwalt-Class destroyer was carried out in the framework of linear strip theory and potential flow. First, the problem was formulated and solved analytically. Second, a program called Ship Motions Analyzer (SMA) was written in MATLABTM to carry out the seakeeping analysis for regular waves in a discretized frequency range. SMA calculates sectional added mass and damping coefficients first. Then, it calculates excitation forces and moments acting on a ship advancing at constant forward speed with arbitrary heading for sway, heave, roll, pitch and yaw modes of motion. Finally, SMA evaluates Response Amplitude Operators (RAO's) in the same modes of motion. In addition, it also includes a subroutine which evaluates steady drift forces acting on a ship in the plane of undisturbed free surface. The added mass and damping coefficients of a fully submerged heaving circle and a semi-circle in heave and sway were calculated to validate the results of SMA. The results were compared to the results of Vugst [1] and Frank [2]. They match each other exactly. In addition, the magnitudes of heave and pitch excitation force and moment, and RAO's in the same modes of motions were calculated. The results agree with the theory. Finally, added resistance of Mariner type ship was calculated by SMA to compare the results to the ones given by Salvasen [3] and to validate the calculations. These results are also in very good agreement with the available computational and experimental results.
by Ilkay Ozer Erselcan.
S.M.in Naval Architecture and Marine Engineering
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DiMino, John Robert. "Fabrication of a SWATH vessel scale model for seakeeping tests using rapid prototyping methods." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83709.
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Thesis (S.B. in Mechanical and Ocean Engineering)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references (page 26).
This paper describes the techniques used to fabricate a one meter long, 1/6 scale model of a Small Waterplane Area, Twin Hull (SWATH) Unmanned Surface Vehicle (USV) that will be used primarily for dynamic seakeeping testing in the MIT Tow Tank. The model represents a design conceived by Stefano Brizzolara, which will be used for launching, recovering, and servicing Unmanned Underwater Vehicles (UUV) at sea. Construction methods included a number of rapid prototyping methods rarely used for this kind of project, including 3D printing, lasercutting, and spraypainting. The benefits and disadvantages of each of these processes will be discussed. Although there was insufficient time to conduct any tow tank tests, several data-recording techniques are reviewed which may be used by future students continuing the research of this vessel.
by John Robert DiMino.
S.B.in Mechanical and Ocean Engineering
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Bacon, Adam N. "Investigation on the Impacts of Vessel Flooding on Roll Motion." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/honors_theses/127.
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This thesis develops a method to analyze the roll response of a vessel during a damaged (flooded) scenario. This was done by developing a time-domain method in which the damaged compartment was flooding while the ship is simultaneously subjected to a seaway. The KRISO containership was used as a test hull and was subjected to three flooding conditions. These flooding conditions involved flooding Hold 5, Hold 3, and Hold 1 separately. Newmark’s Beta method for linear acceleration was used to solve the roll motion of equation in which the hydrodynamic coefficients A44, B44, and C44 were predetermined from linear strip theory for various drafts and trim angles. The roll response in the transient flooding state and the steady state, after flooding ceased (fully damaged state), while in wave action was simulated and plotted. The amplitudes from the initial and damaged steady states were recorded at the given wave frequency and wave amplitude, to generate the roll response amplitude operators for the vessel from wave frequency ω = 0.1 rad/s to ω = 2.1 rad/s. Analysis of the RAO curves revealed that the KRISO was not made significantly more unstable by the flooding, for the conditions that were considered, for nearly all wave frequencies except the natural frequency of 0.5 rad/s.
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Xing-Kaeding, Yan [Verfasser]. "Unified approach to ship seakeeping and maneuvering by a RANSE method / von Yan Xing-Kaeding." Hamburg : Arbeitsbereiche Schiffbau, Techn. Univ. Hamburg-Harburg, 2006. http://d-nb.info/980303303/34.
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Malesci, Cosimo. "USe of seakeeping simulation capabilities in the preliminary phase of the design of multihull vessels." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36276.
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Thesis (S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 190-193).
Seakeeping analysis is a fundamental part of the design process of a ship. Due to its complexity, seakeeping analysis is usually completed in a late stage of the design process. Although this approach can be successfully used for monohull vessels, it is not optimal in designing more innovative hull forms, due to the high degree of uncertainty of the seakeeping performances of these vessels. The recent interest in multihull vessels poses a problem to the naval architecture world as little is known about such hull forms and a limited number of design tools is available to analyze them. These concerns led to the development of the I-Marine Seakeeping Analysis Toolbox that aims to help students and naval architects alike understand the importance of seakeeping analysis and the seakeeping capabilities of multihull vessels. The Toolbox includes five different seakeeping programs suitable for the analysis of multihull vessels and is accessible through a web interface. The integrated nature of I-Marine strongly facilitates the usage of the programs, making it a great educational tool to learn seakeeping analysis without any previous programming knowledge.
(cont.) This thesis shows that a tool such as I-Marine could be effectively used in calculating the seakeeping capabilities of multihulls and successfully integrated in the preliminary design of a vessel, leading to numerous advantages such as a higher efficiency in the design process, a reduction in the risk of designing multihulls, and an expansion of the design envelope.
by Cosimo Malesci.
S.M.in Ocean Systems Management
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Ruggeri, Felipe. "A higher order time domain panel method for linear and weakly non linear seakeeping problems." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-09122016-074844/.
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This thesis addresses the development of a weakly non-linear Higher Order Time Domain Rankine Panel Method (TDRPM) for the linear and weakly non-linear seakeeping analysis of floating offshore structures, including wave-current interaction effects. A higher order boundary elements method is adopted based on the body geometry description using Non-uniform Rational B-splines (NURBS) formulation, which can be generated by many standard Computed Aided Design (CAD) softwares widely available, and the several computed quantities (velocity potential, free surface elevation and others) are described using a B-spline formulation of arbitrary degree. The problem is formulated considering wave-current-body interactions up to second order effects, these ones considering the terms obtained by interaction of zero/first order quantities. In order to provide numerical stability, the Initial Boundary Value Problem (IBVP) is formulated in terms of the velocity potential and the local acceleration potential, the later used to predict the hydrodynamic pressure accurately. The zeroth order problem is solved using the double-body linearization instead of the Neumman-Kelvin one in order to allow bluff bodies simulation, leading to very complex expressions regarding the m-terms computation. The method adopts the Rankine sources as Green\'s function, which are integrated using Gauss quadrature in the entire domain, but for the self-influence terms that are integrated using a desingularized procedure. The numerical method is verified initially considering simplified geometries (sphere and circular cylinder) for both, first and second-order computations, with and without current effects. The derivatives of the velocity potential are verified by comparing the numerical m-terms to the analytical solutions for a hemisphere under uniform flow. The mean and double frequency drift forces are computed for fixed and floating structures and the quantities involved in these computations (wave runup, velocity field) are also compared to literature results, including the free floating response of a sphere under current effects. Two practical cases are also studied, namely the wave-induced second order responses of a semi-submersible platform and the wavedrift-damping effect evaluated through the equilibrium angle of a turret moored FPSO. For the former, some specific model tests were designed and conducted in a wave-basin.Essa tese aborda o desenvolvimento de um método de Rankine de ordem alta no domínio do tempo (TDRPM) para o estudo de problemas lineares e fracamente não lineares, incluindo o efeito de corrente, envolvendo sistemas flutuantes. O método de ordem alta desenvolvido considera a geometria do corpo como descrita pelo padrão Non-uniform Rational Basis Spline (NURBS), que está disponível em diverso0s softwares de Computed Aided Design (CAD) disponíveis, sendo as diversas funções (potencial de velocidades, elevação da superfície-livre e outros) descritos usando B-splines de grau arbitrário. O problema é formulado considerando interações onda-corrente-estrutura para efeitos de até segunda ordem, os de ordem superior sendo calculados considerando as interações somente dos termos de ordem inferior. Para garantir a estabilidade numérica, o problema de contorno com valor inicial é formulado0 com relação ao potencial de velocidade e de parcela local do potencial de acelerações, este para garantir cálculos precisos da pressão dinâmica. O problema de ordem zero é resolvido usando a linearização de corpo-duplo ao invés da linearização de Neumman-Kelvin para permitir a análise de corpos rombudos, o que requer o cálculo de termos-m de grande complexidade. O método adota fontes de Rankine como funções de Green, que são integradas através de quadratura de Gauss-Legendre no domínio todo, exceto com relação aos termos de auto-influência que adotasm um procedimento de dessingularização. O método numérico é inicialmente verificado considerando corpos de geometria simplificada (esfera e cilindro), considerando efeitos de primeira e segunda ordens, com e sem corrente. As derivadas do potencial de velocidade são verificadas comparando os termos-m obtidos numericamente com soluções analíticas disponíveis para a esfera em fluído infinito. As forças de deriva média e dupla-frequência são calculadas para estruturas fixas e flutuantes, sendo as funções calculadas (elevação da superfície, campo de velocidade) comparadas com resultados disponíveis na literatura, incluindo o movimento da esfera flutuante sob a ação de corrente e ondas. São também estudados dois casos de aplicação prática, a resposta de segunda ordem de uma plataforma semi-submersível e o efeito de wave-drift damping para o ângulo de equilíbrio de uma plataforma FPSO ancorada através de sistema turred. No caso da semi-submersível, os ensaios foram projetados e realizados em tanque de provas.
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Gould, Kevin John. "The influence of hullform parabolization on the powering, seakeeping and economic characteristics of the UBC-Ferry." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/35146.
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This work is a hydrodynamic study of a displacement vessel using numerical and experimental methods to improve efficiency. A new hullform is developed that will have significantly reduced wave resistance, lower power requirements and reduced fuel consumption. This process is termed waterline parabolization and can reduce the wave resistance of a parallel mid-bodied displacement vessel by increasing the overall beam of the ship, through the addition of parabolic amidships bulbs. Two approaches have been taken: a “constant displacement” design producing a new hullform with shallower entrance and exit angles, and a “retro-fit” design where amidships bulbs are added to a parent hullform increasing the displacement. Optimal shapes for the amidships bulbs are developed numerically using a potential flow code based on Dawson’s method coupled with a Matlab optimization routine. Tow-tank tests at Istanbul Technical University (ITU) confirmed that amidships bulbs could reduce the effective power (PE) by 15%.
Given the improved powering with parabolization, this thesis also compares the seakeeping characteristics of the parent, “constant displacement”, and “retro-fit” hullforms at high sea state conditions. A strip theory program called SHIPMO PC is used to compare the three different hullforms. Added resistance in waves, roll motions, pitch motions, heave motions and acceleration levels are quantified. There is no significant change in the seakeeping performance except for the roll motions, where there is a shift in the natural frequency of response. This shift is indicative of increased roll stiffness for parabolized hullforms with constant KG’s and increased GM’s as independent variables. Limited tow-tank tests were completed at ITU and they confirm numerical added resistance predictions in head seas between parent and “retro-fit” hullforms.
Finally, a route specific cost benefit analysis of a “retro-fit” amidships bulb for the UBC-Ferry is done. Benefits include a variable fuel savings of 44000 L/year and a reduction in capital costs of installed power of 59,500$. The capital construction costs of the “retro-fit” would be 23,900 $/Tonne, and the payback period would be 18 years. Other then cost, the “retro-fit” would have an improved EEDI (Energy Efficiency Design Index) rating and reduced impacts on the environment.
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Olaya, Sébastien. "Contribution à la modélisation multi-physique et au contrôle optimal d'un générateur houlomoteur : application à un système "deux corps"." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0051/document.
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Cette thèse s’inscrit dans le cadre du 12ème appel à projet du Fonds Unique Interministériel (FUI) lancé par l’Etat au premier semestre 2011. Le projet « EM BILBOQUET » a été colabellisé par les pôles de compétitivité Mer Bretagne, Mer PACA et Tenerrdis. Il consiste en la réalisation d’un nouveau système de génération d’électricité issue du mouvement relatif entre deux corps flottants, mus par la houle. Dans cette thèse, nous nous sommes intéressés au contrôle optimal à appliquer sur la génératrice via les convertisseurs statiques, afin d’extraire le maximum d’énergie de la houle incidente. Dans un premier temps, nous avons établi les équations dynamiques régissant le comportement de la structure dans la houle en adoptant les hypothèses de la théorie potentielle. Pour ce faire, nous avons développé un code de calcul spécifique, basé sur une résolution du problème linéaire de tenue à la mer, par des méthodes dites semi-analytiques. Ce code de calcul permet de déterminer les coefficients hydrodynamiques nécessaires à l’écriture de l’équation dynamique dans le domaine fréquentiel, mais aussi dans le domaine temporel via une modification de la formulation de Cummins. Cette dernière nous permet ainsi, dans un second temps, de formuler le problème de maximisation de l’énergie récupérée comme un problème d’optimisation où la variable à optimiser est le couple résistant de la génératrice. Le problème est résolu en temps réel en adoptant une résolution par algorithme dit à horizon fuyantIn this thesis, we perform a study on a self-reacting point absorber, project FUI 12 “EM BILBOQUET”, in order to optimise energy extraction from incoming waves. Main researches use seabed for providing reference to a floating body, called buoy. However, as it is well-known that ocean energy is greater far away from the shore, sea-depth becomes a constraint. In this thesis a damping plate attached to a spar keel is proposed to allow the floating body to react against it. Energy resulting from the relative motion between the two concentric bodies i.e. the buoy and the spar is harnessed by a rack-and-pinion, which drive a permanent magnet synchronous generator through a gearbox. In the first part of the thesis we have developed a wave-to-wire model i.e. a model of the whole electro-mechanical chain from sea to grid. To this purpose we have developed our own hydrodynamic code, based on linear potential theory and on a semianalytical approach, solving the seakeeping problem. The hydrodynamic coefficients obtained such as added mass, radiation damping, and wave excitation forces are required for solving the dynamic equation based on Cummins formulation. The second part of the thesis focuses on the self-reacting point-absorber optimal control strategy and the Model Predictive Control (MPC) formulation is proposed. Objective function attempting to optimise the power generation is directly formulated as an absorbed power maximisation problem and thus no optimal references, such as buoy and/or spar velocity, are required. However, rather than using the full-order WEC model in the optimisation problem, that can be time-consuming due to its high order, and also because of the linear assumptions, we propose the use of a “phenomenologically" one-body equivalent model derived from the Thévenin’s theorem
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Gao, Qiuxin. "The effect of free surface on classical ship hydrodynamics using RANSE : resistance, manoeuvring, propulsion, seakeeping and stability." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16924.
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In this research, the Computational Fluid Dynamics (CFD) approach, based on the solution of the Reynolds Averaged Navier-Stokes (RANS) equations is used to study the classical ship hydrodynamic problems, all being affected markedly by the presence of free-surface, namely: ship resistance, propulsion, manoeuvring, seakeeping and stability, the latter focusing on flooding of a damaged ship. In this respect, this thesis represents a marked deviation from classical approaches and a unique contribution to ship dynamics and hydrodynamics. The RANS equations with SST K-w two-equation turbulence model and Volume Of Fluid (VOF) formulation were discretised by the finite volume (FV) method and the pressure-coupled governing equations were solved by the SIMPLE algorithm. The geometric reconstruction algorithm was adopted to locate transient free surfaces. The second order upwinding scheme was used for the discretisation of the convection flux and Multi-grid Acceleration was applied to improve convergence. In addressing ship resistance, grid sensitivity studies were carried out according to the “ITTC guideline of quality” manual. The computed results were verified and validated against available model test data. Additionally, the results of the effects of the turbulence models were investigated by comparing turbulence quantities predicted by SST K-w and RSM. In addressing ship propulsion, the propeller was modelled as an actuator disk of equivalent thrust and torque. Distributions of the body force were compared with results from a parametric study and the implementation of the body force approach was validated by model test data. In addressing ship manoeuvring, numerical PMM simulations of pure sway and yaw motions were performed. The numerical results were benchmarked against physical experiments. The computed hydrodynamic derivatives were compared with empirical formulae and subsequently implemented in manoeuvring simulations. In addressing seakeeping, incident waves were generated by a numerical wave maker and the computed results for wave diffraction were validated against physical measurements. Furthermore, RANS simulation for roll decay was undertaken and validated against results from model tests. Finally, a numerical roll tank was established to study the hydrodynamic coefficients of the roll motion in intact and damaged conditions and the corresponding results were compared with available model test data. In conclusion, systematic studies and ensuing results from numerical simulations of classical ship hydrodynamic problems using RANS demonstrated beyond doubt that CFD could and should play an important role in the design, analysis and evaluation of ship hydrodynamic performance. In addition, they provide unshakeable evidence of the level of capability to make the next important step: rendering CFD a routine "tool" in ship dynamics and hydrodynamics.
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Hudson, Dominic A. "A validation study on mathematical models of speed and frequency dependence in seakeeping of high speed craft." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299687.
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Fratello, John David. "Multi-body Dynamics Simulation and Analysis of Wave-adaptive Modular Vessels." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76787.
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Catamarans provide vast deck space, high thrust efficiency, and excellent transverse stability, however, in rough conditions they can be susceptible to deck slamming from head seas or bow diving in following seas and a pitch-roll coupling effect that can lead to uncomfortable corkscrew motion under bow-quartering seas. A new class of catamaran called Wave-Adaptive Modular Vessels (WAM-V™) aims to help mitigate oceanic input from the cabin by allowing for the relative motion of components not common to classic catamaran design. This thesis presents a set of multi-body dynamics simulation models created for two active WAM-Vs™ along with analysis on their suspension characteristics. Both models provide conclusive and realistic results, with the final model being validated against on-water testing data from a 12-ft unmanned prototype WAM-V.
The first of these simulations serves primarily as a tool to evaluate WAM-V™ response characteristics with respect to a variety of parametric variations. The modeling environment is highlighted along with details of the parametric simulation and how it was created. The results fall in line with our expectations and are presented along with analysis of the sensitivity of each parameter at three longitudinal locations. The final simulation attempts to model the response of a 12-ft unmanned surface vessel (USV) prototype of the WAM-V™ configuration. Testing data is collected, processed, and applied to the model for validation of its prediction accuracy. The results of the sea tests indicate that the simulation model performs well in predicting USV motions at sea. Future considerations for testing WAM-Vs™ can include changes in suspension and mass parameters as well as limiting particular degrees-of-freedom by making their joints rigid.Master of Science
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Vanden, Berg Scott M. "Non-linear rolling of ships in large sea waves." Thesis, Monterey, California. Naval Postgraduate School, 2007. http://hdl.handle.net/10945/3003.
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CIVINSThe United States Navy has taken a new interest in tumblehome hulls. While the stealth characteristics of these hull forms make them attractive to the Navy, their sea keeping characteristics have proven to be problematic. Normal approximations of sea keeping characteristics using linear differential equations with constant coefficients predict a very stable platform, while observations in model tests show a ship that is prone to extreme roll transients. This thesis examines a simple method of producing a non-linear simulation of roll motion using a tumblehome hull provided by the Office of Naval Research. This research demonstrates the significant difference that a variable restoring coefficient introduces into a hull's seakeeping characteristics.
Contract number: N62271-97-G-0026
CIVINS
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Jung, Se Yong. "Determining Parameters for a Lagrangian Mechanical System Model of a Submerged Vessel Maneuvering in Waves." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97332.
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In this dissertation, an approach for determining parameters for a nonlinear Lagrangian mechanical system model of a submerged vessel maneuvering near waves is presented. The nonlinear model with determined parameters is capable of capturing nonlinear effects neglected by other linear models, and therefore can be applied to improve maneuvering performance and expand the operating envelope for submerged vessels operating in elevated sea states.
To begin, a first principles Lagrangian nonlinear maneuvering (LNM) model for a surface-affected submerged vessel derived by using Lagrangian mechanics cite{BattistaPhD2018} is reformulated to allow the application of data from a medium fidelity potential flow code. In the reformulation process, the order of integration and differentiation in the integro-differential parameters are switched and partial derivatives of the Lagrangian function are computed with readily available data from the panel code solution. As a result, all model parameters can be computed individually using the panel code, wherein the need for additional numerical discretization is circumvented in the computation process through use of solutions already performed by the basic panel code, enabling higher accuracy and lower computational cost. Furthermore, incident wave effects are incorporated into the reformulated LNM model to yield a Lagrangian nonlinear maneuvering and seakeeping (LNMS) model. The LNMS model is numerically validated by confirming the proposed methods and by comparing steady and unsteady hydrodynamic force calculations from the LNMS model against panel code computations for various vessel motions in calm water and in plane progressive waves. Finally, methods for computing physically intuitive components of the model parameters, as well as methods for making approximations of the terms accounting for memory effects are presented, leading to a model formulation amenable to control design.
By applying the methods proposed in this dissertation, each and every parameter of the Lagrangian mechanical system model of a submerged vessel maneuvering in waves can be obtained accurately and with computational efficiency by using a potential flow panel code. The resulting nonlinear motion model provides higher model fidelity than existing unified maneuvering and seakeeping models, especially in applications such as nonlinear control design and simulation.Doctor of Philosophy
A unified maneuvering and seakeeping model for a submerged vessel maneuvering near waves describes mathematically the relationship between input values to the dynamical system, such as thrust from the propulsors, and output values from the system, such as the position and orientation of the vessel. This unified model has a wide range of applications, ranging from vessel hull form optimization in the early design phase to motion controller tuning after the vessel has been constructed. In order for a unified model to make accurate predictions, for instance, for a submerged vessel making a rapid turn near large waves, nonlinear effects have to be included in the model formulation. To that end, a nonlinear motion model for a marine craft affected by a free surface has been developed using Lagrangian mechanics. This dissertation describes an approach for determining the parameters of the nonlinear motion model using a potential flow panel code, which is originally designed to determine flow velocity of the fluid and pressure distribution over marine vessels. The nonlinear motion model is reformulated and the software implementation is modified to support parameter computations. In addition, the methods are numerically validated by comparing computations using the model against solutions output by the panel code. Compared to traditional parameter estimation approaches, the proposed methods allow for a more accurate and efficient determination of parameters of the nonlinear potential flow model for a submerged vessel operating near waves. The resulting Lagrangian nonlinear maneuvering and seakeeping (LNMS) model with determined parameters is able to capture critical nonlinear effects and has applications such as nonlinear control design, rapid design optimization and training simulator development.
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Anwar, Sohail. "Transient Stress and Strain Assessment of Marine Boiler : Fully Rigid Body Dynamics Coupled Finite Element Analyses." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-95440.
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Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations. In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.
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Rudko, David D. "Logistical analysis of the littoral combat ship." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FRudko.pdf.
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Thesis (M.S. in Operations Research.)--Naval Postgraduate School, March 2003.Thesis advisor(s): David A. Schrady, Kevin J. Maher. Includes bibliographical references (p. 71-74). Also available online.
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Ruggeri, Felipe. "Um método de Rankine 2D no domínio do tempo para análise de comportamento no mar." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-06062013-173918/.
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A capacidade de prever os movimentos de uma plataforma de petróleo sujeita a ondas é bastante importante no contexto da engenharia naval e oceânica, já que esses movimentos terão diversas implicações no projeto deste sistema, com impactos diretos nos custos de produção e tempo de retorno do investimento. Esse trabalho apresenta os fundamentos teóricos sobre o problema de comportamento no mar de corpos flutuantes sujeitos a ondas de gravidades e um método numérico para solução do problema 2D no domínio do tempo. A hipótese básica adotada é a de escoamento potencial, que permitiu a utilização do método de elementos de contorno para descrever a região fluida. Optou-se pela utilização de fontes de Rankine como função de Green no desenvolvimento do método, o qual será abordado somente no contexto linear do problema matemático, delimitado através de um procedimento combinado entre expansão de Stokes e série de Taylor. As simulações são realizadas no domínio do tempo sendo, portanto, resolvido o problema de valor inicial com relação às equações do movimento e equações que descrevem a superfície-livre combinadas com dois problemas de valor de contorno, um para o potencial de velocidades e outro para o potencial de aceleração do escoamento. As equações integrais de contorno permitem transformar o sistema de equações diferenciais parciais da superfície livre num sistema de equações diferenciais ordinárias, as quais são resolvidas através do método de Runge-Kutta de 4a. ordem. As equações integrais são tratadas de forma singularizada e o método utilizado para discretizar as mesmas é de ordem baixa tanto para a função potencial quanto para a aproximação geométrica, sendo as integrações necessárias realizadas numericamente através de quadratura Gauss-Legendre. O algoritmo numérico é testado e validado através de comparações com soluções analíticas, numéricas e experimentais presentes na literatura, considerando os problemas de geração de ondas, cálculo de massa adicional e amortecimento potencial através de ensaios de oscilação forçada, testes de decaimento e, por último, resposta em ondas. Os resultados obtiveram boa concordância com aqueles adotados como paradigma.The ability to predict the seakeeping characteristics of an offshore structure (such as an oil platform) is very important in offshore engineering since these motions have important consequences regarding its design and therefore its cost and payback period. This work presents the theoretical and numerical aspects concerning the evaluation of the 2D seakeeping problem under the potential flow hypothesis, which allows the use a Boundary Elements Method to describe the fluid region with Rankine sources as Green function. The linearized version of the mathematical problem is built by a combined Stokes expansion and Taylor series procedure and solved in time domain. The initial value problem concerning the motion and free surface equations are solved combined to the boundary value problems considering the velocity and acceleration flow potentials, which transform the partial differential equations of the free surface into ordinary differential equations, that are solved using the 4th order Runge-Kutta method. The integral equations are solved in its singularized version using a low order method both for the potential function and the geometrical approximation, with the terms of the linear system evaluated using Gauss Legendre quadrature. The numerical scheme is tested and validated considering analytical, numerical and experimental results obtained in the literature, concerning wave generation, added mass and potential damping evaluation, decay tests and response to waves. The results achieved good agreement with respect to those used as paradigm.
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Dotta, Raul. "Estudo de aplicação de ferramentas numéricas ao problema de ressonância de ondas na operação de alívio lado a lado." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-29062017-085453/.
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Este trabalho apresenta uma abordagem numérica com base em ensaios experimentais previamente realizados, direcionada ao problema de ressonância do campo de ondas em operações de alívio lado a lado (side by side). Os efeitos dessas interferências hidrodinâmicas são responsáveis por alterar drasticamente o campo de ondas em regiões de confino, gerando amplificação nos movimentos de primeira ordem e trazendo risco à operação. Este fenômeno está presente em diversas áreas da exploração e produção offshore e vem sendo o principal objeto de estudo nos últimos anos, principalmente em operações de alívio lado a lado, nos quais existe uma grande preocupação de colisão, rompimento dos cabos e integridade estrutural das defensas, devido à proximidade dos cascos. Neste contexto, devido à complexidade do problema, a modelagem numérica utilizada para interpretar o fenômeno de ressonância em softwares comerciais deve ser realizada com cautela, sendo que a utilização direta desta ferramenta gera amplificações equivocadas da superfície ressonante uma vez que esta resolução tem como base a teoria potencial. As diferenças observadas durante a comparação entre ensaios numéricos e experimentais são causadas em virtude da negligência na avaliação da dissipação de parte da energia das ondas ressonantes provocadas devido aos efeitos como viscosidade, vorticidade e turbulência do escoamento. Com o objetivo de analisar corretamente este fenômeno por meio de ensaios numéricos, uma maneira consiste na inclusão de adaptações no modelo para atingir os resultados desejáveis. Estas adaptações consistem na implementação de métodos artificiais, tais como os chamados \"Modos Generalizados\" e \"Praias Numéricas\", aplicados à região entre as embarcações com o intuito de amortecer as elevações irrealistas da superfície. Sendo assim, este trabalho abordará o problema de ressonância de ondas, investigando o desempenho de duas ferramentas numéricas para a sua predição, o WAMIT (Wave Analysis Massachusetts Institute of Technology) e o TDRPM (Time Domain Rankine Painel Method). Os resultados serão comparados com dados obtidos em um conjunto de ensaios em escala reduzida, realizado previamente no laboratório Tanque de Provas Numérico da USP (TPN). Dessa forma, o estudo dos fenômenos de ressonância será discutido, principalmente, em seu aspecto numérico, visando à verificação do desempenho do WAMIT e do TDRPM.This work presents a numerical study based on previously conducted experimental studies, focused on the problem of resonance of the wave field in operations involving multi-body. The hydrodynamic interferences effects are responsible for drastically changing the wave field in confine regions, generating amplification of first order movements and bringing operational risk. This phenomenon is present in several areas of offshore exploration and production and has been the main object of study in recent years, mainly in side-by-side offloading operations, in which there is a great concern due to the risk of mooring lines breaking, damages to the fenders and also collision. In this context, due to the complexity of the problem, the numerical modeling used to evaluate the resonance phenomenon in commercial software becomes unsuitable, generating erroneous amplifications of the resonant surface since it is based on the potential theory. The differences observed during the comparisons between numerical and experimental tests are caused by negligence in the evaluation of the dissipation of part of the resonant wave energy caused by viscosity, vorticity and flow turbulence effects. In order to correctly analyze this phenomenon through numerical tests, one way is to include adaptations on the model to achieve the desired results. These adaptations consist of the implementation of artificial methods, such as \"Generalized Modes\" and \"Numerical Damping Zones\", applied to the region between the vessels in order to damp the unrealistic elevations of the surface. Thus, this study will approach the problem of gap wave resonance, investigating the performance of two numerical tools for its prediction, WAMIT (Wave Analysis Massachusetts Institute of Technology) and TDRPM (Time Domain Rankin Panel Method). The results will be compared with data obtained from a set of small scale tests previously performed at the Numerical Test Tank of USP laboratory (TPN). Therefore, the study of resonance phenomena will be discussed, mainly, in its numerical aspect, in order to verify the performance of WAMIT and TDRPM.
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Bassler, Christopher Colby. "Analysis and Modeling of Hydrodynamic Components for Ship Roll Motion in Heavy Weather." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23258.
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Ship roll motion has been the subject of many studies, because of the complexities associated with this mode of ship motion, and its impact on operability, safety, and survivability. Estimation and prediction of the energy transfer and dissipation of the hydrodynamic components, added inertia and damping, is essential to accurately describe the roll motions of a ship. This is especially true for ship operations in moderate to extreme sea conditions. In these conditions, a complex process of energy transfer occurs, which alters the physical behavior of the hydrodynamic components, and ultimately affects the amplitude of ship roll motion. Bilge keels have been used on ships for nearly two centuries, to increase damping and reduce the severity of roll motions experienced by a ship in waves. Because ship motions are more severe in extreme sea conditions, large roll angles may occur. With the possibility of crew injury, cargo damage, or even capsize, it is important to understand the behavior of the roll added inertia and damping for these conditions. Dead ship conditions, where ships may experience excitation from beam, or near beam, seas present a worst case scenario in heavy weather. The behavior of a ship in this condition should be considered in both the design and assessment of seakeeping performance.
In this study, hydrodynamic component models of roll added inertia and roll damping were examined and assessed to be unsuitable for accurate prediction of ship motions in heavy weather. A series of model experiments and numerical studies were carried out and analyzed to provide improved understanding of the essential physical phenomena which affect the hydrodynamic components and occur during large amplitude roll motion. These observations served to confirm the hypothesis that the existing models for roll added inertia and damping in large amplitude motions are not sufficient. The change in added inertia and damping behavior for large roll motion is largely due to the effects of hull form geometry, including the bilge keels and topside geometry, and their interactions with the free surface. Therefore, the changes in added inertia and damping must be considered in models to describe and predict roll motions in severe wave environments.
Based on the observations and analysis from both experimental and numerical methods, several time-domain model formulations were proposed and examined to model hydrodynamic components of large amplitude roll motions. These time-domain formulations included an analytical model with memory effects, a piecewise formulation, and several possibilities for a bilge keel force model. Although a piecewise model for roll damping was proposed, which can improve the applicability of traditional formulations for roll damping to heavy weather conditions, a further attempt was undertaken to develop a more detailed model specifically for the bilge keel force. This model was based on the consideration of large amplitude effects on the hydrodynamic components of the bilge keel force. Both the piecewise and bilge keel force models have the possibility to enable improved accuracy of potential flow-based numerical prediction of ship roll motion in heavy weather. However, additional development remains to address issues for further practical implementation.
Ph. D.
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Mousaviraad, Sayyed Maysam. "CFD prediction of ship response to extreme winds and/or waves." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/559.
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The effects of winds and/or waves on ship motions, forces, moments, maneuverability and controllability are investigated with URANS computations.
The air/water flow computations employ a semi-coupled approach in which water is not affected by air, but air is computed assuming the free surface as a moving immersed boundary. The exact potential solution of waves/wind problem is modified introducing a logarithmic blending in air, and imposed as boundary and initial conditions. The turbulent air flows over 2D water waves are studied to investigate the effects of waves on incoming wind flow. Ship airwake computations are performed with different wind speeds and directions for static drift and dynamic PMM in calm water, pitch and heave in regular waves, and 6DOF motions in irregular waves simulating hurricane CAMILLE. Ship airwake analyses show that the vortical structures evolve due to ship motions and affect the ship dynamics significantly. Strong hurricane head and following winds affect up to 28% the resistance and 7% the motions. Beam winds have most significant effects causing considerable roll motion and drift forces, affecting the controllability of the ship.
A harmonic wave group single run seakeeping procedure is developed, validated and compared with regular wave and transient wave group procedures. The regular wave procedure requires multiple runs, whereas single run procedures obtain the RAOs for a range of frequencies at a fixed speed, assuming linear ship response. The transient wave group procedure provides continuous RAOs, while the harmonic wave group procedure obtains discrete transfer functions, but without focusing. Verification and validation studies are performed for transient wave group procedure. Validation is achieved at the average interval of 9.54 (%D). Comparisons of the procedures show that harmonic wave group is the most efficient, saving 75.8% on the computational cost compared to regular wave procedure. Error values from all procedures are similar at 4 (%D). Harmonic wave group procedure is validated for a wide range of Froude numbers, with satisfactory results.
Deterministic wave groups are used for three sisters rogue waves modeling. A 6DOF ship simulation is demonstrated which shows total loss of controllability with extreme ship motions, accelerations and structural loads.
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Kopke, Markus. "A passive suspension system for a hydrofoil supported catamaran." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/1991.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008.This study investigates practical passive methods to improve the seakeeping of a Hydrofoil Supported Catamaran (Hysucat). The Hysucat is a hybrid vessel combining hydrofoil efficiency with the stability of catamarans. The seakeeping of the Hysucat was initially investigated experimentally to determine what seakeeping improvements are inherent to the Hysucat design. The results showed that the seakeeping is improved by 5-30%. A passive suspension system for the main hydrofoil of the Hysucat was designed and tested. A concept development strategy was followed for the design of the suspension system as such a system had never been investigated previously. Detailed specifications for the design were developed and concepts that could satisfy the customer and engineering requirements were generated. Numerical simulation models for the Hysucat and the final concepts were derived assuming a simplified 2nd order system to describe the seakeeping dynamics of the demi-hulls. Unknown parameters were determined using parameter estimation techniques. Representative parameter values were calculated from multiple towing tank experiments. Theory describing the motion of a hydrofoil in an orbital velocity wave field was combined with the hull model to simulate the Hysucat as well as the suspension system concepts. The models indicated that the concept where the main hydrofoil was attached to a spring loaded arm, that was free to pivot in response to orbital waves, was the most feasible in damping out vertical transmitted accelerations. Experimental tests indicated that little improvement was achieved with the suspension system at low frequencies. At resonance the suspension system was effective in decreasing the heave of the vessel by up to 27%. The pitch and acceleration response results showed improvements at the higher encounter frequencies of up to 50%. The calm water resistance of the vessel increased by 10% over the Hysucat with rigidly attached hydrofoils; however was still 24% less than the hull without foils.
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Watai, Rafael de Andrade. "Um método de elementos de contorno do domínio do tempo para análise de comportamento no mar de sistemas oceânicos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-23062015-102357/.
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Esta tese apresenta o desenvolvimento de um método de elementos de contorno (BEM) no domínio do tempo baseado em fontes de Rankine para analise linear de comportamento no mar de sistemas oceânicos. O método e formulado por dois problemas de valor inicial de contorno definidos para os potenciais de velocidade e aceleração, sendo este ultimo utilizado para calcular de maneira acurada a derivada temporal do potencial de velocidades. Testes de verificação são realizados para a solução dos problemas de difração, radiação e de corpo livre para flutuar. Uma vez verificada, a ferramenta e aplicada em dois problemas multicorpos considerados no estado-da-arte em termos de modelagem hidrodinâmica utilizando BEM. O primeiro trata do problema envolvendo duas embarcações atracadas a contrabordo. Este é um caso no qual os códigos baseados na teoria de escoamento potencial são conhecidos por apresentarem dificuldades na determinação das soluções, tendendo a superestimar as elevações de onda no vão entre as embarcações e a apresentar problemas de convergência numérica associados a efeitos ressonantes de onda. O problema e tratado por meio do método de damping lid e a convergência das series temporais e investigada avaliando diferentes níveis de amortecimento. Os resultados são comparados com dados experimentais. O segundo problema se refere a analise de sistemas multicorpos com grandes deslocamentos relativos. Neste problema, ferramentas no domínio da frequência nao podem ser utilizadas, por considerarem apenas malhas fixas. Deste modo, o presente método e estendido para considerar um gerador de malhas de paineis e um algoritmo de interpolação de ordem alta no laco de tempo do código, possibilitando a mudança de posições relativas entre os corpos durante a simulação. Os resultados são comparados com dados de experimentos executados especificamente para fins de verificação do código, apresentando uma boa concordância. De acordo com o conhecimento do autor, esta e a primeira vez que certas questões relativas a modelagem numérica destes dois problemas multicorpos são relatadas na literatura especializada em hidrodinâmica computacional.The development of a time domain boundary elements method (BEM) based on Rankine\'s sources for linear seakeeping analysis of offshore systems is here addressed. The method is formulated by means of two Initial Boundary Value Problems defined for the velocity and acceleration potentials, the latter being used to ensure an accurate calculation of the time derivatives of the velocity potential. Verification tests for solving the difraction, radiation and free floating problems are presented. Once verified, the code is applied for two complex multi-body problems considered to be in the state-of-the-art for hydrodynamic modelling using BEM. The first is the seakeeping problem of two ships arranged in side-by-side, a problem in which all potential flow codes are known to have a poor performance, tending to provide unrealistic high wave elevations in the gap between the vessels and to present numerical convergence problems associated to resonant effects. The problem is here addressed by means of a damping lid method and the convergence of the time series with different damping levels is investigated. Results are compared to data measured in an experimental campaign. The second problem refers to the analysis of multi-body systems composed of bodies undergoing large relative displacements. This is a case that cannot be properly analyzed by frequency domain codes, since they only consider fixed meshes. For this application, the present numerical method is extended to consider a panel mesh generator in the time loop of the code, enabling the change of body relative positions during the computations. Furthermore, a higher order interpolation algorithm designed to recover the solutions of a previous time-step was also implemented, enabling the calculations to progress with reasonable accuracy in time. The numerical results are compared to data of experimental tests designed and executed for verification of the code, and presented a very good agreement. To the author\'s knowledge, this is the first time that certain issues concerning the numerical modelling of these two complex multi-body problems are reported in the literature specialized in hydrodynamic computations.
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Bigi, Nedeleg. "Investigation of the dynamic motions and operability of a ship towed by kite." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0133/document.
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Afin de réduire les émissions de gaz à effet de serre et le coût du transport maritime, l'utilisation des cerfs-volants comme système de propulsion auxiliaire des navires est prometteuse. Pour estimer les performances et l’opérabilité d’un navire tracté par cerf-volant, une modélisation dynamique du système est alors mise en oeuvre. Une modélisation analytique de cerf-volant est utilisée. Ce modèle néglige la masse du cerf-volant et suppose que les lignes sont droites et indéformables. Ces hypothèses conduisent à un modèle cinématique dépendant du coefficient de portance et de la finesse aérodynamique. Une évolution linéaire des coefficients aérodynamiques en fonction de la courbure de la trajectoire de vol est proposée. Par ailleurs, en développant un modèle quasi analytique de ligne, il est montré qu’à partir de 2 m.s-1 de vent relatif que l’hypothèse de ligne droite est raisonnable. En se basant sur un modèle de ligne, un critère analytique de vitesse de vent minimum permettant un vol quasi-statique est présenté. Dans le but de résoudre l’ensemble des termes d’interaction entre le cerf-volant et le navire, un modèle linéarisé de tenue à la mer temporelle est développé. Le produit de convolution de la réponse impulsionnelle du navire est calculé avec des systèmes d’états. Cependant comme celle-ci représente mal les mouvements horizontaux des navires, le modèle développé est alors couplé à un modèle de manoeuvrabilité. Pour étudier les interactions entre le cerf-volant et le navire un couplage monolithique et un couplage dissocié sont comparés. Le couplage dissocié néglige l’influence des mouvements du navire sur le vol du cerf-volant. En cas de mer calme, les résultats obtenus par les deux types de couplage sont très proches. En cas de houle régulière les mouvements du navire sont principalement causés par la houle. Le couplage monolithique montre qu’un réseau de sous-harmoniques basse fréquence apparait alors dans le spectre d’excitation du navire. La fréquence fondamentale des sous-harmoniques est donnée par la différence entre la fréquence de vague et la fréquence de l’harmonique la plus proche de l’excitation du kite. Quand cette différence est suffisamment petite, un phénomène d’accrochage apparait. Ce phénomène est bénéfique pour le cerf-volant et le navire quand le décalage des harmoniques d'excitation correspond à une augmentation. Par ailleurs, une étude de la stabilité de route montre qu'il est nécessaire de contrôler activement le safranIn order to reduce greenhouse gas emissions and shipping costs, the use of kites as an auxiliary propulsion device for ships is promising. In order to estimate the performance and the operability of a kite-towed vessel, a dynamic modeling of the system is implemented. A classical kite modeling is used. This model neglects the mass of the kite and assumes straight and inelastic tethers. These assumptions lead to a kinematic model depending on the lift coefficient and the aerodynamic lift to drag ration angle. A linear evolution of these aerodynamic coefficients as a function of the curvature of the flight path is proposed. In addition, by developing a quasi-analytical line model, it is shown that from 2 m.s-1 of relative wind the straight tether assumption is reasonable. Based on the tether model, an analytical criterion assessing the minimum wind speed to enable a quasi-static kite flight is developed. To solve all the interaction terms between the kite and the ship, a time domain seakeeping model based on the linearized ship equation of motion assuming a potential flow is developed. The convolution product of the impulse response of the ship is computed with state-space systems. However, since horizontal ship motions are not well represented by such theories, a coupling with a maneuvering model is presented.Comparisons to experimental data tests show good agreements. To study the interactions between the kite and the ship, a monolithic coupling and a dissociated coupling are compared. The dissociated coupling neglects the influence of ship motions on the kite flight. In a calm water case, results obtained by the two types of coupling are very close. In regular waves, ship motions are dominated by the wave influence. Thus, with the monolithic coupling, a network of low frequency subharmonic appears in the kite excitation spectrum. The fundamental frequency of the subharmonic is given by the difference between the wave frequency and the frequency of the nearest kite excitation harmonic. When this difference is small enough, a lock-in phenomenon appears. This phenomenon is a benefit for the kite and the ship when the shift of the excitation harmonics corresponds to an increase. Furthermore, a course keeping stability study shows that the rudder needs to be actively controlled
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Malta, Edgard Borges. "Métodos e processos para a análise experimental de sistemas oceânicos de produção de petróleo e gás." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-17082010-113906/.
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O aumento na complexidade das operações de sistemas de produção de petróleo e gás no mar e um fato concreto. Atualmente, a necessidade de avaliar o comportamento no mar destes sistemas requer a compreensão de fenômenos, até então, pouco explorados e que tornam imprescindível uma investigação apoiada em experimentos com modelos reduzidos. Resultados obtidos em tanques de provas, por sua vez, requerem metodologias que contam com a experiência do pesquisador e que, em muitos casos, não são encontradas de maneira detalhada o suficiente na literatura. Ou seja, muitas destas metodologias normalmente são encontradas, no entanto, não em nível para que pesquisadores iniciantes desenvolvam atividades experimentais minimamente pertinentes as eventuais tomadas de decisão ou confrontação com outras linhas de abordagem como a analítica e/ou a numérica. Portanto, e exatamente neste contexto que se insere a presente dissertação de mestrado, buscando descrever em detalhes a teoria e prática envolvida nos procedimentos experimentais para o estudo de comportamento no mar típico de uma plataforma padrão, perfeitamente adaptáveis a outras geometrias mais complexas de sistemas navais e oceânicos. Esses procedimentos envolvem desde o planejamento dos ensaios necessários, passando pelos cuidados durante sua execução, culminando nos métodos de análise dos resultados e formas usuais de documentação. Para facilitar o processo de compreensão, além do próprio texto, este trabalho também contemplou a construção de uma ferramenta matemática dedicada a condução das atividades acima, destacando-se a avaliação e obtenção de parâmetros a partir de ensaios de decaimento e o levantamento expedito das curvas de resposta em ondas regulares, transientes e irregulares.The increasing complexity of o shore system operations for oil and gas production is a reality. Currently, the need to evaluate the seakeeping of these systems requires understanding some phenomena not yet explored and, for that reason, researches using experiments with small scale models become indispensable. Results obtained in model basins require methodologies that rely on the researchers experience and, most of the time, they are not found detailed enough in the literature. When many of these methodologies are usually found, however, they are not ready for beginner researchers to develop experimental activities minimally relevant to any decision and/or confrontation with other lines, such as the analytical and/or numerical approaches. Therefore, the context of this dissertation describes in detail the theory and involved practice in an experimental procedure for the study of seakeeping of a standard platform, perfectly adaptable to other complex geometries and naval systems. These procedures involve the planning of the necessary tests, through the care during their execution, culminating in the methods of result analyses and usual forms of documentation. In order to facilitate the process of understanding, the construction of a dedicated mathematical tool to conduct the activities described above is provided, emphasizing the assessment and quick obtaining parameters from decay tests, curves response in regular and transient waves, among many others.
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Muñoz, Jaime Miguel Mariano Saldarriaga. "Estudo de uma metodologia para o dimensionamento de um tanque de provas do tipo reboque." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-01032011-113219/.
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Um tanque de provas do tipo reboque permite a realização de ensaios hidrodinâmicos com modelos em escala, sua presença é importante devido à possibilidade de obter características hidrodinâmicas que dimensionam a potência e qualidade do comportamento dos navios durante a sua operação, otimizando os projetos de forma particular ou geral, tanto para a navegação marítima, lacustre ou fluvial. O objetivo principal desta pesquisa é estudar e propor uma metodologia para o dimensionamento e concepção de um tanque de reboque para o Serviço Industrial da Marinha (SIMA PERU), principal estaleiro do Peru, de maneira que possa realizar os ensaios hidrodinâmicos correspondentes aos diferentes tipos de embarcações produzidas pelo SIMA PERU. Como propósito de estudo será desenvolvido uma análise de um tanque de reboque que permitirá ensaiar modelos de diferentes tipos de embarcações, levando em consideração as diferentes condições ambientais e climáticas relacionadas ao litoral peruano em toda sua extensão, isto é, uma condição marítima equivalente a uma escala Beaufort 5. Estas são as condições que foram requeridas para atuar na costa peruana. Será proposto um tanque de reboque com características próprias, baseado no razoável dimensionamento dos modelos reduzidos e nas necessidades e requerimentos de ensaio de acordo às recomendações apresentadas pela Conferência Internacional de Tanques de Reboque (International Towing Tank Conference- ITTC).A towing tank allows hydrodynamic testing with scale models, their presence is important because allows to obtain hydrodynamics characteristics that they measure the power and quality of behavior during the operation, optimizing the designs in general or particular form of vessels for sea, lake or river. The main objective of this research is to study and propose a method for sizing and development of a towing tank for the Naval Industrial Service; SIMA - PERU, main shipyard from Peru, so it carry out hydrodynamics tests corresponding to different types of vessels produced by SIMA - PERU. The purpose of study will be developed analysis of a towing tank that will test models of different types of vessels, taking into account the different environmental and climatic conditions related to the Peruvian coast, in other words, sea conditions equivalent to a Beaufort \"5\". These are the conditions that were required to act on the Peruvian coast. Will be offered a towing tank with its own characteristics, needs and requirements based on the consistent sizing of reduced models and according to the recommendations made by the International Towing Tank Conference - ITTC.
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Zhou, Zhengquan. "A theory and analysis of planing catamarans in calm and rough water." ScholarWorks@UNO, 2003. http://louisdl.louislibraries.org/u?/NOD,45.
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Thesis (Ph.D)--University of New Orleans, 2003.Title from electronic submission form. "A dissertation ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Science"--Dissertation t.p. Vita. Includes bibliographical references.
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Descamps, Théo. "Numerical analysis and development of accurate models in a CFD solver dedicated to naval applications with waves." Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0049.
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L’objectif de cette thèse est de développer des solveurs numériques et des méthodologies afin d’améliorer le temps de calcul et la précision des simulations de tenue à la mer et de résistance ajoutée sur houle. Tout d’abord, une synthèse de l’algorithme du solver foamStar développé en interne est effectuée. A partir de cette analyse, une modification est proposée afin de pouvoir utiliser le "Multidimensional Universal Limiterfor Explicit Solution" (MULES) avec un schéma temporel backward d’ordre deux. Ensuite, plusieurs études successives sont réalisées afin de : vérifier l’implémentation du schéma backward ; définir une configuration numérique et des maillages efficaces pour la simulation de houle. Les cas d’étude sont : les tourbillons de Taylor-Green, la houle régulière non linéaire se propageant dans un domaine periodique, et enfin, la houle régulière générée avec des zones de relaxation et des configurations numériques proches de celles utilisées pour des applications navales. Dans la dernière partie de cette thèse, une étude préliminaire est réalisée en simulant un porte-conteneur avec une vitesse d’avance dans des houles régulières de face. Les recommandations définies tout au long de cette thèse sont également évaluéesThe objective of the present thesis is to develop solvers and methodologies in order to improve the computational cost andthe accuracy with regard to the thematics of seakeeping and added resistance. First, a synthetic workflow of the algorithmof the in-house solver foamStar is proposed. From this analysis a modification is proposed in order to use the Multidimensional Universal Limiter for Explicit Solution (MULES) with a second-order backward time scheme. Then, successive studies are done in order to: verify the implementation of the backward scheme; define an efficient numerical set-up and adequate mesh structures for numerical wave simulations. The case studies are, Taylor-Green vortices, nonlinear regular wave propagating in a periodic domain, and finally, regular waves generated with relaxation zones considering numerical configurations close to what is used for naval applications. In the last part of this Thesis, a preliminary study is done simulating a containership with forward speed in head regular waves. The recommendations derived all along this thesis are also evaluated
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Rixmann, D. Bradley. "Time domain seakeeping simulations of some multiple waterplane vessels /." 2001.
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Chun-ChangChou and 周群璋. "The Effect of Different Ship Sailing Attitude on Seakeeping Performance." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/14486568960374173703.
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碩士國立成功大學
系統及船舶機電工程學系
103
This research aims at figuring out the effect of different draft and trim angle of the ships on seakeeping performance by well-developed computer simulation program for ship hydrodynamics. In the research, three different types of ships are to be compared. They are tanker ship, container ship, and bulk carrier ship (series 60), which all have different value of block coefficient (CB). The existing computer program based on strip theory is applied to calculate the ship motions and added resistance. Experimental tests are carried out to verify the results from the computer program. However, the tests only include longitudinal waves conditions due to the limitation of the facilities in NCKU Towing Tank. The experimental test also includes the measurement of moment of inertia for pitch motion of whole ship model. From the results, we found that for container ship, sailing attitudes with trim by stern show good performance in heave motion, pitch motion, and added resistance generally. However, for roll motion, trim by bow 1° status shows the best performance. For tanker ship, sailing attitudes with trim by stern also show good performance in heave motion, pitch motion, and added resistance generally. However, for roll motion, even keel status shows the best performance. For series 60 ship, sailing attitude with trim by stern also has good performance in heave motion, pitch motion, and added resistance. However, trim by stern status has the worst performance in roll motion among all the sailing attitudes. Generally speaking, for series 60 ship, there is no best sailing attitude adapted to all conditions, because each sailing attitude has different advantages and drawbacks of seakeeping performance.