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In this paper, we present several applied as well as fundamental research problems related to the future needs of the offshore engineering. The paper starts out with a detailed discussion of the current uncertainties and constraints. Then, specific research issues on environmental input conditions, on the role of computational fluid dynamics, and on damping and dynamic response are presented. It is suggested that an appreciation of the input parameters, acquisition of extensive data to properly characterize the ocean environment, development of new methods and tools to acquire relevant data, extensive use of the computational methods, basic/applied research on the dynamic response and damping of structures, use of new materials, science-and-technology transfer from sister disciplines (e.g., aerospace industry, keeping in mind the complexities brought about by the presence of the air-water interface), and other related research will significantly enhance our ability to design and build a variety of safer and economical offshore structures in deeper waters as well as over marginal fields in the next few decades. This herculean effort will require several decades of complementary experimental, numerical and analytical studies of ocean-structure interaction which will serve to elucidate the basic as well as applied fluid mechanics phenomena relevant to the offshore mechanics.
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Isaacson, Michael. "Wave and current forces on fixed offshore structures." Canadian Journal of Civil Engineering 15, no. 6 (December 1, 1988): 937–47. http://dx.doi.org/10.1139/l88-125.
The Canadian Standards Association standard S471 "General requirements, design criteria, environment, and loads, Part 1 of the CSA code for the design, construction and installation of fixed offshore structures" contains an appendix "Wave and current loads." To compliment this appendix, the present paper provides a more detailed survey of this topic with a review of the recent literature and recommendations of hydrodynamic data needed in offshore design. In addition, hydrodynamic considerations in the calculation of earthquake and ice loads are mentioned. Key words: currents, current forces, hydrodynamics, ocean engineering, offshore structures, waves, wave forces.
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Faltinsen, O. M. "Hydrodynamics of marine and offshore structures." Journal of Hydrodynamics 26, no. 6 (December 2014): 835–47. http://dx.doi.org/10.1016/s1001-6058(14)60092-5.
The knowledge of the behavior of floating offshore wind turbines (W/T) under wave and/or wind action remains one of the most difficult challenges in offshore engineering which is mostly due to the highly non-linear response of the structure. The present study describes the design process of a 3D physical experiment to investigate the behavior of the most promising structure technology of floating W/T: spar buoy (SB) and tension leg platform (TLP) under different meteo conditions. In order to properly design the two W/T models, the following topics have been analyzed: mooring lines, mass distribution, appropriate scaling factor and data relative to the geometrical characteristics, wave basin dimensions and wind and waves conditions. In addition, the Smoothed Particle Hydrodynamics method (SPH) (Monaghan 1994) has been considered to simulate the 3D behavior of a floating offshore W/T. In particular, the SPH, calibrated and verified on the basis of the experimental observations, may represent a reliable tool for preliminary test of changes in the floater geometry.
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Tao, L., B. Molin, Y. M. Scolan, and K. Thiagarajan. "Spacing effects on hydrodynamics of heave plates on offshore structures." Journal of Fluids and Structures 23, no. 8 (November 2007): 1119–36. http://dx.doi.org/10.1016/j.jfluidstructs.2007.03.004.
Isaacson, Michael, and John Baldwin. "Wave–current effects on large offshore structures." Canadian Journal of Civil Engineering 16, no. 4 (August 1, 1989): 543–51. http://dx.doi.org/10.1139/l89-084.
The various effects that influence loads acting on a large offshore structure due to the combination of waves and currents are reviewed. These may be broadly associated with potential flow effects and viscous effects. The potential flow effects are nonlinear and may generally be investigated by perturbation or time-stepping methods. Viscous effects include the onset of flow separation, which affects the validity of the assumed potential flow, as well as steady and oscillatory forces. The fluid mechanics of the complete wave–current–structure interaction problem are not yet well understood and areas in need of additional research are identified. Key words: currents, drag, drift forces, hydrodynamics, ocean engineering, offshore structures, waves, wave forces.
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Benitz, M. A., M. A. Lackner, and D. P. Schmidt. "Hydrodynamics of offshore structures with specific focus on wind energy applications." Renewable and Sustainable Energy Reviews 44 (April 2015): 692–716. http://dx.doi.org/10.1016/j.rser.2015.01.021.
Isaacson, Michael de St Q. "Recent advances in the computation of nonlinear wave effects on offshore structures." Canadian Journal of Civil Engineering 12, no. 3 (September 1, 1985): 439–53. http://dx.doi.org/10.1139/l85-052.
The present paper provides a review of recent research on various nonlinearities that arise in ocean wave interactions with offshore structures. These include nonlinearities associated with the incident waves alone, the response of slender structural members to waves, and the nonlinear diffraction problem involving wave interactions with large structures. Emphasis is given to areas of current research into two particular nonlinear problems. One concerns an investigation into alternative approximations to the Morison equation for flexible structures and the other concerns the numerical simulation of nonlinear wave diffraction around large structures. Key words: diffraction, hydrodynamics, nonlinear flow, ocean engineering, offshore structures, waves.
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Foschi, Ricardo, Michael Isaacson, Norman Allyn, and Steven Yee. "Combined wave – iceberg loading on offshore structures." Canadian Journal of Civil Engineering 23, no. 5 (October 1, 1996): 1099–110. http://dx.doi.org/10.1139/l96-917.
The Canadian Standards Association has developed and published a code for the design and construction of fixed offshore structures. This code has been subjected to a comprehensive verification process which has identified several issues warranting further study. One of these relates to the combined effects of wave and iceberg collision loading. At present, this combination is treated by the use of a load combination factor specified in the Code. The present paper describes a recent study which was undertaken to determine the appropriateness of the recommended value of the load combination factor. The study involves a numerical analysis in which loads due to waves alone, an iceberg alone, and an iceberg and waves in combination have been calculated for a range of iceberg and wave parameters. These results have been applied to a first-order reliability analysis in order to study the force levels corresponding to an annual probability of 10−4 or to the onset of global sliding with an annual probability of 10−4. The paper thereby makes recommendations for load combination factors applicable to combined wave–iceberg loading. Key words: hydrodynamics, icebergs, ocean engineering, offshore structures, wave forces, waves.
Dissertations / Theses on the topic "Offshore structures – Hydrodynamics":
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Hodgkinson, Derek Anthony Martin. "Computer graphics applications in offshore hydrodynamics." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26705.
The results of hydrodynamic analyses of two problems involving offshore structures are displayed graphically. This form of presentation of the results and the liberal use of colour have been found to significantly help the ease in which the results are interpreted.
For the transformation of waves around an artificial island, a time history of the evolution of the regular, unidirectional wave field around an artificial island is obtained. Through the use of colour, regions in which wave breaking occurs have been clearly defined. The numerical technique used is based on the finite element method using eight noded isoparametric elements. The determination of the transformed wave field takes wave breaking, wave refraction, diffraction, reflection and shoaling into account. The graphical display is achieved by using a plotting program developed for the output of finite element analyses.
The motions of a semi-submersible rig are computed from the RAO curves of the rig, used to obtain its' small response in a random sea. The numerical technique used in the analysis assumes that the vertical members are slender and may be analysed using the Morison equation whereas the hulls are treated as large members which are discretised and analysed using diffraction theory. The discretisation of the cylinders and hulls together with the time history of the rig's motions are displayed graphically. Once again, the graphical display is plotted using a program developed for the output of finite element analyses for four noded elements. In this case, a finite element technique has not been employed but the results were ordered to act as though this is the case. The slender members (cylinders) and large members (hulls) are clearly distinguishable by using different colours. The elements used in the analysis are also clearly shown.
The VAX 11/730 system was used to obtain the results shown. A video tape, using the results of a time stepping procedure, was made by successively recording the hardcopies produced by the VAX printer. The time stepping could also be seen, in real time, on the IRIS. Applied Science, Faculty of Civil Engineering, Department of Graduate
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Schulz, Karl Wayne. "Numerical prediction of the hydrodynamic loads and motions of offshore structures /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Walker, Daniel Anthony Guy. "Interaction of extreme ocean waves with offshore structures." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:6858dc08-1bd4-4195-8893-1af98d5e68e3.
With most of the world's untouched oil and gas resources offshore and the possibility that hurricanes are becoming more frequent and more intense, the risks associated with offshore oil and gas production are increasing. Therefore, there is an urgent need to improve current understanding of extreme ocean waves and their interaction with structures. This thesis is concerned with the modelling of extreme ocean waves and their diffraction by offshore structures, with the ultimate aim of proposing improved tools for guiding airgap design. The feasibility of using linear and second order diffraction solutions with a suitable incident wave field to predict extreme green water levels beneath multi-column structures is investigated. Such tools, when fully validated, could replace the need to carry out model tests during preliminary design. When contemplating airgap design it is crucially important that consideration is given to the largest waves in a sea state, the so-called freak or rogue waves. This thesis studies the nature of one specific freak wave for which field data is available, namely the Draupner New Year wave. Unique features of this wave are identified, distinguishing it from a typical large wave, and an estimate of the probability of occurrence of the wave is given. Furthermore, a design wave, called NewWave, is proposed as a good model for large ocean waves and is validated against field and experimental data. The diffraction of regular waves and NewWaves by a number of structural configurations is studied. In order to assess the validity of using diffraction solutions for the purposes of airgap design, comparisons are made with measured wave data from a programme of wave tank experiments. Wave data for a real platform configuration are examined to highlight the key issues complicating the validation of diffraction based design tools for real structures. The ability of diffraction theory to reproduce real wave measurements is discussed. The phenomenon of near-trapping is also investigated, allowing guidelines for airgap design to be established.
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周奮鵬 and Fun-pang Chau. "Numerical methods in wave loading of large offshore structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B31206797.
Abdolmaleki, Kourosh. "Modelling of wave impact on offshore structures." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0055.
[Truncated abstract] The hydrodynamics of wave impact on offshore structures is not well understood. Wave impacts often involve large deformations of water free-surface. Therefore, a wave impact problem is usually combined with a free-surface problem. The complexity is expanded when the body exposed to a wave impact is allowed to move. The nonlinear interactions between a moving body and fluid is a complicated process that has been a dilemma in the engineering design of offshore and coastal structures for a long time. This thesis used experimental and numerical means to develop further understanding of the wave impact problems as well as to create a numerical tool suitable for simulation of such problems. The study included the consideration of moving boundaries in order to include the coupled interactions of the body and fluid. The thesis is organized into two experimental and numerical parts. There is a lack of benchmarking experimental data for studying fluid-structure interactions with moving boundaries. In the experimental part of this research, novel experiments were, therefore, designed and performed that were useful for validation of the numerical developments. By considering a dynamical system with only one degree of freedom, the complexity of the experiments performed was minimal. The setup included a plate that was attached to the bottom of a flume via a hinge and tethered by two springs from the top one at each side. The experiments modelled fluid-structure interactions in three subsets. The first subset studied a highly nonlinear decay test, which resembled a harsh wave impact (or slam) incident. The second subset included waves overtopping on the vertically restrained plate. In the third subset, the plate was free to oscillate and was excited by the same waves. The wave overtopping the plate resembled the physics of the green water on fixed and moving structures. An analytical solution based on linear potential theory was provided for comparison with experimental results. ... In simulation of the nonlinear decay test, the SPH results captured the frequency variation in plate oscillations, which indicated that the radiation forces (added mass and damping forces) were calculated satisfactorily. In simulation of the nonlinear waves, the waves progressed in the flume similar to the physical experiments and the total energy of the system was conserved with an error of 0.025% of the total initial energy. The wave-plate interactions were successfully modelled by SPH. The simulations included wave run-up and shipping of water for fixed and oscillating plate cases. The effects of the plate oscillations on the flow regime are also discussed in detail. The combination of experimental and numerical investigation provided further understanding of wave impact problems. The novel design of the experiments extended the study to moving boundaries in small scale. The use of SPH eliminated the difficulties of dealing with free-surface problems so that the focus of study could be placed on the impact forces on fixed and moving bodies.
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Cheung, Kwok Fai. "Hydrodynamic interactions between ice masses and large offshore structures." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26686.
The objective of the work described in this thesis is to evaluate the significance of the ambient fluid on the motion of an ice mass in the vicinity of an offshore structure and during the subsequent impact mechanism.
Models for iceberg drift are first reviewed. The changes in flow field around an ice mass drifting in a current near an offshore structure are investigated by potential flow theory. The proximity effects and current interactions are generalized by introducing the added mass and convective force coefficients for the ice mass. A two-dimensional numerical model based on the boundary element method is developed to calculate these coefficients over a range of separation distances up to the point of contact.
A numerical model based on ice properties and geometry is developed to simulate the impact force acting on the structure. Both the 'contact-point' added masses estimated in this thesis and the traditionally assumed far-field added masses are used in the impact model separately. The results from the two cases are compared and the crucial roles played by the ambient fluid during impact are discussed.
Finally, a number of related topics is proposed for further studies. Applied Science, Faculty of Civil Engineering, Department of Graduate
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McTaggart, Kevin Andrew. "Hydrodynamics and risk analysis of iceberg impacts with offshore structures." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30733.
The evaluation of design iceberg impact loads for offshore structures and the influence
of hydrodynamic effects on impact loads are examined. Important hydrodynamic effects include iceberg added mass, wave-induced oscillatory iceberg motions, and the influence of a large structure on the surrounding flow field and subsequent velocities of approaching icebergs. The significance of these phenomena has been investigated using a two-body numerical diffraction model and through a series of experiments modelling the drift of various sized icebergs driven by waves and currents approaching a large offshore structure. Relevant findings from the hydrodynamic studies have been incorporated into two probabilistic models which can be used to determine design iceberg collision events with a structure based on either iceberg kinetic energy upon impact or global sliding force acting on the structure. Load exceedence probabilities from the kinetic energy and sliding force models are evaluated using the second-order reliability method. Output from the probabilistic models can be used to determine design collision parameters and to assess whether more sophisticated modelling of various impact processes is required. The influence of the structure on velocities of approaching icebergs is shown to be significant
when the structure horizontal dimension is greater than twice the iceberg dimension. As expected, wave-induced oscillatory motions dominate the collision velocity for smaller icebergs but have a negligible effect on velocity for larger icebergs. Applied Science, Faculty of Civil Engineering, Department of Graduate
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Lipsett, Arthur William. "Nonlinear response of structures in regular and random waves." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25826.
The problem of the dynamics of a flexible offshore structure in either a regular
or random sea is considered in this thesis. A simple single degree of freedom model of the structure is assumed and the relative velocity formulation of the Morison equation is used to describe the fluid force. The resulting equation of motion is a nonlinear ordinary differential equation with either harmonic or stochastic forcing depending on the wave description.
Solutions are obtained for regular deterministic waves by numerical integration, various linearization methods and a new perturbation method developed in this thesis. The numerical solution is used to assess the accuracy of each of the approximate solution methods. Of these, the perturbation method is found to give the best approximation to the numerical solution over the complete frequency range of interest.
For random seas the response spectrum and the mean square response are obtained by various linearization methods, the method of equivalent linearization, and by the new perturbation method. The perturbation method and the method of equivalent linearization are very similar in that they both yield the same values of effective damping. Comparison of the results obtained by a numerical simulation method with the results of the perturbation method and the widely used method of equivalent linearization shows that the perturbation method gives a better estimate of the response mean square value than does the method of equivalent linearization. For all of the approximate solution methods that are discussed it was found that the use of Hermite polynomials to represent the solution is very effective in obtaining various expected values required in the computational procedure.
In addition to the average response statistics, such as the response mean square value, the probability density of the response is also considered. It is well known that the response of a linear system to Gaussian forcing is itself Gaussian. The wave force given by the Morison equation is non-Gaussian and therefore the response is also non-Gaussian but of unknown form. The hypothesis that for a linear equation, the probability density of the response is of the same form as the probability density of forcing, even for the case of non-Gaussian forcing, is investigated and verified using the results of numerical simulations. Design considerations of interest which follow from the response probability density are also discussed. Applied Science, Faculty of Civil Engineering, Department of Graduate
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Richardson, Mark Damian. "Dynamically installed anchors for floating offshore structures." University of Western Australia. School of Civil and Resource Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0230.
The gradual depletion of shallow water hydrocarbon deposits has forced the offshore oil and gas industry to develop reserves in deeper waters. Dynamically installed anchors have been proposed as a cost-effective anchoring solution for floating offshore structures in deep water environments. The rocket or torpedo shaped anchor is released from a designated drop height above the seafloor and allowed to penetrate the seabed via the kinetic energy gained during free-fall and the anchors self weight. Dynamic anchors can be deployed in any water depth and the relatively simple fabrication and installation procedures provide a significant cost saving over conventional deepwater anchoring systems. Despite use in a number of offshore applications, information regarding the geotechnical performance of dynamically installed anchors is scarce. Consequently, this research has focused on establishing an extensive test database through the modelling of the dynamic anchor installation process in the geotechnical centrifuge. The tests were aimed at assessing the embedment depth and subsequent dynamic anchor holding capacity under various loading conditions. Analytical design tools, verified against the experimental database, were developed for the prediction of the embedment depth and holding capacity.
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Hildebrandt, Arndt [Verfasser]. "Hydrodynamics of breaking waves on offshore wind turbine structures / Arndt Hildebrandt." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1053540329/34.
Book chapters on the topic "Offshore structures – Hydrodynamics":
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Karimirad, Madjid. "Aerodynamic and Hydrodynamic Loads." In Offshore Energy Structures, 187–221. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-12175-8_9.
Jia, Junbo. "Offshore Structures and Hydrodynamic Modeling." In Soil Dynamics and Foundation Modeling, 269–313. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-40358-8_9.
Chandrasekaran, Srinivasan. "Hydrodynamic Response of Perforated Offshore Members." In Dynamic Analysis and Design of Offshore Structures, 173–201. New Delhi: Springer India, 2015. http://dx.doi.org/10.1007/978-81-322-2277-4_5.
Lim, Dong-Hyun, Yonghwan Kim, and Seung-Hoon Lee. "Prediction of Extreme Nonlinear Hydrodynamic Responses and Mooring Line Loads of Floating Offshore Structures." In Lecture Notes in Civil Engineering, 564–78. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4680-8_39.
Kim, M. H. "Hydrodynamics of Offshore Structures." In Developments in Offshore Engineering, 336–81. Elsevier, 1999. http://dx.doi.org/10.1016/b978-088415380-1/50027-3.
Xia, Jinzhu, and Quanming Miao. "Dynamics of deepwater offshore structures – a review." In Hydrodynamics VI: Theory and Applications, 391–98. Taylor & Francis, 2004. http://dx.doi.org/10.1201/b16815-57.
"Models for Ships, Offshore Structures and Underwater Vehicles." In Handbook of Marine Craft Hydrodynamics and Motion Control, 133–86. Chichester, UK: John Wiley & Sons, Ltd, 2011. http://dx.doi.org/10.1002/9781119994138.ch7.
Harries, R., and A. Alexandre. "Evaluating corrections to linear boundary element method hydrodynamics accounting for mean second order forces on spar buoy wind turbine support structures." In Renewable Energies Offshore, 689–95. CRC Press, 2015. http://dx.doi.org/10.1201/b18973-97.
"Summary of hydrodynamic coefficients." In Dynamics of Offshore Structures, 387–92. Elsevier, 1989. http://dx.doi.org/10.1016/b978-0-408-01074-0.50019-7.
Conference papers on the topic "Offshore structures – Hydrodynamics":
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Pang, A. L. J., J. Gullman-Strand, N. Morgan, M. Skote, and S. Y. Lim. "Determining Scour Depth for Offshore Structures Based on a Hydrodynamics and Optimisation Approach." In Offshore Technology Conference Asia. Offshore Technology Conference, 2016. http://dx.doi.org/10.4043/26848-ms.
Kubelka, Bruno Galler, Claudio Rodrigues Olinto, Walter Jesus Paucar Casas, and Waldir Terra Pinto. "Modeling of the hydrodynamics of subsea floating structures for mollusc offshore cultivation." In XXXVIII Iberian-Latin American Congress on Computational Methods in Engineering. Florianopolis, Brazil: ABMEC Brazilian Association of Computational Methods in Engineering, 2017. http://dx.doi.org/10.20906/cps/cilamce2017-0938.
Baar, Job J. "Newman’s Manuscript and His Impact on Offshore Hydrodynamics." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57038.
Prof. Nick Newman has spent an important part of his career researching the mathematical and numerical aspects of the radiation/diffraction Green’s function, i.e. the linearized potential of an oscillatory source submerged below the free surface [1–4]. The first part of the paper pays tribute to Newman’s accomplishments by presenting three thus far unpublished expansions of the oscillatory source potential. The first one is based on an unpublished manuscript by Newman himself [5] and in essence amounts to the backward recursive computation of a one-dimensional Taylor series expansion. The second expansion assumes the form of a remarkably simple Bessel series expansion and was inspired by a paper by Bessho [6]. The third expansion is another remarkably simple asymptotic series expansion in terms of incomplete Gamma functions and Legendre polynomials. The second part of the paper addresses the practical significance of some of Newman’s key accomplishments for the field of offshore hydrodynamics. Attention is focused on his ‘slow drift approximation’ [7], which has proved to be invaluable for the practical estimation of slow wave drift responses of floating structures. The diffraction program WAMIT [8] has by now matured into a de facto industry standard. The combined effectiveness of Newman’s slow-drift approximation and the WAMIT program will be illustrated by comparing some full-scaled measured and numerically hindcasted responses of Shell’s Mars Tension Leg Platform during hurricane Katrina [9].
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Wang, Gang, Tobias Martin, Liuyi Huang, and Hans Bihs. "Numerical Simulation of Hydrodynamics Around Net Meshes Using REEF3D." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18355.
Abstract Hydrodynamics and turbulence around net meshes have drawn more and more attention because it is closely related to forces on the structures and safety issues of offshore fish farms. In terms of numerical modeling of forces on nets, Morison or screen force model is ordinarily adopted to account for its hydrodynamics. However, these methodologies mainly rely on empirical experimental or cylindrical hydrodynamic coefficients, neglecting flow interactions between adjacent cruciforms or net bars. In this study, REEF3D open-source hydrodynamic toolbox is adopted to analyze flow around net meshes explicitly and investigate the hydrodynamics related to forces on the structure. The simulation accuracy is in good agreement with flume experiments and previous research. Flow velocity and vorticity around net bars and knots are investigated. The results demonstrate that 2 × 2 or 3 × 3 mesh cases are more reliable when studying turbulence around net meshes, flow interactions around adjacent net bars, knots should be taken into consideration. Two patterns to control Sn, one is to change the diameter of net bars and the other is to control length, have different effects on the flow around meshes. This paper presents a first step in the aim to derive a new empirical formula for Cd depending on Sn, and Re, which are more related to the physics in offshore conditions.
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Vijay, K. G., and T. Sahoo. "Retrofitting of Floating Bridges With Perforated Outer Cover for Mitigating Wave-Induced Responses." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77054.
An investigation has been carried out based on multi-domain boundary element method to analyze the mitigation of wave-induced hydrodynamic loads on a pair of floating rectangular bridges by retrofitting the structures with external porous plates. The study is based on the assumptions of small amplitude water wave theory in finite water depth with the characteristics of wave-body interactions remain unaltered along the bridge. Wave past porous structure is modelled using Darcy’s law. Various hydrodynamic characteristics are studied by analyzing the wave forces acting on the floating bridges and the retrofitted porous structures for different wave and structural parameters. With the introduction of a retrofit, the horizontal force on the bridge reduces irrespective of wave and structural parameters, whilst vertical force increases under certain conditions. Moreover, when the distance between the bridges is an integer multiple of half of the wavelength of the incident waves, both the bridges experience optima in horizontal and vertical wave forces, with both these forces being 180° out of phase. The present study is expected to be useful in the design of efficient bridge structures which will reduce wave-induced hydrodynamics loads on the structure and thus enhance the service life of floating bridges.
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Cinello, Alexandre, François Pétrié, Eric Le Hir, Bernard Molin, and Guillaume de Hauteclocque. "Shielding Effect on the Overall Hydrodynamic Properties of Complex Subsea Structures." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83063.
Deepwater field developments are usually associated with large submarine packages to be installed such as suction anchors, manifolds and other subsea equipment. Key data for the lowering operation engineering are the added mass and drag coefficients of the package, which is usually a complex structure made of plates (mudmat, drop object protection…), piping and miscellaneous equipment. To extract these hydrodynamics coefficients, it is usual industry practice to consider the package overall volume or to sum the individual components coefficients which may lead to very different results. Experimental investigations on generic complex structures have been conducted within the CITEPH project “Offshore installation of heavy package – phase II”, with the aim of better understanding the hydrodynamics coefficients to be used for the design. This paper presents the work that has been performed during this joint industry project, in 2010/2011, with the support of TOTAL, TECHNIP, SAIPEM and DORIS Engineering, on shielding effect. In particular, model tests set-up and main results are discussed. The trends that have been found and the empirical laws that have been established as functions of dimensionless numbers are also presented.
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Yan, Hongmei, and Yuming Liu. "Efficient Computations of Fully-Nonlinear Wave Interactions With Floating Structures." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20412.
We consider the problem of fully nonlinear three-dimensional wave interactions with floating bodies with or without a forward speed. A highly efficient time-domain computational method is developed in the context of potential flow formulation using the pre-corrected Fast Fourier Transform (PFFT) algorithm based on a high-order boundary element method. The method reduces the computational effort in solving the boundary-value problem at each time step to O(NlnN) from O(N2∼3) of the classical boundary element methods, where N is the total number of unknowns. The high efficiency of this method allows accurate computations of fully-nonlinear hydrodynamic loads, wave runups, and motions of surface vessels and marine structures in rough seas. We apply this method to study the hydrodynamics of floating objects with a focus on the understanding of fully nonlinear effects in the presence of extreme waves and large-amplitude body motions.
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Hoekstra, Carel, Henk Smienk, Joris van Drunen, and Alessio Pistidda. "Applying CFD for In-Line Structure Hydrodynamics in Pipeline Installation Analysis." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54273.
Over the last decade Heerema Marine Contractors (HMC) has successfully performed multiple installation campaigns of large sized in-line structures (ILS) with Deep Water Construction Vessels (DCV) Aegir and Balder. Nowadays steady increase in size and weight of ILS have made these special operations even more complex. Presence of large sized ILS and accompanying buoyancy modules in the catenary have proven to play a dominant role in pipeline integrity. Originally hydrodynamic force formulations in finite element analysis are solely designated for the pipeline itself. These computations comprehend the application of the Morison equation using constant hydrodynamic coefficients of basic shapes in steady flow. Therefore hydrodynamic forces acting on the ILS, characterized by irregular relative motions of a complex shaped and perforated structure, are highly simplified while playing a dominant role in the analyses. Validity of applying the standard Morison equation is debatable, since large ILS cannot be assumed slender. Nonetheless Morison type formulations can provide reasonable results depending on the accuracy of the hydrodynamic coefficients. Deriving these coefficients for complex shaped structures using industry standards is a highly interpretive process involving an accumulation of assumptions. This approach yields varying coefficients, which are applied conservatively in installation analyses, resulting in an unnecessary reduction of DCV offshore workability. To improve workability of these complex installations, HMC has implemented an ILS specific hydrodynamic profile from Computational Fluid Dynamics (CFD) analysis into the installation analyses. This is effectuated by the development of an enhanced methodology with a dedicated hydrodynamic formulation for large perforated ILS. Dependencies on Keulegan-Carpenter (KC) number and local angle of attack are addressed in this formulation to respectively cover the inertia dominated oscillating motions and complex geometric composition. The applied hydrodynamic formulation is based on work of Molin et al. which showed a good agreement to the CFD analysis performed for this study. Development and application of this methodology is initiated as a first assessment towards more accurate ILS installation analyses. Analysis of a study case shows reductions up to 50% of maximum bending strain in a specific regular wave analysis. From the work presented it is concluded that the industry practice vastly overestimates hydrodynamic forcing on large sized ILS. Complementary research is needed on the topics of oscillations for low (<1.0) KC number, effects of relative fluid velocity and finally the implementation of irregular waves.
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Huang, L. L., and H. R. Riggs. "Displacement and Pressure Transfer Between Structural and Fluid Meshes in Fluid-Structure Interaction." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37303.
Nonlinear, time-domain hydroelastic analysis of flexible offshore structures requires that the structural motion be transferred to the fluid model and the resulting fluid pressure at the fluid-structure interface be transferred from the fluid model to the structure. When the structural mesh and the fluid mesh describe two distinct three-dimensional surfaces, the transfer of displacement and pressure is both difficult and non-unique. In this paper, a new transfer strategy based on the variational-based smoothing element analysis (SEA) technique is presented. The displacement transfer uses the original formulation of the SEA method, although the application of the procedure to displacement transfer is new. For energy conservation during the reverse pressure transfer, the original functional in the SEA method is enhanced with a new term that attempts to conserve the work done by the hydrodynamic forces when obtaining the global structural nodal forces. To evaluate the transfer methodology, the hydrodynamic response of three rigid bodies are considered. Pressure contours, hydrodynamic coefficients, and motions that are calculated based on the data transferred with the proposed method are compared with the results that are obtained from standard rigid-body hydrodynamics theory that does not include a structural finite element model. The method is shown to work very well. In addition, it has general applicability and it can deal with relatively large geometric differences in the meshes.
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Garrido-Mendoza, Carlos A., Antonio Souto-Iglesias, and K. P. Thiagarajan. "Numerical Simulation of Hydrodynamics of a Circular Disk Oscillating Near a Seabed." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-11072.
This paper studies how the hydrodynamics coefficients of added mass and damping varies when an oscillating disk approaches a seabed. Analysis was performed by OpenFOAM code using the ‘PIMPLE’ algorithm. The simulations considered the flow as laminar and hence no turbulence model was used. Simulations were conducted for a solid disk of 200 mm diameter, 2 mm thick, oscillating at amplitudes varying from 1–48 mm and elevation ‘h’ of the disk from the seabed varying from 0.2–2 times the disk radius. The geometry and parameters used here were the same as that of Wadhwa et al. (2010) [1] and Vu et al. (2008) [2]. The forces on the disk were calculated using a Tool for post-processing force/lift/drag data with function tool available in OpenFOAM. The motions of the disk were restricted to axial (heave) direction. The calculated forces and displacement were analyzed using a Fourier projection to separate the added mass and damping effects. Numerical results were compared with the experiments conducted by Wadhwa et al. (2010) [1] with a sandy bottom. Results show that the added mass and damping increase monotonically with the Keulegan-Carpenter number (KC) up to a critical value, beyond which the behavior becomes random. The critical KC increases linearly with increasing distance from the seabed. The hydrodynamic problem has important applications in structures such as foundation templates and subsea structures oscillating in proximity to the seabed. The computations show vortex lines of the flow, and the influence of the seabed on the flow around the structure.
