Download or read book Vortex Induced Vibration of a Marine Riser written by Xiangxi Han and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine riser is a key equipment connecting a floating platform and a seabed wellhead. Vortex-induced vibration (VIV) is the main cause of the fatigue damage of the riser. The prediction of marine riser VIV is very difficult because of its strong non-linearity, instability and uncertainty. In recent years, many numerical models of VIV of marine riser have been developed to explore the mechanism of marine riser VIV, providing scientific theoretical basis and practical engineering methods for vibration control and engineering design of marine riser. Combined with the authors,Äô own recent research, this chapter discusses the research progress on marine riser VIV in the ocean engineering, including phenomenon mechanism analysis and different numerical research methods.

Download or read book System Identification of Offshore Marine Riser Due to Vortex Induced Vibration VIV written by Loganathan Radzakrishnan and published by . This book was released on 2014 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Parametric Study of Vortex induced Vibration of a Long Flexible Marine Riser written by Anup Ghimire and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Prediction of the Vortex induced Vibrations of Marine Riser written by and published by . This book was released on 2003 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book New Innovations in Engineering Education and Naval Engineering written by Nur M. S. Hassan and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrodynamics Around Cylindrical Structures written by Jorgen Fredsoe and published by World Scientific. This book was released on 1997-03-17 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the subject of wave/current flow around a cylinder, the forces induced on the cylinder by the flow, and the vibration pattern of slender structures in a marine environment.The primary aim of the book is to describe the flow pattern and the resulting load which develops when waves or current meet a cylinder. Attention is paid to the special case of a circular cylinder. The development in the forces is related to the various flow patterns and is discussed in detail. Regular as well as irregular waves are considered, and special cases like wall proximities (pipelines) are also investigated.The book is intended for MSc students with some experience in basic fluid mechanics and for PhD students.

Download or read book Vortex induced Vibration of Marine Risers written by Harish Mukundan and published by . This book was released on 2008 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) Predictions using the new databases are found to significantly reduce the error in estimating the riser cross-flow response. Finally, data from a comprehensive experiment is utilized to show that the riser response is resonant in the harmonic component, but non-resonant in the third-harmonic component. It is shown that this happens because the spatial dependence of the third-harmonic fluid force component is dominated by the first-harmonic wavelengths. This finding has significant implications for modeling the higher-harmonic forces and the resulting fatigue damage estimation methodologies.

Download or read book Fatigue Damage Prediction in Deepwater Marine Risers Due to Vortex induced Vibration written by Chen Shi and published by . This book was released on 2011 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: Slender marine risers used in deepwater applications often experience vortex-induced vibration (VIV). Fatigue damage associated with VIV is of great concern to offshore engineers; however, it has proven difficult to predict this fatigue damage using existing semi-empirical tools. Similarly, approaches based on theoretical and computational fluid dynamics (CFD) generally rely on simplified assumptions on the fluid flow fields and response characteristics. To gain an understanding of VIV and associated fatigue damage, full-scale field monitoring campaigns as well as reduced-scale laboratory experiments are often carried out, wherein the riser response in the form of strains and/or accelerations is recorded using an array of a limited number of sensors distributed over the length of the riser. Simultaneously, current velocities at a proximate location are also recorded. Such measurements generally reveal complex characteristics of the dynamic response of a riser undergoing VIV, including the presence of multiple vibration harmonics, non-stationary behavior, and the existence of sustained or intermittent traveling wave patterns. Such complex features, often not accounted for in some semi-empirical and theoretical approaches, are critical to take into consideration for accurate fatigue damage estimation. In this study, several empirical methods are employed to first reconstruct the response of an instrumented riser and, then, estimate fatigue damage rates over the entire span of the riser based on a limited number of discrete measurements. The methods presented employ the measured data in different ways. One method, referred to as "weighted waveform analysis'' relies on expressing the riser response as a summation of several weighted waveforms or riser modes; the mode shapes are "assumed'' and time-varying weights for each mode are estimated directly from the measurements. The riser response over the entire span is reconstructed based on these assumed mode shapes and estimated modal weights. Other methods presented extract discrete mode shapes from the data directly. With the help of interpolation techniques, continuous mode shapes are formed, and the riser response is again reconstructed. Fatigue damage rates estimated based on the reconstructed strains obtained using the various empirical methods are cross-validated by comparing predictions against direct measurements available at the same locations (but not used in the analyses). Results show that the empirical methods developed here may be employed to accurately estimate fatigue damage rates associated with individual recorded segments of measurements. Finally, a procedure for prediction of long-term fatigue damage rates of an instrumented marine riser is presented that relies on combining (multiplying) the fatigue damage rates associated with short recorded segments for specific current profile types, with the relative likelihood of different incident current profiles, and integration over all current profiles. It should be noted that the empirical approaches to fatigue damage estimation presented in this study are based only on measured data; also, they explicitly account for different riser response characteristics and for site-specific current profiles developed from metocean studies. Importantly, too, such estimation procedures can easily accommodate additional data that become available in any ongoing field monitoring campaign to improve and update long-term fatigue damage prediction.

Download or read book Dynamic Simulation of Marine Risers with Vortex Induced Vibration written by Ryan Stuart Nicoll and published by . This book was released on 2006 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of the work described here is to analyse vortex induced vibration VIV) effects on marine risers and unorthodox forms of suppression of this phe?nomenon. which can cause structural failure through metal fatigue. Two suppression methods are explored: flex joints and buoyancy modules. Flex joints. which act like a hinge at a point on the riser due to the large reduction in bending stiffness. can suppress higher modes of vibration from propagating along or appearing in the riser. Buoyancy modules, with their local 100% increase in riser diameter. can decorrelate vortex shedding along the span of the riser and reduce the resonant effect of VIV. The numerical finite element cable model and rigid body model developed at the University of Victoria were modified and used as a foundation for the research. The modifications include an algorithm to estimate the forces clue to ocean surface interaction with rigid bodies and a model to produce the appropriate VIV response in the numerical cable model. The resulting VIV model was calibrated and validated with analytical. experimental, and numerical data available in the literature. In general. the model produces qualitative effects of VIV. including its self-starting and self-limiting nature, frequency lock-in. multi-mode response. and limited structural response on the order of one diameter. A simulation of a testbed riser in a variety of ocean currents was generated to observe the effects of installing flex joints and buoyancy modules at various locations along the riser span. The performance of the testbed riser was gauged by comparing the time series of von Mises stress and the associated safety factor, ns. from fatigue failure at many points along the span to an unmodified testbed riser. The stress fluctuation was drastically reduced within the flex joints for all water currents studied, which greatly increases fatigue performance. Flex joints placed at the top of the testbed riser had less impact. as the stresses are dominated by the large and unavoidable tensions found there. Flex joints placed in the bottom region of the riser did not affect the ns, . of the remaining riser span until very high modes of vibration were present. At these higher modes. some testbed riser configurations changed their vibration envelope and frequency. which indicates that a possible alternate and less damaging mode of vibration was induced. Flex joints therefore act effectively as a local patch against poor fatigue performance and placement of several flex joints does not negatively impact the behaviour of the rest of the riser in the cases examined. However. the explicit relationship between placement and spacing of flex joints with environment conditions remains unknown. Buoyancy modules introduced spatial fluctuations in the entire nu profile of the testbed riser, unlike flex joints. In addition. the buoyancy modules decreased n, performance due to the hydrodynamic load concentrations induced by their large diameters. However, the 16% coverage case increased n., . elsewhere along the riser, though the 10% covered riser did not match this performance. Since in both cases the modules were evenly spaced along the riser. performance benefits from increased coverage implies a minimum coverage of 16% needed for significant improvement in fatigue performance for devices of this type. This coverage requirement may apply to traditional VIV suppression devices such as helical strokes. since they decorrelate vortex shedding along the span of the riser albeit in a different manner than buoyancy modules. Finally. the buoyancy modules changed the stress oscillation frequency more than the flex joint cases from the unmodified riser. This is desirable since lowering the frequency of oscillation also increases the fatigue performance of the riser.

Download or read book Dynamic Simulation of Marine Risers with Vortex Induced Vibration written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of the work described here is to analyse vortex induced vibration VIV) effects on marine risers and unorthodox forms of suppression of this phenomenon. which can cause structural failure through metal fatigue. Two suppression methods are explored: flex joints and buoyancy modules. Flex joints. which act like a hinge at a point on the riser due to the large reduction in bending stiffness. can suppress higher modes of vibration from propagating along or appearing in the riser. Buoyancy modules, with their local 100% increase in riser diameter. can decorrelate vortex shedding along the span of the riser and reduce the resonant effect of VIV. The numerical finite element cable model and rigid body model developed at the University of Victoria were modified and used as a foundation for the research. The modifications include an algorithm to estimate the forces clue to ocean surface interaction with rigid bodies and a model to produce the appropriate VIV response in the numerical cable model. The resulting VIV model was calibrated and validated with analytical. experimental, and numerical data available in the literature. In general. the model produces qualitative effects of VIV. including its self-starting and self-limiting nature, frequency lock-in. multi-mode response. and limited structural response on the order of one diameter. A simulation of a testbed riser in a variety of ocean currents was generated to observe the effects of installing flex joints and buoyancy modules at various locations along the riser span. The performance of the testbed riser was gauged by comparing the time series of von Mises stress and the associated safety factor, ns. from fatigue failure at many points along the span to an unmodified testbed riser. The stress fluctuation was drastically reduced within the flex joints for all water currents studied, which greatly increases fatigue performance. Flex joints placed at the top of the testbed riser had less impact. as the stresses.

Download or read book Dynamic Simulation of Marine Risers with Vortex Induced Vibration written by Ryan Stuart Nicoll and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of the work described here is to analyse vortex induced vibration VIV) effects on marine risers and unorthodox forms of suppression of this phe?nomenon. which can cause structural failure through metal fatigue. Two suppression methods are explored: flex joints and buoyancy modules. Flex joints. which act like a hinge at a point on the riser due to the large reduction in bending stiffness. can suppress higher modes of vibration from propagating along or appearing in the riser. Buoyancy modules, with their local 100% increase in riser diameter. can decorrelate vortex shedding along the span of the riser and reduce the resonant effect of VIV. The numerical finite element cable model and rigid body model developed at the University of Victoria were modified and used as a foundation for the research. The modifications include an algorithm to estimate the forces clue to ocean surface interaction with rigid bodies and a model to produce the appropriate VIV response in the numerical cable model. The resulting VIV model was calibrated and validated with analytical. experimental, and numerical data available in the literature. In general. the model produces qualitative effects of VIV. including its self-starting and self-limiting nature, frequency lock-in. multi-mode response. and limited structural response on the order of one diameter. A simulation of a testbed riser in a variety of ocean currents was generated to observe the effects of installing flex joints and buoyancy modules at various locations along the riser span. The performance of the testbed riser was gauged by comparing the time series of von Mises stress and the associated safety factor, ns. from fatigue failure at many points along the span to an unmodified testbed riser. The stress fluctuation was drastically reduced within the flex joints for all water currents studied, which greatly increases fatigue performance. Flex joints placed at the top of the testbed riser had less impact. as the stresses are dominated by the large and unavoidable tensions found there. Flex joints placed in the bottom region of the riser did not affect the ns, . of the remaining riser span until very high modes of vibration were present. At these higher modes. some testbed riser configurations changed their vibration envelope and frequency. which indicates that a possible alternate and less damaging mode of vibration was induced. Flex joints therefore act effectively as a local patch against poor fatigue performance and placement of several flex joints does not negatively impact the behaviour of the rest of the riser in the cases examined. However. the explicit relationship between placement and spacing of flex joints with environment conditions remains unknown. Buoyancy modules introduced spatial fluctuations in the entire nu profile of the testbed riser, unlike flex joints. In addition. the buoyancy modules decreased n, performance due to the hydrodynamic load concentrations induced by their large diameters. However, the 16% coverage case increased n., . elsewhere along the riser, though the 10% covered riser did not match this performance. Since in both cases the modules were evenly spaced along the riser. performance benefits from increased coverage implies a minimum coverage of 16% needed for significant improvement in fatigue performance for devices of this type. This coverage requirement may apply to traditional VIV suppression devices such as helical strokes. since they decorrelate vortex shedding along the span of the riser albeit in a different manner than buoyancy modules. Finally. the buoyancy modules changed the stress oscillation frequency more than the flex joint cases from the unmodified riser. This is desirable since lowering the frequency of oscillation also increases the fatigue performance of the riser.

Download or read book A Critical Review of the Intrinsic Nature of Vortex Induced Vibrations written by Turgut Sarpkaya and published by . This book was released on 2003 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a concise and comprehensive review of the progress made during the past two decades on vortex induced vibration (VIV) of mostly circular cylindrical structures subjected to steady uniform flow. The critical elements of the evolution of the ideas, theoretical insights, experimental methods, and numerical models are traced systematically; the strengths and weaknesses of the current state of the understanding of the complex fluid/structure interaction are discussed in some detail. Finally, some suggestions are made for further research on VIV. The organization of the paper is given at the end of the next section.

Download or read book Time domain Simulation of Vortex induced Vibration for Deepwater Marine Risers written by Peter Ma and published by . This book was released on 2012 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improving Time domain Prediction of Vortex induced Vibration for Marine Risers written by Boyang Zhang and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As offshore exploration and production is moving into deepwaters, the prediction of the Vortex-Induced Vibration (VIV) of marine risers becomes a critical issue in the design process. VIV can lead to a reduced fatigue life and even the structural failure of the riser. Currently, frequency-domain models are widely used in the offshore industry to predict riser VIV. However, the nonlinearities encountered in complex deepwater environments make linear approaches unreliable. In contrast, time-domain models can capture the nonlinearities in a straightforward manner. In this thesis, a time-domain model was further developed to predict the VIV of both rigid and flexible risers. Through a zero up-crossing analysis of the crossflow displacement, the two state variables, amplitude-to-diameter ratio and reduced velocity, were determined to interpolate the database of hydrodynamic coefficients obtained from forced oscillation tests at high Reynolds numbers. The hydrodynamic forces were then calculated and incorporated into an enhanced global-coordinatebased finite element method program, MAPS-Mooring, to investigate riser behaviours in the time domain. The enhanced program, MAPS-Mooring, comprises a two-stage computation: the riser profile under static equilibrium is first obtained based on a Newton iterative method, and the dynamic profile and tension of the riser are then solved by the second-order semi-implicit Adams method in the time domain. The enhanced program was first validated by using experimental results of mooring line tests in the literature to prove its reliability and robustness. Validation studies were then carried out to the enhanced time-domain VIV model for a rigid riser in a uniform flow and a flexible riser in a step current. Good agreement was observed between the numerical results and the experimental measurements.

Download or read book Numerical Simulations of Vortex induced Vibrations in Marine Riser Pipes and Circular Cylinders written by R.J. McSherry and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Jets Wakes and Cavities written by Zarantonello Eduardo H. and published by Elsevier. This book was released on 2012-12-02 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: Applied Mathematics and Mechanics, Volume 2: Jets, Wakes, and Cavities provides a systematic discussion of jets, wakes, and cavities. This book focuses on the general aspects of ideal fluid theory and examines the engineering applications of fluid dynamics. Organized into 15 chapters, this volume starts with an overview of the different types of jets and explores the atomization of jets in carburetors in connection with gasoline engine design. This text then emphasizes the formal treatment of special flows and examines the flows that are bounded by flat plates and free streamlines. Other chapters consider the flows that are bounded by the cavity behind a symmetric wedge. This book discusses as well the intuitive momentum and similarity considerations. The final chapter deals with several surprising physical complications. Mathematician, physicists, engineers, and readers interested in the fields of applied mathematics, experimental physics, hydraulics, and aeronautics will find this book extremely useful.

Download or read book Vortex induced Vibration of a Circular Cylinder with Combined In line and Cross flow Motion written by Jason Michael Dahl and published by . This book was released on 2008 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: Deep water, string-like, marine risers subject to strong ocean currents, suffer from vortex-induced vibrations (VIV), where vortex shedding interacts with the structural properties of the riser, resulting in large amplitude vibrations in both in-line and cross-flow directions. This thesis presents an experimental approach to model and quantify the motions and hydrodynamic forces associated with the excitation of a deep water marine riser by considering the combined cross-flow and in-line excitation of a rigid cylinder. For deep water risers, the excitation of the structure through vortex shedding can lead to a condition of dual resonance, where the vortex shedding frequency locks in to the effective natural frequency (adjusted for added mass effects) in both in-line and cross-flow directions. Large motion amplitudes are observed in this condition along with large magnitude third harmonic forces in lift. Flow visualization of the wake behind the cylinder in combined in-line and cross-flow motion, shows that third harmonic forces are caused by the relative motion of the cylinder with respect to a '2P' (two pairs of vortices) or '2T' (two triplets of vortices) shedding pattern, since vortices shed in these modes remain in close proximity to the cylinder over one cycle of motion. Forced motions of a cylinder with combined in-line and cross-flow motions are performed, generating a database of force coefficients to be used in riser VIV prediction. The assumption of dual resonance is used to predict the motions of an elastically mounted rigid cylinder using measurements from forced cylinder motions. Two passive vortex suppression methods are studied for eliminating combined cross-flow and in-line cylinder motions and suppressing large third harmonic forces.