Dynamic Behavior Analysis of a Deepwater Self Standing Hybrid Riser System

2012 ◽  
Author(s):  
Celso K. Morooka ◽  
Denis A. Shiguemoto
Keyword(s):  
Dynamic Behavior ◽  
Maximum Amplitude ◽  
Ocean Waves ◽  
Numerical Approach ◽  
Sea Surface ◽  
Hydrodynamic Drag ◽  
Floating Platform ◽  
Riser Pipe ◽  
Sea Bottom ◽  
Flexible Jumper

Self Standing Hybrid Riser (SSHR) system is an attractive option for deepwater application. The system is composed by a vertical riser pipe coming from the sea bottom to a subsurface buoy which is placed in around one hundred meter water depth from the sea surface. It is connected to a floating production facility at the sea surface by a flexible jumper. It almost eliminates all the undesired dynamic effects from ocean waves, in addition to relief the total riser system weight from the floating platform. Recent discoveries of petroleum in ultra-deep water Pre-salt Offshore Brazil stimulated development of innovative and nontraditional riser system configurations. The present work deals with the dynamic behavior of a SSHR system excited by sea current, waves and displacements induced by sea surface platform motions. In plane and out of plane displacements for the SSHR system is analyzed and subsurface buoy maximum motions amplitude have been observed. Effects from current drag and vortex induced forces are investigated by numerical simulations of the dynamic behavior of the SSHR system. Analysis procedure is presented with details, and fundamentals of the semi-empirical approach for hydrodynamic drag and vortex induced forces in the riser length and subsurface buoy are described. Numerical simulation results are presented, and evaluations are conducted for deepwater condition. Maximum amplitude of vibration is observed near from to lock-in conditions, and effects of the subsurface buoy vortex induced motion (VIM) are discussed. Hydrodynamic forces previously obtained from reduced model tests are used for the numerical approach.

TEMPERATURE VARIABILITY AT SENUNU BAY, WEST SUMBAWA

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Syamsul Hidayat ◽  
Mulia Purba ◽  
Jorina Waworuntu
Keyword(s):  
Layer Thickness ◽  
Mixed Layer ◽  
Cross Correlation ◽  
Sea Surface ◽  
Thermocline Depth ◽  
Kelvin Wave ◽  
The West ◽  
Sea Bottom ◽  
Annual Period ◽  
Regional Processes

The purposes of this study were to determine the variability of temperature and its relation to regional processes in the Senunu Bay. The result showed clear vertical stratifications i.e., mixed layer thickness about 39-119 m with isotherm of 27°C, thermocline layer thickness about 83-204 m with isotherm of 14–26°C, and  the deeper layer from the thermocline lower limit to the sea bottom with isotherm <13°C. Temperature and the thickness of each layers varied with season in which during the Northwest Monsoon the temperature was warmer and the mixed layer was thicker than those during Southeast Monsoon. During Southeast Monsoon, the thermocline layer rose  about 24 m. The 2001, 2006, and 2009 (weak La Nina years),  the Indonesia Throughflow (ITF) carried warmer water, deepening thermocline depth and reducing upwelling strength.  In 2003 and 2008 thickening of mixed layer occurred in transition season  was believed  associated with the  arrival of Kelvin Wave from the west. In 2002 and 2004 (weak El Nino period,) ITF carries colder water shallowing thermocline depth and enhancing upwelling strength. In 2007 was believed to be related with positive IODM where the sea surface temperature were decreasing due to intensification of southeast wind which induced strong upwelling. The temperature spectral density of mixed layer and thermocline was influenced by annual, semi-annual, intra-annual and inter-annual period fluctuations. The cross-correlation between wind and temperature showed significant value in the annual period.  Keywords: temperature, thermocline, variability, ENSO, IODM.

ИССЛЕДОВАНИЯ АКУСТИЧЕСКИХ ХАРАКТЕРИСТИК ВЕРХНЕГО СЛОЯ МОРЯ МЕТОДОМ МНОГОЧАСТОТНОГО АКУСТИЧЕСКОГО ЗОНДИРОВАНИЯ

2020 ◽  
Author(s):  
V.A. Bulanov ◽  
I.V. Korskov ◽  
A.V. Storozhenko ◽  
S.N. Sosedko
Keyword(s):  
High Frequency ◽  
Wave Motion ◽  
High Spatial Resolution ◽  
Wind Waves ◽  
Acoustic Parameter ◽  
Sea Surface ◽  
Near Surface ◽  
Acoustical Properties ◽  
Acoustic Spectroscopy ◽  
Sea Bottom

Описано применение акустического зондирования для исследования акустических характеристик верхнего слоя моря с использованием широкополосных остронаправленных инвертированных излучателей,устанавливаемых на дно. В основу метода положен принцип регистрации обратного рассеяния и отраженияот поверхности моря акустических импульсов с различной частотой, позволяющий одновременно измерятьрассеяние и поглощение звука и нелинейный акустический параметр морской воды. Многочастотное зондирование позволяет реализовать акустическую спектроскопию пузырьков в приповерхностных слоях моря,проводить оценку газосодержания и получать данные о спектре поверхностного волнения при различных состояниях моря вплоть до штормовых. Применение остронаправленных высокочастотных пучков ультразвукапозволяет разделить информацию о планктоне и пузырьках и определить с высоким пространственным разрешением структуру пузырьковых облаков, образующихся при обрушении ветровых волн, и структуру планктонных сообществ. Участие планктона в волновом движении в толще морской воды позволяет определитьпараметры внутренних волн спектр и распределение по амплитудам в различное время.This paper represents the application of acoustic probingfor the investigation of acoustical properties of the upperlayer of the sea using broadband narrow-beam invertedtransducers that are mounted on the sea bottom. Thismethod is based on the principle of the recording of thebackscattering and reflections of acoustic pulses of differentfrequencies from the sea surface. That simultaneouslyallows measuring scattering and absorption of the soundand non-linear acoustic parameter of seawater. Multifrequencyprobing allows performing acoustic spectroscopy ofbubbles in the near-surface layer of the sea, estimating gascontent, and obtaining data on the spectrum of the surfacewaves in various states of the sea up to a storm. Utilizationof the high-frequency narrow ultrasound beams allows us toseparate the information about plankton and bubbles and todetermine the structure of bubble clouds, created during thebreaking of wind waves, along with the structure of planktoncommunities with high spatial resolution. The participationof plankton in the wave motion in the seawater columnallows determining parameters of internal waves, such asspectrum and distribution of amplitudes at different times.

scholarly journals Impact of Sea Spray and Sea Surface Roughness on the Upper Ocean Response to Super Typhoon Haitang (2005)

2021 ◽  
Author(s):  
Lianxin Zhang ◽  
Xuefeng Zhang ◽  
William Perrie ◽  
Changlong Guan ◽  
Bo Dan ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Ocean Waves ◽  
Sea Surface ◽  
Sea Spray ◽  
Upper Ocean ◽  
Surface Cooling ◽  
Super Typhoon ◽  
Sea Surface Roughness ◽  
Momentum Fluxes ◽  
The Right

AbstractA coupled ocean-wave-sea spray model system is used to investigate the impacts of sea spray and sea surface roughness on the response of the upper ocean to the passage of the super typhoon Haitang. Sea spray mediated heat and momentum fluxes are derived from an improved version of Fairall’s heat fluxes formulation (Zhang et al., 2017) and Andreas’s sea spray-mediated momentum flux models. For winds ranging from low to extremely high speeds, a new parameterization scheme for the sea surface roughness is developed, in which the effects of wave state and sea spray are introduced. In this formulation, the drag coefficient has minimal values over the right quadrant of the typhoon track, along which the typhoon-generated waves are longer, smoother, and older, compared to other quadrants. Using traditional interfacial air-sea turbulent (sensible, latent, and momentum) fluxes, the sea surface cooling response to typhoon Haitang is overestimated by 1 °C, which can be compensated by the effects of sea spray and ocean waves on the right side of the storm. Inclusion of sea spray-mediated turbulent fluxes and sea surface roughness, modulated by ocean waves, gives enhanced cooling along the left edges of the cooling area by 0.2 °C, consistent with the upper ocean temperature observations.

scholarly journals Wave interaction with Floating platform of different shapes and supports using BEM approach

2017 ◽  
Vol 14 (2) ◽  
pp. 115-133
Author(s):  
Anoop I. Shirkol ◽  
Nasar Thuvanismail
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Wave Interaction ◽  
Wave Force ◽  
Ocean Waves ◽  
Wave Forces ◽  
Thin Elastic Plate ◽  
Floating Platform ◽  
Floating Elastic Plate ◽  
Different Shapes

Wave interaction with a floating thin elastic plate which can be used as floating platform is analyzed using Boundary Element Method (BEM) for different shapes such as rectangular, circular and triangular. Different support conditions are considered and the performance of the floating platform under the action of ocean waves is explored. The study is performed under the assumption of linearized water wave theory and the floating elastic plate is modelled based on the Euler-Bernoulli beam theory. Using Galerkin’s approach, a numerical model has been developed and the hydrodynamic loading on the floating elastic plate of shallow draft (thickness) is investigated. The wave forces are generated by the numerical model for the analysis of the floating plate. The resulting bending moment and optimal deflection due to encountering wave force is analysed. The present study will be helpful in design and analysis of the large floating platform in ocean waves.

Impact—Response Behavior of Offshore Pipelines

1982 ◽  
Vol 104 (4) ◽  
pp. 325-329 ◽  
Author(s):  
P. G. Bergan ◽  
E. Mollestad
Keyword(s):  
Plastic Material ◽  
Material Behavior ◽  
Hydrodynamic Drag ◽  
Offshore Pipelines ◽  
Sea Floor ◽  
Drag Forces ◽  
Sea Bottom ◽  
Nonlinear Dynamic Equations ◽  
Numerical Formulation ◽  
Inertia Forces

A method for analyzing the dynamic behavior of marine pipelines subjected to impact loads or sudden forced movements is outlined. Inertia forces (also from hydrodynamic mass), hydrodynamic drag forces as well as friction and lift effects for a pipe at the sea bottom are accounted for. An extensive nonlinear formulation is used for the pipe itself; it includes large displacements and elasto-plastic material behavior. Aspects of the numerical formulation of the problem and the solution of the nonlinear dynamic equations are discussed. The examples show computed dynamic response for pipelines lying on the sea floor and for a pipe section freely submerged in water when subjected to various force and displacement histories.

Dynamic Behavior of String Subjected to Travelling Mass

2019 ◽  
Author(s):  
Shakti P. Jena ◽  
S. Naresh Kumar ◽  
Hemanth Cheedella
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Green’S Function ◽  
Dynamic Behavior ◽  
Green's Function ◽  
Transverse Vibration ◽  
Element Model ◽  
Numerical Approach ◽  
Complete Analysis ◽  
Numerical Example

Abstract The present study is based on the transverse vibration analogy of a string subjected to a travelling mass. The string is considered to be fixed at their both ends. The responses of the string due to the dynamic behavior of the travelling mass are determined using a numerical approach i.e. Green’s function. A Finite Element Model (FEM) has been developed to authenticate the numerical approach. For the responses analysis of the string, numerical example has been illustrated to study the behavior of the string due to the travelling mass and to check the convergence of the two proposed analogies (Green’s function and FEM). The complete analysis has been performed at constant travelling speed and different masses. The two approaches converge well and the Green’s function methodology found to be suitable one.

Dynamic Behavior of a Novel Heave-Compensated Floating Platform for Well Interventions

2020 ◽  
Author(s):  
Marcelo A. Jaculli ◽  
Bernt J. Leira ◽  
Sigbjørn Sangesland ◽  
Celso K. Morooka ◽  
José Ricardo P. Mendes
Keyword(s):  
Dynamic Behavior ◽  
Small Diameter ◽  
Floating Platform ◽  
Floating Structure ◽  
Cross Sectional ◽  
Platform Design ◽  
The North ◽  
The North Sea ◽  
Heave Motion ◽  
Intervention Costs

Abstract A new type of floating platform design has been investigated. It consists of a relatively small semi-submersible floating structure with an air chamber that aims to keep a constant buoyancy, thus effectively reducing heave motion and enabling its use under harsh environmental conditions such as in the North Sea. It aims to provide an alternative solution compared to large floating structures, such as drillships and semi-submersible platforms, in terms of time availability, drilling costs and operational flexibility. One recent focus has been on the application of this platform for reducing well intervention costs. A small diameter (workover) riser may be used for installing the well control stack on the wet Christmas tree and for performing well intervention through the riser using a wireline cable. Alternatively, the operation can take place without a riser; this operation is termed riserless well intervention (RLWI). In this work, we investigate the dynamic behavior of this system, which is attached either to a wireline — for RLWI — or to a small-sized riser for well service through the riser. By modeling this system — which acts similarly to a passive heave compensation system — we have verified that this new platform indeed experiences smaller displacements when compared to conventional platform. The reduction observed varies depending on the platform design; in some cases, it reduces the displacement by a factor of two. A relatively heavier platform with a small cross sectional water plane area is found to be the best design option, but a lighter platform might be preferable for increased flexibility, as long as its dynamic behavior is satisfactory for safe operations.

scholarly journals Dynamic Analysis of Suction Stabilized Floating Platforms

2020 ◽  
Vol 8 (8) ◽  
pp. 587
Author(s):  
Susheelkumar C. Subramanian ◽  
Michaela Dye ◽  
Sangram Redkar
Keyword(s):  
Floquet Theory ◽  
Normal Forms ◽  
Ocean Waves ◽  
Offshore Structures ◽  
Harsh Environment ◽  
Time Varying ◽  
Floating Platform ◽  
Dynamical Characteristics ◽  
Floating Platforms ◽  
Generic Design

The occurrence of parametric resonance due to the time varying behavior of ocean waves could lead to catastrophic damages to offshore structures. A stable structure that could withstand the wave perturbations is quintessential to operate in such a harsh environment. In this work, the authors detail the relevance of a Suction Stabilized Float (SSF) or a Suction Stabilized Floating platform towards such an application. A generic design of a symmetrically shaped float structure along with its inherent stabilization behavior is discussed. Furthermore, the authors extend their prior research on this topic towards modelling the dynamics of SSF and perform stability analysis. The authors demonstrate the dynamical characteristics of SSF analytically using Floquet theory and Normal Forms technique, in this work. Additionally, the simulation results are verified and validated with the numerical methods.

scholarly journals Spatial and Temporal Characterization of Sea Surface Temperature Response to Tropical Cyclones*

2013 ◽  
Vol 26 (11) ◽  
pp. 3745-3765 ◽  
Author(s):  
Wei Mei ◽  
Claudia Pasquero
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Tropical Cyclones ◽  
Mixed Layer ◽  
Temperature Response ◽  
Maximum Amplitude ◽  
Sea Surface ◽  
Translation Speed ◽  
Linear Behavior ◽  
Sst Anomaly

Abstract The spatial structure and temporal evolution of the sea surface temperature (SST) anomaly (SSTA) associated with the passage of tropical cyclones (TCs), as well as their sensitivity to TC characteristics (including TC intensity and translation speed) and oceanic climatological conditions (represented here by latitude), are thoroughly examined by means of composite analysis using satellite-derived SST data. The magnitude of the TC-generated SSTA is larger for more intense, slower-moving, and higher-latitude TCs, and it occurs earlier in time for faster-moving and higher-latitude storms. The location of maximum SSTA is farther off the TC track for faster-moving storms, and it moves toward the track with time after the TC passage. The spatial extension of the cold wake is greater for more intense and for slower-moving storms, but its shape is quite independent of TC characteristics. Consistent with previous studies, the calculations show that the mean SSTA over a TC-centered box nearly linearly correlates with the wind speed for TCs below category 3 intensity while for stronger TCs the SSTA levels off, both for tropical and subtropical regions. While the linear behavior is expected on the basis of the more vigorous mixing induced by stronger winds and is derived from a simple mixed-layer model, the level-off for intense TCs is discussed in terms of the dependence of the maximum amplitude of the area-mean SSTA on TC translation speed and depth of the prestorm mixed layer. Finally, the decay time scale of the TC-induced SSTA is shown to be dominated by environmental conditions and has no clear dependence on its initial magnitude and on TC characteristics.

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