bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advances in Nonlinear Waves With Emphasis on Aspects for Ship Design and Wave Forensics
Authors: Osborne Alfred R. 
Published: November 2013

Prof. D. Faulkner emphasized the importance of the study of extreme/rogue waves when he noted that the use of sine waves for computing pressures in the design of ships was no longer tenable, primarily because of the large number of cases where extreme structural damage has been encountered due to highly nonlinear large waves. This perspective resulted in the creation of the European program MaxWave and the subsequent program Extreme Seas soon followed. Recently my own studies of nonlinear effects in water waves at Nonlinear Waves Research Corporation (NWRC) have resulted in a number of successes with regard to the fundamental physical understanding of rogue waves. These studies enlarge our ability to understand the requisite impact of extreme waves on the design of ships. Some of these advances are:
(1) The determination of analytical techniques for describing rogue wave packets in two dimensions for random sea states which are directionally spread.
(2) The description of wave overturning and breaking in directional sea states with the Type II (lateral) instability.
(3) The development of hyperfast computer models for the deterministic simulation of directional sea states.
(4) The development of a fast approach for computing the full Boltzmann integral (FBI) for the nonlinear wave/wave interactions in wind/wave models.
(5) The identification of the actual physical location in the power spectrum for the nonlinear Fourier rogue wave components.
(6) The development of nonlinear Fourier techniques for analyzing times series of ocean waves for the presence of rogue wave states.
(7) The development of fully nonlinear directional spectra (in terms of frequency and direction) from arrays of instruments.
(8) The development of hindcasting and predicting capability for the assessment of the onset of a rogue sea.
I also discuss a number of future developments now underway at NWRC.
Connectors for Production Risers
Authors: Figoni Marco , Chand Sudheer 
Published: November 2013

Increased interest in deepwater and ultra-deepwater field development is leading the industry to revisit the standard design and testing methods of production risers. The main challenges involved in a deepwater project are the riser sizing, management of external pressure at maximum water depth with acceptable weight to keep low stress at riser-vessel interface, the riser/vessel dynamic interaction and riser installation. The most critical areas on the riser system are the top section, where most of the damage occurs, and the touch-down zone. While the second area can be addressed by effective riser design, the connection to the production facility is always required and it must be sufficiently strong to provide an appropriate fluid containment. A connector failure can lead to highly flammable fluid leakage, putting in danger the entire production vessel and the surrounding environment. Technological advancements are leading to new equipment layouts with more efficient materials selection. The top section and connector can be subjected to different kinds of loads and environment induced degradation.
Applying the actual standards is sometimes difficult due to the fact that they generally are too conservative. With the objective of closing this gap, this paper provides an overview of the issues regarding different types of connectors in different working environments. The criteria for achieving an optimum connection selection depends on the type of riser utilized, riser configuration, metocean conditions, support vessel type, properties of fluid/chemicals transported inside the riser, life expectancy, maintenance and accessibility. Three main kinds of connection seals were analyzed, namely pure metallurgical (i.e. welding), pure mechanical (i.e. flange, threaded connections) and a combination thereof for line-end interface (i.e. metal-to-composite). All of the seals must provide retention of internal fluids and exclusion of external fluids and impurities. In an offshore environment, both of these characteristics must be achieved through the use of at least one metal-to-metal contact between mating interfaces and one static seal (i.e. metal rings).
Comparative Evaluation of the Cloud Dispersion of a Liquefied Natural Gas Leakage Using the UDM and a CFD Model
Authors: MirallesSchleder Adriana , Martins Marcelo Ramos 
Published: November 2013

Large reserves of natural gas exist worldwide, particularly in areas in which there is no market or where the resources exceed the demand; this natural gas is liquefied for shipping to areas where there is a demand. As the liquefied natural gas is a flammable substance, a leakage in this process may cause undesired events like fires and explosions.
The consequence analysis is used to define the extent and nature of effects caused by undesired events and thus to quantify the damage caused by such events. Specific models are used to analyze the spills or jets of gas and liquid, gas dispersion, explosions and fires. The central step in the analysis of consequences is to determine the concentration of the vapor cloud of hazardous substances released into the atmosphere, in space and time. Gaussian and integral tools are extensively used in risk analysis, mainly to develop analysis about gas flow over flat terrain, providing fast dispersion estimations. Recently, with the computational advances, computational fluid dynamics (CFD) tools are used to short and medium range gas dispersion scenarios. However the advantages and disadvantages of each approach according with the scenario evaluated have not been widely discussed.
This paper evaluates, using a CFD model, the cloud dispersion of a LNG leakage. Then the results are compared with the results previously obtained by UDM (Unified Dispersion Model) and some advantages and disadvantages of each model are discussed. This study contributes to the decision making about the choice of most appropriated model to evaluate the consequences analysis.
Dynamic Excitation of Monopiles by Steep and Breaking Waves: Experimental and Numerical Study
Authors: Bredmose Henrik , Slabiak Peter , Sahlberg-Nielsen Lasse , Schlütter Flemming 
Published: November 2013

An experiment with a flexible pile subjected to steep and breaking irregular waves has been conducted. The pile was constructed to represent a monopile wind turbine at scale 1:80. Two point masses were mounted on the pile to achieve the right scaled values for the first and second natural frequency. Emphasis is given to the observed impulsive excitation of the natural modes by steep and breaking waves. Additionally, springing and ringing-type continuous forcing of the first natural mode is seen for the moderately steep waves.
The experiments were carried out at three depths and with two wave climates. The measured data for structural acceleration is analysed with respect to individual wave parameters. It is found that the largest accelerations occur for breaking waves.
The measured wave field and structural response are reproduced numerically with a fully nonlinear potential flow solver for the undisturbed wave kinematics, combined with a finite element model with Morison-based forcing. A good overall reproduction of the wave field and structural response is achieved for two selected episodes. For some of the waves, however, the numerical response magnitude does not match the observed excitations. Ongoing work is therefore an investigation of breaking wave load models and their implementation into the present numerical frame work.
An Investigation of the Tolerance of Riser to Corrosion Pitting
Authors: Urthaler Yetzirah , Cerkovnik Mark , Yin Fengjie , Saldana David , Gordon Robin 
Published: November 2013

When risers are designed it is common for corrosion to be accounted for by including a corrosion allowance in the wall thickness [3]. However, when designing risers which are subject to fatigue loading from various sources, simply allowing extra thickness in the wall is inadequate to protect against the accelerated fatigue crack growth driven by corrosion.
This paper illustrates a methodology for assessing the fitness for service of a steel catenary riser with various levels of pitting corrosion. The methodology uses FEA tools, as well as classical fracture mechanics, to predict the rates of crack growth and arrive at predictions of life. Once corrosion begins and pits form, the structure may experience an increase in crack growth rate, caused by the influence of the chemistry of the produced fluid on the steel and by the stress effects of the pit geometry. Further complications arise if extreme storms cause riser stresses to exceed yield, which then requires the use of strain based methodology.
The results of the illustrative study demonstrate that riser designs should account for the potential of accelerated crack growth where there is a potential for pitting corrosion, and that by only adding a corrosion allowance to account for loss of burst capacity, an inadequate design can easily result.
Non Linearity of Extreme Vertical Bending Moment: Comparison of Design Wave Approaches and Short Term Approaches
Authors: de Hauteclocque Guillaume , Derbanne Quentin , Mienahou Therard 
Published: November 2013

The evaluation of extreme bending moment corresponding to a 25 years return period requires very long simulations on a large number of sea states. This long term analysis is easy to do with a linear model of the ship response, but is impractical when using a time consuming model including non linear loads (Froude-Krylov and hydrostatic non linear forces). In that case some simplified methods need to be applied. These methods are often based on equivalent Design Sea States (DSS) or Equivalent Design Waves (EDW).
The different methods are applied to large database of ships, containing 19 tankers, 29 bulk carriers, and 9 container-ships, in full load or ballast condition. Linear hydrodynamic calculations are carried out to define the extreme linear vertical bending moment, and to define the DSS and the EDW. Then non linear time domain sea-keeping computations are performed, taking into account Froude-Krylov hydrostatic pressure correction and large motions. The difference between linear and non linear hogging and sagging extremes are computed for each type of DSS and EDW.
Nano-Scale Characterisation of Shale Caprock/Acidic Brine Interaction
Authors: Olabode Abiola , Radonjic Mileva 
Published: November 2013

Shale-caprock integrity is critical in ensuring that subsurface injection and storage of anthropogenic carbon dioxide (CO2) is permanent. The interaction of clay-rich rock with aqueous CO2 under dynamic conditions requires characterization at the nano-scale due to the low-reactivity of clay minerals. Geochemical mineral-fluid interaction can impact properties of shale rocks primarily through changes in pore geometry/connectivity. Several simulation results had predicted that influx-triggered mineral dissolution/precipitation reactions within clay-rich rock can continuously diminish micro-fracture networks, while pressure and effective-stress evolution initially increase then gradually constrict them. However, most of these studies have not investigated changes under experimental conditions and applying experimental techniques capable of detecting changes at nano-scale, which are ultimately representing pathways for molecular diffusion of fluids through porous media.
The experimental work reported in this paper applied specific analytical techniques in investigating changes in surface/near-surface properties of crushed shale rocks after exposure (by flooding) to CO2-brine for a time frame ranging between 30 days to 92 days at elevated pressure and fractional flow rate. Initial capillary entry parameters for the shale were estimated from digitally acquired pressure data evolution. Flooding of the shale samples with CO2-brine was followed by Nano-scale measurement of changes in internal specific surface area, pore volume and linear/cumulative pore size distribution. The BET Technique showed that changes in the shale caprock occurred due to geochemical interaction with aqueous CO2 will impact petrophysical properties of the rock. The intrinsically low permeability in shale may be altered by changes in surface properties as the effective permeability of any porous medium is largely a function of its global pore geometry. Diffusive transport of CO2 as well as carbon accounting could be significantly affected over the long term. The estimation of dimensionless quantities such as Peclet (Pe) and Peclet-Damkohler (PeDa) Numbers that are associated with geochemical reactivity of rocks and acidic fluid transport through porous media gave insight into the impact of diffusion and reaction rate on shale caprock.
Finite Element Contact/Impact Modeling Capability of Complex Surface Effect Ship Dynamics: Preliminary Assessment
Authors: Challa Ravi , Newborn David , Yim Solomon 
Published: November 2013

Experimental tests were conducted on a large scale captive Surface Effect Ship (SES) specimen at the US Navy’s Large Cavitation Channel (LCC) to primarily determine the mechanics of bow finger seal motions. In this paper, preliminary qualitative comparisons between the experimental and numerical simulations comprised of test dependent variables such as spatially distributed channel water elevation, channel water speed and air-cushion pressure are presented.
A surface effect ship is an air-cushion supported vessel with two side hulls and fore and aft flexible seals. The side hulls of the SES along with the wet deck, seals and the fluid-water surface constitute the boundary of the air-cushion. An evaluation of the predictive capabilities of the existing technology of a state-of-the-art nonlinear multi-physics finite element code (LS-DYNA) with its arbitrary Lagrangian Eulerian (ALE) technique in modeling the coupled fluid-structure interaction (FSI) behavior of the boundary of a SES with the water surface is studied.
The predictive capability of the code to model a single stern seal deployment, a single seal impacting a rigid flat surface, multiple seals impacting a water free surface and the centerline profile of multiple stern seal deployment between two rigid surfaces were verified. Simple numerical models for a five-finger bow seal with partial submergence in uniform current have been developed. Additional features including the mechanism to pressurize the air cushion chamber were included. Preliminary finite element (FE) simulation results show that the robust contact and impact algorithm is shown to capture the physics of the complex flexible body FSI problem well. In view of the good qualitative comparison between the experimental and numerical simulations, the ALE feature is being employed for studying the complex flexible structural mechanics including bow and stern seal motions interacting with air cushion and free-surface hydrodynamics.
On Sampling Between Data of Significant Wave Height for Long-Term Analysis With Equivalent Triangular Storm Model
Authors: Arena Felice , Laface Valentina 
Published: November 2013

This work proposes an analysis of storms in Pacific and Atlantic Ocean, which is carried out by applying the Boccotti’s Equivalent Triangular Storm (ETS) model. The ETS model represents any actual storm by means of two parameters. The former gives the storm intensity, which is equal to the maximum significant wave height during the actual storm; the latter represents the storm duration and it is such that the maximum expected wave height is the same in the actual storm and in the equivalent triangular storm. Data from buoys of the NOAA-NDBC (National Data Buoy Center, USA) are used in the applications, by considering different sampling Δt between two consecutive records, which varies between 1 and 6 hours. The sensitivity of the ETS model with the variation of Δt is investigated for the long-term modeling of severe storms. The results show that the structure of storms is strongly modified as Δt increases: both the intensity and the duration may change significantly.
The effects of this results for long term statistics are investigated by means of the return period R(Hs > h) of a storm in which the maximum significant wave height exceeds the threshold h, which is evaluated by using data with different sampling Δt between two consecutive records. Finally for different values of the return period R, the return value of significant wave height and the mean persistence Dm(h), giving the mean time during which the significant wave height is greater than fixed threshold (in the storms where the threshold is exceeded), are calculated.
Response Sensitivity to Swell Spectra Off West Africa
Authors: Ewans Kevin , Forristall George Z. , Prevosto Marc , Olagnon Michel 
Published: November 2013

Both hindcast and measured wave data were used to establish various descriptions of the swell spectra off West Africa in the West Africa Swell JIP (WASP). The effect on system responses of the various data types and swell spectral descriptions has been estimated.
The response of single degree of freedom oscillators to wave spectra can be used to produce maximum responses as a function of natural period and damping, analogous to the approach used in earthquake engineering. The results can be used to gain insight into the sensitivity of floating systems to the swell characteristics of the location and also to the differences between hindcast and measured data sets. Extreme values of system response can be calculated and used to estimate design spectra, by scaling the measured or hindcast spectrum that produced the largest response.
The sensitivity of the responses of floating systems to various simplifications of the hindcast spectra was evaluated by calculating the responses of an FPSO and CALM buoy for a location off Nigeria and southern Angola. It was found that there is little loss of accuracy if the hindcast spectra are decomposed into a maximum of two partitions, one of which may be a wind-sea, and the swell partitions are described with a lognormal function, the wind-sea partition with a JONSWAP-Glenn frequency function, and the directional spreading with a wrapped normal function, together with parametric forms for the widths of the lognormal and wrapped normal functions. As a consequence it is concluded that the parametric forms for the swell frequency and direction spreading can be used in design.
Development of a Calculation Method for Fuel Consumption of Ships in Actual Seas With Performance Evaluation
Authors: Tsujimoto Masaru , Kuroda Mariko , Sogihara Naoto 
Published: November 2013

Greenhouse gas shall be reduced from shipping sector. For that purpose the regulation of EEDI (energy efficiency design index for new ships) and SEEMP (ship energy efficiency management plan) have been entry into force from 2013. In order to improve the energy efficiency in ship operation it is necessary to predict the fuel consumption accurately.
In actual seas the wave effect is the dominant component of the external forces. In particular it is well known the bow shape above water affects the added resistance in waves. To reflect the effect of the bow shape a method which takes into account the result of simplified tank tests is proposed here. Using the results of tank tests the effect of the bow shape above water can be evaluated with accuracy as well as with robustness.
Regarding to the fuel consumption it should be evaluated by combining the ship hydrodynamic performance with the engine characteristics. Especially the operating limits of the main engine, such as the torque limit and the over load protection, are affected to the ship hydrodynamic performance. In rough weather condition the revolution of the main engine will be reduced to be below the operating limits of the engine. This causes the large decrease of ship speed. To prevent the increase of fuel consumption, a control system by Fuel Index as an index of fuel injection has been applied to some ships. The calculation method for the fuel consumption by using Fuel Index is presented.
In this paper following contents are reported; 1) development of a calculation method for the added resistance due to waves combined with the simplified tank tests in short waves, 2) comparison of the calculation method with onboard measurement, 3) development of a calculation method for the fuel consumption considering the engine operating mode in actual seas and 4) comparison of the method with onboard measurement of a container ship.
From these investigations the availability of the present method is confirmed.
Improvement of Waterflood Oil Recovery by Wettability Alteration in Carbonate Reservoirs
Authors: Dakik Ahmad , Gupta Anuj 
Published: November 2013

Most carbonate rocks tend to be oil wet, which negatively affects the recovery of hydrocarbons in waterflooding. Studies have shown that alteration of wettability through ion adjustment and surfactant addition can alter the wettability of the carbonate rock from oil wet to moderate or water wet. Through alteration of wettability recovery can be increased to higher values than what is expected when the reservoir is flooded with seawater. Adjustment in concentration of Mg2+, Ca2+, and SO42− ions and addition of surfactants have shown to be most effective in altering wettability. There has been limited research related to imbibition of carbonate rock samples representing reservoirs in brines containing solely Mg2+, Ca2+, or SO42− at atmospheric conditions. The effect of Non-Ionic and mixed Non-ionic with cationic surfactants on the alteration of wettability has been addresses in previous research.
In this study, Imbibition experiments were done on samples using brines of different ion components and concentrations to study the effect of salinity and ion composition on the recovery. Imbibition of lower salinity brines showed noticeably higher recovery than high salinity brines. The results are presented in dimensionless form of recovery and time for better comparison of wettability alteration and effect between samples. Lower salinity brines of Ca2+ and SO42− ion composition showed highest improvement in recovery. Surfactants were added during the imbibition measurement to view any further enhanced recovery at atmospheric conditions.
MARINET: The Research Infrastructure Network Gaining International Support and Accelerating the Development of Marine Renewable Energy
Authors: Healy Mark , Alcorn Raymond , Lewis Tony 
Published: November 2013

MARINET (Marine Renewables Infrastructure Network) is an EC-funded marine renewable energy infrastructure initiative which seeks to accelerate the development and commercial deployment of marine renewable energy technologies — wave, tidal & offshore-wind — by streamlining the testing process. World-class research centers and organizations are coming together in a network to offer periods of free-of-charge access to their world-class testing facilities and to develop a joint approach to testing standards, testing research and industry training & networking.
The growing network, with more than 30 full and associate partner research centers, has over 40 specialist marine research facilities covering all scales from laboratory to sea. It is spread across 11 EU countries and international partner countries such as Brazil, Taiwan, Canada and the US.
This paper outlines what MARINET is, what it has already achieved at the half-way point in the initiative, where it is going and who can benefit now and in the future.