bluuebunny/crossref_metadata_2025_split huggingface dataset:
Less=Moor: A Time-Efficient Computational Tool to Assess the Behavior of Moored Ships in Waves
Authors: Wang Yijun , van Deyzen Alex , Beimers Benno 
Published: October 2017

In the field of port design there is a need for a reliable but time-efficient method to assess the behavior of moored ships in order to determine if further detailed analysis of the behavior is required. The response of moored ships induced by gusting wind and/or waves is dynamic. Excessive motion response may cause interruption of the (un)loading operation. High line tension may cause lines to snap, introducing dangerous situations. A (detailed) Dynamic Mooring Analysis (DMA), however, is often a time-consuming and expensive exercise, especially when responses in many different environmental conditions need to be assessed.
Royal HaskoningDHV has developed a time-efficient computational tool in-house to assess the wave (sea or swell) induced dynamic response of ships moored to exposed berths. The mooring line characteristics are linearized and the equations of motion are solved in the frequency domain with both the 1st and 2nd wave forces taken into account. This tool has been termed Less=Moor.
The accuracy and reliability of the computational tool has been illustrated by comparing motions and mooring line forces to results obtained with software that solves the nonlinear equations of motion in the time domain (aNySIM). The calculated response of a Floating Storage and Regasification Unit (FSRU) moored to dolphins located offshore has been presented.
The results show a good comparison. The computational tool can therefore be used to indicate whether the wave induced response of ships moored at exposed berths proves to be critical. The next step is to make this tool suitable to assess the dynamic response of moored ships with large wind areas, e.g. container ships, cruise vessels, RoRo or car carriers, to gusting wind. In addition, assessment of ship responses in a complicated wave field (e.g. with reflected infra-gravity waves) also requires more research effort.
Comprehensive Instrumentation of Two Offshore Rigs for Wellhead Fatigue Monitoring
Authors: Nilsen Svein Herman , Russo Massimiliano , Grytøyr Guttorm 
Published: October 2017

Over the last decades, the complexity and duration of offshore drilling operations have steadily increased. The size and weight of the risers and BOP stack has grown significantly. These factors have led to an increase in fatigue loads imposed on the wellhead structures during drilling and completion operations. Wellhead fatigue might ultimately lead to loss of well structural integrity and pressure containment and therefore safe and reliable drilling of subsea wellheads has gained high priority in the global oil and gas industry. This paper presents two of the most complex real time instrumentation campaigns for drilling operations.
Analyses of a connected drilling riser system including the well structure are complex and involve several engineering disciplines. In addition, there are many unknowns going into the equations when accumulated fatigue damage of the wellhead is estimated. Therefore, assumptions need to be made, very often on the conservative side. A typical example are the global drilling riser analyses where the environmental conditions, actual rig motion and riser / BOP behavior are uncertain.
With the duplex scope of accurately documenting the wellhead fatigue status during drilling operations and of achieving a better understanding of the actual risk level of wellhead fatigue, Statoil decided to start a very comprehensive monitoring campaign. Two MODU representing very different generations of rigs in terms of weights and types of equipment were instrumented from topside to BOP connector. Strain gauges were installed around the BOP connector as close as possible to the wellhead in order to capture wellhead response as accurately as possible. Due to the large number of sensors, high accuracy requirement and high sampling frequency of data to be shown live, a cabled solution was selected vs remote battery operated sensors transmitting via acoustic. Double set of cables, sensors and topside equipment were installed in order to make the instrumentation system fully redundant and suited for permanent installation. All data were additionally made available real time onshore to allow the full overview of the operation. To author’s knowledge, these two instrumentation systems are the most comprehensive and complex of this type installed on a drilling riser as of today. The first of the two system was installed approximately three years ago and it is still in operation. This paper describes the instrumentation systems installed and gives an extract of the quality data extracted and already used in already published studies [1, 2, 3].
Simulation of Wave Impacts at Belwind Offshore Wind Farm and Comparison With Full-Scale Measurements
Authors: Bunnik Tim , Weijtjens Wout , Devriendt Christof 
Published: October 2017

The effects of operational wave loads and wind loads on offshore monopile wind turbines are well understood. For most sites, however, the water depth is such that steep and/or breaking waves will occur causing impulsive excitation of the monopile and consequently considerable stresses, displacements and accelerations in the monopile, tower and turbine.
At Belwind offshore wind farm (offshore Zeebrugge, Belgium) the waves and accelerations of a Vestas V90 3MW wind turbine have been monitored since November 2013, using wave radar and several accelerometers. During this period the wind turbine was exposed to several storms and experienced several wave impacts, resulting in vibrations in the monopile.
The measurements were compared with results from a numerical model for the flexible response of wind turbines due to steep waves. Previously this model was compared with scale model tests with satisfying results. The full-scale measurements provide an additional cross-check of the model.
The numerical model consists of a one-way coupling between a CFD model for wave loads and a simplified structural model based on mode shapes. An iterative wave calibration technique has been developed in the CFD model to ensure a good match between the simulated and measured incoming wave profile, obtained with the wave radar. This makes a deterministic comparison between simulations and measurements possible. This iteration is carried out in a 2D CFD domain (assuming long-crested waves) and is therefore relatively cheap. The calibrated numerical wave is then simulated in a 3D CFD domain including a (fixed) wind turbine. The resulting wave pressures on the turbine have been used to compute the modal excitation and subsequently the modal response of the wind turbine. The mode shapes have been estimated from the measured accelerations at the Belwind turbine. A grid refinement study was done to verify the results from the numerical model. The horizontal accelerations resulting from this one-way coupling are in fair agreement with the measured accelerations.
Simulations of Dynamic Interaction Between a Bluff Body and Installation Vessel During Launch and Recovery in Rough Seas
Authors: Bashir Musa B. , Evans Mathew , Benson Simon D. , Murphy Alan J. 
Published: October 2017

Simulation of marine operations for launch and recovery of bluff bodies such as autonomous underwater vehicles (AUV), remotely operated vehicles (ROV) or subsea templates is traditionally performed in calm to moderate sea conditions. The reason for doing so is partly due to the interaction between the complex dynamic response of an installation vessel, a moving bluff body and the wave kinematics of the rough sea condition. This is in addition to the need for accurate hydrodynamic coefficients that would enable proper simulation and modelling of the launch and recovery process. The key objective of the current methodology is to minimize risks of damage to the vessel and total loss of assets during the deployment and recovery process for marine operations in rough sea conditions.
The aim of this paper is to present the results of experimental and numerical investigation on the prediction of dynamic response of a bluff body during launch and recovery from a surface vessel in rough sea condition. Experimental measurements of hydrodynamic coefficients and responses of a large scale bluff body using a scaled model were completed. Further studies using a time-domain numerical tool have been undertaken to measure the response characteristic of bluff bodies in rough seas. The study also predicted the contributions of vessel motion in rough seas to the dynamic response of the bluff bodies. The results obtained have shown that simulation of launch and recovery operations in rough seas can be carried out efficiently if their hydrodynamic coefficients through the wave active regions of the rough seas are predicted and then adequately implemented in the simulations.
Transportation of Hydrogen Gas From a Local Plant to Remote Markets via High Pressure Submarine Pipelines
Authors: Hval Morten , Gråberg Stig Vemund 
Published: October 2017

Hydrogen is about to become a very important energy carrier. It is regarded as clean since its only bi-product is water when it is converted to electric energy in a fuel cell. Hydrogen gas needs, however to be transported to the end user from the hydrogen plant. If the end user is remote from the plant and the total energy demand is high, the hydrogen gas is best transported through a pipeline. Low pressure hydrogen gas pipeline distribution systems already exist onshore and have been in operation for years both in Europe and USA. REINERTSEN has performed a study to evaluate the possibilities for transporting pure hydrogen gas or natural gas/hydrogen mixtures under high pressure through a submarine pipeline from an onshore plant to an end-user either offshore or overseas from where the hydrogen gas is produced. Hydrogen under high pressure is known to have some possible detrimental effects with respect to material brittleness and enhancement of fatigue crack growth which must be carefully considered before a steel submarine pipeline is constructed and installed. The severity of the detrimental effect may be attributed to both the material type and welding procedure, something which must also be taken into the consideration.
This paper is devoted to the possible changes and limitations in material properties caused by pressurized hydrogen gas that must be considered when designing and installing a submarine transport pipeline or converting an existing natural gas pipeline to hydrogen service.
Limitations in Scaling Towing Tests for Simple Pontoon Shapes
Authors: Krijger Jan Willem , Chalkias Dimitris 
Published: October 2017

For merchant vessels full scale resistance is determined by extrapolating the towing tank tests using Hughes’ method. For blunt and simple shapes this approach might not be valid due to significant Reynolds dependency.
In this paper a study is presented on two semi-submersible pontoon shapes and one drillship. The resistance for these hulls was calculated using URANSE simulations. Four different scales: 1:1, 1:10, 1:20 and 1:40 were investigated for all the different hull shapes. The goal of the study was to determine a form factor to use when scaling towing test results to full scale. However due to the simple shapes of the pontoons it was found that there was a significant Reynolds dependency at all the different scales. This Reynolds dependency had much more influence on the full scale resistance than a form factor. For the drillship no significant Reynolds dependency was found and applying ITTC 1978 method [1] with a form factor improved the accuracy of the resistance prediction compared to using the Froude method which is not using a form factor.
The simple pontoon shapes used were based on a combination of boxes, cylinders and spheres. The cylindrical and spherical shapes have a Reynolds regime where a drag crisis occurs. For all the shapes the drag crisis regimes were right in the same Reynolds number range at which typical model tests would be performed. Therefore performing towing tests and making accurate full scale resistance predictions for these simple shapes is not straightforward. Applying the ITTC 1978 method does not provide the same level of accuracy as it does for merchant vessels.
The paper identifies limitations involved in scaling towing test results for typical offshore hull shapes. Further possible solutions are proposed to improve the accuracy of the resistance predictions.
Performance Assessment of the Anaconda WEC in Regular Waves at 1:50 Model Scale
Authors: Mendes A. C. , Braga F. P. , Paredes L. M. A. , Chaplin J. R. 
Published: October 2017

The Anaconda WEC belongs to a new generation of wave-energy converters that are currently on their way to reach a pre-commercial stage. It consists of a long rubber tube that is designed to float head to waves. The tube is filled with water and its stern is connected to a power take-off system (PTO). As a result of the interactions with the incoming ocean waves, the tube conveys internal pressure bulges whose intensity grows in the direction of the PTO. A pneumatic system is considered herein, in which electrical energy can be produced from a turbo-generator set.
The present research focuses on the performance assessment of a free-floating Anaconda model with air-flow PTO. The results of a series of tests with a 1:50 scale physical model in wave-tank are presented and discussed. In this model the pneumatic chamber connects with the atmosphere through an orifice plate. Several calibrated orifices of different diameters have been tested. The tests were undertaken in regular waves that translate to waves of 7 to 14 seconds in full-scale. Pressure in the pneumatic chamber and the water-column oscillations in the shaft were monitored. They provide estimates of the extracted power and energy capture efficiency of the system.
One of the aims of the study is to account for the effects of compressibility on the power output of the system, as well as properly assessing the impact of scale effects upon performance estimates. The results, presented as a function of the wave frequency, are ultimately used to predict prototype performance.
Evolution of Residual Stress in Tensile Armour Wires of Flexible Pipes During Pipe Manufacture
Authors: Fernando Upul S. , Davidson Michelle , Yan Kun , Roy Matthew J. , Pirling Thilo , Withers Philip J. , Francis John A. 
Published: October 2017

Tensile armour layers in unbonded flexible pipes are constructed by the parallel helical wrapping of several rectangular wires. Pairs of layers, wound in opposite directions and with different helical shapes are used to provide the necessary axial strength, water depth capacity and torsion balance.
The forming of armour wires as supplied by the vendor into a helix shape on the pipe involves significant plastic straining; twisting and repeated bending of the wires in different planes. The wires that are wrapped on the pipe are not unloaded. Therefore the armour wires in flexible pipes are considered to contain residual stress (RS). Knowledge of RS in the wires of the manufactured pipe is essential in making appropriate design decisions with high confidence to meet material utilization requirements and subsequently predict the integrity and fatigue durability of the pipe.
This paper describes an investigation performed to examine the evolution of RS in the tensile wires during various stages of the pipe manufacturing process. To this end, different methods including a relatively simple and inexpensive stress relaxation method termed the contour method, as well as diffraction methods were used to evaluate RS in the wire.
A finite element (FE) model has been developed to simulate the wire deformation involved in the pipe manufacturing process. The procedure was used to predict the evolution of RS in a tensile wire and change in material response during the pipe manufacturing process. A comparison of FE model predictions and measured data is given.
The results show that the RS measured by the contour method give comparable values to those obtained from more advanced methods such as high energy synchrotron X-ray and neutron diffraction. The need for using representative material properties and deformation boundary conditions in FE models to predict RS accurately is highlighted.
Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications
Authors: Bentley Nicole L. , Seaman Calvin H. , Brower David V. , Tang Henry H. , Le Suy Q. 
Published: October 2017

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system capable of measuring pressure, strain, and temperature that can be deployed on existing subsea structures. A summary is provided of the design concept, prototype development, prototype performance testing, and subsequent design refinements of the device. The results of laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are also included. Limitations of the initial concept were identified during testing and future design improvements were proposed and later implemented. These new features enhance the coupling of the sensor device and improve the monitoring system measurement capabilities.
A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on flowlines, risers, and other subsea structures. The work described in this paper investigates the design and test of a friction-based coupling device (herein referred to as a friction clamp) which is suitable for pipelines and structures that are suspended in the water column as well as for those that are resting on the seabed. The monitoring elements consist of fiber-optic sensors that are bonded to a stainless steel clamshell assembly with a high-friction surface coating. The friction clamp incorporates a single hinge design to facilitate installation of the clamp and dual rows of opposing fasteners to distribute the clamping force along the structure. The friction clamp can be modified to be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain measuring capabilities of the design under different loading scenarios. The testing revealed some limitations of the initial design concept, and subsequent refinements were explored to improve the measurement performance of the system.
This study was part of a collaboration between NASA-JSC and Astro Technology Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance technologies that will benefit the environment, the public, and commercial industries.
Response Variability in Flexible Cylinder VIV Model Test Data
Authors: Resvanis Themistocles L. , Vandiver J. Kim 
Published: October 2017

This paper presents some results from the 2011 SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented 38m long flexible cylinders at Reynolds numbers up to 220,000. The main objective it to present the experimental results in a manner that describes the response variability that exists in the measured response data.
Despite the fact that VIV is known to be a stochastic process, this is rarely addressed in the literature and currently there is no framework or ‘best-practice’ in the VIV community that can address statistically non-stationary data. In this paper, the experimental measurements are treated like non-stationary time-series and all statistical quantities which are typically of interest are computed with the use of short duration moving windows (or time-gates). A novel way of plotting and presenting VIV response data for flexible cylinders is introduced that is capable of revealing the inherent variability that exists in the cylinder’s response.
Tensile Strength of Nylon Netting Subjected to Various Concentrations of Disinfecting Chemicals
Authors: Moe Føre Heidi , Dahle Stine Wiborg , Gaarder Rune H. 
Published: October 2017

This paper presents a study of traditional netting materials subjected to disinfecting chemicals during fish farming and treatment of net cages. A series of tests were performed in order to study the effect of various concentrations of disinfecting chemicals on the tensile strength of Raschel knitted Nylon netting materials.
Simulated spill of diluted hydrogen peroxide to the jump fence during de-lousing did not affect the strength of the applied new and used knotless nylon netting samples. Hydrogen peroxide reacted with biofouling forming gas bubbles, but this did not result in reduced netting strength.
The performed tests did not indicate any effect on netting strength from a simulated single, traditional bath disinfection as performed at service stations applying the disinfectant Aqua Des containing peracetic acid. However, increasing the Aqua Des concentration from 1 to 10 % resulted in a strength reduction of 3–6 %. Simulated spill of concentrated Aqua Des on the jump fence of a net with copper coating residuals resulted in a severe reduction in strength of 45 %. This strength loss was probably a consequence of chemical reaction between copper and Aqua Des, and uncoated netting did not experience any loss in strength subjected to the same chemical exposure. These findings from application of Aqua Des should also apply to other peracetic acid disinfection chemicals with trade names as for example Perfectoxid and Addi Aqua.
Comparison of a Simplified Vessel Response Estimation With a State of the Art Vessel Response Prediction Computer Tool
Authors: Ildstad Jens B. , Kolstad Thomas M. , Halse Karl H. 
Published: October 2017

Within ship design it is of great importance to predict the vessels movement while at sea so the designer can ensure safety and comfort of passengers and crew. In early stages of the design process, where main dimensions are not yet set, it is useful to have a qualified estimate of what the vessel behavior will be. In 2004 Jensen et.al proposed a series of closed form expressions to calculate the wave induced motions for a monohull ship. Jensen’s formulas were based on a semi analytical approach and the input data is restricted to main dimensions together with forward speed and heading.
The main idea behind a simplified vessel response estimate is to be able to make qualified evaluations of a vessel’s hydrodynamic characteristics at an early stage in the design process. Recently, several applications have been developed based on Jensen’s method. An independent comparison of the method was therefore sought after, in order to increase the understanding of the accuracy level of the simplified method. In this paper we compare the ship motion estimated with Jensen’s simplified method with the vessel prediction from a state-of-the-art linear hydrodynamic vessel prediction module in ShipX.
J.J. Jensen’s simplified method delivers significant differences in response amplitude and resonance range. While more general trends seem to be well captured. The differences originate mainly from Jensen’s assumptions about constant added mass, the definition of the damping coefficient and that the ship is considered box-shaped. These differences give that the simplified method is not suitable as a tool for detail design of ships, but more suitable as support during concept development of ship designs.