bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Effects on the Anchoring of Flexible Pipe Tensile Armors
Authors: Otte Filho Olaf O. , Tanaka Rafael L. , Morini Rafael G. , Torres Rafael N. , Vilela Thamise S. V. 
Published: October 2015

In the design of flexible pipes, predict the anchoring behavior on end fittings is always challenging. In this sense, Prysmian Surflex has developed a finite element model, which should help the end fitting design as well the prediction of the structural behavior and the acceptable maximum loads. The current model considers that the contact between armor-resin is purely cohesive and has been suitable for the design of end fittings [1] and [2]. But tests and new studies [3] and [4] indicate that only cohesive assumption would not be the best approach. Experimental data from prototype tests also show that the current model would not predict acceptable results for loads higher than those used in previous projects.
This document will describe a study developed considering the friction and thermal contraction, instead of the cohesive phenomenon in the anchoring behavior analysis. Small scale tests were conducted in order to understand the anchoring relation between the resin and the wire used in the tensile armor. For this purpose, a special test device was developed to simulate an enclosure system. A parametric study was also performed to identify the cooling temperatures, coefficients of friction and contact properties parameters taken from small scale tests. The finite element model considers the thermal effects during exothermic curing.
Using the new parameters obtained, a second model was developed. This model consists of only one real shaped bended wire inside an end fitting cavity. To validate the model, samples were tested on laboratory according anchoring design. The results of this round of tests were studied and corroborate the argument that use friction and thermal effects is better than use only the cohesive condition.
Model Tests of a Spar-Type Floating Wind Turbine Under Wind/Wave Loads
Authors: Duan Fei , Hu Zhiqiang , Wang Jin 
Published: October 2015

Wind power has great potential because of its clean and renewable production compared to the traditional power. Most of the present researches for floating wind turbine rely on the hydro-aero-elastic-servo simulation codes and have not been exhaustively validated yet. Thus, model tests are needed and make sense for its high credibility to master the kinetic characters of floating offshore structures.
The characters of kinetic responses of the spar-type wind turbine are investigated through model test research technique. This paper describes the methodology for wind/wave model test that carried out at Deepwater Offshore Basin in Shanghai Jiao Tong University at a scale of 1:50. A Spar-type floater was selected to support the wind turbine in this test and the model blade was geometrically scaled down from the original NREL 5 MW reference wind turbine blade. The detail of the scaled model of wind turbine and the floating supporter, the test set-up configuration, the mooring system, the high-quality wind generator that can create required homogeneous and low turbulence wind, and the instrumentations to capture loads, accelerations and 6 DOF motions are described in detail, respectively. The isolated wind/wave effects and the integrated wind-wave effects on the floating wind turbine are analyzed, according to the test results.
Analysis of Uncertainty Attributed to Measurement Error in Directional Surveying With Different Models
Authors: Mittal Manish , Samuel Robello , Kumar Aniket 
Published: October 2015

The current interest in directional survey calculations is related to the increased number of highly deviated holes drilled from offshore platforms. Positional accuracy is important because, when two wellbores closely approach one another, it is essential to avoid intersection. Also, when a relief well is drilled, it is important to achieve intersection with the wild cat well. Unfortunately, there is no set of calculations that can be used to analytically determine exact bottomhole position relative to the top hole. Therefore, uncertainty with respect to estimating the wellbore position should be determined using directional surveys and the different models being used.
Errors in estimating the target primarily derive from two sources — model errors and measurement errors. Model errors occur in the calculations used to estimate borehole position because of a lack of complete information, which can only be tackled by having an infinite number of survey stations throughout the well path. On the contrary, measurement errors occur in the readings of inclination angle (I), azimuthal angle (A), and the distance between two stations (L). This paper focuses on estimation of measurement error, which is an inherent property of measuring instruments being used for the survey and can be evaluated numerically after making some assumptions necessary for such an analysis. The said analysis would ultimately provide ellipses of uncertainty for the target point based on different survey models.
The study is based on a paper by Walstrom et al. [1], which uses the angle averaging (AA) method for survey calculations. The study is extended for calculating measurement errors in the following models: the radius of curvature (ROC), minimum curvature (MC), and natural curve (NC) methods.
Uptake Riser for P-25 Platform in Albacora Field in Campos Basin
Authors: Franciss Ricardo , Custódio Anderson Barata 
Published: October 2015

The P-25 platform is located at 575 m water depth in Campos Basin, offshore Brazil. In the time of its conversion (1996), its process plant was designed to use cold water streaming from the Antartic continent to cool its equipment, accessories and compressing gas plant for exportation.
The uptake riser installed in 1997 is 330 m long, 24″ OD pipe, hanging from the pontoon and the cold water flowing through it enters a sea chest located next to the support.
This fully rigid riser was recently asked to be replaced. This paper presents the stages of the reanalysis of this compliant structure under conditions of low cost, so that the platform continues to suck cold water. Because of the presence of the uptake riser, the platform does not have a cooling plant that would else request area and weight, two important items in an arrangement, besides the high cost involved.
Within the scope of the analyses, the replacement of the material (originally steel) with offloading hoses is tried out, in search for weight savings and lower cost. These hoses were reinforced with steel cables and their behavior was checked. Some tests were performed to verify the mechanical strength of this material and vibrations by VIV that occur in this structure.
Monitoring systems were designed to check all forces and displacements during the referred installation.
These actions will consolidate the technology for Petrobras leading to another riser system option for production in ultra deep waters.
Numerical Method Research on Nonlinear Roll System of Large Container Ship
Authors: Liu Yachong , Hu Ankang , Han Fenglei , Lu Yu 
Published: October 2015

When dealing with the ship-roll problem, the roll motion is mainly regarded as a single degree-of-freedom dynamical system, and the nonlinear properties are reflected in the nonlinear damping term and restoring moment term. Previous studies have shown that transverse chaotic phenomenon means the damage of ship-roll stability which will lead to ship capsizing, and for ultra large container ships, the wind area above water surface can not be neglected, which turns the ship-roll system into asymmetric dynamical system.
The concept of safe basin is usually used to express the boundedness of motion. It is defined as the set of bounded solution to dynamical system, and the erosion phenomenon of safe basin is normally explained as the global instability. This concept was firstly brought out by Thompson [1] when he studied the problem of ship capsizing and then was applied to different fields of engineering.
Based on this background, the following three tasks are completed in this paper. a) For the calculation of chaos threshold, two numerical methods, namely, Pade approximation and Gauss-Legendre integration are adopted, analyzed and compared. b) One 9200TEU container ship is selected and the chaos threshold is calculated by virtue of Gauss-Legendre method. As numerical verification, the gradually erosion phenomenon of ship’s safe basin is observed and phase trajectories of points located in broken domain are traced; c) When encountered with crosswind (When winds are not parallel to or directly against the line of travel, the wind is said to have a crosswind component; that is, the force can be separated into two vector components, a crosswind component and a headwind or tailwind component.), the symmetry of ship-roll system begin to break. In the last part of this paper, the effect of crosswind on safe basin, asymmetry, and stability are studied.
Rheological and Wall-Slip Behaviors of Polymer Based Drilling Foams
Authors: Sherif Testi , Ahmed Ramadan , Shah Subhash , Amani Mahmood 
Published: October 2015

This paper present experimental study conducted on rheology of hydroxyethyl cellulose (polymer) based foams. The effects of foam quality, wall-slip, and polymer concentration on foam rheology have been experimentally investigated using a circulating flow loop. Foam quality and flow rate were varied from 50 to 80 percent and 1 to 52 L/min, respectively. To identify the existence of wall-slip, tests were performed using different diameter (13.4, 19.6 and 31.8 mm ID) pipe viscometers.
Experimental results show expected trends; pressure loss increased with increasing flow rate and reduced with increasing pipe diameter. Slight wall-slip was observed in the small diameter viscometer. However, the measurements obtained from other viscometers do not indicate wall-slip. All tested foams exhibited strong non-Newtonian behavior, which increases with foam quality and polymer concentration. The rheology of foams best fits the power-law fluid model. Applying regression analysis, new correlations have been developed to predict rheology of polymer-based foams.
New Semi-Submersible Floating Wind Turbine for South China Sea
Authors: Li RongFu , Qi Xiaoliang , Gao Wei , Li Hui 
Published: October 2015

With the demand of renewable energy due to the pressure from environmental pollution and global warming, the wind industry has been growing rapidly over the past decades during which the offshore wind innovation is becoming more and more attractive because of vast offshore wind resources.
In this paper, a novel tapered-column semi-submersible floating foundation with economical mooring system is developed to support 6MW wind turbine in South China Sea. The coupled aero-hydro-servo-structural analysis is done in GH-Bladed software to obtain the global dynamic response of the whole floating wind turbine. By combining the derived wind loads with the wave and current induced loads, the global performances of the foundation and attached mooring system under both extreme conditions and normal operation conditions are analyzed in AQWA software. The result reveals that the floating foundation complies with the design standard and meets requirements of wind turbine.
This novel patent-pending floating foundation with tapered columns is proved as a successful design with high material efficiency and good seakeeping performance. Also a reliable and efficient design methodology of floating foundation based on optimal cost is provided in this paper which can be used as design reference of floating foundations.
The Underwater Laser Ranging for Dynamics Measurement Around Subduction Zone
Authors: Yoshida Hiroshi , Ishibashi Shojiro , Sakaguchi Hide , Saito Takashi , Denou Motoi , Tashiro Masatoshi , Tanaka Kiyotaka , Suzuki Minoru 
Published: October 2015

An underwater laser ranging system to capture microscopic fluctuations in relative plate motion around subduction zone has been developed since 2010. We believe that direct detection of the fluctuations resulted from plate motion suggests the degree of interplate mechanical instability for long-term prediction of oceanic intraplate earthquake.
In April 2011, sea trial using the first prototype was carried out in shallow water zone in Okinawa. Distance measurements could be performed in the distance of 10 meters but results included large error variation of 0–10 cm. To improve measurement resolution and accuracy of the sub-millimeter fluctuations, we have developed the second prototype of laser ranging system based on the first one.
The main part of the system consists of a transmitting unit (Tx) and a receiving unit (Rx). One of the units is composed of a transparent acrylic cylindrical pressure hull (PH), a main PH, a battery pack, and sensors, which are installed on an aluminum alloy frame. The transparent PH of Tx is equipped with a 1 Watt semiconductor blue laser, a modulator and a driver which are set on a horizontal turntable with elevation adjustment. Its Rx has an avalanche photo diode as detector and a demodulator on a same type turntable. A controller and an optical communication device are installed in each main PH. The Tx is connected with the Rx via thin optical glass fiber to transmit reference signal.
We carried out a sea-trial in Okinawa by the second prototype in February 2014. We received optical signal at distance between the Tx and the Rx of up to 20 meters. The ranging was performed at 10 meters and measurement raw data errors were within a range of millimeters. On the other hand, automatic optical alignment at 20 meters was completely failed. These results show that measurement accuracy is closer to a goal but system completion is away from the goal. We need review not only the algorithm but also optical hardware of the alignment.
Experimental Study on a Motion of “Underwater Platform” Including Hydro-Elastic Deformation in Waves
Authors: Murai Motohiko , Haneda Ken , Yamanoi Jun , Abe Yuta 
Published: October 2015

A new type of floater for floating offshore wind turbine (FOWT) was proposed. The floater, named an “underwater platform”, aims at high economic efficiency of energy generation of floating wind farm. The underwater platform is a large scale submerged structure which has small water plane area and can support several wind turbines. It is expected that the platform has small motion characteristics in waves because of its small water plane area, and it contributes for FOWT to generate energy safety.
In this study, the feasibility and usefulness study about the platform was carried out through experiments and numerical simulations. The first experiment was conducted with partial rigid model of the platform to verify the feasibility. From the experiment, it was confirmed that the model has small motion characteristics in waves. The experimental results were compared with numerical simulations of potential theory and they were well matched. Besides, the coupling analysis with aero-hydro dynamics was also carried out and it was confirmed that the stability of the platform was enough in steady wind condition.
The second experiment was conducted with elastic body model to study the elastic deformation of the platform in waves. From the experiment, it was confirmed that the deformation is small when the draft was 250mm (50m in the actual model).
The Influence of Drilling Fluid Rheological Properties on Primary Solids Control
Authors: Saasen Arild , Hodne Helge 
Published: October 2015

Throughout the last decades, the design and performance of the primary solid control devices have changed significantly. Some five decades ago, the circular motion shakers dominated the marked. These shakers operated by sending the drilling fluid downhill a vibrating screen. Thereafter appeared the elliptical motion or linear motion shakers where the cuttings particles were vibrated upwards a tilted screen. Onto these shakers, the use of double screen decks and finally triple screen decks became common. Within the last years also the vacuum devices appeared.
Throughout the last two decades, there has been an effort to increase the g-forces on these shakers and the industry seems to have preferred the high g-force devices recently. Laboratory studies, however, has indicated that the very high g-forces are not necessary to perform proper solids control. Instead, different vibration modes interacts with the gel structure of the drilling fluid and remove yield stresses. Hence, the fluid becomes mobile for flow through the screen.
Flow through screens is strongly dependent on the extensional properties within the drilling fluid rheology. Drilling fluids with high extensional viscosity seldom has a very strong gel structure, and are generally not affected equally much by vibrations. This explains why solids control is more difficult using a KCl/polymer water based drilling fluid than if using an oil based drilling fluid.
This article focuses on describing how the drilling fluid rheological properties alter during primary solids control. It is based on theoretical analysis, rheological studies in the laboratory and finally on practical applications in two recent exploration drilling operations. The solids control efficiency resulting from using different screen configurations is outside the scope of this article, as this topic requires a higher focus on separation technology.
Steel Lazy Wave Riser Configuration for Turret Moored FPSO With Disconnectable Turret in Deepwater
Authors: Karunakaran Daniel , Subramanian Sankar , Baarholm Rolf 
Published: October 2015

Recently turret-Moored FPSOs have been used in many deep water developments worldwide, with consideration of disconnectable turrets for harsh environment applications. This trend makes the interactions between FPSO and risers system more important. Further, Steel Lazy Wave Risers (SLWR), which is a compliant variant of the mostly commonly used Steel Catenary Risers (SCR), is becoming an attractive riser option.
The paper provides a review of the various riser systems that can be considered for turret-moored FPSOs, and specific emphasis on Steel Lazy Wave Risers. A detailed case study of Steel Lazy Wave Risers for a typical turret moored FPSO with disconnectable turret is presented. This system is described in terms of design and functionalities, the fabrication and installation methods are presented. The case study shows clearly that SLWR are an attractive alternative to be used for FPSO with disconnectable turret and is very efficient to fabricate and install in a very cost effective manner.
Pros and Cons for SLWR are discussed, with consideration of the particular challenges of turret-moored FPSOs with large floater motions, hang-off geometry constraints at turret, hang-off loads, riser interferences, risers pre-installation, and turret disconnection constraints.
Reliable, Low Footprint and Cost-Effective Monitoring of Wellhead Loads Using Autonomous IMUs for Fatigue Estimates
Authors: Authen Kristian , Grytøyr Guttorm , Melbø Hallgeir 
Published: October 2015

Wellhead systems in the North Sea are frequently subjected to large bending loads, due to shallow waters, heavy seas and semi-submersible drilling rigs. This makes fatigue of wellhead systems a challenge.
The fatigue estimates of such wells are often conservative when based on global FE riser simulations. To reduce the conservatism from such simulations, measurements of the actual wellhead loads have been performed on certain occasions. This is often a costly and intricate process that usually require a subsea cable from the rig. This paper presents an alternative method for measuring WH loads by the use of autonomous motion sensors (IMUs) on the BOP and lower end of the drilling riser.
Measured inclinations from the IMU on the riser are used to capture the loads acting from the riser onto the BOP. The inclinations from the sensor on the BOP are used to capture the dynamic response of the BOP and well system. The combination of the measured excitation load and the measured dynamic behavior, makes it possible to reliably estimate the WH bending moment, without the use of riser simulations.
The accuracy of the proposed methodology is demonstrated in a FE riser simulation. The model acts as a controlled environment where both input parameters and WH loads are known. The sensor data is extracted from the analysis at the relevant locations, run through the proposed methodology and then compared with the WH loads in the model.
As a final verification, the method is tested on data from an actual measurement campaign where both IMU and strain gauge measurements are available. The WH loads will be calculated based on the proposed method and IMU data, and the results will be compared to the data from the strain gauge based load sensors.
Bilge Keel Loads and Hull Induced Pressures: Experimental Results and CFD Validation
Authors: van ‘t Veer Riaan , Schut Xavier , Pelerin Jean-Luc 
Published: October 2015

This paper present results obtained in an experiment with a rotating cylinder to which a single bilge keel was fitted. Forced oscillations were performed leading to a KC range between 1 and 16. The loads acting on the bilge keel were measured as well as the vortex induced hull pressures in the vicinity of the bilge keel.
Computational Fluid Dynamic simulations were conducted with a 2D representation of the experiment. Good correlation in the bilge keel loads and vortex induced pressures is obtained.
Using Fourier analysis the first and first two higher harmonic (3ω and 5ω) drag and inertia coefficients of the bilge keel load were calculated. It is shown that the higher harmonic drag and inertia terms are essential to obtain a good load representation.
The vortex induced pressure in front of the moving bilge keel is found to be KC independent. The pressure jump over the bilge keel can be correlated to the instantaneous normal force on the bilge keel. In the wake of the moving bilge keel the pressure depend on KC. These findings are in agreement with the observations reported by Ikeda et al. [1].
Power Generation Potential of a VLFS Equipped With OWC Type WECs and Damper Effects on Elastic Motion
Authors: Ikoma Tomoki , Masuda Koichi , Watanabe Yuka , Eto Hiroaki , Rheem Chang-kyu , Kinoshita Takeshi 
Published: October 2015

This paper describes potential of PTO (Power Take-Off) and the damper effect of motion in a large scale pontoon type floating structure on which lots of oscillating water column (OWC) type wave energy convertors (WEC) are installed. It is enable to use upper space for utilizing marine renewable energy such as wind power, tidal power, wave power generation farm using large pontoon structure. Due to the concept, it should reduce cost of maintenance as well.
For investigation of PTO and elastic motion behaviours of large floating structures, we calculated three types of models on which OWC devices were installed differently. We examined how much reduction was possible when including elastic motion effects and the fixed type which radiation wave was not taken into account. In this paper, a boundary condition in order to give effect of a free water surface with air pressure is theoretically modeled. We can directly consider influence of wave energy absorption to hydrodynamic forces and wave exciting forces on the floating structure with the Green’s function method based on the linear potential theory. In the modeling, a boundary condition on a free water surface and an equation of state within an air-chamber above OWC are mathematically and linearly formulated. Air-pressures and vertical displacement within OWC areas can be simultaneously and directly solved by setting both the variables and by solving the simultaneously equations of the air-pressure and the vertical displacement.
As a result, performance of PTO and hydroelastic motion of the floating structure increased when including elastic motion effect. In addition, expected value of annual PTO was about 4.4MW with 146 OWCs.