bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of the Roll Decay of a Container Ship Moving With Forward Speed in Calm Water
Authors: Lungu Adrian 
Published: November 2019

Abstract
In the present paper the roll damping decay is investigated for the KRISO Container Ship in various working conditions. For this purpose flow is simulated by solving numerically the unsteady three dimensional equations of fluid motion in which closure to the turbulence is achieved through the DES-SST model. The governing equations are solved by using the finite volume method and the free surface elevation is determined by using a VOF technique. Comparisons with the experimental data are provided to validate the numerical approach in terms of the time history of the roll angle variation for different roll motions and ship speeds.
Experimental Investigation of Stresses in Winch Drums Subjected to Multilayer Spooling Loads From Synthetic Fibre Ropes
Authors: Skarbøvik Reidar André , Piehl Henry , Torben Sverre , Nedreberg Mette Lokna , Æsøy Vilmar 
Published: November 2019

Abstract
In many marine applications, modern high-performance synthetic fibre ropes have replaced, and are continuing to replace, well-known steel wire rope solutions due to the low weight of the synthetic ropes removing limitations for operations at large water depths. In some cases, replacement of steel wires with synthetic ropes has caused permanent deformations and damage to multilayer winch drums, indicating that synthetic fibre ropes can cause larger pressure on winch drums than steel wire. This paper presents the first results from a novel experimental investigation of a multilayer winch subjected to a selection of braided high-performance synthetic fibre ropes and a reference steel wire rope. The tested ropes, with nominal diameters between 12 and 20mm, are spooled at different tensile loads and with maximum number of layers in the range of 10 to 19. The experiments utilize a test rig with two winch drums, controllable spooling gear and sheaves with load cells to apply and control required load and speed during spooling. Measurements from twelve biaxial strain gauges on the inside of a thick high-strength drum are used to measure stresses in the structure. The results show that the selected fibre ropes induce considerably larger stress in the winch drum than the steel wire rope. This confirms that design of multilayer winch drums with high-performance synthetic fibre ropes requires special considerations and that the guidance for multilayer stress calculations, related to steel wire ropes, in DNV-GL-0378 “Standard for offshore and platform lifting appliances” is not applicable for synthetic fibre rope applications.
Effect of Local Model Dynamics on Flexible Riser Tensile Armor Wire Stress Predictions
Authors: Rombado Gabriel , Doynov Krassimir , Cooke Nathan , Majed Arya 
Published: November 2019

Abstract
Accurate time-consistent computation of tensile armor wire stresses remains a major challenge in flexible riser fatigue life predictions and integrity management. Accuracy requires capturing the kinematics of the flexible’s helically contra-wound tensile armor layers and their interaction with the other metallic and thermo-plastic layers in a dynamic simulation. It is generally accepted that high fidelity 3D Finite Element Models (FEMs) can best capture the complex kinematics and produce accurate stresses. The local model is typically constructed of few “pitch lengths” of the 3D FEM. Local analysis involves enforcing tension and nodal rotation time-histories on the local model and extracting wire stresses at critical fatigue locations along risers. While local analysis involving a few bending cycles can be executed on modern multi-core computers, static simulations typically require computation times of 24–48 hours for a single cycle and do not capture the effect of dynamics of the local model. With this computational constraint, 1-hr long irregular wave fatigue simulations with 3D FEM local model become computationally infeasible. The nonlinear dynamic substructuring (NDS) approach has been utilized in the past to overcome this computation challenge.
Reduced order models are numerical methods for efficiently solving high fidelity FEM. NDS utilizes reduced-order models and numerical algorithms to significantly decrease the computation time associated with the irregular wave fatigue simulations of the high fidelity flexible FEM. Because NDS is a simulation-based approach, effects such as local model tension stiffening and inertial resistance to the global rotation inputs are fully captured and the impact on wire stresses can be discerned.
A 14” inner diameter (ID) flexible riser with a four-tensile armor layer configuration is modeled and simulated using the NDS approach. The 5m long local model is first driven at different “speeds” of harmonic (regular wave) rotation inputs to illustrate inertial effects. For the faster input, the impact of local model inertia on wire stresses is immediately apparent by the increase in wire stresses and change in the shape of the wire stress hysteresis curve. Next, the local model is simulated to irregular wave inputs. It is again shown that the inclusion of local model inertia increases wire stresses and modifies the shape of the wire stress hysteresis.
Predicting Roll Damping for Barge-Type FPSO Using CFD
Authors: Koop Arjen , Jaouën Frédérick , Wadbled Xavier , Corbineau Erwan 
Published: November 2019

Abstract
An accurate prediction of the non-linear roll damping is required in order to calculate the resonant roll motion of moored FPSO’s. Traditionally, the roll damping is obtained with model tests using decays or forced roll oscillation tests. Calculation methods based on potential flow are not capable of predicting this hydrodynamic damping accurately as it originates from the viscous nature of the fluid and the complex vortical flow structures around a rolling vessel. In recent years Computational Fluid Dynamics (CFD) has advanced such that accurate predictions for the roll damping can be obtained.
In this paper CFD is employed to predict the roll damping for a barge-type FPSO. The objectives of the paper are to investigate the capability and accuracy of CFD to determine roll damping of an FPSO and to investigate whether two-dimensional calculations can be used to estimate the roll damping of a three-dimensional FPSO geometry.
To meet these objectives, extensive numerical sensitivity studies are carried out for a 2D hull section mimicking the midsection of the FPSO. The numerical uncertainty for the added mass and damping coefficients were found to be 0.5% and 2%, respectively. The influence of the turbulence model was found to be significant for the damping coefficient with differences up to 14%. The 2D CFD results are compared to results from two-dimensional model tests. The calculated roll damping using the k-ω SST 2003 turbulence model matches the value from the experiments within 2%.
The influence of various physical parameters on the damping was investigated through additional 2D calculations by changing the scale ratio, the roll amplitude, the roll period, the water depth, the origin of rotation and the bilge keel height.
Lastly, three-dimensional calculations are carried out with the complete FPSO geometry. The 3D results agree with the 2D results except for the largest roll amplitude calculated, i.e. for 15 degrees, where the damping coefficient was found to be 7% smaller. For this amplitude end-effects from the ends of the bilge keels seem to have a small influence on the flow field around the bilge keels. This indicates that the 2D approach is a cost-effective method to determine the roll damping of a barge-type FPSO, but for large roll amplitudes or for different vessel geometries the 2D approach may not be valid due to 3D effects.
A Critical Review of Rules and Regulations for Permanently Plugged and Abandoned Wells
Authors: Khalifeh Mahmoud , Akbari Babak , Khan Ahsan , Braga Daniel C. 
Published: November 2019

Abstract
Permanent Plug and Abandonment (P&A) of wells has been an inevitable part of hydrocarbon exploration and production; however, the methodology has not evolved with the same pace as the rest of the industry. Nonetheless, after the environmental impact of some recent events including the Deepwater Horizon oil spill, permanent P&A of hydrocarbon wells has been receiving more attention. Accordingly, regulatory authorities who oversee the P&A activities and operators have tried to improve the pre-existing P&A methodology by defining a modern P&A philosophy, zero leakage criterion. Although the legislated criterion, adapted by most authorities, has challenged the industry and it had a constructive impact on P&A operations, due to technology deficiencies, the associated cost of operation has significantly increased. In this work, most of the publicly available regulations and their recommended practices addressing P&A have been reviewed and discussed. The focus has been given to zero leakage acceptance policy, conventional versus risk-based approach, barrier verification, human factor in P&A, and technology deficiencies. Although Norway is not a major hydrocarbon producer based on the daily production rate, but because of its stricter requirement on P&A, its recommended practice (NORSOK D-010) for P&A has been used in different oil producing countries. As P&A and its impact on environment is a transnational subject, it is suggested to formulate an international guideline or standard on P&A, given the fact that every well is unique when considering P&A operation.
Experimental and Numerical Study of Oil Whip in Propeller Shaft
Authors: Divakaran Adarsh , Vijayan K. , Kartheek A. 
Published: November 2019

Abstract
An experimental study and theoretical study is carried out to understand the vibration signature of a propeller shaft. A test rig consists of a rotor shaft and three-disc supported on hydrodynamic bearing was analyzed.
Presence of hydrodynamic bearing makes the systems natural frequency speed dependent. A theoretical model of the rotor disc system was developed using FEM. The rotor was formulated on Euler–Bernoulli beam theory. Proportional damping was assumed for the shaft. The stiffness and damping coefficients of the bearing are calculated by short bearing assumption. A Campbell diagram was plotted to observe the variation in natural frequencies with rotational speed. There was an indication of mode approaching each other with a speed which could result in the self-excited phenomena such as “Oil whip”. The hydrodynamic forces in the fluid film produce Oil whip. The presence of Oil whip was ascertained by carrying out the experimental study. The time-frequency plot during the run-up indicated the presence of a whip. The study indicated the influence of modes on the whip phenomena. This can be used in forming guidelines for the safe operating regime for the propeller shaft.
Local Blockage Effects for Idealised Turbines in Tidal Channels
Authors: Chen Lei , Bonar Paul A. J. , Vogel Christopher R. , Adcock Thomas A. A. 
Published: November 2019

Abstract
In this paper, idealised analytical and numerical models are used to explore the potential for local blockage effects to enhance the performance of turbines in tidal channels. Arrays of turbines modelled using the volume-flux-constrained actuator disc and blade element momentum theories are embedded within one-dimensional analytical and two-dimensional numerical channel domains. The effects of local blockage on the performance of arrays comprising one and five rows of actuator discs and tidal rotors operating in steady and oscillatory channel flow are then examined. In the case of steady flow, numerical results are found to agree very well with the two-scale actuator disc theory of Nishino & Willden [1]. In the case of oscillatory flow, however, numerical results show that the shorter and more highly blocked arrays produce considerably more power than predicted by the one-dimensional two-scale theory. These results support the findings of Bonar et al. [2], who showed that under certain oscillatory flow conditions, the power produced by a partial-width tidal turbine array can be much greater than predicted by two-scale theory. The departure from theory is most noticeable in the case of five turbine rows, where the two-scale theory predicts that the maximum available power should decrease with increasing local blockage but the numerical model shows the maximum available power to increase. The effects of local blockage are found to be less pronounced for the more realistic tidal rotor than for the highly idealised actuator disc but for both models, the results show that in oscillatory flow, considerably more power is available to the shorter and more highly blocked turbine arrays.
Nano-Modified Rock-Based Geopolymers As Supplement to Portland Cement for Oil Well Cementing
Authors: Khalifeh Mahmoud , Salehi Saeed , Jamrozik Aleksandra , Kimanzi Raymos , Abdollahpour Saeid 
Published: November 2019

Abstract
Geopolymers being inorganic polymers, pumpable, gaining compressive strength, bonding to steel and formation, and showing durability at downhole conditions make them a possible barrier material. However, having low tensile strength, and being contaminated severely with water-based fluids are the challenges to be mitigated. These challenges have also been observed in recently developed rock-based geopolymers. Different researchers have suggested the application of nanoparticles as additive to geopolymers for increasing the mechanical properties. Of these one could list nanosilica, nano titanium di-oxide, nanocarbon graphene, carbon nanotubes, and nano aluminium. However, their reasoning for utilization of these nano particles originated from their effect on properties of Portland cement.
In this study, the effect of nano titanium di-oxide and nanocarbon graphene is considered on the rock-based geopolymers. The two main criteria for selection of these materials are in-house availability, and the published prior art. The effect of the nano materials on rheological behavior, mechanical strength and microstructure of the geopolymers are the main investigated parameters. The obtained result shows that the nano materials improve the pumpability of the geopolymers but not improving the tensile strength effectively.
Experimental Assessment of Form Based Approach for Predicting Extreme Value Distribution of Hull Girder Bending Moment in a Ship
Authors: Takami Tomoki , Komoriyama Yusuke , Ando Takahiro , Iijima Kazuhiro 
Published: November 2019

Abstract
This paper describes a series of towing tank tests using a scaled model of a recent container ship for validating the First Order Reliability Method (FORM) based approach to predict the maximum response. The FORM based approach is adopted in conjunction with the nonlinear strip method as an estimation method for the most probable wave episodes (MPWEs) leading to the given extreme wave-induced vertical bending moments (VBMs). Tank tests under the pre-determined MPWEs are conducted to evaluate the extreme wave-induced VBMs. Numerical simulations based on the coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are also conducted and are compared with the test results under the MPWEs. Furthermore, to estimate the extreme VBM statistics, tank tests under random irregular waves are conducted. A series of validations of the probability of exceedances (PoEs) of the VBM evaluated from the FORM based approach is carried out. The effect of hydroelastic (whipping) vibrations on the extreme VBM statistics are finally discussed.
Edge Effect on Numerical Calculation of Nonlinear Radiation Forces for a Submerged Body
Authors: Yang Jianye , Teng Bin , Gou Ying 
Published: November 2019

Abstract
To investigate the edge effect on numerical calculation of nonlinear forces for a moving body in the time domain, a large body motion model with linear free surface condition is developed with higher-order boundary element method. Five numerical formulations are used to compute the nonlinear radiation forces on submerged surging bodies with sharp edge and a small chamfer radius at the edge. It is found that for those bodies with smooth surface, the nonlinear radiation forces obtained by all of the numerical formulations are close to each other, but large disperses exist for the body with sharp edge. Examination on the vertical nonlinear radiation forces shows that the method on momentum change rate is insensitive to the small edge radius even the chamfer radius is zero, but the other formulations diverse when the edge radius approaches zero. It is suggested that for a body with sharp edge, the method on momentum change rate should be used, or to replace the body surface by the body with a small radius at its sharp edge.
Numerical Simulation of the Fluid-Solid Two-Phase in the Horizontal Pipe Based on DEM-CFD Coupling Method
Authors: Pu Jin-Shan , Chen Yong-Ping , Yao Peng 
Published: November 2019

Abstract
Compared to the conventional CFD method, the CFD–DEM coupling is proposed to simulate the solid–liquid two–phase flow in the horizontal pipe in this paper. The standard k–ε model was utilized for fluid turbulent flow, the standard wall functions for near-wall zone treatment, and the Hertz–Mindlin (no slip) model for particle–particle and particle–wall contact. The movements and distribution of particles in different inlet velocities and pressure drop in pipeline are investigated in this paper. The results show that the coarse particles appear starting, discontinuous movement as bedload, continuous movement as bedload, and suspension in order with mean velocity of fluid media increase; with the increasing inlet velocity, the distribution of partilces in the pipe becomes more even, however, the concentration of the particles on the botton is larger than that on the top. Moreover, the pressure drop predicted by this method is compared with the Churchill pressure drop model and results are not identical. Therefore, the regular of pressure drop is demonstrated in this paper.
Theoretical Modeling of Steel Strip Reinforced Flexible Pipe With Swaging End Fitting by Taking Into Account Stress Concentration Effect
Authors: Gao Yifan , Chen Wei , Bai Yong 
Published: November 2019

Abstract
A new theoretical model was proposed to calculate the burst pressure of steel strip reinforced flexible composite pipes (steel strip PSP) based on the thin wall cylindrical shell theory and the squeeze pressure expression between layers was derived. The radial displacement discontinuity of pipe wall in pipe-end fitting joint area takes in account in this model which could result in Stress Concentration Effect (SCE) in reinforcement layers. The SCE is caused by swaging end fitting clamped tightly at the end of the pipe. The result of the hoop strain in the joint area calculated by this model is greater than the one calculated by the classic elastic model, which leads to relative conservative burst strength of the pipe. The hoop stress variation via internal pressure on innermost reinforcement layer is introduced to predict the burst strength of the pipe. As the stress in the joint area reaches its ultimate strength, the strain on the same layer in the point far away from this area (x→∞) is extracted and the corresponding internal pressure is obtained as the burst strength of the pipe. The calculated data from two models were compared with the experiment results and the proposed new model showed better accuracy than the classic elastic model. Final additional parametric studies were conducted, while the effect of the pipe diameter, the winding angle, the number and thickness of the reinforcement layer on the burst strength of the pipe were studied. Useful conclusions were drawn for the design and application of the steel strip PSP in offshore engineering.
An Ontology-Based Approach for Developing Offshore and Onshore Process Equipment Inspection Knowledge Base
Authors: Rachman Andika , Ratnayake R. M. Chandima 
Published: November 2019

Abstract
A collection of inspection results is an essential input in assessing and managing the technical integrity of offshore and onshore process equipment. The inspection results enable the current condition of the equipment, the type of damage mechanism, and the severity and location of the degradation to be investigated. Typically, the inspection results are documented in a text-format report and stored in a conventional data repository. Conventional inspection data storage has drawbacks in terms of the sharing, exchange, and retrieval of information within an inspection knowledge domain, due to the lack of knowledge representation. This study proposes an ontology-based approach for developing an inspection knowledge base, in order to improve the degree of retrieval, distribution, and administration of inspection results. Ontology provides a semantic structure and relations for concepts in the inspection knowledge domain, which facilitate semantic search capability and enable increased utilization, enhanced communication and improved exchange of inspection information. A case study of a static equipment inspection is shown, to demonstrate the application of an ontology-based approach in facilitating data and information retrieval from an inspection knowledge base.
Fluid Dynamics Numerical Assessment to Evaluate the Ice Formation Around the Pipeline
Authors: Blasioli Giuseppe , Marchesani Furio 
Published: November 2019

Abstract
In response to the UNCCC held in Paris in 2015 the need to reduce the global warming, due to CO2 release in atmosphere, led to a new business for the capture and storage of CO2 in dedicated deep water reservoir. In this sense the transport of the CO2 at low temperature, necessary to condensate the gas, through offshore pipeline is a commercial and technical valid strategy.
One of the issues related to the transport of a condensate gas is the thermal exchange between the transport system, in this case offshore pipelines, and the environment. The gas is usually carried by ships in a liquid phase at very low temperatures, for example −30 °C in case of CO2. The fluid is introduced into the pipeline at the same temperature to not further consume energy for warming up.
The design of the offshore pipeline subject to these operating conditions, very cold fluid internally and a water temperature slightly over 0°C at external side, can be affected by the ice formation around the pipe. The ice thickness formation is primarily governed by the external convection coefficient.
For the offshore pipelines located in deep waters where the sea currents are negligible, only the natural convection phenomena can occur on the external surface of the pipeline. Considering steady state scenario the heat transfer from the internal fluid to the external environmental is governed by the thermal resistance of each component of the system like fluid, steel, anticorrosion coating, thermal insulation if any and external convection due to the seawater. The low temperatures of both seawater and ice formation, approximately at −2°C, allow to be close to the maximum value of the seawater density: usually this occurs at a slightly colder temperatures depending on salinity and water depth (for the fresh water the maximum is at 4°C).
The natural convection is driven by the buoyancy effect due to fluid density variation with temperature: the scenario described above lead to minimizes these effects and consequently the heat transfer due to the natural convection (increasing the thermal resistance).
Most of the correlations in literature are related to different temperature ranges, far away from this particular situation: a numerical investigation using computational fluid dynamics technique has been performed.
The analysis is executed by means of commercial CFD software FLUENT: the model is based on a two dimensional grid of a pipe submerged in water.
In this paper:
• The state-of-the-art about the natural convection coefficient estimate for submerged cylinders proposed by different authors through Nusselt number assessment;
• A description of the proposed numerical approach is given highlighting the different approaches based on the boundary layer behavior;
• A typical application is shown.