bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Harmonic Polynomial Cell Method for Moving Bodies Immersed in a Cartesian Background Grid
Authors: Hanssen Finn-Christian W. , Greco Marilena , Shao Yanlin 
Published: October 2015

In numerical simulations with moving bodies, and often with complex geometries, generation of high-quality body-fitted grids is a cumbersome and time-consuming task. An alternative is to use a fixed (Cartesian) background grid, and allow the body to move freely over this. The challenge in such methods is to transfer the body-boundary conditions of the moving body to fixed grid nodes in a rational manner. In this paper, an Immersed Boundary Method (IBM) is proposed to simulate potential flow about a moving body on a Cartesian background grid. The recently developed Harmonic Polynomial Method, proven both accurate and computationally efficient, is used to represent the velocity potential in the fluid. The body-boundary conditions are interpolated by using ghost nodes inside the body with mirror interpolation points in the fluid.
The method is first tested for a fixed cylinder in oscillatory flow to determine the accuracy of the proposed IBM, before considering the equivalent case of an oscillating cylinder in still fluid. Finally, a steadily-advancing cylinder is studied, which is considered as the most challenging case with respect to spurious pressure oscillations. These are known to be a challenge in many IBMs, and special attention is therefore devoted to this aspect.
CIP and Parallel Computing Based Numerical Solutions of 3-D Slamming Problems
Authors: Wen Peng , Qiu Wei 
Published: October 2015

This paper presents the further development of numerical simulation method to solve 3-D highly non-linear slamming problems using parallel computing algorithms. The water entry problems are treated as multi-phase problems (solid, water and air) and governed by the Navier-Stokes (N-S) equations. They are solved by the three-dimensional constrained interpolation profile (CIP) method. The interfaces between different phases are captured using density functions. In the computation, the 3-D CIP method is employed for the advection phase of the N-S equations and a pressure-based algorithm is applied for the non-advection phase. The bi-conjugate gradient stabilized method (BiCGSTAB) is utilized to solve the linear equation systems. A Message Passing Interface (MPI) parallel computing scheme was implemented in the computations. For the parallel computations, the three-dimensional Cartesian decomposition of the computational domain was used. The speed-up performance of various decomposition schemes were studied.
Validation studies were carried out for the water entry of a 3-D wedge and a 3-D ship section with prescribed velocities. The computed slamming force, pressure distribution and free-surface elevations are compared with experimental results and numerical results by other methods.
Experimental Studies of Hydrodynamic Interaction of Two Bodies in Waves
Authors: Zhou Quan , Liu Ming , Peng Heather , Qiu Wei 
Published: October 2015

There are challenges in the prediction of low-frequency load and especially the resonant free surface elevation between two bodies in close proximity. Most of the linear potential-flow based seakeeping programs currently used by the industry over-predict the free surface elevation between the vessels/bodies and hence the low-frequency loadings on the hulls. Various methods, such as the lid technique, have been developed to suppress the unrealistic values of low-frequency forces by introducing artificial damping coefficients. However, without the experimental data, it is challenging to specify the coefficients.
This paper presents the experimental studies of motions of two bodies with various gaps and the wave elevations between bodies. Model tests were performed at the towing tank of Memorial University. The objective was to provide benchmark data for further numerical studies of the viscous effect on the free surface predictions. The experimental data were compared with numerical solutions based on potential flow methods. The effect of tank walls were examined. Preliminary uncertainty analysis was also carried out.
Issues in Welding Residual Stress Model in Fitness for Service Assessment of Crack-Like Defect in Weld Area
Authors: Hong Jeong K. (J. K.) , Brodzinski Richard P. , Vargas Pedro M. , Rhee H. Chong , Young K-John , Penso Jorge A. 
Published: October 2015

Current Industry Code and Standard (ICS) Fitness for Service Assessment (FFSA) procedures for crack-like defect in weld area tend to impose high level of conservatism. In addition to the necessity for using conservative Welding Residual Stress (WRS) model due to the uncertainty inherent in the WRS estimation, using the original WRS regardless of crack depth in the crack driving force calculation, like the applied operating load, is the primary reason for this solution conservatism. In addition, current ICS weld area defect assessment procedures involve ambiguities in boundary condition effects on WRS models, as well as in the fracture mode of weld area crack being treated in the context of opening mode only, even though there is no weld area geometric symmetry essential for precluding fracture modes other than mode I.
To clarify these technical issues in the ICS FFSA practices rigorous numerical simulation analyses of welding process and crack growth following joint fabrication have been performed, using the finite element analysis procedure. A crack driving force calculation procedure for weld area cracks, which was developed to quantify the crack extension effects on WRS for growing crack, was used for the finite element crack growth simulation analyses. The rigorous finite element analysis results for boundary condition effects on WRS, the fracture mode of weld toe crack, and crack growth effects on crack driving force parameters caused by WRS are compared with those of current ICS solutions. These comparisons demonstrate the need for an improvement of the current ICS FFSA procedures for weld area crack-like defects.
The primary objective of the present paper is to motivate the industry to improve ICS FFSA procedures by clarifying these ambiguous technical issues in weld area crack-like defect assessment parameters, as well as considering crack extension effects on WRS properly in calculating the crack driving force of growing crack to reduce undue conservatism in FFSA.
Updating of Probabilistic Corrosion Model Based on Bayesian Procedure
Authors: Yamamoto Norio 
Published: October 2015

Corrosion condition is predicted based on the corrosion model. The corrosion model is necessary to be identified according to the corrosion data collected from the various vessels because corrosion phenomenon is stochastic. However, in order to predict corrosion condition of one specific vessel, such corrosion model is necessary to be modified to reflect the effect of specific corrosion environment of the subject vessel.
In the study, procedure of updating corrosion model was investigated based on Bayesian inference on the parameters in the probabilistic corrosion model which utilizes the thickness measurements data. The developed procedure was demonstrated by the application of actual thickness measurements data of the vessel. Even though the amount of corrosion data was limited, the corrosion prediction model was well updated which could be verified by the concentration of posterior distribution which shows the degree of belief on the parameters in the probabilistic corrosion model. The estimated distributions of coating life and corrosion wastage were compared with the frequency distributions obtained by the corrosion data. The estimated distributions of coating life and corrosion wastage showed good agreement with the frequency distributions obtained by the corrosion data.
Modelling of Pressure Fluctuations in a Wellbore While Tripping
Authors: Tarasevich Vladimir , Podryabinkin Evgeny , Bocharov Oleg , May Roland 
Published: October 2015

Assembling or dismantling drillstring sections during tripping operations results in a periodically accelerated or decelerated motion of the drillstring in the borehole. While running in or pulling out of hole the drillstring induces a flow of displaced fluid and a pressure change in the borehole. These pressure changes can be divided into two components: First, the “steady” pressure change associated with the mud viscous friction; and second, the pressure fluctuations caused by induced acceleration of the drilling fluid. Pressure surges are especially dangerous for the uncased well sections and at the bottom of the well, because they can damage and destroy the wellbore. The accurate prediction of pressure fluctuations is significant for wells where the pressure must be maintained within a narrow range to enable safe drilling and completion of the well. Sudden pressure changes in such wells may lead to the so-called water-hammer effect that can be observed in wells when pump operation modes change or when the string is accelerated. A large-scale water-hammer effect may damage the uncased section of a well, leading to fractures or formation fluid inflow.
The objective of this paper is to estimate the magnitude of the pressure surges caused by accelerated movement of the drillstring. A mathematical model was formulated to describe the unsteady behavior of flow rate and pressure change along the well. The model involves a one-dimensional system of equations, which are a modification of the equations for hydraulic shocks in the annulus, and the cylindrical part of a well.
When frictional losses are neglected, it is possible to derive an exact analytical solution of the problem. This analytical solution was used to estimate the maximum and minimum pressure in the borehole.
When combined with the methods for frictional pressure losses, the suggested method can predict the pressure change in a wellbore while tripping. Newtonian and power law fluids were considered for the parameter study.
Lessons Learned From Deepwater-Spool Design on Aasta Hansteen
Authors: Jacobsen Tore , Norland Kristian , Tharigopula Venkatapathi 
Published: October 2015

Spools are frequently used to tie-in pipelines to subsea structures with the purpose of absorbing expansions at the pipeline end, in addition to the connection between pipeline and structure. Deepwater rigid spools have to be designed to accommodate expansion movements resulting from high product temperatures, low strength soils and phenomena such as pipe walking. They also have to accommodate spool fabrication and installation tolerances. These requirements drive the spool geometry and can lead to complex spool geometries that are difficult to install.
The design code usually used for spool analysis is DNV-OS-F-101 [1] which is a primary design code for pipeline design. While using this design code for straight-linepipe and bends, careful considerations should be made because the bends tend to behave different from a straight pipe. Especially the ovality response under in-plane bending is of interest for establishment of a design criteria. The most accurate way to establish this design criteria is by utilising a 3-D non-linear finite element (FE) analysis. The bending moment at failure should be compared with the corresponding bending moment under design conditions. By using FE analyses, more flexible spool can be designed giving lower reaction forces and moments. In addition there are other design-optimization methods to reduce the required spool size and complexity which are further described in this paper. The present paper shows the reduction in wall thickness that is possible through design by analyses. The spool design process is also outlined, and a comparison made on different spool size optimization concepts.
Axial Excitation Tool String Modelling
Authors: Forster Ian 
Published: October 2015

Current types of axial excitation tool have been shown to produce beneficial results — in terms of load transfer to the bit, general reductions in string friction and reductions in drill dysfunctions — such as stick slip.
The positioning of such tools to achieve optimum benefit is therefore extremely important — in order to maximize the axial excitation to the areas of the string that require a reduction in friction, and also to minimize the axial excitation to the surface and to sensitive string tools (such as MWD) — where damage may occur.
This paper describes a string model that allows the position of axial excitation tools to be assessed — in terms of the string response — both locally and remotely from the tool.
The model breaks the string down in to springs and masses — with 10 nodes in the upper string; and 5 nodes in the BHA. Additional components can also be added to the string — such as shock tools, jars and accelerators — in terms of mass and stiffness.
The equations of motion are used to connect the nodes in terms of differential equations.
The model is Mathcad based, and as a result, executes very quickly — so allowing comparative studies to be carried out with relative ease.
Data input into the model is also achieved quickly.
The speed with which the model can be used lends itself to fine tuning input data.
The model has been compared with and ANSYS spring mass model, and good agreement has been reached.
Additionally, the model allows more than one axial excitation tool to be added to the string — in order to gauge the benefits of such a configuration.
Damping can also be varied at different locations in the string model.
The results from this model have been used to compare with field test data — derived from a string with instrumentation tool located at various points in the string.
The results show that good agreement can be reached between the model and the field test results, however, careful consideration needs to be taken of the damping assumed in the model.
The model can, never the less, be used for comparative studies — i.e. tool location, number of tools and optimum frequencies.
Further work is recommended in comparing model results with field test results — in order to get a better understanding of the effect of damping.
The damping model could be improved in the model presented here, or alternatively, the lessons learned here could be merged into an existing string model.
Design Aspects of a High Speed Monohull RoPax Ferry
Authors: Kluwe Florian , Martinsen Kay , Krüger Stefan , Lübcke Adele , Will Johannes 
Published: October 2015

This paper describes the design process of a high speed mono hull RoPax ferry which operates at a Froude number of 0.4. The design task was quite challenging, as two possible transport concepts were in principle possible: Two ships were needed with a total speed of 50knots, which could result in a combination of a 30kn high speed Catamaran plus a conventional 20kn RoPax Ferry or alternatively in two identical sister vessels of 25kn each. The solution with the high speed catamaran plus the conventional RoPax-Ferry defined the total cost budget, which must not be exceeded by the design of the two sister vessels. This resulted in a tough boundary condition and made life cycle cost evaluations necessary.
Due to harbor restrictions, the length of the ships was limited by abt. 110m, resulting in a Froude number of abt. 0.4. This resulted in high costs for the propulsion system. The ferries should initially have open RoRo-Cargo spaces for cost reasons, which made the stability requirements (weather criterion plus Stockholm Agreement) quite challenging. This also strongly influenced the design of the final hull form. As the ship is very sensitive to weight, detailed steel structure optimizations had to be carried out to optimize the main grillage systems of the vehicle decks. The hull form and the appendage design required careful optimization to guarantee the required service speed with the engine power which was available in the price budget. As no vessel of comparison was available, the speed power estimation as well as all design tasks had fully to rely on numerical predictions. As the ship had further demanding requirements for course keeping and comfort in waves, the optimization of the hull form must include also these issues.
The paper shows that the design of complex ships is actually a holistic task which includes many engineering disciplines. The paper also shows that 1st principle based design methods can support the design process of specialized vessels significantly.
Design of Reelable Bulkheads: Application of Pressure Vessel and Subsea Pipeline Codes
Authors: Manouchehri Soheil , Kaye David 
Published: October 2015

Midline bulkheads are often used as a restraining mechanism in High Pressure / High Temperature (HP / HT) pipe-in-pipe (PIP) systems. Their primary function is to share the loads between the inner and outer pipes and / or to minimize the extent of damage in an operational or installation incident. They can also be used during reeled pipelay to facilitate the reel-to-reel or trip-to-trip weld tie-in. Design of a reeled bulkhead, which is categorized as a “pipeline component” under DNV-OS-F101, requires the careful adaptation of a Pressure Vessel Code (PVC), a subsea pipeline code and compliance with the additional requirements of reeling, welding and fabrication. Modern pipeline codes, such as DNV-OS-F101, are LRFD based codes in which different limit states (failure modes) have been formulated and calibrated based on a given probability of failure. The PVCs, however, do not specifically address the pipeline design and careful consideration in selecting load factors, load combinations and the analysis method are necessary.
This paper summarizes a procedure that has been adopted in design of reeled midline bulkheads. The methodology can also be used in design of reeled end bulkheads. Firstly, the initial geometric dimensions of the reelable bulkhead are defined and its reelability is confirmed. Then, appropriate load combinations are identified from ASME BPVC Section VIII – Division 2. Finally, a series of Finite Element Analyses (FEA) are performed to show the fitness-for-service of the bulkhead. The importance of selecting an appropriate and justifiable “code break” is highlighted here.
Local Analysis of Wave Fields Produced From Hindcasted Rogue Wave Sea States
Authors: Dias Frédéric , Brennan Joseph , Ponce de León Sonia , Clancy Colm , Dudley John 
Published: October 2015

Global-scale wave climate models, such as WAVEWATCH III, are widely used in oceanography to hindcast the sea state that occurred in a particular geographic area at a particular time. These models are applied in rogue-wave science for characterizing the sea states associated with observations of rogue waves (e.g., the well known “Draupner” [1] or “Andrea” [2] waves). While spectral models are generally successful in providing realistic representations of the sea state and are able to handle a large number of physical factors, they are also based on a very coarse grained representation of the wave field and therefore unsuitable for a detailed resolution of the wave field and refined wave-height statistics.
On the other hand, local wave models based on first-principle fluid dynamics equations (such as the Higher Order Spectral Method) are able to represent wave fields in detail, but in general they are hard to interface with the full complexity of real-world sea conditions. This paper displays our efforts in coupling these two types of models in order to enhance our understanding of past extreme events and provide scope for rogue wave risk evaluation. In particular, high resolution numerical simulations of a wave field similar to the “Andrea” wave one are performed, allowing for accurate analysis of the event.
Interference Assessment Between Top Tensioned Risers Using a Comprehensive Screening Approach
Authors: Sundararaman Shankar , Saldana David , Patel Suneel , Andrew Ben , Padelopoulos Pete , Karayaka Metin , Raghavan Kamaldev , Hays Paul 
Published: October 2015

Interference between top tensioned risers (TTRs) is a key design challenge. Due to TTR tensioner stroke limits combined with large vessel offsets, the space out of wellheads is limited. Therefore, riser-to-riser contact is more likely to occur in extreme current conditions.
Riser clearance between adjacent risers is evaluated accounting for the effects of wake, vortex-induced vibrations, current directionality (including variation through-depth), vessel offset, riser configuration, and drilling sequence. Accounting for all of these effects simultaneously and in detail when assessing TTR interference can be challenging.
The typical TTR array interference approach consists of a combination of riser deflection shape matching and detailed wake assessment. In this paper, a revised TTR interference analysis approach is discussed, with the inclusion of an intermediate step involving screening for critical riser pairs using a simplified wake model assessment. Riser deflection shape matching ensures that the likelihood of clashing is minimized. The riser interference screening process avoids detailed wake modelling of non-critical riser pairs. The screening analysis method emphasizes avoidance of false positives (unrealistic riser clashing pairs) and false negatives (missing riser clashing pairs). It employs a simplified conservative wake model using a stratified downstream current profile to determine which riser pairs are critical and warrant detailed wake modelling. To illustrate the efficiency of the screening approach, results from this approach are compared to results from analysis with detailed wake modelling.
An implementation of this approach is presented for riser joints with fairings and strakes. Nominal drag coefficients for these joints are obtained based on experimental testing and/or computational fluid dynamics simulations. Drag amplification of the upstream riser is obtained from vortex induced vibration (VIV) analysis and is also incorporated in the analysis.