bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fully-Nonlinear Wave-Current-Body Interaction Analysis by a Harmonic Polynomial Cell (HPC) Method
Authors: Shao Yan-Lin , Faltinsen Odd M. 
Published: November 2013

In the Ronald W. Yeung Honoring Symposium on Offshore and Ship Hydrodynamics in OMAE2012 hold in Rio de Janeiro, Shao & Faltinsen [1] have proposed a new numerical 2D cell method based on representing the velocity potential in each cell by harmonic polynomials. The method was named the Harmonic Polynomial cell (HPC) method. The method was later extended to 3D to study potential-flow problems in marine hydrodynamics [2]. With the considered number of unknowns that are typical in marine hydrodynamics, the comparisons with some existing boundary element based methods including the Fast Multipole Accelerated Boundary Element Methods showed that the HPC method is very competitive in terms of both accuracy and efficiency. The HPC method has also been applied to study fully-nonlinear wave-body interactions [1, 2], for example, sloshing in tanks, nonlinear waves over different sea-bottom topographies and nonlinear wave diffraction by a bottom-mounted vertical circular cylinder. However, no current effects were considered.
In this paper, we study the fully-nonlinear time-domain wave-body interaction considering the current effects. In order to validate and verify the method, a bottom-mounted vertical circular cylinder which has been studied extensively in the literature will first be examined. Comparisons are made with published numerical results and experimental results. As a further application, the HPC method will be used to study multiple bottom-mounted cylinders. An example of the wave diffraction of two bottom-mounted cylinders is also presented.
High-Order Simulation of the Flow Instability Over a Non-Circular Structure
Authors: Minguez Matthieu , Meliga Philippe , Serre Eric 
Published: November 2013

Bluff bodies can be prone to well-known self-excited instability such as galloping. Opposite to classical and well documented Vortex Induced Vibrations (VIV), oscillation amplitude is not bounded in such a way galloping-like instability can alter the integrity of the structure on short term. Although stability criteria exist in the literature [1], there is a real lack considering the cause and the way to inhibit such instability.
It is consequently proposed in this paper to investigate the flow over the classical ‘non-circular’ structure, i.e. the square box body, by means of advanced Spectral Large Eddy Simulation (LES) solver, [16], [17] & [18]. The main objectives of this numerical analysis will be to provide an accurate solution to underline the possible mechanisms that trigger the instability as well as a base solution for future wake stability & control analysis, [6].
Fatigue Study of Conductors at the Conductor Guides’ Level on North Sea Platform
Authors: Mosalam Bita Jalali , Gudmestad Ove Tobias 
Published: November 2013

This paper presents the method and results from a fatigue study of conductors at the conductor guides’ levels as well as a static and dynamic hydrodynamic analysis of a 20″ conductor installed on a North Sea jacket platform using the OrcaFlex 9.5 computer program. This study presents only the results of the analyses and does not comment on the program’s efficiency or ability to model the various physical effects. Due to the conductor guides’ situation with gaps between the conductor and its guides, which was reported by the offshore survey, there was great demand for a fatigue life study of the conductors. The hydrodynamic analysis was performed with Finite Element Software, the OrcaFlex 9.5, for regular waves for 1-, 10- and 100-year return period sea states. Afterwards, fatigue calculations were carried out according to the output from the hydrodynamic analysis. The main achievements from this study are:
• Some elements have been identified as key factors, which have a great influence on the fatigue life of the conductors at the guides’ levels: bending moment, wall tension of the conductor, hydrodynamic & structural damping factors (which are seen to be main sources of uncertainty) as well as the clearances (gaps) between the conductor and its guides at the different guide decks.
• The bending moment could be reduced by decreasing the gap for the conductor in the guides.
• Selecting a DFF (Dynamic Fatigue Factor) of 2 means that the fatigue life of the conductors at the guide levels will not match the requirement for conductor fatigue service life, according to our analysis; and the conductors need inspection and modification.
Structural Integrity of a Spar in Collision With a Large Supply Vessel
Authors: Ning Xinguo , Zhang Bob L. , Tallavajhula Sudhakar 
Published: November 2013

The objectives of this study are to establish numerical approaches to evaluate the structural integrity of a generic Spar hull in collision with a large supply vessel and to reveal its progressive collision damage characteristics.
Dynamic and nonlinear finite element analysis is implemented using ABAQUS/Explicit module [1] respectively for two collision scenarios. One is a realistic simulation where the impact kinetic energy governed by an initial impact speed and total mass of a ship is gradually depleted during the collision. The other is a simplified analytical method where the impact speed of a ship bow throughout the collision is constant or the total impact energy is unlimited.
With a combination of calibrated material progressive damage models and Mises plasticity, progressive collision damages of the hull structures are accurately captured for structural integrity assessment. The collision energy absorption characteristics, the impact force-deformation curves, the progressive damage modes and the correlation between the impact force, kinetic energy and damages are revealed. Based on numerical investigation, the two analytical scenarios are compared and the implication for the design analysis is elucidated. As a complementary to the ABS code [2], the alternative collision damage criterion in ABS MODU [3] applicable to column-stabilized units is justified to be applicable to a Spar subjected to high-energy impact.
Lazy Wave Catenary Risers: Scaling Factors and Analytical Approximation of the Static Stress Range in the Touchdown Zone
Authors: Quéau Lucile M. , Kimiaei Mehrdad , Randolph Mark F. 
Published: November 2013

Offshore exploration and production of oil and gas continue to increase and move into ever deeper water. Steel catenary risers (SCRs) are one of the most cost effective type of risers in deep water. However, high sensitivity to vessel motions and hydrodynamic loading in the touchdown zone may limit the feasibility of SCR applications. In recent years, there has been a growing interest in the use of Lazy-wave catenary riser (LWR) due to their better fatigue performance in the touchdown zone through the damping effect of the buoyancy section.
The design of LWR involves numerous parameters that lead to a wide range of configurations. Each of these configurations needs to be evaluated against several criteria with respect to geometry, strength and fatigue for instance. This paper presents how tools recently proposed to improve the design of standard SCRs can be extended to benefit LWR applications. The dimensionless groups governing the structural response of LWRs are established in the aim of easing sensitivity analysis to key input parameters for LWR design, assisting experiments and reducing the number of numerical simulations. Moreover, the DAF (dynamic amplification factor) approach for dynamic response which has previously been explored for SCRs could also be used to simplify design of LWRs. As DAF relies on the analytical determination of static response, this framework shows that analytical boundary layer solutions in conjunction with the use of a Winkler type soil model can efficiently and accurately predict the static stress range of LWRs observed in the TDZ.
Temporary-Creep and Post-Creep Properties of Aquaculture Netting Materials With UHMWPE Fibres
Authors: Moe Føre Heidi , Endresen Per Christian , Jensen Østen 
Published: November 2013

This paper presents test results on temporary-creep properties, recovery of strain post creep and post-creep tensile properties of a Raschel knitted netting material with a combination of UHMWPE and Polyester fibres. Specimens of the material were subjected to uniaxial loading over a period of 30 minutes, at a constant creep target load of 10–90 % of average tensile strength. The specimens were wet and tested in room temperature.
The netting structure experienced significant creep strain, with mean values in the range of 1.3–4.5 %, increasing with increased creep target load. Large proportions of the elongation accumulated during on-loading and creep were long lasting and possibly permanent. Tensile tests showed that for the highest creep target load, strength and elongation at break increased by 17 %.
The UHMWPE-netting experienced larger creep strains than PA6-netting for relatively large creep target loads (60–90 % of the average breaking strength), while creep strains were smaller for low loads. PA6-netting had a larger and faster recovery of strain post creep than the UHMWPE-netting, and the length and force at break were not significantly affected by the creep load history.
Drilling Riser VIV Analysis Using Time Domain Code SimVIV
Authors: Sidarta Djoni E. 
Published: November 2013

Drilling risers are often subjected to VIV from ocean currents, which may vary in directions over depth. VIV of drilling riser has commonly been analyzed using frequency domain code. This paper presents an alternative tool of analyzing VIV of drilling riser using time domain code SimVIV. With this tool it is possible to apply currents in varying directions over depth.
Measured currents and VIV responses of a drilling riser available in the literature are used in this study. The results of time domain analysis using SimVIV are compared against measured responses. The effect of current directionality over depth on drilling riser VIV response is also analyzed.
Physical and Numerical Modelling of Installation and Pull-Out of Dynamically Penetrating Anchors in Clay and Silt
Authors: Hossain Muhammad Shazzad , Kim Youngho , Wang Dong 
Published: November 2013

Dynamically penetrating anchors (DPAs) are a recent type of mooring technology that have been shown to provide a cost-effective alternative to other forms of anchoring system in deep waters. This paper reports the results from a series of model tests undertaken to provide insight into the behavior of DPAs during dynamic installation and monotonic pull-out in normally consolidated clay and calcareous silt. The tests were carried out in a drum centrifuge at 200 g, varying the drop height and hence the terminal velocity. The pull-out angle at the mudline was also varied to encompass various mooring systems.
This paper also reports the results from finite element (FE) analyses simulating dynamic installation of anchors. The 3D large deformation FE (LDFE) analyses were carried out using the Coupled Eulerian-Lagrangian (CEL) approach in the commercial FE package Abaqus/Explicit. A parametric study was undertaken, exploring a range of anchor geometry in terms of diameter, tip angle and number and length of fins; impact velocity and soil strength.
For dynamic installation, two interesting aspects of the soil flow mechanisms were identified: (a) downward soil movement, concentrating around the advancing anchor, being reduced gradually with reducing penetration velocity and more rapidly with increasing number of fins and anchor projected area; (b) mobilisation of end bearing mechanism at the base of the anchor as well as fins, with the latter reduced significantly for shorter fins. The depth of anchor penetration increased as the drop height (and terminal velocity) increases and the soil strength decreases. For static pull-out, the mooring angle at the mudline influenced the pull-out mechanism and the capacity significantly. The anchor rotation and hence the anchor displacement required for attaining maximum capacity reduced as the angle increases.
Strain Based Design: Crossing of Local Features in Arctic Environment
Authors: Bartolini Lorenzo , Bruschi Roberto , Spinazzè Maurizio , Torselletti Enrico , Vitali Luigino 
Published: November 2013

In arctic pipeline projects, seismic risk and differential settlements are common, whether local or distributed across long stretches. For buried pipelines, seismic hazards are generally classified as wave propagation hazard (WP) or permanent ground deformation (PGD) hazard. Below ground crossing of seismic faults has been the real challenge in a series of pipeline projects. STress Based Design (STBD) criteria has been used in the past. Application of this method is straightforward as simple linear elastic analysis is required to calculate the load effects in the specified conditions. In the assessment of the structural integrity of a pipeline, load effects are compared with allowable states of stress. Unfortunately, unsatisfactory design, both from economic and safety points of view, may result. StraiN Based Design (SNBD) is an attractive option in these situations.
The use of SNBD in pipeline technology has been widely discussed during the last decade, particularly for offshore applications. In many instances the offshore pipeline engineer can adopt SNBD to avoid onerous measures necessary to meet the traditional STBD criteria. First introduced to make allowance for crossing bottom roughness and harsh environments, more recently for High Pressure/High Temperature (HP/HT) applications, SNBD is currently used in a series of strategic project developments in North America and East Siberia, for both offshore and land pipelines crossing regions affected by ice gouging and geo-hazards from seismic activity such as land slides, active faults, soil lateral spreading due to soil liquefaction etc. Conditions for which SNBD are applicable, as well as permissible deformations in relation to line pipe material and safe operation of the pipeline in the long run, are of major concern.
In this paper, the following is discussed:
• Relevant hazards for arctic land and offshore pipelines such as ice scouring, permafrost thaw, frost heave etc..
• The design approach and design philosophy for Buried Pipeline Crossing active faults. In particular:
○ The Pipeline Crossing Layout of local features to minimize Load Effects;
○ Material and Steel Wall Thickness Selection vs. Crossing Location;
○ Pipeline Deformation Capacity (PDC) Assessment;
○ Pipeline Strain Demand (PSD) Assessment;
○ Pipeline Trench Design including Shape, Back-filling etc. vs. Pipe-Soil and Temperature Effects.
Validation of the HVS Semisubmersible Global Performance by Model Tests
Authors: Kyoung Johyun , Yang C. K. , O’Sullivan Jim , Miliante Thiago 
Published: November 2013

Validation of the HVS (Heave and VIM Suppressed) semi-submersible’s global performance is carried out through wave basin model tests and correlation with numerical analysis. As an application for a wet-tree floater, Technip designed the HVS semisubmersible to have reduced heave and VIM (Vortex Induced Motion) response. The HVS semisubmersible has blisters attached to the columns. The blister breaks the coherence of the vortex shedding along the length of the column and as a result reduces the VIM response. The redistribution of pontoon volume because of the blister reduces the heave excitation loading. The blister also provides adequate buoyancy for quayside integration.
To validate the improved hull global performance, the wave basin model tests were performed. In the tests, collinear hurricane environments of the Gulf of Mexico were considered for two different headings. Truncated mooring was applied to simulate prototype mooring system. Wind loading was applied by means of a dynamic controlled wind winch. Current was generated by a wire attached to a system of pulleys. The measured hull responses were correlated with MLTSIM, a Technip in-house time-domain nonlinear motion analysis program. Through the correlation with model test results, the improved HVS semisubmersible global motion in hurricane environments is validated.
Maximum Wave Forces: Evaluation and Case Studies
Authors: Barbaro Giuseppe , Foti Giandomenico , Sicilia Carmelo Luca 
Published: November 2013

To define and predict all forces exerted by sea storms on structures is necessary to give support to coastal and offshore engineering.
In this paper the horizontal force on offshore gravity platforms and on breakwaters is analyzed. Two cases study in two different locations are proposed, the first one concerns Italian coasts (Ortona), the second one is in the USA (Alaska). The results will be compared.
The purpose of this paper is to compare recent methods for calculating force on structures with the well-known Morison’s equation and the Goda’s model.
Wave climate was studied using the ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale) and NDBC (National Data Buoy Center) measurements.
Ocean Space Utilization Using Very Large Floating Semi-Submersible
Authors: Srinivasan Nagan , Sundaravadivelu R. 
Published: November 2013

Very Large Floating Structures (VLFS) are highly specialized floating structures with variety of applications in the civil engineering of ocean. Their economic design is based on their hydro-elastic behavior due to wave environmental forces. VLFS are extra large in size and mostly extra long in span in the design feature for their applications. For that reason they are mostly modularized into several smaller structures and joined together in the site. The critical problem is the longitudinal bending moment of the long floating vessel in severe wave environment. With the result of that the present available VLFS designs become not economical for applications in hostile-ocean.
This paper presents ocean space utilization using an innovative VLFS with truss pontoon concept. The concept uses a strong deck with strong longitudinal beams to take care of the needed bending moment of the vessel for the survival, standby and operational conditions of the ocean environment. At the submerged bottom just above the keel-tank top, a simple open-frame truss-structure is used instead of a heavy shell type pontoon. The truss-pontoon provides the necessary flow transparency for the reduction of the wave exciting forces and consequently reduces heave amplitude of motions and the vertical acceleration. Each individual columns of the truss pontoon semi-submersible is tuned to have heave-period over 22 sec, independently, such that minimum hydrodynamic-motions are obtained for the overall structure.
The VLFS is designed with minimum heave for the extreme storms unlike the conventional column stabilized semi-submersible unit with conventional pontoon. The paper proposes a new VLFS concept which is feasible for applications in harsh environment. Most importantly cost effective VLFS is achieved. This paper presents the details of the VLFS design, stability, motion, and experimental verification from the physical wave-tank with the scaled-down model. At the end of the paper, a few comprehensive example applications are illustrated.
Development of a Fatigue Life Assessment Tool for Pipelines With Local Wrinkles
Authors: Bakhtyar F. , Kenny S. 
Published: November 2013

Pipelines may be subject to ground movement events or external interference that imposes axial and moment loading into the pipeline. This system demand may cause localized deformation mechanisms to develop, that may be observed as local wrinkling or buckling of the pipe wall. The local buckle amplitude may increase with continued external loading and may fracture due to low cycle fatigue failure caused by operational conditions.
There exists limited data and engineering guidance on the mechanical performance of energy pipelines with a local wrinkle or buckle. The literature suggests the fatigue service life can be significantly reduced by the presence of local wall deformation mechanisms.
In this study, continuum numerical modelling procedures are developed to assess the influence of pipeline damage in the form of a local wrinkle or buckle on the low-cycle fatigue life. The simulation tool is calibrated from the available literature and a parametric study is conducted to examine the influence of wrinkle bend radius, pipe wall thickness, cyclic displacement amplitude, material grade and constitutive models on the pipe mechanical performance.
An Auxiliary Thruster for Free-Running Model Ship Test
Authors: Tsukada Yoshiaki , Ueno Michio , Miyazaki Hideki , Takimoto Tadanori 
Published: November 2013

The free-running model ship test is an important measure to investigate into ship performance and response in various situations. Its basis is the Froude’s similarity law. Since Reynolds number remains quite different between model ships and full-scale ones, phenomena concerning viscosity cannot be similar.
One of the most specific features related to the viscosity is the friction resistance and thus propeller load that differs to a large extent between model ships and full-scale ones. This difference affects torque and thrust responses in waves and wind, and also rudder effectiveness or manoeuvrability.
The authors have developed a prototype of auxiliary thruster that assists free-running model ships’ propeller. The auxiliary thruster can control its forward force and adjusts the model ship propeller load to arbitrarily time varying target values. The prototype consists of a duct fan, a load cell mounting the duct fan on it, an amplifier for the duct fan, and a PC. The PC controls the auxiliary thrust, or forward force generated by the duct fan, using the model ship speed and the force data measured by the load cell.
This report presents the prototype of auxiliary thruster and its trial test applied to a free-running model ship to study the effect of propeller load on manoeuvrability. The trial test clarified how the auxiliary thrust or the propeller load affects the model ship responses to steering. Theoretical calculations simulating the effect of propeller load corresponding to the trial test confirmed these effects. Applicability of the auxiliary thruster to other free-running model tests is also discussed.