bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Methods for Wave Structure Interaction Modelling in Coastal Environments Under Consideration of Bathymetric Attributes
Authors: Dempwolff León-Carlos , Martin Tobias , Windt Christian , Melling Gregor , Bihs Hans , Goseberg Nils 
Published: October 2022

Abstract
In recent years, increasing ship-sizes and associated increasing wave loads have led to a demand for prediction tools quantifying the ship-induced loads on waterways. Depth-averaged numerical models, using a free surface pressure term, are a prominent method to obtain the relevant design parameters. These models incorporate the wave deformation processes due to attributes of complex bathymetries, while allowing for an efficient simulation of large computational domains. The non-hydrostatic shallow water equations model REEF3D::SFLOW uses a quadratic pressure approximation and high-order discretisation schemes. This paper presents the implementation of a pressure term to account for the displacement of the free surface by solid moving objects. Two test cases verifying the implementation are shown based upon the analytical 1-dimensional solution of the wave propagation due to surface pressure and the estimation of Havelock angles. These verification tests are the first step towards a holistic model, combining a large scale model with CFD simulations near waterway banks.
On Simulating Variability of Sloshing Loads in LNG Tanks
Authors: Remmerswaal Ronald A. , Veldman Arthur E. P. 
Published: October 2022

Abstract
Local pressure measurements during liquid impacts in LNG tanks show a large variability, due to the free-surface roughness and the liquid fragmentation resulting from free-surface instabilities initiated by the gas escaping redfrom the closing gas pocket. It also makes the experimental discrimination of the effect of any multiphase parameter (density ratio, compressibility, phase transition) on impact loads more complex. The main challenges are (i) to capture both experimentally and numerically the development of the free surface instabilities; and (ii) to quantify their effect on the variability of local pressures.
Numerical modeling of the initiation of the free surface instabilities requires an accurate VOF-variant. Surface tension forces are modelled via a Young-Laplace jump condition, where the interface curvature is computed using a local height function. A parabolic interface reconstruction is required to ensure convergence of the curvature in space and time. Advection is performed with a modified EMPFA method. Spurious velocities are avoided by careful treatment of the (almost) discontinuities of the flow field. The model will be demonstrated on various simulations of breaking waves.
System Simulation-Based Feasibility and Performance Study of Alternative Fuel Concepts for Aquaculture Wellboats
Authors: Æsøy Lene , Piehl Henry , Nerheim Ann Rigmor 
Published: October 2022

Abstract
Climate change and population growth are increasing the need for sustainable food production. The ocean covers around 70% of the earth’s surface area and there is a great potential in utilizing this for ocean farming. However, the maritime traffic needs to decrease the emissions per transported mass with 50% by 2030 to meet the Paris Agreement. With an increased ocean space utilization, the vessel fleet will increase due to operational demands. Hence, with increased energy consumption, the need for decarbonization will increase further.
Wellboats are one of the main contributors to the CO2-emission related to traditional fish farming production of Atlantic Salmon, not counting the actual feed production. Within the well-boat the fuel system has the highest potential to reduce the carbon footprint. However, one of the major challenges with the renewable fuels are their low energy density compared to fossil fuels. New, promising energy concepts have emerged, but they lack a quantifiable performance evaluation within the complete aquaculture supply chain. Further, the choice of the vessel’s engine, generator and consumer modules affect each other. For example, changing to a fuel with lower energy density may lead to a larger fuel storage tank which then limits the available space for the fish tank.
The main objective of this study is to use graphical system simulation to model and evaluate the performance of new concepts for low- and zero-carbon fuels. Based on these simulations, new fuel concepts can be compared with conventional marine diesel systems. The simulation model can be used to detect operational limitations with respect to range, transported mass (fish), vessel size, weight, and refueling possibilities. Further, it can also be used to identify bottlenecks in terms of size, weight, and voyage limitations.
Based on the outcome of the wellboat system simulation model, the feasibility of fuel systems can be evaluated and used as recommendation for the design of new wellboats. The industry needs feasible solutions which are sustainable in terms of reliability and cost. The insights gained from using the simulation model aim to assist the industry to reach their emissions reduction goals by 2030, and to provide decision support for retrofitting the fuel and energy system of wellboats.
Conductor Instability – Experience From 10 Years of Monitoring Drilling Operations on Subsea Wells in Harsh Environments
Authors: Molven Håkon , Pöcher Per Kristian , Martinsen Vegard , Holden Harald 
Published: October 2022

Abstract
Subsea production and exploration wells are subjected to loads from the drilling riser and subsea BOP. Over time, BOPs have grown in size and weight resulting in larger wellhead loads. The main task of a subsea conductor is to transfer these loads into the seabed. The bending loads applied on the wellhead will be transferred into the conductor, which again will transfer the loads through the cement and into the soil.
In cases where the load exerted on the soil and cement exceeds the capacity, the soil around the conductor fails. Further can the cement filling the cavity between the conductor and the soil crack and consequently lose its intended function. Support degradation reduces the conductor’s ability to support the well. More load will have to be taken by the conductor and casing structure.
4Subsea has delivered the Subsea Wellhead Integrity Monitoring (SWIM) service for operations on subsea wells for over 10 years. Sensors monitoring the motion and loads near the subsea wellhead have been mounted on more than 300 drilling campaigns. For the last couple of years, more than 70% of the drilling operations with semi-submersible drilling rigs on the Norwegian Continental Shelf (NCS) have been monitored using this SWIM service. As a part of the SWIM service, integrity parameters showing whether the conductor gives the intended amount of support are calculated. Loss of conductor support during drilling operations has been observed in several of these campaigns. An introduction to these integrity parameters will be given together with a discussion on the integrity issues that can be detected using these parameters.
The main purpose of this paper is to summarize the observations of conductor instability over the last 10 years. Examples of monitoring results showing how the instability issues were detected will be presented. Examples of actions taken to react to conductor instability will also be discussed. Finally, statistics on some core metadata such as water depth, region, and well type will be summarized and discussed.
Propeller Wake Measurement and Uncertainty Assessment by a Towing-Tank LDV
Authors: Long Xin , Liu Liwei , Zhang Zhiguo , Ye Bin , Wang Xianzhou 
Published: October 2022

Abstract
A towing-tank underwater Laser-Doppler Velocimeter (LDV) system equipped with an optical fp50 shift probe and a high-precision 3D moving coordinate frame was developed to measure propeller wake. The Nd: YAG-laser head was available in a power range from 50mW up to 500mW, different wavelengths and mounted directly in the probe. The towing carriage speed of initial point and predetermined moved points were repeatedly measured by the 2D probe. The test duration was changed to obtained appropriate sample sizes, which was applied into the later test. Uncertainty analysis of LDV calibration follows ITTC-recommended procedures and guidelines. The uncertainty assessment of test data follows ASME standard procedures to quantify the comparisons and reach conclusions regarding the quality. The uncertainty analysis results of the repeated uniform flow measurements on initial point presented high measurement accuracy of the probe. The uncertainty analysis results and the comparison between the initial point and predetermined moved points verified the high moving accuracy of the coordinate frame in uniform flow measurements. All completed repeated uniform flow measurements were considered as an important contribution to estimate systematic uncertainty of the whole LDV system. The propeller wake field of a modified E1619 was measured in open water test. According to the test condition, an in-house viscous CFD code was used to carried out simulation. The test results agreed well with the CFD results. The uncertainty assessment was carried out following the same standard procedures. This LDV measurement system is reliable enough, and its advantage of non-intrusive measurement can be perfectly presented in propeller wake measurement.
On the Validity of Miner’s Rule and Its Application in Offshore Pile Design Practice
Authors: Stark Anne , Breidenstein Sebastian , Grabe Jürgen 
Published: October 2022

Abstract
Current design practice simplifies complex loading scenarios, i.e. highly cyclic loads from varying direction offshore, using classification methods by combining different cycle packages with constant frequency, mean load level and amplitude. This procedure assumes the resulting accumulated deformation in the soil to be independent of the ordering of the cycle packages, i.e. the validity of miner’s rule. This paper presents an experimental study on the validity of Miner’s rule in non-cohesive soils based on high cyclic direct simple shear tests. The test program comprises monotonic and high cyclic direct simple shear tests in fine silica sand, which is routinely used at Centre of Offshore Foundation Systems. The paper investigates the effect of ordering of the cycle packages on the resulting cyclic deformation accumulation for different loading scenarios with varying mean and cyclic load level. The results are evaluated in terms of the accumulated volumetric and the resulting shear strain. Based on the literature, Miner’s rule is assumed to be valid for a deviation of the relevant variables of &lt; 20 %. Conclusions with respect to the influence of cyclic preloading are drawn and related to current design practices.
Decline in Slope Stability as a Consequence of Gassy Soil in Submarine Slopes on the Balearic Promontory
Authors: Kaminski Pauline , Grabe Jürgen , Sager Thore F. , Urlaub Morelia 
Published: October 2022

Abstract
Submarine landslides can entail a substantial hazard for offshore infrastructure as they are capable of triggering tsunamis and may develop into highly mobile turbidity currents capable of breaking seabed cables. Despite considerable research activity, the trigger mechanisms for such landslide events cannot be clearly defined. Recently, marine gas occurrence has been investigated as a possible trigger mechanism. The behaviour of a fine-grained gassy soil is influenced by a variety of micromechanical processes; amongst destructuring due to fracture formation or gas bubble expansion, and bubble flooding with subsequent cavity collapse. Capturing and modeling these processes in order to assess the destructive potential of enclosed gas bubbles in submarine slopes is to date a considerable scientific challenge. With the help of a large number of Finite Element Limit Analyses (FELA), which are based on laboratory tests on a gravity core from the western Mediterranean Sea, submarine slope stability in the respective region was evaluated. Based on these analyses, gassy soil can be defined as a preconditioning factor but not as a capable trigger mechanism for submarine landsliding.
Integrated Optimization of Hybrid Steam-Solvent Processes in a Post-CHOPS Reservoir With Consideration of Wormhole Networks
Authors: Zhao Min , Yang Daoyong 
Published: October 2022

Abstract
In this paper, an integrated technique has been developed to evaluate and optimize performance of hybrid steam-solvent processes in a post-CHOPS reservoir with consideration of wormhole networks. A reservoir geological model is developed and calibrated by history matching reservoir pressure with the oil, gas, and water production rates as the input constraints, while its wormhole network is characterized with a newly developed pressure-gradient-based (PGB) sand failure criterion. Once calibrated, the reservoir geological model incorporated with the wormhole network is then employed to evaluate and optimize performance of hybrid steam-solvent processes under various conditions, during which the net present value (NPV) is maximized with an integrated optimization algorithm by taking injection time, soaking time, production time, and injected fluid composition as controlling variables. It is found that a huff-n-puff process imposes a positive impact on enhancing oil recovery when wormhole network is fully generated and propagated. Among all solvent-based methods, a pure CO2 huff-n-puff process shows a better performance than flue gas, while the addition of alkane solvents leads to a higher oil recovery compared with that of the CO2 only method. Since the addition of C3H8 and n-C4H10 will significantly decrease heavy oil viscosity and enhance oil swelling, all hybrid steam-solvent injection achieves high oil recovery by taking advantage of both thermal energy and solvent dissolution. It is found that the NPV reaches its maximum of C$5.36 × 107 when the steam temperature is 200°C for the optimized hybrid steam-solvent scenario.
Semisubmersible in Service Experiences on the Norwegian Continental Shelf
Authors: Ersdal Gerhard , Halsne Marita , Oma Narve , Andersen Terje , Langøy Morten , Bjørheim Lars G. 
Published: October 2022

Abstract
Semisubmersible Mobile Offshore Units (MOUs) have been used on the Norwegian Continental Shelf since the mid 1960’s and since the late 1980’s also as production units. During these years a significant amount of experience data has been gathered and systemized.
This paper gives an overview of reported incidents in the period between 2000 and 2020, related to the structure and the maritime systems on semisubmersibles operating on the Norwegian Continental Shelf. Incidents, accidents and damages are reported by operators and rig owners to the PSA. These are summarised in this paper and includes cracks, dents from wave actions, anchor impact on structures, horizontal and vertical wave impacts and ship collisions. In addition, failure of the dynamic position keeping system, mooring system breakage and incidents related to stability and ballasting have been reported.
The paper provides numerical values of the occurrence of many of these incidents, where possible, in addition to an overview of the number of semisubmersibles active on the Norwegian Continental Shelf. In addition, a listing of accidents and incidents are provided and to some extent a summary of the incidents are provided for a possible further evaluation of common causes, importance and the possible consequences of these accidents, incidents and damages.
One fatality due to horizontal wave impact have been experienced in the period evaluated and a continued focus on air gap and wave in deck loading is important. However, these issues have later been better standardized by the class societies and the focus from PSA now is to ensure that the operators and rig owners are operating according to these standards. The main challenge for semisubmersibles continues to be operational issues related to stability and ballasting incidents, both because of the observed frequency and the potential consequence of such incidents.
Storm Models for the Calculation of Extreme Wind Speed
Authors: Laface Valentina , Arena Felice , Romolo Alessandra 
Published: October 2022

Abstract
This paper proposes a new approach for the calculation of extreme wind speed. Specifically, the storm approach widely employed for long-term statistics of ocean storms is reviewed and adapted for the analysis of windstorms. This approach is based on the substitution of the sequence of real event at a given site with a sequence of simplified events characterized by a kind of equivalence with the actual ones. Basing on that, analytical solution for the calculation of the return period of a storm event whose peak exceeds a given threshold is developed. The windstorm model characterizes the simplified windstorm event by means of two parameters which are the maximum average wind speed over the windstorm and a duration parameter determined by imposing that the maximum expected gust in the simplified event is the same of that in the actual one. First, an attempt is made to assimilate the peak gust to a “maximum expected gust” and to relate this quantity to the windstorm duration. Then, in order to validate the new model, a data analysis is carried out to estimate average wind speed return values with the proposed approach and results are compared with those provided by well-established peak over threshold method.
Optimization of Oil Recovery and CO2 Sequestration in Tight Reservoirs During CO2 WAG Flooding With Hydraulic Fracture
Authors: Li Bao Zhen , Zhang Jian , Kang Xiaodong , Wang Liqi , Tang Engao , Zhou Wensheng 
Published: October 2022

Abstract
Tight oil reserves are of great significance in oil exploration and development in China. CO2 flooding is promising in tight reservoirs due to its high mobility and better injectivity, and water alternative gas (WAG) flooding could improve sweep efficiency and oil recovery, which is extensively used. However, its injectivity in tight reservoirs is limited. The feasibility of improving CO2-water alternations performance in tight reservoirs by hydraulic fracturing was investigated in this study.
In this paper, numerical reservoir simulation was conducted to simulate CO2 WAG flood process with typical reservoir characteristics and hydraulic fracture properties of the YC formation. The optimization of hydraulic fracturing during CO2 alternative water injection process were performed with numerical simulation, response surface and multiple response optimization method, which could be done with acceptable accuracy by performing a limited number of runs, hence, reducing the engineering time, effort and money. With the simplified equation between the NPV or CO2 storage and different hydraulic fracture parameters, operators can determine the best combination of all the factors for different objectives. The results show that moderate fracture length, large fracture height and small water-gas ratio could achieve the optimal economic benefits and CO2 storage in low permeability reservoirs.
This work can provide a better understanding of the physical mechanisms and key parameters affecting the effectiveness of CO2 WAG flooding for enhanced oil recovery in the tight formation.
Hydrodynamic Interactions of Multiple Surface-Piercing Struts by Smoothed Particles Hydrodynamics
Authors: Vernengo Giuliano , Demirel Yigit Kemal , De Marco Muscat-Fenech Claire , Gaggero Stefano , Villa Diego 
Published: October 2022

Abstract
The hydrodynamics of surface piercing struts and pile-like structures in general presents some very complex fluid dynamics phenomena that are worth investigating. Among them there are the forward wave pile-up at stagnation, the wave breaking with flow reversal like that observed in Bidone-type hydraulic jumps, flow separation caused by interactions of steep free-surface waves and the turbulent wall boundary layer. Such a type of flow structures plays a key role in several engineering applications, ranging from naval architecture to civil and ocean engineering.
The hydrodynamic analysis of different surface-piercing struts in tandem configuration has been done in the framework of a Smoothed Particle Hydrodynamic approach available through the open-source software DualSPHysics, developed to exploit the GP-GPU architecture to speed up the computation. A numerical wave tank has been set-up to carry out calm water tests. Beyond the influence of the forward speed, the analysis has focused on the effect of three main geometric parameters establishing the configuration: the longitudinal and the lateral distance among the vertical, surface-piercing, struts and the relative size among them.
The mean and the rms values of the unsteady near-field free surface elevation have been analyzed and compared among the selected cases and interaction effects are studied in comparison to the free surface obtained for the equivalent single strut configuration.
Increase of Wave Drift Forces in Severe Seastates Due to Wave Frequency Viscous Damping
Authors: Fonseca Nuno , Ommani Babak 
Published: October 2022

Abstract
Calculation of wave drift forces in the context of mooring analysis is usually performed by potential flow boundary element methods. For monohulls with large waterplane area, such as floating, production, storage and offloading vessels (FPSOs), the assumption is that heave and pitch damping is dominated by inviscid radiation of waves. The present study investigates the effects of heave and pitch wave frequency viscous damping on the horizontal wave drift forces of a FPSO. Experimental evidence indicates the presence of non-negligible viscous damping in case of moderate and severe seastates. Such observation is confirmed by computational fluid dynamic (CFD) simulations of forced harmonic motions with different periods and amplitudes. On a second step, a numerical analysis shows that the surge wave drift forces increase significantly at the low frequency range when realistic heave and pitch viscous damping is considered. The frequency range where standard potential flow calculations appear to underestimate wave drift forces coincides with the range where design seastates have most of the energy. Finally, the wave drift coefficients calculated with realistic additional viscous damping are compared with empirical coefficients identified from model test data. The identification procedure follows a second order signal analysis technique known as cross bi spectral analysis.
Wave Energy Converter Optimal Design Under Parameter Uncertainty
Authors: Giorcelli Filippo , Sirigu Sergej Antonello , Pasta Edoardo , Gioia Daniele Giovanni , Bonfanti Mauro , Mattiazzo Giuliana 
Published: October 2022

Abstract
In the field of renewable technologies, the possibility to obtain energy exploiting seas and oceans’ wave motion has been known for a long time. Devices that transform wave energy into electric energy exploiting wave motion are called Wave Energy Converters (WEC). Following the design studies carried out in recent years, the research now proceeds towards the development of useful processes for the optimization of these devices. In this work we develop a preliminary robust optimal design process for the WEC system devices, in order to increase their reliability and robustness. Robust optimal design is a probabilistic optimization method for realistic optimization problems, in which, the uncertainty that occurs between real-world implementations and their ideal project value is taken into account. This method studies these parameters and finds suitable solutions to avoid unsatisfactory system performances and designs which can compromise their performances. Therefore, the process final purpose is to obtain a robust optimum instead of a global optimum. In this work, we developed the robust design optimization strategy for the design of a pitching wave energy converter, able to minimize its Levelized Cost of Energy (LCoE). This is done exploiting information given by two selected robustness indexes.