bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study of Displacement Flows in a Vertical Eccentric Annulus
Authors: Zhang Ruizi , Jung Heeseok , Renteria Alondra , Frigaard Ian 
Published: October 2022

Abstract
Primary cementing is an essential part in constructing an oil or gas well. Leakage occurs due to a poor seal of the cement in the annulus, which may be caused either during or after placement. Key in controlling leakage is to ensure the integrity of the surface casing, which is primarily vertical. This paper addresses the underlying fluid mechanics that may affect cement placement in vertical casings. We present results of miscible Newtonian displacement flow experiments carried out in a dimensionally scaled laboratory set-up. The experimental set-up has been described in detail (Renteria and Frigaard, J. Fluid Mech, 905, 2020) [1], and used previously in horizontal orientation. We use the same annular flow loop but in vertical configuration. The effects of density difference, viscosity ratio and eccentricity of the annulus have been studied. We find that the eccentricity is always dominant in affecting the displacement, and the narrow side view gives us more detail of residual layers. The buoyancy number and Reynolds number are key factors that affect the stability of the whole process. Large buoyancy number and small Reynolds number lead to stable interface and less dispersion. The residual layer at the narrow side can be removed out to a degree, under significant density difference and at lower flow rates. However, the viscosity ratio appears to play only a secondary role in vertical displacement flows. Our future directions will use the present experiments for comparison with 2D and 3D models, and we then aim to extend the experimental program to shear-thinning non-Newtonian fluids.
Order Reduction of a Transient Model of Viscous Pressure Loss Gradient in Laminar Flow for Non-Newtonian Fluid Flowing in Circular Pipes
Authors: Cayeux Eric 
Published: October 2022

Abstract
When circulating non-Newtonian fluids in pipes, the flowrate may vary because of inherent fluctuations of the mudpumps, swab and surge due to axial displacement of the drill-string, variations caused by a positive displacement motor (PDM) while drilling. Steady state estimations of viscous pressure loss gradients are not anymore valid under accelerated flowrate conditions. It is possible to precisely calculate the dynamic response in transient conditions, but such numerical calculations tend to be slow and incompatible with real-time constraints when used during a drilling operation. It is therefore desirable to derive a reduced order model that is fast, yet accurate.
Numerical schemes utilized to estimate viscous pressure gradients under fluctuating flowrate conditions need to solve a larger problem than just the evolution of the pressure drop. Indeed, they need to calculate the whole fluid velocity field in a cross-section. However, when only the pressure gradient is of interest, a reduced order model would be sufficient. To find a possible reduced order dynamic model that mimics the dynamic response of the advanced numerical model, the method of sparse identification of non-linear dynamic (SINDy) is used on synthetic datasets generated using the advanced model. The SINDy method allows to discover the non-linear ordinary differential equation (ODE) that models precisely the dynamic that is observable from the synthetic dataset. Nevertheless, the calibrated parameters of the discovered non-linear ODE are only valid for specific a fluid density and rheological behavior. Therefore, the method is applied multiple times on various combinations of fluid densities and fluid rheological behavior parameters, and an interpolator function is generated. The interpolator is built using radial basis functions. The interpolator can then be used to find the correct parameters of the non-linear ODE as a function of the current rheological behavior of the fluid that flows in a pipe section and the dynamic pressure gradients can be estimated as a function of the fluctuating flowrate by solving a simple ODE, for example by using the Runge-Kutta method.
The reduced order model is very efficient, yet accurate, and can therefore be used in a real-time context. This is possible because many high-quality simulations are made upfront and used by machine learning methods (SINDy and radial basis functions) to discover a non-linear ODE and its associated parameter interpolator. The application of these two machine learning methods results in a solution that has good generalization capabilities. The reason for providing good estimation of the dynamic response outside the domain of the training examples is due to the ability of the SINDy method to extract ODEs that represent a good approximation of the real physical behavior of the system.
Modified Environmental Contours Approach for Long-Term Extreme Response Prediction of Marine Risers
Authors: Miao Qingqing , Low Ying Min 
Published: October 2022

Abstract
Accurate prediction of the long-term extreme response of offshore structures is challenging for complex systems under varying marine environments. The long-term uncertainties come from the varying environmental parameters such as significant wave height and spectral peak period, while the short-term uncertainties are due to the random wave amplitudes and phases. The conventional environmental contour lines method provides a fast approximate way to estimate the extreme response by performing simulations along the environmental contours. However, the method is unconservative if the short-term uncertainties are neglected. Current methods to account for the short-term uncertainties are approximate and require an empirical parameter that is case-dependent. This paper presents a modified environmental contour line approach, based on introducing an additional multiplicative random variable to account for the short-term variability. It is efficient as additional simulations are performed only in the critical direction determined by the conventional approach. The method is first tested on a single-degree-of-freedom model representing the surge motion of a floating offshore structure. Subsequently, it is applied on the top riser stress of a catenary moored floating production system. Monte Carlo simulation is impractical here as a validation tool due to the extensive simulation time. Hence, the results are compared with subset simulation, which is known to be asymptotically unbiased.
Importance of the Inertial Components in Modal State Covariances
Authors: Geuzaine Margaux , Fenerci Aksel , Øiseth Ole , Denoël Vincent 
Published: October 2022

Abstract
The modal state responses of very large floating structures subjected to sea waves are addressed in this paper. Semi-analytical approximations for their second order statistics are first provided. They are derived by using the multiple timescale spectral analysis and they aim at calculating the variances of the nodal state responses much more rapidly than with the traditional time and frequency domain methods. Based on these approximate formulas, such expressions are developed for the correlation coefficients in this paper. They allow to understand in which cases the covariances between two modal state responses are significant and cannot legitimately be neglected. They are for instance important to consider when the natural frequencies of the corresponding modes are close to one another or when their shapes are similar. The accuracy of the proposed expressions is then verified on a realistic example inspired by an actual floating pontoon bridge. The results are shown to be less precise, although still acceptable, when the peak frequency of the loading and the natural frequencies of the structure are of the same order of magnitude. This is to be expected since the validity of the proposed approximations is conditioned upon the separation of these timescales.
A Reliable Multilevel Method for Simulation-Based Load Determination on Deck Cell Guides
Authors: Detlefsen Ole , Reiner Carl , Abdel-Maksoud Moustafa 
Published: October 2022

Abstract
The loss of containers at sea endangers ships and crew and causes environmental pollution. Within the Joint Research Project RetroLadung, weight-optimized container cell guides with integrated motion sensors and AI-based decision support (DSS) are developed as a technical solution for increased safety in marine transportation. Therefore, the authors developed an efficient simulation-based approach to determine the motion-induced loads acting on the containers. For the validation of the applied numerical methods, model tests have been performed in the towing tank operated by the Institute for Fluid Dynamics and Ship Theory (FDS). The paper describes the applied numerical methods for the load determination and first preliminary results from the ongoing experimental validation work. Finally, the application of the developed method is demonstrated by calculating the loads for the structural design and optimization of the cell guides for a towed container barge operated at the US east coast.
Experimental Investigation of Methane Absorption for Offshore Gas Influx Management
Authors: Mahmud Shahriar , Chen Yuanhang 
Published: October 2022

Abstract
During oil and gas drilling operations, formation gas (mostly methane) may enter the wellbore annulus or the drilling riser. This gas influx may get absorbed into the surrounding mud causing complexity for kick detection. Absorption mass transfer experiments of methane into four different fluid systems were performed. The continuous phase for all these fluids was Internal olefins (IO) which is widely used within the drilling industry as a base fluid. Two of the fluids were emulsions (Water as the second phase) and the other fluid comprised of Internal Olefins with Suspentone. Ultrahigh purity methane was used as the absorbing gas phase. The system pressure was kept at 100psi (0.689MPa) with a superficial velocity of 0.009 m/s. Volumetric mass transfer coefficients (kLa) from these experiments were individually determined using a bubble column with an internal diameter of 0.0381m. The volume of the liquid was kept constant during each of the tests. It was observed that methane in pure IO has the highest kLa value while its value is the lowest when it was flown through the IO/Water/suspentone fluid system. The reduction of kLa values was attributed to the increase of viscosity of the fluid and reduction of interfacial area of the IO due to the addition of water.
On the Influence of Hull-Shape on the Location of Roll-Axis
Authors: Johnsen Lars , Krüger Stefan 
Published: October 2022

Abstract
The location of the average roll axis of a ship in water is around the combined center of mass of the ship itself and the so-called added mass of the fluid surrounding it. The location of this combined center is often assumed to be somewhere in the middle between the waterline and the center of mass of the ship, as e.g. in the interim guidelines of the second generation intact stability criteria. These assumptions are approximately valid for deeply submerged ships with low B/T ratios and small bilge radius, but not necessarily for the hull forms of fast, modern roro- or ropax-ferries or other ship types with equal properties. For these ships, the center of added mass and thus the average roll-axis can be located way above the waterline, leading to different accelerations and loads on cargo and personnel on the ship. The paper shows systematically how section wise added mass behaves for certain trends in frame shape and compares numerical results based on strip theory for the location of the roll axis of two different ships with full-scale measurements.
Dynamic Reservoir Behaviour and Production Due to Periodic Supply of Wind Power
Authors: Bergmo Per E. S. , Holt Torleif , Skogestad Jan Ole 
Published: October 2022

Abstract
Wind power can replace power from gas turbines and thus reduce the CO2 emissions related to oil production. However, a main challenge with wind power is the variability in power production due to weather variations. The water injection pumps are often major power consuming units. The water pumps were therefore identified as possible non-critical loads in an isolated power system with variable power supply. The power to a non-critical load can be varied and even stopped depending on the power supply. The objective of the present work was to study how variable water injection rates affects oil production.
Using simulated wind power curves, water injection profiles for a model oil field were constructed. Reservoir simulations show that the oil production is almost insensitive to variable injection rates if the injected volumes were the same. Lower injected rates and volumes resulted in lower oil production. This was most pronounced in the plateau phase of the production, but later the differences become gradually smaller. Thus, reducing the water injection volumes with 30 % decreased the total oil recovery by less than 5 % after 28 years.
If constant water injection rates are needed thermal power can supply wind power. This will increase the CO2 emissions. However, if wind power not used by the water injection pumps can be utilised for other unit operations significant reductions in CO2 emission can still be obtained.
Investigation of Eccentricity on Cuttings Transport With Oil-Based Drilling Fluids
Authors: Ytrehus Jan David , Lund Bjørnar , Taghipour Ali , Pedrosa Camilo , Saasen Arild 
Published: October 2022

Abstract
Deviated well sections are common in modern well construction. In mature areas like the North Sea region, practically all producers or injector wells will have highly deviated sections. These wells must be drilled and completed in an optimal manner with respect to drill time, cost, risk and functionality. Most cuttings transport and hydraulic models are developed based on tests with model fluids and often in small diameter test sections. Hole cleaning and hydraulics with field fluids are different than the properties considered with most model fluids. Furthermore, results from small diameter tests with model fluids may not always be relevant for, nor scalable to, field applications due to time, length, and other scales. Hence, there is a need for studies in controlled laboratory environments with various field application designed drilling fluids to improve engineering models and practices.
This paper presents results from laboratory studies with geometries that permits comparison with field operations when oil-based drilling fluids from Norwegian offshore operations are applied. The oil-based drilling fluids have densities and viscosities within the relevant shear rate range applied during drilling operations and in the tests.
The experiments have been performed in a flow loop that consists of a 10 meters long test section with 2″ OD freely rotating steel drill string inside a 4″ ID wellbore made of cement. Sand particles were injected while circulating the drilling fluids through the test section. Experiments were performed at different wellbore inclinations. The applied flow loop dimensions are designed so that the results are scalable to field applications; especially for the 12,25″ and 8,5″ sections. The selected setup is designed to provide correct shear rate ranges and equal Reynolds number to the field application when the same fluids are applied.
Results show that hole cleaning is significantly better in fully eccentric annulus compared to 50% degree of eccentricity. It is also observed in horizontal sections that for the same eccentricity a reduction in fluid viscosity can provide improved cuttings transport efficiency when the drill string is not rotated.
Experimental Study on Local Scour of Triangular Artificial Reef
Authors: Zhao Fenfang , Xu Shiji , Yang Mingda , Tang Yanli , Huang Liuyi , Fang Guangjie 
Published: October 2022

Abstract
Artificial reef (AR) is one of the key methods to restore the offshore fishery resources and ecological environment. To secure its ecological effects, it is of great significance to study the possible instability of the AR, like sinking and reversing caused by change of the submarine topography, water flow and sediment movement. In the present study, the model experiments of the triangular ARs on the mechanism of the local scour are carried out. The prototype of the triangular ARs is used in Xiaoshidao National Marine Ranching in Weihai, Shandong Province. The effects of the heights, the bottom angles and the length of the bottom of the triangular ARs on the scour volume and the equilibrium scour depth are investigated. The results show that for the ARs with the same heights, the scour depth increases with the increasing bottom angles. For the ARs with the same bottom angles, the scour depth increases with the increasing heights. A generalized linear model is used to derive the effect of the bottom angle of the triangular AR on the scour depth. The research results can provide references for the design optimization and deployment of the ARs. This proposed study will provide theoretical support and practical guidance for the optimized engineering design and construction of the ARs.
Nonlinear Reconstruction and Prediction of Regular Waves
Authors: Desmars Nicolas , Hartmann Moritz , Behrendt Jasper , Klein Marco , Hoffmann Norbert 
Published: October 2022

Abstract
A method for the reconstruction of nonlinear ocean surfaces is presented and applied to regular waves. From random samples of surface elevation, the method reconstructs the nonlinear features of the observed waves by means of the High-Order Spectral approach. The reconstructed surface is then propagated to provide a prediction at a later time. The agreement of the reconstructed and predicted surfaces with the reference one is quantified for a wide range of wave steepness. In each case, the accuracy of the surface elevation and surface velocity potential is evaluated for the first-, second- and third-orders of nonlinearity, while the reference surface corresponds to a fourth-order solution. This way, the improvement of the solution pertaining to each order of nonlinearity can be easily identified. The results show that the grid-based method is able to correctly reconstruct highly nonlinear regular waves, providing an accurate initial solution for the surface propagation. Due to the effect of the nonlinear dispersion, it is further shown that the third order of nonlinearity is necessary to obtain an accurate reconstruction/prediction of steep waves.
Hydrodynamic Performance of 3-D Hydrofoil Under the Free Surface Based on Taylor Expansion Boundary Element Method
Authors: Huang Jianghao , Yao Chaobang , Feng Dakui , Sun Xiaoshuai 
Published: October 2022

Abstract
The boundary element method is widely used in solving potential flow problems. This paper uses Taylor expansion boundary element method (TEBEM) to analyze hydrodynamic characteristics of hydrofoils under the free surface, which mainly applies the Taylor expansion to the dipole strength of the boundary integral equation (BIE), and then keeps the first-order derivatives, finally takes the two tangential derivatives with respect to the field points on the boundary to form the closed equations. Combine the equations then solve the potential and its tangential derivatives. The method is applied to three dimensional hydrofoil of the asymmetric NACA4412 profile moving beneath the free surface with constant speed. The free surface condition is linearized in terms of the Double-Body method. Upstream waves are prevented by the use of a one-sided, upstream, finite difference operator for the free surface condition. After solving the doublets on the foil and sources on the free surface, the numerical results of pressure, lift and resistance coefficients and also wave profiles can then be evaluated for different Froude numbers and depths of submergence to demonstrate the influence of free surface and aspect ratio effects on performance of the hydrofoil. Compared to traditional constant panel method (CPM) method, the TEBEM method can extremely improve the accuracy of the tangential derivatives on the non-smooth body surface.
Axial Stiffness and Expansion Behaviour of a Flexible Flowline for Various Extents of Axial Restraint When Subject to Pressure and Thermal Loads
Authors: Tørnes Knut , Nestor Ruairi , Thuen Kristian , Picksley John , Connaire Adrian , Bakken Bård Owe 
Published: October 2022

Abstract
The conditions to which flexible pipes are being exposed are becoming increasingly severe. In particular, flexible flowlines that are fully or partially restrained by back fill or rock cover can become exposed to large axial compression forces under pressure and temperature loading.
A high True axial compression force may lead to a radial outward displacement of the tensile armour which could eventually exceed the allowable limits of API spec 17J if the axial force exceeds a critical level.
Furthermore, when the net Effective axial compressive pipe force exceeds a critical level, the pipe may undergo global buckling either upwards (upheaval buckling) or laterally, which needs to be addressed in detail at design stage, typically by using global finite element (FE) simulations in which equivalent mechanical properties are applied to pipe beam elements to capture the overall behaviour of the flexible pipe.
The overall global mechanical properties of a flexible pipe, such as axial stiffness and thermal and pressure expansion coefficients, which are important parameters in capturing the global buckling behaviour, are dependent on the local behaviour of the various flexible pipe layers.
In this paper an advanced local FE model developed using the industry standard numerical FE tool, Abaqus, together with the assessment methodology is presented in order to study local layer interactions and their influence on the equivalent axial mechanical properties.
A Numerical Investigation on Wave Spectrum Identification and Transformation From Deep to Shallow Waters for the Coastal and Offshore Installations
Authors: Wang Weizhi , Kamath Arun , Pákozdi Csaba , Bihs Hans 
Published: October 2022

Abstract
Nowadays, many aquaculture and marine renewable energy facilities are developed at the shallow and intermediate water areas close to the bathymetric transition to the deep seas. The transition from deep to shallow water has a strong influence on the wave spectrum shape. Consequently, it is challenging to choose the appropriate spectrum for the sites of interest. In this study, a fully nonlinear potential flow (FNPF) model is used to investigate the wave spectrum transformations from deep to shallow water conditions. A series of JONSWAP spectra with different parameters is used as inputs. For each input spectrum, simulations are performed for wave propagations at constant shallow water conditions as well as for wave transformations from deep to shallow water conditions. The resulting spectra at the shallow water regions are compared to each other as well as the transformation (TMA) spectra. The differences are related to wave shoaling, reflection and breaking. The findings are confirmed in a computational fluid dynamics (CFD) domain. The study reveals the correlation between wave transformations and spectrum transformations at bathymetric variations. It is also found that a simulation of the complete wave transformation process produces a more accurate representation of the irregular wave field after the bathymetric transition than directly applying a specific spectrum at the shallow water region.