The application of mathematical analysis has been an essential tool applied on Catenary Anchor Leg Mooring (CALM) buoys, Wave Energy Converters (WEC), point absorber buoys, and various single point ...mooring (SPM) systems. This enables having mathematical models for bonded marine hoses on SPM systems with application with CALM buoys, which are obviously a requisite for the techno-economic design and operation of these floating structures. Hose models (HM) and mooring models (MM) are utilized on a variety of applications such as SPARs, Semisubmersibles, WECs and CALM buoys. CALM buoys are an application of SPM systems. The goal of this review is to address the subject of marine hoses from mathematical modeling and operational views. To correctly reproduce the behavior of bonded marine hoses, including nonlinear dynamics, and to study their performance, accurate mathematical models are required. The paper gives an overview of the statics and dynamics of offshore/marine hoses. The reviews on marine hose behavior are conducted based on theoretical, numerical, and experimental investigations. The review also covers challenges encountered in hose installation, connection, and hang-off operations. State-of-the-art, developments and recent innovations in mooring applications for SURP (subsea umbilicals, risers, and pipelines) are presented. Finally, this study details the relevant materials that are utilized in hoses and mooring implementations. Some conclusions and recommendations are presented based on this review.
Helical springs have been widely used in various engineering applications for centuries. For many years, there is no significant development in the design methods of helical springs. Recently, a ...renewed interest is raised from the industry in exploring new designs for the helical springs with novel configurations due to the requirements of customised properties, such as specific spring stiffness and natural frequency for better performance of valve train systems. In this paper, an innovative method which combines the techniques of Finite Element Analysis (FEA), constrained Latin Hypercube sampling (cLHS) and Genetic Programming (GP) is developed to design and analyse helical springs with arbitrary shapes. cLHS method is applied to generate 300 sets of spring samples within a constrained design domain, and FE analysis is conducted on these spring samples. Two meta-models are developed from the 300 sets of FE results by using GP. They successfully describe the relationships between the design parameters and the overall mechanical performances including compression force and fundamental natural frequency of helical springs. The results show that the developed models have robust abilities on designing helical springs with arbitrary shapes, which significantly expands the design domain of the engineering design methods and potential for precise optimization of helical springs.
Short glass fiber reinforced composites (SGFRC) are frequently used to manufacture parts with complex surfaces by injection or compression molding. It was found that the length of fibers is often ...reduced during the manufacturing processes. To understand the causes of the change in fiber length, ex-situ 3D CT images are taken from tensile experiments to extract the information of the microstructure of the SGFRC, including fiber length, orientation and breakage. In the calculation of the critical length, the Kelly model is modified to include the effect of the stresses at fiber ends and the mechanical effect of internal pore defects on the composites. It is found that the microscopic interaction of short fibers breaks longer fibers, until they are shorter than the critical length. Through comparisons, it is found that the modified Kelly model is more accurate in predicting critical length of short fibers. In this study, micro-failure modes, such as fiber pulling out, interface debonding, matrix damage and pore destruction, are all characterized by micro-CT and scanning electronic microscope to analyze the complex failure mechanisms. The micro failure modes are mainly attributed to the micro geometric features and mass fraction of short fibers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Silica-enriched mineral groundwater is exposed in non-volcanic area.•The permeability decrease from top to bottom in granite fracture network.•The velocity estimated by water chemistry is consistent ...to the average permeability.•Granite fracture network dominantly contributes silica-enriched mineral groundwater.•Granite fracture network may cause geothermometer underestimation.
Silica-enriched mineral groundwater has important commercial and health value and is most common in volcanic areas and high-temperature geothermal areas. But we found abundant silica-enriched mineral groundwater (dissolved SiO2 up to 51.57 mg/L) exposed from the granite fracture network in Suining, South China, where is no volcanoes and high-temperature hydrothermal system. Pumping test and hydrogeochemistry were employed to investigate the formation mechanism of silica-enriched mineral groundwater in granite fracture network. It is HCO3-Ca type and high content of dissolved silica, formed warm groundwater on the F86-1 fault and recharged by meteoric water with a close distance of 3.90 km. Pumping test results indicate that the hydraulic conductivity decreases from top to bottom in the granite fracture network (in order of 2.27 × 10−1 m/d, 5.42 × 10−2 m/d, 7.04 × 10−4 m/d), and they are much smaller than that of the F86-1 fault zone (0.751 m/d). The flow framework constructed by water chemistry suggest the groundwater has experienced the maximum temperature of 68–75 °C and reached the maximum depth of 1.93 km. And the average seepage velocity is about 2.8 × 10−3 m/d and 1.5 × 10−3 m/d in the horizontal and vertical directions, respectively. Water-rock interaction confirms that the granite fracture network provides long-term and sufficient water-rock interaction and dominantly contributes the formation of silica-enriched mineral groundwater because of the weatherability of granite. But the temperature of SiO2-geothermometer will be slightly underestimated for the deep warm groundwater continuously mixing with the shallow groundwater in the granite fracture network.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A three-dimensional finite element model is developed, validated and used in the parametric study to investigate the influence of shear stud’s position and profiled sheeting thickness on the ...strength, ductility and failure modes of the headed shear stud welded to the modern profiled sheeting. A total of 240 push tests were analysed with different sheeting thicknesses, positions of the shear stud in the trough, concrete strengths and transverse spacings. The results showed that the sheeting thickness influenced the shear connector resistance of studs placed in the unfavourable position more than studs placed in favourable and central positions. The strength of the shear connector placed in the unfavourable position increased by as much as 30% when the sheeting thickness was increased. The shear connector resistance of the unfavourable stud was found to be primarily a function of the strength and the thickness of the profiled sheeting rather than the concrete strength. The strength prediction equations for unfavourable and central studs were also proposed. The results suggested that the strength of the shear connector increased as the distance of the shear stud increased from the mid-height of the deck rib in the load bearing direction of the stud. The load–slip behaviour of the studs in the unfavourable position was more ductile than the studs in the favourable position, with slip of 2–4 times higher. It was found that the increase in sheeting thickness and transverse spacing improved the ductility of the stud in unfavourable position, but had no effect on the stud in the favourable position. The failure modes suggested that the favourable and central studs failed by concrete cone failure and unfavourable studs failed by rib punching together with crushing of the narrow strip of the concrete in front of the stud.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Roughly 75% of normal myocardial tissue volume is comprised of myocytes, however, fibroblasts by number are the most predominant cells in cardiac tissue. Previous studies have shown distinctive ...differences in cellular electrophysiology and excitability between myocytes and fibroblasts. However, it is still unclear how the electrical coupling between the two and the increased population of fibroblasts affects the electromechanical dynamics of cardiac tissue. This paper focuses on investigating effects of fibroblast-myocyte electrical coupling (FMEC) and fibroblast population on atrial electrical conduction and mechanical contractility by using a two-dimensional Discrete Element Method (DEM) model of cardiac tissue that is different to finite element method (FEM). In the model, the electro-mechanics of atrial cells are modelled by a biophysically detailed model for atrial electrical action potentials and myofilament kinetics, and the atrial fibroblasts are modelled by an active model that considers four active membrane ionic channel currents. Our simulation results show that the FMEC impairs myocytes’ electrical action potential and mechanical contractibility, manifested by reduced upstroke velocity, amplitude and duration of action potentials, as well as cell length shortening. At the tissue level, the FMEC slows down the conduction of excitation waves, and reduces strain of the tissue produced during a contraction course. These findings provide new insights into understandings of how FMEC impairs cardiac electrical and mechanical dynamics of the heart.
Recent design challenges in ocean observations, energy storage, offloading/discharging, and loading operations in both the offshore-renewable industry have led to advances in the application of ...catenary anchor leg moorings (CALM) buoys. Due to different seabed profiles, soil stiffness and environmental conditions, there is the need for numerical assessment to investigate the behaviour of the submarine hoses, based on the structural and hydrodynamic behaviour. In this study, experimental and numerical investigations are carried out on the dynamic behaviour of the submarine hoses attached to a CALM buoy in Lazy-S configuration. Six mooring lines are attached to the CALM buoy with a water depth of 100 m in the numerical model. A hydrodynamic model utilising ANSYS AQWA was developed then coupled unto the dynamic model in Orcina’s Orcaflex. The studies were carried out to study the effect of flow angles, wave height, soil stiffness and hydrodynamic loads on the structural behaviour of the submarine hoses. Waves at different angles to the submarine hose affected the effective tension more where the hose bends due to the floats attached. Parametric studies were carried out on both linear and nonlinear seabed models, and recommendations were made from the investigations on the submarine hose models.
The application of marine bonded hoses has increased in recent times, due to the need for more flexible conduits and flexible applications in the offshore industry. These marine structures include ...Catenary Anchor Leg Moorings (CALM) buoys and ocean monitoring buoys. Their attachments include floating hoses, submarine hoses and submarine cables. However, the structural performance challenges of a CALM buoy system from its hydrodynamics water waves and other global loadings, have led to the need for this investigation. In this study, a detailed presentation on the motion characterisation of the CALM buoy hose system is presented. The CALM buoy is a structure with six degrees of freedom (6DoF). A well-detailed experimental presentation on the CALM buoy hose model conducted in Lancaster University Wave Tank is presented using three novel techniques, which are: a digital image captured using Imetrum systems, using an Akaso 4K underwater camera, using wave gauges arranged in a unique pattern and using underwater Bluetooth sensors. The buoy model was also found to respond uniquely for each motion investigated under water waves. The results showed that the higher the profile, the higher the response of the buoy. Thus, this study confirms the existence of flow patterns of the CALM buoy while floating on the water body.
Floating offshore structures (FOS) must be designed to be stable, to float, and to be able to support other structures for which they were designed. These FOS are needed for different transfer ...operations in oil terminals. However, water waves affect the motion response of floating buoys. Under normal sea states, the free-floating buoy presents stable periodic responses. However, when moored, they are kept in position. Mooring configurations used to moor buoys in single point mooring (SPM) terminals could require systems such as Catenary Anchor Leg Moorings (CALM) and Single Anchor Leg Moorings (SALM). The CALM buoys are one of the most commonly-utilised type of offshore loading terminal. Due to the wider application of CALM buoy systems, it is necessary to investigate the fluid structure interaction (FSI) and vortex effect on the buoy. In this study, a numerical investigation is presented on a CALM buoy model conducted using Computational Fluid Dynamics (CFD) in ANSYS Fluent version R2 2020. Some hydrodynamic definitions and governing equations were presented to introduce the model. The results presented visualize and evaluate specific motion characteristics of the CALM buoy with emphasis on the vortex effect. The results of the CFD study present a better understanding of the hydrodynamic parameters, reaction characteristics and fluid-structure interaction under random waves.
We investigate the effect of mechano-electrical feedback and atrial fibrillation induced electrical remodelling (AFER) of cellular ion channel properties on the dynamics of spiral waves in a discrete ...2D model of human atrial tissue. The tissue electro-mechanics are modelled using the discrete element method (DEM). Millions of bonded DEM particles form a network of coupled atrial cells representing 2D cardiac tissue, allowing simulations of the dynamic behaviour of electrical excitation waves and mechanical contraction in the tissue. In the tissue model, each cell is modelled by nine particles, accounting for the features of individual cellular geometry; and discrete inter-cellular spatial arrangement of cells is also considered. The electro-mechanical model of a human atrial single-cell was constructed by strongly coupling the electrophysiological model of Colman et al. to the mechanical myofilament model of Rice et al., with parameters modified based on experimental data. A stretch-activated channel was incorporated into the model to simulate the mechano-electrical feedback. In order to investigate the effect of mechano-electrical feedback on the dynamics of spiral waves, simulations of spiral waves were conducted in both the electromechanical model and the electrical-only model in normal and AFER conditions, to allow direct comparison of the results between the models. Dynamics of spiral waves were characterized by tracing their tip trajectories, stability, excitation frequencies and meandering range of tip trajectories. It was shown that the developed DEM method provides a stable and efficient model of human atrial tissue with considerations of the intrinsically discrete and anisotropic properties of the atrial tissue, which are challenges to handle in traditional continuum mechanics models. This study provides mechanistic insights into the complex behaviours of spiral waves and the genesis of atrial fibrillation by showing an important role of the mechano-electrical feedback in facilitating and promoting atrial fibrillation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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