A review of floating semisubmersible hull systems:Column stabilized unit

Abstract Column stabilized semisubmersible is one of the most commonly used hull systems for the design and development of drilling and production platforms used for offshore deep water operations. Recent reconfiguration and design alterations have improved its hydrodynamic behaviour in rough weather conditions and, thus, its application and functionality in ocean engineering. Semisubmersible dry-trees applications and large wind turbine foundation systems in ultra-deep waters require high payload integration for reduced motion responses in all degrees of freedom. This paper presents a review of recent industrial and academic contributions to the development of column stabilized semisubmersible hulls used for deep water operations. It also provides an overview of the motion and structural attachments of semisubmersibles. The type and formation of dry-trees semisubmersibles are discussed. The dynamic behaviour and comparative advantages of them are also explained

Investigation on hydrodynamic characteristics, wave-current interaction, and sensitivity analysis of submarine hoses attached to a CALM buoy

There is an increase in the utilisation of the floating offshore structure (FOS) called Catenary Anchor Leg Mooring (CALM) buoys and the attached marine hoses due to the increasing demand for oil and gas products. These hoses are flexible and easier to use but have a short service life of about 25 years. They are adaptable in ocean locations of shallow, intermediate, and deep waters. In this research, the numerical model was developed using a coupling method modelled by utilising ANSYS AQWA and Orcaflex dynamic models of the CALM buoy hoses. Two cases were compar-atively studied: Lazy-S and Chinese-lantern configurations, under ocean waves and current. Comparisons were also made between coupled and uncoupled models. This research presents the hydrodynamic characteristics with sensitivity analysis on the influence of waves, current attack angle, soil gradient, soil stiffness, and environmental conditions that influence the performance of marine hoses. The study comparatively looked at the configurations from dynamic amplification factors (DAF) on marine hoses. The results show that marine hoses can be configured easily to suit the designer’s need, seabed soil type, seabed topography, and the profiles are useful for manu-facturers. The sensitivity analysis also shows the effect of hose parameters on its hydrodynamic behaviour from wave-current interaction (WCI)

Mathematical Modelling of Bonded Marine Hoses for Single Point Mooring (SPM) Systems, with Catenary Anchor Leg Mooring (CALM) Buoy Application:A Review

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

Experimental study on motion characterization of CALM buoy hose system under water waves

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 characterization of 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 capturing using Imetrum systems, using 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 the higher the profile, the higher the response of the buoy. Thus, this study confirms the existence of flow patterns on the CALM buoy while floating on the water body

Numerical Assessment on the Dynamic Behaviour of Submarine Hoses Attached to CALM Buoy Configured as Lazy-S under Water Waves

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

Sensitivity Studies on Offshore Submarine Hoses on CALM Buoy with Comparisons for Chinese‑Lantern and Lazy‑S Configuration:OMAE2019‑96755

With more developments into cost-effective offshore designs, the application of offshore hoses has been adapted for water depths that are not too deep, and for short-service life platforms. This has led to the advances on offloading and loading operations in the offshore industry based on the utilization of Catenary Anchor Leg Moorings (CALM) buoys. However variations in the soil stiffness and environmental conditions necessitates the investigation on the behaviour of the submarine hoses based on the structural and hydrodynamic behaviour. The sensitivity study will help hose manufacturers in the problem of submarine hose failures due to high curvatures. In this study, dynamic analysis is carried out based on the design of the submarine hoses attached to a CALM buoy for both cases of the Chinese-lantern configuration and Lazy-S configurations. Six mooring lines are attached to the CALM buoy with a water depth of 26 m and 100 m, respectively. Hydrodynamic simulation using ANSYS AQWA is first conducted and later coupled into the dynamic models in Orcaflex. Sensitivity studies were conducted to study the effect of wave height, flow angles, soil stiffness and hose hydrodynamic loads on the structural behaviour of the submarine hoses

Strength of submarine hoses in Chinese-lantern configuration from hydrodynamic loads on CALM buoy

Catenary Anchor Leg Moorings (CALM) buoys are offshore structures that have been used for offloading, loading and discharge purposes. In this study, dynamic analysis is carried out on the submarine hoses attached to a CALM buoy and moored by six mooring lines in a water depth of 23.0 m. Two submarine hose-strings in Chinese-lantern configuration are attached underneath the buoy. Three environmental conditions are considered, representing West Africa Sea, North Sea and Gulf of Mexico (GoM), respectively. Hydrodynamic simulation using ANSYS AQWA is first conducted to determine response amplitude operators (RAOs) of the buoy. Coupled dynamic models, where both buoys and hoses are included, are developed using Orcaflex. Parametric studies are conducted to investigate the effects of hose hydrodynamic loads and flow angles on the structural behaviour of the hoses, including bending moments, effective tension and minimum bend radius. From the study, a guidance dynamic amplitude factor of 2.0 considering hydrodynamic loads on hose DAFhose is proposed

A SAMPLING STRATEGY FOR RECENT AND FOSSIL BRACHIOPODS: SELECTING THE OPTIMAL SHELL SEGMENT FOR GEOCHEMICAL ANALYSES

Recent and fossil brachiopod shells have a long record as biomineral archives for (palaeo)climatic and (palaeo)environmental reconstructions, as they lack or exhibit limited vital effects in their calcite shell and generally are quite resistant to diagenetic alteration. Despite this, only few studies address the issue of identifying the best or optimal part of the shell for geochemical analyses. We investigated the link between ontogeny and geochemical signatures recorded in different parts of the shell. To reach this aim, we analysed the elemental (Ca, Mg, Sr, Na) and stable isotope (δ18O, δ13C) compositions of five recent brachiopod species (Magellania venosa, Liothyrella uva, Aerothyris kerguelensis, Liothyrella neozelanica and Gyphus vitreus), spanning broad geographical and environmental ranges (Chile, Antarctica, Indian Ocean, New Zealand and Italy) and having different shell layer successions (two-layer and three-layer shells). We observed similar patterns in the ventral and dorsal valves of these two groups, but different ontogenetic trends by the two- and three-layer shells in their trace element and stable isotope records. Our investigation led us to conclude that the optimal region to sample for geochemical and isotope analyses is the middle part of the mid-section of the shell, avoiding the primary layer, posterior and anterior parts as well as the outermost part of the secondary layer in recent brachiopods. Also, the outermost and innermost rims of shells should be avoided due to diagenetic impacts on fossil brachiopods