Sea Based Container Culture (SBCC) hydrodynamic design assessment for European lobsters (Homarus gammarus)

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The presented work describes the hydrodynamic assessment studies of a much needed technical innovation of Sea Based Container Culture (SBCC) as part of a semi intensive, passive aquaculture culture system for farming the European lobster (Homarus gammarus). Factors that are known to influence growth and survival rates were obtained from previous literature, including flow rate, wave energy and motion characteristics; these factors defined performance criteria for SBCC containers. The internal flow velocities and external flow patterns for different SBCC container designs were measured and used to inform design decisions. Suitable graphical representations have been developed to assess SBCC containers on specific performance criteria. Oyster SBCC containers were found to provide stable motion characteristics but perform poorly against the lower velocity limit, indicating insufficient supply of Dissolved Oxygen (DO) to allow for optimal growth of European lobsters. Internal flow velocities were also measured on un-fouled and fouled SBCC containers; results showed SBCC 2 would not provide enough DO with 66% biofouling coverage (66% biofouling replicates one year deployment) and triggered a redesign. SBCC 1 at 90° yaw angle of attack demonstrated all round good performance against upper and lower velocity limits and motion characteristics; thus showed greatest promise for cultivation of European Lobster.The research was gratefully supported and funded by BBSRC (BB/M005208/1) and Innovate UK (131597) through the Agri-Tech Catalyst, Early Stage Awards. The project consortium consisted of the National Lobster Hatchery, University of Exeter, Falmouth University, Centre for Environment, Fisheries and Aquaculture Science, West Country Mussels of Fowey and Fusion Marine. Follow on work will also be supported by BBSRC and Innovate UK through the Industrial Stage of Agri-Tech catalyst and supported by funding from the Worshipful Company of Fishmongers

Framework for evaluating external and internal parameters associated with Sea Based Container Culture (SBCC): Towards understanding rearing success in European lobsters (Homarus gammarus)

This is the final version. Available on open access from Elsevier via the DOI in this recordSea Based Container Culture (SBCC) is a mariculture technique that relies on the natural maintenance of environmental conditions, such as Dissolved Oxygen (DO) concentration and feed availability. This paper discusses a framework to evaluate the rearing success of European Lobsters (Homarus gammarus) in SBCC based on temporal and spatial variations of external parameters, including current velocity, wave velocity, turbulent fluctuations and dissolved oxygen concentrations. The temporal variations considered annual changes to the environment and the effect of biofouling growth, and the spatial variations considered the geographical location (case study of Falmouth bay, Cornwall) and vertical position in the water column. The internal parameters of the containers were modelled using transfer functions derived from previous experimental data. The internal parameters were compared to rearing limitations selected from available literature, which included foraging and mobility behaviours, and DO consumption. The time that internal parameters exceeded the rearing limitations was quantified, allowing rearing success to be predicted. This paper uses a case study of external parameters measured in Cornish waters, UK, to demonstrate the framework methodology. The framework showed that in situ measurements of current, wave and turbulence could be used to predict the internal parameters of SBCC containers, which can be used to predict theoretical rearing success based on rearing limitations. The framework indicated that DO concentrations within the containers should not affect rearing success; however, the foraging and mobility limits were exceeded by 0 to 30% of the time (depending on vertical position in the water column and assessment method). The paper aims to demonstrate the generic framework methodology and understands its limitations in predicting rearing success. The framework provides a tool to optimise the SBCC design for spatial and temporal varying conditions related to a geographical location or (vice versa) identify suitable mariculture sites based on SBCC design and environmental conditions. Additionally, the framework can optimise the vertical position of the SBCC in the water column and identify, from parameters considered, those that are most likely to affect rearing success.The research was gratefully supported and funded by BBSRC (BB/M005208/1 and BB/N013891/1) and Innovate UK (131597 and 102531) through the Agri-Tech Catalyst, Early Stage and Industrial Stage Awards

Evaluating Mooring Line Test Procedures Through the Application of a Round Robin Test Approach

This is the final version. Available from MDPI via the DOI in this record. Innovation in materials and test protocols, as well as physical and numerical investigations, is required to address the technical challenges arising due to the novel application of components from conventional industries to the marine renewable energy (MRE) industry. Synthetic fibre ropes, widely used for offshore station-keeping, have potential application in the MRE industry to reduce peak mooring line loads. This paper presents the results of a physical characterisation study of a novel hybrid polyester-polyolefin rope for MRE mooring applications through a round robin testing (RRT) approach at two test facilities. The RRT was performed using standard guidelines for offshore mooring lines and the results are verified through the numerical modelling of the rope tensile behaviour. The physical testing provides quantifiable margins for the strength and stiffness properties of the hybrid rope, increases confidence in the test protocols and assesses facility-specific influences on test outcomes. The results indicate that the adopted guidance is suitable for rope testing in mooring applications and there is good agreement between stiffness characterisation at both facilities. Additionally, the numerical model provides a satisfactory prediction of the rope tensile behaviour and it can be used for further parametric studies.European Unio

Tension-tension testing of a novel mooring rope construction

This is the author accepted manuscript.Synthetic fibre ropes are in widespread use in maritime applications ranging from lifting to temporary and permanent mooring systems for vessels, offshore equipment and platforms. The selection of synthetic ropes over conventional steel components is motivated by several key advantages including selectable axial stiffness, energy absorption (and hence load mitigation), fatigue resistance and low unit cost. The long-term use of ropes as safety critical components in potentially high dynamic loading environments necessitates that new designs are verified using stringent qualification procedures. The International Organization for Standardization (ISO) is one certification body that has produced several guidelines for the testing of synthetic ropes encompassing quasi-static and dynamic loading as well as fatigue cycling. This paper presents the results of tension-tension tests carried out to ISO 2307:2010, ISO 18692:2007(E) and ISO/TS 19336:2015(E) on three different 12-strand rope constructions manufactured by Ashimori Industry Co. Ltd from polyester and Vectran® fibres. The purpose of the tests was to characterise the performance of a novel 12-strand construction and compare this to a conventional 12-strand construction. Utilising the Dynamic Marine Component test facility (DMaC) at the University of Exeter several key performance metrics were determined including; elongation, minimum break load (MBL) and quasi-static and dynamic stiffness. During the ISO 2307:2010(E) test programme the samples were tested dry and during the ISO 18692:2007(E) and ISO/TS 19336:2015(E) test programmes the samples were fully submerged in tap water after being soaked for at least 24 hours. Two methods were used to quantify sample extension: i) an optical tracking system and ii) a draw-wire potentiometer. Axial compression fatigue and cyclic loading endurance tests were also carried out on two Vectran® samples. Further load-to-failure tests and sample analysis were also carried out by Ashimori Industry Co. Ltd. It was found that the MBL of the samples exceeded the values specified by the manufacturer (by 7.7-29.5% for the polyester samples) with failure occurring at the splices in all cases and minor abrasion noted in several locations. The measured MBL of the novel polyester Straight Strand Rope (SSR) construction was up to 16% higher than the conventional construction with increases of quasi-static and dynamic stiffness of up to 6.8%. Differences between the viscoelastic and viscoplastic behaviour of the samples were also noted. The data obtained during these tests will provide insight into the behaviour of these materials and different rope constructions which will be of use to rope manufacturers, mooring system designers in addition to offshore equipment and vessel operators.The authors at the University of Exeter would like to thank their colleagues at Nagasaki University and Ashimori Industry Co. Ltd for being given the opportunity to carry out the interesting work reported in this paper. Through the Peninsula Research Institute for Marine Renewable Energy (PRIMaRE) consortium, the DMaC test facility was funded from the ERDF Convergence programme and South West Regional Development Agenc

Integrity and Reliability Testing of a HDPE Taut Mooring System Belt

This is the author accepted manuscript. The final version is available from EWTEC via the link in this recordThe integrity of the mooring system is critical for the safe station-keeping of any floating structure. For motion dependent wave energy converters, the additional requirement is to provide sufficient compliance to allow the power take-off working principle to function. This paper presents the physical testing carried out as part of the MARINET2 test programme. The mooring system design for the Calwave wave energy converter is tested in order to validate the actual physical performance of the mooring system. The tests are carried out at the Dynamic Marine Component Test facility (DMaC), capable to replicate the forces (up to 30 tonnes) and motions (up to 1m / 30°) with submersed test specimens of up to 6 meters length. The tests explore the Minimum Breaking Strength (MBS) as a primary measure of integrity, but will also perform repeated cyclic loading, simulating low-cycle fatigue behaviour of the mooring system. The tests also assess the mooring response and integrity under simulated Accidental Limit State (ALS) conditions, where the device’s power take-off will be locked and the mooring loads are expected to increase considerably. A key finding of the tests is the importance of the termination pattern and quality, which has a direct influence on the mooring MBS. The static and dynamic stiffness for the tested HDPE belts is also determined. The paper will be of interest to technology developers, mooring designers and stakeholders concerned with the integrity, durability and validation of offshore mooring systems.European Union Horizon 202

Hydroelastic inflatable boats: relevant literature and new design considerations

Inflatable boats are considerably more flexible than conventional metal or composite vessels. The RNLI have developed an inflatable boat, the IB1, with improved performance which has been attributed to its flexibility or hydroelasticity. Current design methodologies for planing vessels predict the performance assuming it is rigid. Designing an entirely hydroelastic boat presents completely new design challenges and will require new design methodologies in the future. This paper considers how to approach an entirely hydroelastic planing vessel and how to divide the boat into practical problems. A design approach taking into account hydroelasticity could potentially improve the performance further by decreasing boat motions, reducing added resistance in waves and minimising the slamming accelerations. This paper reviews the literature relevant to rigid inflatable and inflatable boats and shows the construction of the IB1. The hydroelastic design problem is broken down into three main hydroelastic events: global hydroelasticity, hydroelastic planing surfaces and hydroelastic slamming. Each event is defined, the relevant literature is reviewed and the possible advantages are discussed. A design approach is suggested using a hydroelastic design cycle. The hydrodynamic problem of interacting sponsons is briefly discussed. <br/

Round robin testing of synthetic fibre ropes for application in marine renewable energy

This is the author accepted manuscript. The final version is available from CRC Press via the DOI in this recordRENEW 2020: 4th International Conference on Renewable Energies Offshore, 12-15 October 2020, Lisbon, PortugalThe unique design requirements of mooring systems in Marine Renewable Energy (MRE) installations re-quire detailed numerical and empirical investigations as well as offshore experience to adopt and certify fi-bre ropes in the marine renewable energy industry. Laboratories provide a controlled environment for quick, inexpensive and repeatable testing compared to field deployment and enable a range of parameters to be studied. Uncertainties may be introduced in the laboratory test results because of effects associated with in-dividual facilities (such as instrumentation accuracy, control system and analysis methods) despite following the same protocol. This paper presents the outcomes of a round robin testing campaign conducted at two test facilities to conduct a comparative analysis by monitoring the implementation of the test program and ana-lysing the results to highlight differences between facilities and suggest best practice for fibre rope testing in the MRE industry.European Union Horizon 202

Design and performance of inflatable boats: flexibility and environmental considerations

This paper investigates the design and performance of inflatable boats where the structural stiffness is supplied by the inflatable tubes and jointed composite sandwich panels which allow large deformations in the hull form. Anecdotal evidence has shown that this flexibility or hydroelasticity of an inflatable boat (IB) improves its performance, especially in waves. It is hoped that this hydroelasticity can be optimised to improve aspects of the performance, including reductions to the boat motion therefore minimising the human exposure to vibrations and added resistance in waves.This paper discusses each area of hydroelasticity found in an inflatable boat, it defines each problem, shows the current literature and possible methods of investigation. The areas of hydroelasticity include; globalhydroelasticity, hydroelastic planing surfaces and hydroelastic slamming. This paper also discusses the wave and spray generation of a vessel with sponsons and relates it to the effect on boat motion and resistance. Finally this paper discusses the air and water borne noise produced by these types of vessels

Double braid mooring damper for floating offshore wind application

This is the author accepted manuscript.Introduction of innovative mooring components can reduce the risk and cost associated to mooring systems of floating offshore wind turbines. The Intelligent Mooring System (IMS) is an active, hydraulic, nonlinear mooring component developed by Intelligent Moorings Limited that provides functionality akin to a shock absorber. It offers a combination of desirable stiffness characteristics for floating offshore wind application; an initial compliant response that reduces loads on the structure and a stiffer nonlinear response for larger loads to reduce platform motion and ensure effective station keeping. A salient feature of the IMS is that through variation of the internal pressure, the stiffness of the system can be adjusted in accordance with the prevailing environmental conditions. This paper presents the results of the physical testing of a double braided IMS at the Dynamic Marine Component test facility and compares the stiffness and strength characteristics to a single braid sleeve. The comparative analysis shows that the stiffness profiles of the double braid for the various configurations are consistent with the single braid design. Importantly, the use of a double braid results in a 50% increase of the tensile strength of the IMS. The investigation presented in this paper will aid in the design of a robust IMS for field testing prior to commercial applications in floating wind installations.Innovate U

Demonstration of the intelligent mooring system for floating offshore wind turbines

This is the author accepted manuscript. The final version is available from ASME via the DOI in this recordExisting mooring systems for floating offshore wind turbines are largely based on designs from the oil and gas industry. Even though these can ensure the safe station keeping of the floating wind platform, the design of the mooring system is currently largely conservative, leading to additional expense in an industry striving to achieve cost reduction. Recent interest in the usage of mooring materials with non-linear stiffness has shown that they have the potential to reduce peak line loads, ultimately reducing cost. This paper reports on the combined physical testing and numerical modeling of a hydraulic-based mooring component with these characteristics. The results suggest that the inclusion of the component as part of the OC4 semi-submersible platform can reduce the peak line loads by 10%. The paper also discusses a number of challenges associated with modeling and testing dynamic mooring materials.Innovate U