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Journal of Ocean Engineering and Marine Energy
Journal Prestige (SJR): 0.913  Citation Impact (citeScore): 2 Number of Followers: 3  Hybrid journal (It can contain Open Access articles)ISSN (Print) 2198-6444 - ISSN (Online) 2198-6452 Published by Springer-Verlag  [2468 journals]
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- Hydrodynamic coefficients of mussel dropper lines derived from large-scale
experiments and structural dynamics-
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Abstract: Abstract The expansion of marine aquaculture production is driven by a high market demand for marine proteins and a stagnation of wild catch of fish. Bivalve farming, i.e., the cultivation of oysters, mussels and scallops, is an important part of the ongoing market dynamics and production expansion. As marine spatial planning is considering various use purposes, available space for near-shore aquaculture is already becoming scarce; this has fueled research and development initiatives to enable production installations further offshore. The highly energetic conditions at more exposed offshore marine sites lead to increased loads on aquaculture systems and their components and it is still not sufficiently understood how the load transfer from oceanic environmental conditions onto shellfish-encrusted surfaces attached to elastic ropes may be appropriately quantified. This study data gathered large-scale data sets in a wave tank facility, which are used to validate a novel, numerical model, building on the dynamics of rope structures which allows for the determination of the hydrodynamic loads transferred to the dropper lines. The forces and hydrodynamic parameters are measured and numerically analyzed. Based on the results, drag and inertia coefficients are determined. A drag coefficient of \(C_\textrm{D} = 1.1\) and an inertia coefficient of \(C_\textrm{M} = 1.7\) are recommended to model shellfish-encrusted dropper lines exposed to oscillatory flows with KC \(=\) 40–90. The numerical model for the determination of wave-induced forces on mussel dropper lines is developed and validated using the experimental data. It employs a modified Morison equation, which takes into account the displacement of the mussel dropper line. The influence of varying aquaculture-related parameters is discussed by applying the numerical model. Based on the gathered insights, recommendations can be given from an engineering point of view concerning the optimal placement of mussel aquaculture within the water column.
PubDate: 2023-11-28
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- Future predictions of wave and response of multiple floating bodies based
on the Kalman filter algorithm-
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Abstract: Abstract The present work explores the possibility of predicting future waves by extending the Kalman filter algorithm by incorporating the spatial distance between two points. Experimental data at 2D tank are used to validate the effectiveness of the proposed method. When causality limitation is fulfilled, it is found that 3–8 s or several cycles of waves ahead can be predicted in model scale, depending on the distance between the two points. If a scaling of 1/100 is adopted, this means 30–80 s waves ahead can be estimated. The longer the distance, the longer future predictable time will be. Response predictions using wave prediction data are also investigated. The results for the response prediction also exhibits high accuracy, with even higher predictable future time (80–120 s ahead given 1/100 scale ratio) compared to its associated predictable future time of waves.
PubDate: 2023-11-26
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- Experimental comparison of passive adaptive blade pitch control strategies
for an axial-flow current turbine-
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Abstract: Abstract Two passive blade pitch control strategies for an axial-flow current turbine were developed and tested experimentally in a recirculating flume. The goal of the control is to regulate mechanical power, while limiting rotor loads, when flow conditions exceed the rated condition. Both strategies use blades fabricated with unidirectional carbon fiber oriented off-axis, such that the blades twist passively as they deflect in response to loading. One control strategy combines passive adaptive blades with overspeed control (operating at a rotational speed above the tip-speed ratio corresponding to peak efficiency) while the other combines passive adaptive blades with active pitch control (actuating blade pitch using motors at the blade root). Both strategies were implemented with a 0.45-m diameter turbine in linearly increasing inflow from 0.7 to 0.8 m/s and compared to control strategies using rigid, aluminum blades under the same flow conditions. The passive adaptive blades combined with active pitch control saw no improvement in steady-state load reductions relative to rigid blades used with active pitch control. However, the passive adaptive blades combined with overspeed control successfully produced constant torque with an only 12% increase in thrust, relative to the rated flow condition. The flow confinement likely enhanced the relative benefit of passive adaptive blades compared to speed control strategies with rigid blades. Overall, results indicate that passive adaptive blades combined with overspeed control can be an effective strategy in currents above the rated flow speed, removing the need for an active pitch mechanism in some applications. In addition to measuring turbine loads, deflection and twist of the passive adaptive blades during experimental testing were observed using a high-speed camera to support our understanding of the bend–twist behavior during turbine operation over a range of flow speeds, rotation rates, and preset pitch angles.
PubDate: 2023-11-25
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- Wave energy conversion using a small tubular free-floating device
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Abstract: Abstract Wave energy devices traditionally tend to be large, as their sizes are often determined by power conversion targets and their operating wave climates. Here we examine a size-constrained device designed to fit within narrow tubes, and using well-known analysis techniques show that converted power amounts may be large enough to meet or exceed the needs of instrumentation to serve a majority of oceanographic and defense ocean measurement needs. The device examined in this paper is designed to fit within, and to be deployed from, torpedo tubes or other equivalently sized cylindrical containers. Examined in this paper is a traditional tubular oscillating water column device, and particular interest here is in designs that lead to optimization of power converted in anticipated wave climates. A two-step design procedure is investigated here, wherein a more approximate two-degree-of-freedom model is first used to identify relative dimensions (of device elements) that optimize power conversion from relative oscillations between the device elements. A more rigorous mathematical model based on the hydrodynamics of oscillating pressure distributions within solid oscillators is then used to provide the hydrodynamic coefficients, forces, and flow rates for the device. These results are next used together with a power take-off model, to provide a quick but rigorous way to estimate the energy conversion performance of the device in various wave climates. A power take-off based on a self-rectifying turbine system is used, and its representative conductance and susceptance values are derived for a chosen geometry and configuration. Calculations are carried out to illustrate the design procedure, and converted power values exceeding ten watts are noted in wind-sea like conditions. Further, performance comparisons with solar panels in Arctic latitudes indicate that such designs may yield considerably better energy conversion during seasons of low insolation. These devices could be designed to convert enough power to perform designated ocean measurement operations while storing any excess energy to support vehicle recharging operations.
PubDate: 2023-11-13
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- A prediction tool for maintenance costs estimation during the design
process of a ship engine room-
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Abstract: Abstract When dealing with maintenance in ships engine room, the space available around machinery and systems (clearance) plays an important role and may significantly affect the cost of the maintenance intervention. In a first part of a current research study Gualeni et al. (Ship Technol Res, 10.1080/09377255.2021.2020949, 2022), a quantitative relation between the maintenance costs increment due to the clearance reduction is determined, using a Bayesian approach to General Linear Model (GLM), with reference to a single item/component of a larger system Sánchez-Herguedas et al. (Reliability Eng Syst Saf 207: 107394, 2021). This paper represents the second part of the activity and it enforces a systemic view over the whole machinery or system Sanders and Klein (Proc Comput Sci 8:413–419, 2012). The aim is to identify not only the relation between maintenance costs and clearance reduction, but also how the clearance reductions of the single components/items interact and affect the whole system/machinery accessibility and maintainability, meant as relevant emerging properties. The system emerging properties are investigated through the design and application of a Hidden Markov Model Salvatier et al. (Peer J Comput Sci 2: e55, 2016); i.e., the system is modeled by a Markov process with unobservable states. The sequence of states is the maintainability of the system (which incorporates each one of the single components) while the evidence is the increase in cost of maintenance related to the space reduction. By predicting a sequence of states, it is therefore possible to predict the interactions between the system components clearances and determine how the emerging maintainability property is affected by the engine room design.
PubDate: 2023-11-01
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- Theoretical and CFD modelling of single and slug oil, water and gas flows
in a deepwater rigid jumper-
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Abstract: Abstract In the present work, computational fluid dynamics modelling (CFD) of single-phase flow (oil, water, gas) and two-phase flows (oil/water, oil/gas, gas/oil) was performed, to study the behaviour of these types of flow in a rigid jumper employed for the production of oil and gas in deepwater hydrocarbons fields. The jumper conducts the produced fluids from a subsea tree to a PLET. The modelled fluids were extracted from a drill stem testing study, corresponding to multiphase flow of water, gas and oil. In the present modelling strategy, the jumper and was considered thermally insulated to avoid heat transfer between internal fluids and external environmental conditions, and the end connectors of the jumpers were also considered insulated along with tree and PLET connection points. The flow patterns, pressure drops, slugs and flow velocity variations through the jumper were obtained from CFD simulations to visualize and study their behaviour in the jumper during the flow. The CFD pressure results were compared with theoretical calculations with good agreement, producing fast results. However, CFD results allowed to visualize internal flow behaviour, calculate the time needed by each flow condition from jumper inlet to jumper outlet, flow patterns, pressure drops, etc. The methodology can also be used to estimate the production rate of the different modelled flows, to identify critical flow conditions inside a rigid jumper and select the appropriate jumper internal diameter.
PubDate: 2023-11-01
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- Coupled dynamic analysis of hybrid STLP-WEC offshore floating wind turbine
with different mooring configurations-
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Abstract: Abstract The novel concept of six cone-cylinder-shaped point absorbers around the submerged tension leg platform (STLP) in a circular pattern is studied considering the STLP fixed in position using tensioned mooring cables. The hybrid floating platform consisting of offshore wind turbine platform with a wave energy converter (WEC) reduces the overall logistic cost and eases the transportation process. The stability and safety of the hybrid floating concept depend significantly on the integrity of the tensioned tendons. The present study proposes four different mooring configurations (four, five, eight and nine) to stabilize the hybrid STLP-WEC floater. The numerical simulation in the time domain is performed using the aero-servo-hydro-elastic simulation. The time histories and the motion response spectrums of the surge, sway, heave, roll, pitch and yaw motion of the hybrid system for each mooring configuration are analyzed to study the behaviour of the hybrid system under irregular wave conditions. The time history and spectrum of the generator power are analysed to observe the effect of second-order wave load and turbulent wind loads on the power production of the hybrid floater under each mooring configuration. Further, the study is performed to determine the forces and moments developed at the base of the floating wind turbine to analyze the impact of wind load on the responses of the hybrid floater. The study also analyses the tension developed on each tendon for different mooring configurations and reports the importance of mooring and the influence of the mooring system on the dynamic responses of the combined floater.
PubDate: 2023-11-01
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- Sensitivity analysis of parameters governing the iceberg draft through
neural network-based models-
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Abstract: Precise estimation of the iceberg draft may significantly reduce the collision risk of deep keel icebergs with the offshore facilities comprising the submarine pipelines, wellheads, communication cables, and hydrocarbon loading equipment crossing the Arctic shallow waters. As such, in this study, the iceberg drafts were simulated using a self-adaptive machine learning (ML) algorithm entitled self-adaptive extreme learning machine (Sa-ELM) for the first time, to the best of our knowledge. Initially, the parameters governing the iceberg drafts were specified, and then nine Sa-ELM models were defined using these parameters. To test and train the Sa-ELM models, a comprehensive dataset was constructed, where 60% of the dataset was utilized for model training and 40% for model validation. In addition, several hyper parameters have been optimized during the training procedure to obtain the most accurate results. The superior Sa-ELM model and the most influencing input parameters were determined by conducting a sensitivity analysis. The comparison of the premium Sa-ELM model with the artificial neural network (ANN) and extreme learning machine (ELM) models demonstrated that the Sa-ELM model had the highest level of accuracy and correlation as well as the lowest degree of complexity. Ultimately, a Sa-ELM-based equation was presented to estimate the iceberg draft in practical applications. Graphical abstract
PubDate: 2023-11-01
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- Instability of curved panels under external pressure: experiments and
numerical analyses-
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Abstract: Abstract The structural behavior of reinforced curved panels under uniform external pressure is investigated through experimental tests and numerical simulations. The collapse pressures and post-buckling characteristics of five panels are derived from tests conducted within a pressure vessel pressurized in a near volume control approach. The mechanical properties of the steel plates utilized in manufacturing the specimens are determined via tensile tests. Nonlinear finite element analyses are employed to replicate the physical experiments and subsequently conduct parametric studies. The impact of geometric parameters and imperfections on the collapse pressure and mode is assessed through parametric analyses, considering both clamped and simply supported boundary conditions. Imperfect geometries are incorporated into the numerical model utilizing the first buckling mode shape obtained from linearized stability analyses. It is observed that the simply supported condition has a significantly more detrimental effect compared to the clamped condition. It is observed that the simply supported condition has a significantly more detrimental effect compared to the clamped condition. The presented experimental results and numerical analyses offer valuable insights for the practical design of such reinforced panels.
PubDate: 2023-11-01
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- Benchmarking study of 10 MW TLB floating offshore wind turbine
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Abstract: Abstract This paper presents a benchmarking study of four floating wind platform’ motion and dynamic tension responses to verify an innovative design with the intention of overall cost reduction of a durable, reliable, safe design. An aero-hydro-servo-elastic code is applied to benchmark a 10 MW tension leg buoy (TLB) floating wind turbine to the current leading technology types for floating offshore wind platforms, specifically spar buoy, Semi-submersible and tension leg platform (TLP) floating wind turbines. This study assumes that the platforms will deploy in the northern region of the North Sea, with a water depth of 110 m under various environmental conditions, including wind field descriptions covering uniform wind to fluctuating turbulent wind. The obtained dynamic response results showed low motion responses for the TLB platform for all design load cases. More specifically, the TLB surge and pitch motion responses are insignificant under both operational and survival conditions, allowing decreased spacing between individual wind turbines and increasing wind farms' total energy generation capacity. An additional benefit is that the wind turbine systems can be installed without significant pitch modification to the control system. The TLB platform is less complex which simplifies the construction process and has the potential for significant cost reductions.
PubDate: 2023-10-31
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- The global techno-economic potential of floating, closed-cycle ocean
thermal energy conversion-
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Abstract: Abstract Ocean Thermal Energy Conversion (OTEC) is an emerging renewable energy technology using the ocean’s heat to produce electricity. Given its early development stage, OTEC’s economics are still uncertain and there is no global assessment of its economic potential, yet. Here, we present the model pyOTEC that designs OTEC plants for best economic performance considering the spatiotemporally specific availability and seasonality of ocean thermal energy resources. We apply pyOTEC to more than 100 regions with technically feasible sites to obtain an order-of-magnitude estimation of OTEC’s global technical and economic potential. We find that OTEC’s global technical potential of 107 PWh/year could cover 11 PWh of 2019 electricity demand. At ≥ 120 MWgross, there are OTEC plants with Levelised Cost of Electricity (LCOE) below 15 US¢(2021)/kWh in 15 regions, including China, Brazil, and Indonesia. In the short-to-medium term, however, small island developing states are OTEC’s most relevant niche. Systems below 10 MWgross could fully and cost-effectively substitute Diesel generators on islands where that is more challenging with other renewables. With the global analysis, we also corroborate that most OTEC plants return the best economic performance if designed for worst-case surface and deep-sea water temperatures, which we further back up with a sensitivity analysis. We lay out pyOTEC’s limitations and fields for development to expand and refine our findings. The model as well as key data per region are publically accessible online.
PubDate: 2023-10-20
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- Experimental and finite element analysis of the buckling response of thin
spherical shells under hyperbaric pressure-
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Abstract: Abstract Spherical shell plays an important role in deep-water submersibles. This work reports the analysis and testing of spherical shells with an inner diameter of 150 mm and a wall thickness of 1 mm. Five spherical shell models are manufactured and subjected to hyperbaric pressure. By using a bridge gauge and ultrasonic thickness gauge, imperfection and thickness are measured respectively at various grid points. The shell is pressurized in steps until it is permanently collapsed. The pressure at which the shell collapses is compared to the pressure calculated based on a nonlinear buckling analysis. Analyses are performed considering both geometric and material nonlinearities. Results obtained from analysis and experiments are comparable. It is important to note that the initial imperfections have a significant impact on the buckling performance of the spheres.
PubDate: 2023-10-19
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- Preliminary study of the performance of a new wave energy converter
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Abstract: Abstract The power generation challenge of any wave energy converter (WEC) depends on the efficiency of the power take-off (PTO) system. The complexity of the WEC represents a relevant factor in installation and maintenance. To increase the power generation in a direct mechanical drive PTO system the gearbox represents a necessary component, a high gear ratio affects the cost, size, complexity and maintenance of this component. This study aims to address the first analysis of power performance and operation of a new wave energy converter composed of a point absorber, a hinged arm and a direct mechanical drive PTO system. The PTO is characterized by a pulley system, the main components of PTO such as the gear ratio, the electric generator and the main pulley are analyzed in the WEC performance, a cylindrical point absorber is considered in the present study. A wave-to-wire model is developed to simulate the coupled hydro-electro-mechanical system in regular waves. The performance of the wave energy converter is analyzed using the potential linear theory but considering the viscous damping effect according to the Morison equation to avoid the overestimated responses. The new WEC shows a maximum mean power of about 28 kW. The capture width ratio shows a maximum value of 36.5% indicating that the WEC shows a better performance at small values of height and period of wave.
PubDate: 2023-10-17
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- Impact of cavitation and inflow perturbation on the performance of a
horizontal-axis tidal turbine-
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Abstract: Abstract The impact of cavitation and inflow perturbation by an upstream support structure on the performance of a horizontal-axis tidal turbine has been studied by experiments at model scale in a depressurized water channel at CNR-INM. Measurements of turbine generated power and thrust have been carried out at varying channel flow speed, tip-speed ratio, and cavitation number. The visualization of cavitation patterns has been associated with the performance measurements to identify the role played by different cavitation types on turbine behavior. Radiated noise measurement were also performed to assess the impact of cavitation phenomena on turbine induced acoustic signature.
PubDate: 2023-08-25
DOI: 10.1007/s40722-023-00296-9
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- Performance of a distensible-tube wave attenuator in a slender focusing
channel-
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Abstract: Abstract A wave energy device utilizing a water-filled distensible tube aligned head to waves is analyzed. The wave-excited pressure bulges in the tube activate a stationary forward-bent circular oscillating water column (OWC) at its stern. This system has been extensively tested in wave-tank, at different scales. However, further improvements to its efficiency are possible. The present research assesses its performance at 1:20 scale, while operating in a slender focusing channel. Complementarily, two other situations are considered: one at the nearshore, where the system is assembled to a bottom-standing jacket structure, and an onshore design where the tube operates in front of a sea wall in constant depth or over a sloping bottom. Deep and intermediate regular waves of small and finite amplitudes are generated in the wave-tank, representing the wave climate in the Occidental Group of the Azores islands. A non-linear power take-off impedance is imposed by a set of calibrated orifice plates and its characteristic is then obtained assuming compressible airflow. Measurements of air pressure in the pneumatic chamber, OWC free-surface displacement, and incident wave-field provide estimates of energy capture-width, which are then compared with analytical predictions and benchmark test results. Photographs further help to understand the physics underlying the tube’s working modes. Moreover, the performance of the system is obtained with and without the tube and then compared with standard values for OWCs. It is demonstrated that the addition of a distensible tube and a suitable focusing channel can significantly improve the capacity factor of a conventional OWC system.
PubDate: 2023-08-17
DOI: 10.1007/s40722-023-00297-8
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- The influence of ship stability in waves on naval vessel operational
profiles-
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Abstract: Abstract Ensuring a widely safe operational profile of naval vessels is one of the leading aspects of the design process. With reference to weather conditions, this kind of vessels often cannot avoid heavy situations to guarantee the continuity and the effectiveness of service. For this reason, an applied research investigation aimed to define guidance in operations is deemed as a worthwhile activity. In particular, the performance in waves under the perspective of intact stability has been considered in this work. The IMO second-generation intact stability criteria have been identified as a suitable tool for these investigations: as a result, there is evidence that operational guidance can be developed for a set of representative naval vessels, following the relevant guidelines. Outcomes have been represented by means of comprehensive polar diagrams addressing the intact stability failures modes. Bearing in mind the actual operational profile, results have been analysed and discussed considering how ship and operating decisions in a seaway condition may affect the performance in terms of ship stability.
PubDate: 2023-08-05
DOI: 10.1007/s40722-023-00291-0
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- Analysis of wave resource model spatial uncertainty and its effect on wave
energy converter power performance-
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Abstract: Abstract Wave models used for wave energy resource assessments are subjected to uncertainties, which differ from one location to another over the defined model area. This is because the models are typically calibrated and validated using a single or few validation points, and the model uncertainties of the wave parameters generally grow with the distance to the validation point. The spatial uncertainty of wave resource is one of the vital considerations in wave resource numerical modelling, since it is used to estimate the confidence in site assessments of potential wave energy device locations away from the validation point and is a necessary requirement of a resource assessment to IEC TS 62600-101. This paper focuses on developing a methodology for determining the spatial uncertainty by analysing how wave parameter uncertainties may change with location over the model area. A test site is modelled using the SWAN third-generation numerical wave model and validated at a single location for several wave parameters. A set of Monte-Carlo simulations are used to generate estimates of model uncertainties for locations around the validation point and a step-wise procedure is demonstrated with appropriate justifications to evaluate the uncertainties at these locations with respect to the validation point. Finally, the obtained results are used with a Wave Energy Convertor (WEC) numerical model to estimate the uncertainties on the power capture of the device.
PubDate: 2023-08-02
DOI: 10.1007/s40722-023-00294-x
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- Temporal upsampling of wave parameters and impact on time-domain floating
body response and wave power-
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Abstract: Abstract Power production of wave energy converters (WEC) predicted in the time domain use wave resource parameters and time-domain hydrodynamic model simulations that provide high temporal resolutions (10s of Hz). However, wave resource parameters are often based on frequency-domain calculations with temporal resolution of 30 min to an hour. Real ocean wave conditions vary on much shorter time scales. Relying on frequency-domain calculations will not be sufficient to capture short-term variability and accurately predict WEC power production for a standardized methodology that follows power system requirements. Low temporal resolution data sets are being used in a majority of studies to generate representative wave conditions as inputs to numerical simulations by generating wave spectra. Spectra are then used to predict the efficiency of systems that will not accurately capture the variability of waves in short timeframes. Creating a standardized methodology to increase the temporal resolution of metaocean conditions to inform model development can provide better power production forecasting. In this paper, random amplitude, Fourier coefficient methods have been used for WEC simulations of finite durations to improve the observed variability in wave heights and power production. Variability using this method does increase for finite durations compared to the commonly used deterministic amplitude method.
PubDate: 2023-07-28
DOI: 10.1007/s40722-023-00292-z
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- Effects of turbine damping and wave conditions on OWC performances for
optimal wave energy conversion-
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Abstract: Abstract The oscillating water column (OWC) devices constitute the most widely used systems for the wave energy conversion. Optimizing the performances of such devices mainly composed with a bidirectional air turbine and a water–air chamber still remains of great interest. The present investigations focus on the numerical analysis of an OWC system, the air turbine damping, and on its coupling with the OWC chamber. A validated 2D RANS-VoF numerical model was implemented to determine the optimum induced damping of the OWC device in case of an impulse turbine. The model is based on the concept of the Numerical Wave Tank (NWT). In the present model, the turbine quadratic behavior was simulated with an orifice. Simulations have been conducted in typical cases located on the central zone of the Moroccan Atlantic coast. All the simulated cases are of intermediate water waves which are in compliance with the use of the Stokes’ second-order wave generation. The pneumatic power corresponding to the various values of turbine-induced damping is computed, and the optimum damping accounting for the wave climate variability is identified. It was found that the damping induced by the air turbine is the factor that influence most the OWC chamber efficiency, followed by the climate conditions.
PubDate: 2023-07-21
DOI: 10.1007/s40722-023-00293-y
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- The retrofitting of ships by applying retractable bow hydrofoils: a case
study-
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Abstract: Abstract Increasing environmental requirements and a relatively long ship life of 30 years mean more attention is needed to retrofit existing ships. One possibility is using hydrofoils to reduce the ship’s resistance and improve comfort and safety in rough sea conditions. This study investigates the influence of retractable bow hydrofoils on the seakeeping performance and operational conditions of a selected case study vessel (V-shaped bulbous bow). The methods used were full-scale computational fluid dynamics (CFD) simulations and towing tank experiments for validation. The analysis was conducted for bow waves of different lengths and a ship’s operating speed. The most beneficial effect of hydrofoils was observed for wavelengths from λ/LWL = 1.0 to λ/LWL = 1.2. For the wavelength λ/LWL = 1.2, the reduction of heave motion was equal to 33%, pitch motion was equivalent to 28%, and the reduction of wave-added resistance was equal to 25%. The analysis also showed unfavourable conditions for which hydrofoil folding is needed to avoid causing an excessive increase in resistance. A generalized procedure has been developed to assess the potential for resistance and motion reduction by retrofitting existing ships using hydrofoils.
PubDate: 2023-07-20
DOI: 10.1007/s40722-023-00289-8
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