Academic literature on the topic 'Cross-Flow tidal turbine'
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Journal articles on the topic "Cross-Flow tidal turbine"
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VENNELL, ROSS. "Tuning turbines in a tidal channel." Journal of Fluid Mechanics 663 (October 12, 2010): 253–67. http://dx.doi.org/10.1017/s0022112010003502.
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As tidal turbine farms grow they interact with the larger scale flow along a channel by increasing the channel's drag coefficient. This interaction limits a channel's potential to produce power. A 1D model for a tidal channel is combined with a theory for turbines in a channel to show that the tuning of the flow through the turbines and the density of turbines in a channel's cross-section also interact with the larger scale flow, via the drag coefficient, to determine the power available for production. To maximise turbine efficiency, i.e. the power available per turbine, farms must occupy the largest fraction of a channel's cross-section permitted by navigational and environmental constraints. Maximising of power available with these necessarily densely packed farms requires turbines to be tuned for a particular channel and turbine density. The optimal through-flow tuning fraction varies from near 1/3 for small farms occupying a small fraction of the cross-section, to near 1 for large farms occupying most of the cross-section. Consequently, tunings are higher than the optimal through-flow tuning of 1/3 for an isolated turbine from the classic turbine theory. Large optimally tuned farms can realise most of a channel's potential. Optimal tunings are dependent on the number of turbines per row, the number of rows, as well as the channel geometry, the background bottom friction coefficient and the tidal forcing.
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Vogel, C. R., and R. H. J. Willden. "Designing multi-rotor tidal turbine fences." International Marine Energy Journal 1, no. 1 (Aug) (2018): 61–70. http://dx.doi.org/10.36688/imej.1.61-70.
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An embedded Reynolds-Averaged Navier-Stokes blade element actuator disk model is used to investigate the hydrodynamic design of tidal turbines and their performance in a closely spaced cross-stream fence. Turbines designed for confined flows are found to require a larger blade solidity ratio than current turbine design practices imply in order to maximise power. Generally, maximum power can be increased by operating turbines in more confined flows than they were designed for, although this also requires the turbines to operate at a higher rotational speed, which may increase the likelihood of cavitation inception. In-array turbine performance differs from that predicted from single turbine analyses, with cross-fence variation in power and thrust developing between the inboard and outboard turbines. As turbine thrust increases the cross-fence variation increases, as the interference effects between adjacent turbines strengthen as turbine thrust increases, but it is observed that cross-stream variation can be mitigated through strategies such as pitch-to-feather power control. It was found that overall fence performance was maximised by using turbines designed for moderately constrained (blocked) flows, with greater blockage than that based solely on fence geometry, but lower blockage than that based solely on the turbine and local flow passage geometry to balance the multi-scale flow phenomena around tidal fences.
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GARRETT, CHRIS, and PATRICK CUMMINS. "The efficiency of a turbine in a tidal channel." Journal of Fluid Mechanics 588 (September 24, 2007): 243–51. http://dx.doi.org/10.1017/s0022112007007781.
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There is an upper bound to the amount of power that can be generated by turbines in tidal channels as too many turbines merely block the flow. One condition for achievement of the upper bound is that the turbines are deployed uniformly across the channel, with all the flow through them, but this may interfere with other uses of the channel. An isolated turbine is more effective in a channel than in an unbounded flow, but the current downstream is non-uniform between the wake of the turbines and the free stream. Hence some energy is lost when these streams merge, as may occur in a long channel. We show here, for ideal turbine models, that the fractional power loss increases from 1/3 to 2/3 as the fraction of the channel cross-section spanned by the turbines increases from 0 to close to 1. In another scenario, possibly appropriate for a short channel, the speed of the free stream outside the turbine wake is controlled by separation at the channel exit. In this case, the maximum power obtainable is slightly less than proportional to the fraction of the channel cross-section occupied by turbines.
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VENNELL, ROSS. "Tuning tidal turbines in-concert to maximise farm efficiency." Journal of Fluid Mechanics 671 (March 7, 2011): 587–604. http://dx.doi.org/10.1017/s0022112010006191.
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Tuning is essential to maximise the output of turbines extracting power from tidal currents. To realise a large fraction of a narrow channel's potential, rows of turbines not only have to be tuned for a particular tidal channel, they must also be tuned in the presence of all the other rows, i.e. ‘tuned in-concert’. The necessity for in-concert tuning to maximise farm efficiency occurs because the tuning of any one row affects a channel's total drag coefficient and hence the flow through all other rows. Surprisingly, in several circumstances the optimal in-concert tunings are the same or almost the same for all rows. Firstly, in both constricted and unconstricted channels, rows with the same turbine density have the same optimal tuning. Secondly, turbine rows in channels with a quasi-steady dynamical balance typically have almost the same optimal in-concert tunings, irrespective of their turbine density or any channel constrictions. Channel constrictions, occupying a large fraction of the cross-section or adding more rows of turbines, also make optimal tunings more uniform between rows. Adding turbines to a cross-section increases a farm's efficiency. However, in a law of diminishing returns for quasi-steady channels, turbine efficiency (the output per turbine) decreases as turbines are added to a cross-section. In contrast, for inertial channels with only moderate constrictions, turbine efficiency increases as turbines are added to a cross-section.
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Hoerner, Stefan, Iring Kösters, Laure Vignal, et al. "Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions." Energies 14, no. 4 (2021): 797. http://dx.doi.org/10.3390/en14040797.
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Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.
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Draper, S., T. Nishino, T. A. A. Adcock, and P. H. Taylor. "Performance of an ideal turbine in an inviscid shear flow." Journal of Fluid Mechanics 796 (April 28, 2016): 86–112. http://dx.doi.org/10.1017/jfm.2016.247.
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Although wind and tidal turbines operate in turbulent shear flow, most theoretical results concerning turbine performance, such as the well-known Betz limit, assume the upstream velocity profile is uniform. To improve on these existing results we extend the classical actuator disc model in this paper to investigate the performance of an ideal turbine in steady, inviscid shear flow. The model is developed on the assumption that there is negligible lateral interaction in the flow passing through the disc and that the actuator applies a uniform resistance across its area. With these assumptions, solution of the model leads to two key results. First, for laterally unbounded shear flow, it is shown that the normalised power extracted is the same as that for an ideal turbine in uniform flow, if the average of the cube of the upstream velocity of the fluid passing through the turbine is used in the normalisation. Second, for a laterally bounded shear flow, it is shown that the same normalisation can be applied, but allowance must also be made for the fact that non-uniform flow bypassing the turbine alters the background pressure gradient and, in turn, the turbines ‘effective blockage’ (so that it may be greater or less than the geometric blockage, defined as the ratio of turbine disc area to cross-sectional area of the flow). Predictions based on the extended model agree well with numerical simulations approximating the incompressible Euler equations. The model may be used to improve interpretation of model-scale results for wind and tidal turbines in tunnels/flumes, to investigate the variation in force across a turbine and to update existing theoretical models of arrays of tidal turbines.
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Bennecke, Timo, Shokoofeh Abbaszadeh, Karla Ruiz-Hussmann, et al. "Methodology to capture the single blade loads on a cross-flow tidal turbine flume model." International Marine Energy Journal 8, no. 2 (2025): 197–206. https://doi.org/10.36688/imej.8.197-206.
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The OPTIDE project aims to improve the efficiency and durability of hydrokinetic cross-flow tidal turbines (CFTT). CFTT are attractive for the exploitation of tidal energy, because of high area-based power densities of such turbine arrays, a simple design and the ability to operate under varying flow conditions.Nevertheless, the efficiency of single CFTT is lower relative to the most commonly used axial turbine type. Furthermore the life time is often limited due to alternating and pulsating stresses.A promising approach to overcome these drawbacks is intracycle blade pitching. In this case the angle of attack is continuously adjusted individually for each blade during the rotation. The project aims to explore the influence of active blade pitching on CFTTs and to optimize it by numerical and experimental means.Therefore, a lab-scaled three-bladed experimental turbine with embedded pitch actuators is developed.The turbine is equipped with multiple full-bridges of strain gauges for the detection of tangential and radial components of the blade loads, from which the structural stress is calculated subsequently.To ensure the turbines mechanical durability, weakly coupled fluid-solid-interaction (FSI) simulations have been performed. Additionally, the FSI simulations show that a setup with strain gauges on a single blade support only allows for the measurement of the radial blade load component, as the measurements are distorted by pitching moments and secondary force paths.A revised instrumentation setup is developed and presented. The FSI simulations are adapted, to prove the suitability of the revised setup.
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Ruiz-Hussmann, Karla, Pierre-Luc Delafin, Cyrille Bonamy, Yves Delannoy, Dominique Thévenin, and Stefan Hoerner. "Objective Functions for the Blade Shape Optimisation of a Cross-Flow Tidal Turbine under Constraints." International Marine Energy Journal 8, no. 1 (2025): 47–55. https://doi.org/10.36688/imej.8.47-55.
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Hydro-kinetic cross-flow tidal turbines (CFTT) are omni-directional and offer higher area-based power density compared to horizontal-axis tidal turbines, making them very attractive for tidal energy exploitation. However, the rotating motion around the vertical axis results in continuously varying angles of attack, causing alternating loads, which may lead to fatigue failure and structural damage. The OPTIDE Project addresses these challenges by implementing intracycle blade pitching to individually control the angle of attack, increasing the power coefficient CP and reducing structural loads. For this purpose a Darrieus turbine is designed with embedded actuators in each blade. Firstly a blade shape optimization will be conducted to fit the actuator at the quarter-chord position while ensuring sufficient thickness. The optimization procedure couples Computational Fluid Dynamics (CFD) with a Genetic Algorithm. The employed optimizer OPAL++ sets ten variables for each individual, which describe the hydrofoil shape, length and tip speed ratio (TSR). A smooth hydrofoil shape is generated from the variables, followed by an automatic mesh generation. Subsequently, numerical simulations of each individual at the desired TSR are conducted, while keeping the blade pitch angle constant. Simulation results provide the CP and stress acting on the turbine blades, which are the two optimization objectives (maximize CP while minimizing stress). This process is repeated during the optimization, aiming to determine the most suitable blade shape, that fits the actuator, and operating point (TSR) in a trade-off between CP and structural loads. This will lead to the increase of efficiency and a longer turbine lifetime.
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Nishino, Takafumi, and Richard H. J. Willden. "The efficiency of an array of tidal turbines partially blocking a wide channel." Journal of Fluid Mechanics 708 (August 20, 2012): 596–606. http://dx.doi.org/10.1017/jfm.2012.349.
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AbstractA new theoretical model is proposed to explore the efficiency of a long array of tidal turbines partially blocking a wide channel cross-section. An idea of scale separation is introduced between the flow around each device (or turbine) and that around the entire array to assume that all device-scale flow events, including ‘far-wake’ mixing behind each device, take place much faster than the horizontal expansion of the flow around the entire array. This assumption makes it possible to model the flow as a combination of two quasi-inviscid problems of different scales, in both of which the conservation of mass, momentum and energy is considered. The new model suggests the following: when turbines block only a small portion of the span of a shallow channel cross-section, there is an optimal intra-turbine spacing to maximize the efficiency (limit of power extraction) for a given channel height and width. The efficiency increases as the spacing is reduced to the optimal value due to the effect of local blockage, but then decreases as the spacing is further reduced due to the effect of array-scale choking, i.e. reduced flow through the entire array. Also, when the channel is infinitely wide, the efficiency depends solely on the local area blockage rather than on the combination of the intra-turbine spacing and the channel height. As the local blockage is increased, the efficiency increases from the Lanchester–Betz limit of 0.593 to another limiting value of 0.798, but then decreases as the local blockage is further increased.
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Rahmani, Hamid, Mojtaba Biglari, Mohammad Sadegh Valipour, and Kamran Lari. "Assessment of the numerical and experimental performance of screw tidal turbines." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 7 (2018): 912–25. http://dx.doi.org/10.1177/0957650917753778.
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This study was aimed at the numerical and experimental modeling of water flow during collision between water and vertical screw turbine blades with different cross sections (i.e. Darrieus, spoon, and airfoil). ANSYS Fluent was used to model water flow under tidal currents in a flume, and mesh independence was ensured after the selection of appropriate geometry. The collision problem was then solved in the transient state, and results on the momentum and power generated by different inlet velocities and different blade cross sections were analyzed. The findings showed that torque and turbine power increased with increasing inlet velocity. Subsequently, a turbine was experimentally created, with cross sections drawn in the numerical model and tested under the same conditions as that imposed on the model. Installing a multimeter on the turbine enabled the generation of turbine power in different dimensions. The resultant power increased with rising turbine dimensions. After obtaining the numerical and experimental results, the value of the output power of the turbine was validated. The validation indicated a 7% difference in output power between the numerical and experimental results, indicating acceptable accuracy.
Dissertations / Theses on the topic "Cross-Flow tidal turbine"
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Consul, Claudio Antonio. "Hydrodynamic analysis of a tidal cross-flow turbine." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:0f9c201f-882d-4f44-b4c6-96f7658b1621.
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This study presents a numerical investigation of a generic horizontal axis cross-flow marine turbine. The numerical tool used is the commercial Computational Fluid Dynamics package ANSYS FLUENT 12.0. The numerical model, using the SST k-w turbulence model, is validated against static, dynamic pitching blade and rotating turbine data. The work embodies two main investigations. The first is concerned with the influence of turbine solidity (ratio of net blade chord to circumference) on turbine performance, and the second with the influence of blockage (ratio of device frontal area to channel crosssection area) and free surface deformation on the hydrodynamics of energy extraction in a constrained channel. Turbine solidity was investigated by simulating flows through two-, three- and four-bladed turbines, resulting in solidities of 0.019, 0.029 and 0.038, respectively. The investigation was conducted for two Reynolds numbers, Re = O(10^5) & O(10^6), to reflect laboratory and field scales. Increasing the number of blades from two to four led to an increase in the maximum power coefficient from 0.43 to 0.53 for the lower Re and from 0.49 to 0.56 for the higher Re computations. Furthermore, the power curve was found to shift to a lower range of tip speed ratios when increasing solidity. The effects of flow confinement and free surface deformation were investigated by simulating flows through a three-bladed turbine with solidity 0.125 at Re = O(10^6) for channels that resulted in cross-stream blockages of 12.5% to 50%. Increasing the blockage led to a substantial increase in the power and basin efficiency; when approximating the free surface as a rigid lid, the highest power coefficient and basin efficiency computed were 1.18 and 0.54, respectively. Comparisons between the corresponding rigid lid and free surface simulations, where Froude number, Fr = 0.082, rendered similar results at the lower blockages, but at the highest blockage an increase in power and basin efficiency of up to 7% for the free surface simulations over that achieved with a rigid lid boundary condition. For the free surface simulations with Fr = 0.082, the energy extraction resulted in a drop in water depth of up to 0.7%. An increase in Fr from 0.082 to 0.131 resulted in an increase maximum power of 3%, but a drop in basin efficiency of 21%.
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Stringer, Robert. "Numerical investigation of cross-flow tidal turbine hydrodynamics." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760981.
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The challenge of tackling global climate change and our increasing reliance on power means that new and diverse renewable energy generation technologies are a necessity for the future. From a number of technologies reviewed at the outset, the cross-flow tidal turbine was chosen as the focus of the research. The numerical investigation begins by choosing to model flow around a circular cylinder as a challenging benchmarking and evaluation case to compare two potential solvers for the ongoing research, ANSYS CFX and OpenFOAM. A number of meshing strategies and solver limitations are extracted, forming a detailed guide on the topic of cylinder lift, drag and Strouhal frequency prediction in its own right. An introduction to cross-flow turbines follows, setting out turbine performance coefficients and a strategy to develop a robust numerical modelling environment with which to capture and evaluate hydrodynamic phenomena. The validation of a numerical model is undertaken by comparison with an experimentally tested lab scale turbine. The resultant numerical model is used to explore turbine performance with varying Reynolds number, concluding with a recommended minimum value for development purposes of Re = 350 × 103 to avoid scalability errors. Based on this limit a large scale numerical simulation of the turbine isconducted and evaluated in detail, in particular, a local flow sampling method is proposed and presented. The method captures flow conditions ahead of the turbine blade at all positions of motion allowing local velocities and angles of attack to be interrogated. The sampled flow conditions are used in the final chapter to construct a novel blade pitching strategy. The result is a highly effective optimisation method which increases peak turbine power coefficient by 20% for only two further case iterations of the numerical solution.
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Moreau, Martin. "Comportement d'une hydrolienne carénée à double axe vertical dans une diversité de conditions d'écoulement en mer et en bassin d'essais." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN028.
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Limiter le réchauffement climatique nécessite, entre autres adaptations, une réduction substantielle de l'utilisation des énergies fossiles et une électrification généralisée basée sur des systèmes de production faiblement émetteurs de gaz à effet de serre. Dans ce contexte, l'exploitation de l'énergie des courants de marée et autres énergies marines renouvelables gagne en intérêt. Ainsi, la dernière décennie a vu les premiers essais en mer de plusieurs concepts d'hydroliennes. Parmi eux, la première hydrolienne carénée à double axe vertical de 1 mégawatt, développée par HydroQuest, a été testée au large de l'île de Bréhat, en Bretagne, de 2019 à 2021. Dans la perspective des prochaines générations de turbines, l'entreprise souhaite améliorer ses outils de conception expérimentaux et numériques afin de gagner en confiance dans sa capacité à prédire les performances et les chargements mécaniques à l'échelle réelle à partir des expériences à échelle réduite. Cela ne peut se faire qu'en comparant les résultats obtenus en mer à ceux obtenus en laboratoire afin d'évaluer les potentiels effets d'échelle. Par conséquent, nous commençons ce mémoire par l'analyse des mesures en mer pour caractériser le comportement du prototype in-situ. Ensuite, nous étudions la réponse d'une maquette à l'échelle 1/20 de ce prototype à partir d'essais réalisés dans le bassin à houle et courant de l'Ifremer à Boulogne-sur-mer. Nous considérons de nombreuses conditions d'écoulement, allant de conditions idéales vers des conditions plus complexes et réalistes. Au-delà de la comparaison des résultats entre échelle réduite et échelle réelle, les analyses présentées dans cette thèse visent également à mieux comprendre l'influence de chacune des caractéristiques de l'écoulement des courants de marée sur le comportement de l'hydrolienne carénée. À partir de mesures de puissance, d'efforts et de sillage, nous étudions les effets du cisaillement de l'écoulement incident, de sa direction relative, de la turbulence générée par des obstacles bathymétriques et des vagues en surface sur la réponse de la maquette. Les résultats montrent que la génération de puissance est, en moyenne, insensible aux conditions d'écoulement incidentes alors que les fluctuations de puissance et d'efforts peuvent être fortement affectées. Enfin, nous discutons des effets d'échelle, notamment de l'influence du nombre de Reynolds, en comparant les résultats en bassin d'essais à ceux obtenus sur le prototype en mer. Les résultats permettent d'affiner la correction qu'il convient d'appliquer aux mesures à échelle réduite pour prédire la génération de puissance à échelle réelle. Bien que les efforts et le sillage semblent moins affectés par les effets visqueux, une comparaison détaillée avec les résultats à échelle réelle nécessiterait des améliorations sur les mesures en mer afin de mieux quantifier les potentiels effets d'échelle. Ces améliorations pourront être mises en œuvre dans les années à venir avec le lancement de la prochaine génération d'hydroliennes à double axe vertical<br>Limiting human-caused global warming requires, among other adaptations, a substantial reduction of fossil fuel use and a widespread electrification based on low greenhouse gas emission production systems. In this context, harnessing the tidal current energy and other marine renewable energy sources has gained interest for the last decade, which lead to the first offshore tests for several tidal energy converter concepts. Among them, the first 1 megawatt ducted twin vertical axis tidal turbine prototype, developed by HydroQuest, was tested off the northern coast of Brittany, France, from 2019 to 2021. In the prospect of the next turbine generations, the company wants to improve its experimental and numerical design tools to gain confidence in its capacity to predict the full-scale performance and loads from the experiments at reduced-scale. That can only be done by comparing the results obtained at sea to those obtained in the laboratories to assess the potential scale effects. Therefore, we first analyse the measurements at sea to characterise the behaviour of the prototype. Then, we study the response of a 1/20 scale model of that prototype tested in the Ifremer wave and current flume tank in Boulogne-sur-mer, France. We consider many flow conditions, increasing the complexity from idealised towards more realistic conditions. Beyond the comparison between reduced- and full-scale results, the analyses presented in that thesis also aim at better understanding the influence of each of the tidal current flow characteristics on the ducted turbine. In more details, from power performance, loads and wake measurements, we study the effects of the incident flow shear, of the relative flow direction, of the turbulence generated by bathymetry obstacles and of surface waves on the model response. The results show that the average power performance is rather insensitive to the incident flow conditions whereas the power and load fluctuations can be strongly affected. Finally, we discuss the scale effects on the results by comparing the power performance, the loads and the wake results in the tank with those obtained on the prototype at sea. The results allow to refine the evaluation of the correction needed at reduced-scale to predict the power performance at full-scale, mainly due to Reynolds number difference. Even if the loads and the wake results seem less affected by the viscous effects, a detailed comparison with the full-scale results would require improvements on the measurements at sea to better quantify the potential scale effects. Those improvements may be implemented in the coming years with the launch of the next generation of twin vertical axis tidal turbines
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Garcia-Oliva, Miriam. "The impact of tidal stream farms on flood risk in estuaries." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/22972.
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There is a growing interest in tidal energy, owing to its predictable nature in comparison to other renewable sources. In the case of the UK, its importance also lies on the availability of exploitable areas as well as their total capacity, which is estimated to cover more than 20% of the country demand. However, the level of development of this kind of technology is still far behind other types of renewable energy. However, several studies focused on a variety of individual devices, followed by more recent research on the deployment of large arrays or tidal farms. Potential sites for energy extraction can be found in narrows between islands and the coast or estuaries. The latter present some advantages for the installation and the connection to the grid but estuaries are often prone to flood risk from tides and surges. Therefore, the objective of this thesis is to evaluate the effect that very large groups of turbines could have on peak water levels during flooding events in the case of being deployed in estuarine areas. For that purpose, a new methodology has been developed, which implies the use of a numerical model (MIKE 21 by DHI), and it has been demonstrated against a real case study in the UK: the Solway Firth estuary. Another objective has consisted of integrating in this thesis the results from detailed CFD modelling and optimisation techniques involved in the project. A literature review has been carried out in order to identify the current state of the art for the different subjects considered in the thesis. Different aspects of the numerical model used for this study (MIKE 21) have been presented and the modelling of the turbines within the code has been validated against experimental and CFD data. The procedure to include large numbers of turbines in the code is also developed. An analysis has been done of the different estuaries existing in the UK suitable for tidal energy extraction, identifying their main geometrical features. Based on this, idealised models of estuaries have been used to assess the influence that the channel geometry could have on the impact of tidal farms under extreme water levels. The effect has been measured by comparing the results of the numerical model between the case with and without turbines under different flooding scenarios. Finally, the same methodology has been applied to a real case study selected from the previous group of estuaries namely the Solway Firth. An initial model has been created, according to the available data at the start of the research, which contained some errors related to the water depth at the intertidal areas in the upper estuary. Therefore, when a more realistic dataset became available, an improved model was created. The improved model has been used to assess the effects of tidal farms in the estuary under a coastal flooding event. It is concluded that there is significant influence of the channel geometry over the locations where the maximum changes in water levels due to the tidal farms will happen. Nevertheless, the effects seem to be more relevant in terms of the decrease rather than the increase of peak water levels for all geometries and the maximum changes seem to be in the order of dm. This is in agreement with the results of the Solway Firth models and can be summarised as a positive net effect over flood risk. On the other hand, a concern has been raised about the impact on intertidal areas, which could be the subject of future research.
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Ferrer, Esteban. "A high order Discontinuous Galerkin - Fourier incompressible 3D Navier-Stokes solver with rotating sliding meshes for simulating cross-flow turbines." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:db8fe6e3-25d0-4f6a-be1b-6cde7832296d.
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This thesis details the development, verification and validation of an unsteady unstructured high order (≥ 3) h/p Discontinuous Galerkin - Fourier solver for the incompressible Navier-Stokes equations on static and rotating meshes in two and three dimensions. This general purpose solver is used to provide insight into cross-flow (wind or tidal) turbine physical phenomena. Simulation of this type of turbine for renewable energy generation needs to account for the rotational motion of the blades with respect to the fixed environment. This rotational motion implies azimuthal changes in blade aero/hydro-dynamics that result in complex flow phenomena such as stalled flows, vortex shedding and blade-vortex interactions. Simulation of these flow features necessitates the use of a high order code exhibiting low numerical errors. This thesis presents the development of such a high order solver, which has been conceived and implemented from scratch by the author during his doctoral work. To account for the relative mesh motion, the incompressible Navier-Stokes equations are written in arbitrary Lagrangian-Eulerian form and a non-conformal Discontinuous Galerkin (DG) formulation (i.e. Symmetric Interior Penalty Galerkin) is used for spatial discretisation. The DG method, together with a novel sliding mesh technique, allows direct linking of rotating and static meshes through the numerical fluxes. This technique shows spectral accuracy and no degradation of temporal convergence rates if rotational motion is applied to a region of the mesh. In addition, analytical mappings are introduced to account for curved external boundaries representing circular shapes and NACA foils. To simulate 3D flows, the 2D DG solver is parallelised and extended using Fourier series. This extension allows for laminar and turbulent regimes to be simulated through Direct Numerical Simulation and Large Eddy Simulation (LES) type approaches. Two LES methodologies are proposed. Various 2D and 3D cases are presented for laminar and turbulent regimes. Among others, solutions for: Stokes flows, the Taylor vortex problem, flows around square and circular cylinders, flows around static and rotating NACA foils and flows through rotating cross-flow turbines, are presented.
Book chapters on the topic "Cross-Flow tidal turbine"
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Ferrer, Esteban, and Soledad Le Clainche. "Simple Models for Cross Flow Turbines." In Recent Advances in CFD for Wind and Tidal Offshore Turbines. Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-11887-7_1.
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Gaba, Vivek Kumar, and Shubhankar Bhowmick. "A CFD-based study of cross-flow turbine for tidal energy extraction." In Sustainable Engineering Products and Manufacturing Technologies. Elsevier, 2019. http://dx.doi.org/10.1016/b978-0-12-816564-5.00007-4.
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Furukawa, Akinori, and Kusuo Okuma. "On Applicability of Darrieus-type Cross Flow Water Turbine for Abandoned Hydro and Tidal Powers." In World Renewable Energy Congress VI. Elsevier, 2000. http://dx.doi.org/10.1016/b978-008043865-8/50577-8.
Full textConference papers on the topic "Cross-Flow tidal turbine"
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Bates, Patrick, Jerod Ketchum, Richard Kimball, and Michael Peterson. "Experimental Characterization of High Solidity Cross-Flow and Axial Flow Tidal Turbines." In SNAME 29th American Towing Tank Conference. SNAME, 2010. http://dx.doi.org/10.5957/attc-2010-033.
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This paper outlines the experimental testing of high solidity cross-flow type hydrokinetic turbines in the towing tank at the University of Maine and axial flow turbines tested at MIT. These turbines are being developed for commercial scale tidal energy production at megawatt scale tidal energy sites. Details of the testing apparatus, experimental methods, instrumentation and data are presented. Hydrokinetic turbines extract the kinetic energy of a flowing stream and therefore differ from the more conventional head based hydroelectric turbine systems. Hydrokinetic energy farms have more resemblance to a wind farm placed underwater. The testing of such devices in scale model in Tow tanks presents special problems but is similar in many respects to the testing and characterization of propeller performance. Tow tanks provide excellent simulation of a flowing stream, providing a valuable experimental tool in the development of high performance, efficient hydrokinetic turbines. Important to the characterization of hydrokinetic turbines is the power extraction efficiency (in the form of power coefficient) versus the turbine tip speed ratio. In order to fully characterize the cross-flow turbine, a highly quality sensitive dynamometer and load control system has been implemented which addresses the issue of starting and maintaining a constant load on the turbine during the tow tank run. This system allows for a full range of performance data to be collected at a range of loading conditions. In addition the force data on the rotor is encoded so the phase-averaged force data versus rotation position can be collected. The details of the design of the instrumentation and control system are presented along with samples of the data collected. In addition the development and construction of a similar dynamometer for the testing of axial flow turbines is presented. Data is presented for a cross-flow turbine of relatively high blade solidity ratio (blade area greater than 20% of cylinder area). Though data for lower solidity ratio cross flow turbines have been frequently published, this work presents data for turbines with high blade area that are being developed for hydrokinetic applications. The data is being used to validate and improve numerical design models based on the vortex lattice method as a design tool for high solidity ratio tidal turbines. Prior numerical models were accurate in predicting performance of low solidity designs but suffered when solidity exceeded 20%. Results of the numerical models versus experimental data are presented for both overall performance measures as well as detailed phase averaged forces. Test data is also presented for an axial flow turbine designed by the numerical code OpenProp. The turbine was tested on the Axial flow dynamometer at the MIT water tunnel. The testing methodologies presented in this paper are also being utilized to draft engineering guidelines and procedures for the testing of scale model hydrokinetic turbines. Some discussion of the standards development activities underway and the relevance of this work to those efforts is discussed.
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Zhao, Ruiwen, Angus C. W. Creech, Alistair G. L. Borthwick, Takafumi Nishino, and Vengatesan Venugopal. "Numerical Model of a Vertical-Axis Cross-Flow Tidal Turbine." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18514.
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Abstract An array of close-packed contra-rotating cross-flow vertical-axis tidal rotors, a concept developed to maximize the fraction of flow passage swept, has potential advantages for hydrokinetic power generation. To predict the commercial feasibility of such rotors in large-scale application, a numerical model of a vertical-axis turbine (VAT) with a torque-controlled system is developed using an actuator line model (ALM). The open-source OpenFOAM computational fluid dynamics (CFD) code is first coupled with this ALM model, and efficiently parallelized to examine the characteristics of turbulent flow behind a vertical axis tidal turbine. The numerical model is validated against previous experimental measurements from a 1:6 scale physical model of a three-bladed reference vertical axis tidal turbine at the University of New Hampshire (UNH-RM2). Satisfactory overall agreement is obtained between numerical predictions and measured data on performance and near-wake characteristics, validating the numerical model. Details of the model setup and discussions on its output/results are included in the paper.
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Walsh, G. P., R. Keough, V. Mullaley, H. Sinclair, and M. J. Hinchey. "Cross-flow helical turbine for energy production in reversing tidal and ocean currents." In OCEANS 2014. IEEE, 2014. http://dx.doi.org/10.1109/oceans.2014.7003267.
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Polagye, Brian L., Robert J. Cavagnaro, and Adam L. Niblick. "Micropower From Tidal Turbines." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16604.
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In addition to utility-scale power generation (e.g., rated capacities greater than 106 W), there are also possibilities for tidal current generation at the micro-scale (e.g., rated capacities less than 102 W) that could provide power to autonomous oceanographic instrumentation. This paper presents performance characteristics of a high-solidity, helical, cross-flow turbine rotor for a tidal current micropower system. Studies are conducted on a 1/4-scale turbine in a laboratory flume and a full-scale turbine prototype using open-water tows. Results suggest this type of turbine rotor can achieve efficiencies as high as 25% and can smoothly self-start at water velocities less than 0.5 m/s. The sharp peak around optimal efficiency displayed by the power performance curves suggests a need for generator control in a micropower system using this type of rotor.
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Johnston, Alex, and Martin Wosnik. "Analytical and Numerical Modeling of Performance Characteristics of Cross-Flow Axis Hydrokinetic Turbines." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-07021.
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A model for cross-flow axis hydrokinetic turbines based on blade element theory (BET) was developed. The model combines an extensive experimental and numerical high Reynolds number data set for symmetric airfoils with governing equations to predict performance characteristics of the turbines. The model allows for any number of turbine blades and for variable hydrofoil sweep angles; both straight blade (H-Darrieus) and helical blade (Gorlov) cross-flow axis turbines are modeled. In this model the free stream velocity and the turbine’s rate of rotation are not coupled hydrodynamically, and experimental calibration of the model for a specific turbine design is necessary. The calibrated model is then used with real inflow data from an actual tidal energy site to predict instantaneous power and energy yield over a period of time. Investigation of tip speed ratios allows for predictions of unsteady loadings, optimal performance and power outputs. The model provides the versatility to predict characteristics of many different shapes and sizes of cross-flow axis turbines. Through investigation of turbine stall characteristics predicted by the model, two, turbine-specific tip speed ratios of interest were determined: the critical and optimal tip speed ratios. The “critical tip speed ratio” is defined as the tip speed ratio above which there are no longer regions of negative torque during the turbine rotation. The “optimal tip speed ratio” is defined as the tip speed ratio for which the coefficient of torque, averaged over one rotation, is maximized. It is hypothesized that these tip speed ratios correspond to specific turbine operating points: A turbine operating under no load conditions will spin near the optimal tip speed ratio, and a turbine operating at peak power conditions will spin near the critical tip speed ratio.
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Hosseini, Arian, and Navid Goudarzi. "CFD Analysis of a Cross-Flow Turbine for Wind and Hydrokinetic Applications." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88469.
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Tidal current and wind energies have become dominant sources of renewable energies in the modern culture. In this work, the aerodynamic characteristics of a novel hybrid vertical axis turbine (VAT) have been studied in flow fields of water and air using CFD analyses. A parametric study was conducted on the hybrid rotor design with the goal of optimizing the solidity ratio to cover a wide operation range, increase initial torque and maintain high coefficient of power values. The hybrid turbine design with a solidity ratio of 0.5 demonstrated improvements to the self-startup feature and achieved the highest coefficient of power (Cp) values of 44.5% and 50% in air and water flows, respectively. The results were in favor of utilizing this design in flow fields of water and air as an enhancement to previous literature. Further studies are required to assess the aerodynamic properties of the model in 3D CFD analyses.
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Schnabl, Andrea M., Tulio Marcondes Moreira, Dylan Wood, et al. "Implementation of Tidal Stream Turbines and Tidal Barrage Structures in DG-SWEM." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95767.
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Abstract There are two approaches to extracting power from tides — either turbines are placed in areas of strong flows or turbines are placed in barrages enabling the two sides of the barrage to be closed off and a head to build up across the barrage. Both of these energy extraction approaches will have a significant back effect on the flow, and it is vital that this is correctly modelled in any numerical simulation of tidal hydrodynamics. This paper presents the inclusion of both tidal stream turbines and tidal barrages in the depth-averaged shallow water equation model DG-SWEM. We represent the head loss due to tidal stream turbines as a line discontinuity — thus we consider the turbines, and the energy lost in local wake-mixing behind the turbines, to be a sub-grid scale processes. Our code allows the inclusion of turbine power and thrust coefficients which are dependent on Froude number, turbine blockage, and velocity, but can be obtained from analytical or numerical models as well as experimental data. The barrage model modifies the existing culvert model within the code, replacing the original cross-barrier pipe equations. At the location of this boundary, velocities through sluice gates are calculated according to the orifice equation. For simulating the turbines, a Hill Chart for low head bulb turbines provided by Andritz Hydro is used. We demonstrate the implementations on both idealised geometries where it is straightforward to compare against other models and numerical simulations of real candidate sites for tidal energy in Malaysia and the Bristol Channel.
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Karsten, Richard. "An Assessment of the Potential of Tidal Power From Minas Passage, Bay of Fundy, Using Three-Dimensional Models." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49249.
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Large tidal currents exist in Minas Passage, which connects Minas Basin to the Bay of Fundy off the northwestern coast of Nova Scotia. The strong currents through this deep, narrow channel make it a promising location for the generation of electrical power using instream turbines. These strong currents are clearly illustrated in the results of a high-resolution, three-dimensional model of the flow through Minas Passage presented here. The simulations also clearly indicate the asymmetry of the flood and ebb tides and the 3D structure of the flow. A previous study has indicated that as much as 7000 MW could be extracted from the tidal currents through Minas Passage. However, this estimate was based on a complete fence of turbines across the passage, in essence a tidal barrage. In this paper, the power potential of partial turbine fences is examined. In order to estimate the power potential of turbine arrays, the theory of partial turbine fences is adapted to the particular dynamics of Minas Passage. The theory estimates the potential power of the fence and the change in flow that would result. The results are presented in terms of the portion of the cross-sectional area that the turbines occupy and the drag coefficient of the turbines. When the turbine fence occupies a large portion of the passage, the potential power of the fence rises significantly, to a value much larger than estimates based on the kinetic energy flux. The increase in power comes from the increased tidal head that a large turbine fence creates and the resulting increase in the turbine drag. We also present the efficiency of the turbine fence — given as the ratio of the power associated with the turbine drag over the total power extracted from the flow — and the impact of the turbines on the tidal flow. The results of the theory are compared to numerical simulations of the flow through the passage with turbines represented as regions of increased drag. The numerical simulations give power values that are three to six time as high as the theory suggests is possible. This discrepancy is examined by plotting the changes in tidal currents caused by the turbine fence.
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Shimizu, Seiji, Masayuki Fujii, Tetsuya Sumida, et al. "Starting System for Darrieus Water Turbine of Tidal Stream Electricity Generation." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-55143.
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Darrieus type vertical axis water turbine in a cylindrical shape which consists of some straight blades is simple, efficient and easy to install a generator upward. However, it has difficulty in starting revolution. As a method to cope with such a problem, a starting revolution assist mechanism was fabricated and set on a prototype of the turbine. Assist experiment was carried out. It resulted helping well the starting revolution. The improved prototype of tidal stream turbine can generate 1.4 W under a water flow of 1 m/s where impossible to self-start. Besides that, Darrieus water turbine’s generating torque property was investigated by the famous original experimental data of lift coefficient Cl and drag coefficient Cd for straight blades of NACA63 3-018 cross section. It was found that setting two or four blades in a turbine would help to improve the difficulty of starting revolution.
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Gorlov, Alexander M. "The Helical Turbine and Its Applications for Hydropower Without Dams." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33193.
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The objective of this paper is to introduce an environmentally friendly Helical Turbine that has been developed to operate in free or ultra low-head water currents without dams. The turbine is a cross flow unidirectional rotation machine that makes it particularly valuable for ocean applications, such as reversible tidal streams in ocean bays, estuaries and canals, streams in open ocean, underwater currents generated by wave fluctuations etc.