Articoli di riviste sul tema "Cross-Flow tidal turbine"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Cross-Flow tidal turbine.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 articoli di riviste per l'attività di ricerca sul tema "Cross-Flow tidal turbine".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
VENNELL, ROSS. "Tuning turbines in a tidal channel". Journal of Fluid Mechanics 663 (12 ottobre 2010): 253–67. http://dx.doi.org/10.1017/s0022112010003502.
Abstract (sommario):
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.
2
Vogel, C. R., e R. H. J. Willden. "Designing multi-rotor tidal turbine fences". International Marine Energy Journal 1, n. 1 (Aug) (3 settembre 2018): 61–70. http://dx.doi.org/10.36688/imej.1.61-70.
Abstract (sommario):
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.
3
GARRETT, CHRIS, e PATRICK CUMMINS. "The efficiency of a turbine in a tidal channel". Journal of Fluid Mechanics 588 (24 settembre 2007): 243–51. http://dx.doi.org/10.1017/s0022112007007781.
Abstract (sommario):
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.
4
VENNELL, ROSS. "Tuning tidal turbines in-concert to maximise farm efficiency". Journal of Fluid Mechanics 671 (7 marzo 2011): 587–604. http://dx.doi.org/10.1017/s0022112010006191.
Abstract (sommario):
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.
5
Hoerner, Stefan, Iring Kösters, Laure Vignal, Olivier Cleynen, Shokoofeh Abbaszadeh, Thierry Maître e Dominique Thévenin. "Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions". Energies 14, n. 4 (3 febbraio 2021): 797. http://dx.doi.org/10.3390/en14040797.
Abstract (sommario):
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.
6
Draper, S., T. Nishino, T. A. A. Adcock e P. H. Taylor. "Performance of an ideal turbine in an inviscid shear flow". Journal of Fluid Mechanics 796 (28 aprile 2016): 86–112. http://dx.doi.org/10.1017/jfm.2016.247.
Abstract (sommario):
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.
7
Nishino, Takafumi, e Richard H. J. Willden. "The efficiency of an array of tidal turbines partially blocking a wide channel". Journal of Fluid Mechanics 708 (20 agosto 2012): 596–606. http://dx.doi.org/10.1017/jfm.2012.349.
Abstract (sommario):
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.
8
Rahmani, Hamid, Mojtaba Biglari, Mohammad Sadegh Valipour e 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, n. 7 (22 gennaio 2018): 912–25. http://dx.doi.org/10.1177/0957650917753778.
Abstract (sommario):
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.
9
Pucci, Micol, Debora Bellafiore, Stefania Zanforlin, Benedetto Rocchio e Georg Umgiesser. "Embedding of a Blade-Element Analytical Model into the SHYFEM Marine Circulation Code to Predict the Performance of Cross-Flow Turbines". Journal of Marine Science and Engineering 8, n. 12 (9 dicembre 2020): 1010. http://dx.doi.org/10.3390/jmse8121010.
Abstract (sommario):
Our aim was to embed a 2D analytical model of a cross-flow tidal turbine inside the open-source SHYFEM marine circulation code. Other studies on the environmental impact of Tidal Energy Converters use marine circulation codes with simplified approaches: performance coefficients are fixed a priori regardless of the operating conditions and turbine geometrical parameters, and usually, the computational grid is so coarse that the device occupies one or few cells. In this work, a hybrid analytical computational fluid dynamic model based on Blade Element Momentum theory is implemented: since the turbine blades are not present in the grid, the flow is slowed down by means of bottom frictions applied to the seabed corresponding to forces equal and opposite to those that the blades would experience during their rotation. This simplified approach allowed reproducing the turbine behavior for both mechanical power generation and the turbine effect on the surrounding flow field. Moreover, the model was able to predict the interaction between the turbines belonging to a small cluster with hugely shorter calculation time compared to pure Computational Fluid Dynamics.
10
Rowell, Matthew, Martin Wosnik, Jason Barnes e Jeffrey P. King. "Experimental Evaluation of a Mixer-Ejector Marine Hydrokinetic Turbine at Two Open-Water Tidal Energy Test Sites in NH and MA". Marine Technology Society Journal 47, n. 4 (1 luglio 2013): 67–79. http://dx.doi.org/10.4031/mtsj.47.4.15.
Abstract (sommario):
AbstractFor marine hydrokinetic energy to become viable, it is essential to develop energy conversion devices that are able to extract energy with high efficiency from a wide range of flow conditions and to field test them in an environment similar to the one they are designed to eventually operate in. FloDesign Inc. developed and built a mixer-ejector hydrokinetic turbine (MEHT) that encloses the turbine in a specially designed shroud that promotes wake mixing to enable increased mass flow through the turbine rotor. A scaled version of this turbine was evaluated experimentally, deployed below a purpose-built floating test platform at two open-water tidal energy test sites in New Hampshire and Massachusetts and also in a large cross-section tow tank. State-of-the-art instrumentation was used to measure the tidal energy resource and turbine wake flow velocities, turbine power extraction, test platform loadings, and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The mean velocity deficit in the wake downstream of the turbine was found to recover more quickly with increasing levels of free stream turbulence, which has implications for turbine spacing in arrays.
11
Agit Prakoso, Sayyid Alkahfi, Tri Mulyanto e Sunyoto . "Perancangan Dan Simulasi Performa Prototipe Turbin Air Tidal Tipe Propeler Naca S814 Sebagai Sumber Energi Petani Tambak Garam Daerah Cirebon". Jurnal Pendidikan Teknik Mesin Undiksha 10, n. 1 (31 marzo 2022): 86–103. http://dx.doi.org/10.23887/jptm.v10i1.45389.
Abstract (sommario):
Telah dilakukan perancangan dan pengujian performa turbin air tidal untuk penggerak pompa di tambak garam menggunakan blade hydrofoil standar NACA S814 untuk menghasilkan desain turbin tidal, optimasi bilah turbin tidal dan juga coefficient of power (Cp) pada turbin tidal. Perancangan geometri turbin tidal menggunakan rumus yang tersedia dan pengujian turbin tidal menggunakan bantuan software Qblade. Variasi kecepatan aliran air yang pertama 1 m/s, Variasi kecepatan aliran air yang kedua 1,536 m/s, Variasi kecepatan aliran air yang ketiga 2,072 m/s, Variasi kecepatan aliran air yang keempat 2,608 m/s, Variasi kecepatan aliran air yang kelima 3,144 m/s, Variasi kecepatan aliran air yang keenam 3,68 m/s. Hasil perancangan yang didapatkan adalah panjang chord 0,02 m, panjang blade 0,4 m, diameter poros 0,16 m, diameter bilah 1,1 m, jumlah blade 3. Hasil dari pengujian performa dari turbin tidal untuk masing-masing varian kecepatan adalah 22,474; 9,136; 4,703; 2,642; 1,539; 0,900. Dari data hasil pengujian tersebut diolah dengan menggunakan metoda ANOVA. Kesimpulan yang didapatkan adalah karena nilai F (kecepatan) =2,219512 F crit =2,53355 maka tidak terdapat perbedaan hasil uji pada varian kecepatan dan karena nilai F (uji) =25,59739 F crit =2,42052 maka terdapat perbedaan hasil uji pada varian hasil.Kata kunci: ANOVA, Coefficient of Power,Turbin Tidal, QbladeThe design and performance test of a tidal water turbine for pump driving in salt ponds has been carried out using a standard NACA S814 hydrofoil blade to produce a tidal turbine design, optimization of tidal turbine blades, and also the coefficient of power (Cp) on a tidal turbine. Tidal turbine geometry design using the available formulas and tidal turbine testing using the Qblade software. The first variation of airflow velocity is 1 m/s, the variation of the second airflow velocity is 1.536 m/s, the variation of the third airflow velocity is 2.072 m/s, the variation of the fourth airflow velocity is 2.608 m/s, the fifth variation of airflow velocity is 3.144 m/s, Variation of water flow velocity 3.68 m/s. The design results obtained are chord length 0.02 m, blade length 0.4 m, shaft diameter 0.16 m, blade diameter 1.1 m, number of blades 3. The results of testing the performance of the tidal turbine for each speed variant are 22.474; 9.136; 4,703; 2,642; 1,539; 0.900. From the test results, data are processed using the ANOVA method. The conclusion obtained is because the value of F (speed) = 2.219512 < F crit = 2.53355 then there is no difference in the test results on the speed variant and because the value of F (test) = 25.59739 > F crit = 2.42052 then there is the difference in test results on the variance of results.Keywords : ANOVA, Coefficient of Power, Tidal Turbine, QbladeDAFTAR RUJUKANBaihaqiy, A. R. (2017). Prototype Pembangkit Listrik Tenaga Pasang Surut Air Laut Di Kelurahan Tugurejo Kecematan Tugu Kota Semarang. Universitas Negri Semarang.FE, M. N. S. (2016). Rancang Bangun Simulasi Turbin Air Cross Flow. Jurnal Pendidikan Teknik Mesin, 1(2).Febrianto, A., & Santoso, A. (2017). Analisa perbandingan torsi dan rpm turbin tipe darrieus terhadap efisiensi turbin. Jurnal Teknik ITS, 5(2).Fridayana, E. N. (2018). Analisis Kinerja Aerodinamik dari Vertical Axis Wind Turbine (VAWT) Darrieus Tipe H-Rotor dengan Pendekatan Computational Fluid Dynamic (CFD). Institut Teknologi Sepuluh Nopember,Ginting, J. W., & Setiawan, I. K. D. (2018). Kinerja Prototipe Papan Osilasi Pada Pompa Flap Tenaga Gelombang Untuk Pemanfaatan Mata Air Di Pantai Banyu Asri, Kota Singaraja-Bali. Jurnal Teknik Hidraulik, 9(2).Kurniawan, A., Jaziri, A. A., Amin, A. A., & Salamah, L. N. m. (2019). Indeks Kesesuaian Garam (IKG) Untuk Menentukan Kesesuaian Lokasi Produksi Garam; Analisis Lokasi Produksi Garam Di Kabupaten Tuban Dan Kabupaten Probolinggo. JFMR (Journal of Fisheries and Marine Research), 3(2), 236-244.Lopulalan, R. M. (2016). Desain blade turbin pembangkit listrik tenaga arus laut di Banyuwangi berbasis CFD. Institut Teknologi Sepuluh Nopember Surabaya,Oktavianto, D., Budiarto, U., & Kiryanto, K. (2017). Analisa Pengaruh Variasi Bentuk Sudu, Sudut Serang dan Kecepatan Arus Pada Turbin Arus Tipe Sumbu Vertikal Terhadap Daya yang Dihasilkan Oleh Turbin. Jurnal Teknik Perkapalan, 5(2).Patittingi, F. (2012). Dimensi hukum pulau-pulau kecil di Indonesia: studi atas penguasaan dan pemilikan tanah: Rangkang Education.Priliawan, R. A. (2016). Pengaruh Jumlah Sudu Turbin Wells Dan Variasi Gelombang Laut Terhadap Performa Prototype Pembangkit Listrik Tenaga Gelombang Laut Sistem Oscillating Water Column (OWC).Sapto, A. D., & Rumakso, H. P. (2021). Uji Coba Performa Bentuk Airfoil Menggunakan Software Qblade Terhadap Turbin Angin Tipe Sumbu Horizontal. Jurnal Teknik Mesin, 10(1).Sari, Y. R., & Rani, M. (2021). Penerapan Logika Fuzzy Metode Mamdani Dalam Menyelesaikan Masalah Produksi Garam Nasional. JATISI (Jurnal Teknik Informatika dan Sistem Informasi), 8(1), 341-356.
12
Wang, Yi, Bin Guo, Fengmei Jing e Yunlei Mei. "Hydrodynamic Performance and Flow Field Characteristics of Tidal Current Energy Turbine with and without Winglets". Journal of Marine Science and Engineering 11, n. 12 (12 dicembre 2023): 2344. http://dx.doi.org/10.3390/jmse11122344.
Abstract (sommario):
In order to gain a more comprehensive understanding of the influence of winglets on the hydrodynamic performance and flow field characteristics of tidal current energy turbines, two different shapes of winglets are designed, and numerical simulation results for turbines with and without winglets are compared and analyzed. The results show that both shapes of winglets can improve the energy conversion efficiency, and the winglets with a cant angle (60°) are more effective than the flat (0°) winglets; the winglets transfer the tip vortices to the winglet tips and weaken the tip vortices, increase the pressure coefficients of the cross-section in the tip region, and inhibit the three-dimensional flow phenomenon in the tip region; the winglets will make the wake axial velocity deficit larger in the near-wake region, and with the axial distance increases, the axial velocity of the wake flow with winglets recovers faster than that without winglets; winglets can make the vortex pairing and breaking of the turbine tip vortex faster, which can also be observed by the change in the turbulent kinetic energy (TKE).
13
Rumaherang, Wulfilla Maxmilian, e Jonny Latuny. "FLUID FLOW STUDY IN VARIOUS SHAPES AND SIZES OF HORIZONTAL AXIS SEA CURRENT TURBINE". SINERGI 25, n. 3 (10 agosto 2021): 289. http://dx.doi.org/10.22441/sinergi.2021.3.006.
Abstract (sommario):
The ducted tidal turbine models have been developed to utilize the conversion of the kinetic energy on ocean currents. The research in refining the turbine characteristics has been carried out by modifying the turbine’s shape and size. This study investigated flow characteristics in the meridional section of five ducted turbines models for seawater flow with velocity U0 = 1.5 m/s. The ducted turbine design and construction have five different impeller house diameters and fixed inlet and outlet diameters. The potential energy flow theory and experimental data are used to analyze the flow characteristics of the model. The results show that flow velocity in the x-direction at the inlet and outlet cross-section is getting smaller, reducing the impeller house cross section. Each impeller house size reduction increases the flow speed in the impeller house cross-section and also pressure on all other cross-sections tested. In the inlet area, the increased pressure indicates a decrease in speed flow and discharge coefficient value. The discharge coefficient value decreases from CQ = 0.9 at the diameter ratio of dr = 1 to CQ = 0.56 at the diameter ratio of dr = 0.375. The maximum value of power coefficient was determined at dr = 0,61÷0.73 or dr = 0.69 which is equivalent to average internal flow velocity Vr =2.0÷2.6 m/s and the static pressure ps = 97.1÷ 94.4 kPa. At the ratio value of D0/D2 = 0.83, the optimal diameter ratio dropt=0,61÷0.73 is in line with the duct model of case 3 and case 4, but it may be determined solely as for case 4.
14
NAKASE, Yoshiyuki, Junichiro FUKUTOMI e Hirotaka IIDA. "A study of the cross-flow turbine for tidal power generation. 1st report The characteristics of a cross-flow turbine with symmetrical nozzle shapes." Transactions of the Japan Society of Mechanical Engineers Series B 52, n. 473 (1986): 367–71. http://dx.doi.org/10.1299/kikaib.52.367.
15
Kara-Mostefa, Mohamed-Larbi, Ludovic Chatellier e Lionel Thomas. "Effect of Vertical Confinement and Blade Flexibility on Cross-Flow Turbines". Energies 16, n. 9 (25 aprile 2023): 3693. http://dx.doi.org/10.3390/en16093693.
Abstract (sommario):
Both scientific and industrial communities have a growing interest in marine renewable energies. There is a wide variety of technologies in this domain, with different degrees of maturity. This study focuses on two models of a mast-free vertical axis Darrieus tidal turbine with the objective of characterizing the effect of vertical confinement, rotor configuration, and fluid–structure interactions on their performances in free-surface flows. The first model comprised four straight rigid blades maintained by circular flanges on both ends of the rotor and the second model is equipped with free-ended interchangeable blades attached to a single upper flange. Two configurations of the second model mounted with either rigid or flexible blades were used, first for comparison with the dual-flange turbine, then in order to address the effect of fluid–structure interactions on the turbine performances. While the single-flange models exhibit a significantly lower efficiency at all operating points, it is observed that the use of flexible blades tends to enhance turbine performances at low Reynolds numbers. The flow topology obtained from PIV measurement at selected operating points is discussed with respect to the performance of each turbine model in order to highlight the role of the dynamic stall and blade–vortex interactions.
16
Garrett, Chris, e Patrick Cummins. "The power potential of tidal currents in channels". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, n. 2060 (24 giugno 2005): 2563–72. http://dx.doi.org/10.1098/rspa.2005.1494.
Abstract (sommario):
Interest in sources of renewable energy has led to increasing attention being paid to the potential of strong tidal currents. There is a limit to the available power, however, as too many turbines will merely block the flow, reducing the power generated. The maximum average power available from a tidal stream along a channel, such as that between an island and the mainland, is estimated and found to be typically considerably less than the average kinetic energy flux in the undisturbed state through the most constricted cross-section of the channel. A general formula gives the maximum average power as between 20 and 24% of the peak tidal pressure head, from one end of the channel to the other, times the peak of the undisturbed mass flux through the channel. This maximum average power is independent of the location of the turbine ‘fences’ along the channel. The results may also be used to evaluate the power potential of steady ocean currents.
17
Zanforlin, Stefania, Fulvio Buzzi e Marika Francesconi. "Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations". Energies 12, n. 2 (16 gennaio 2019): 272. http://dx.doi.org/10.3390/en12020272.
Abstract (sommario):
With the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuser, equipped with a pair of counter-rotating turbines, and a bi-directional symmetrical diffuser were compared in terms of coefficient of power (CP), torque ripple, overall thrust on diffuser and wake characteristics. Slightly better CP were predicted for the symmetrical diffuser, due to the convergent walls that address the flow towards the blade with a greater attack angle during early and late upwind and to the viscous interactions between the turbine wakes and strong vortices shed by the diffuser. A CP’s extraordinary improving resulted when yaw increased up to 22.5° for the hydrofoil shaped and up to 30° for the symmetrical diffuser. Similar behaviour in yawed flows also occurred in case of a ducted single rotor, demonstrating that it is a characteristic of CFTs. The insertion of a straight throat in the diffuser design proved to be an effective way to mitigate torque ripple, but a CP loss is expected.
18
Gaurier, Benoît, Grégory Germain e Jean-Valéry Facq. "Determination of the Response Amplitude Operator of a tidal turbine as a spectral transfer function". International Marine Energy Journal 5, n. 2 (7 ottobre 2022): 151–60. http://dx.doi.org/10.36688/imej.5.151-160.
Abstract (sommario):
A transfer function determination method is proposed in this study to predict the unsteady fluctuations of the performance of a tidal turbine model. This method is derived from the Response Amplitude Operator (RAO) applied in the offshore industry to predict linear wave-induced loads on large structures. It is based on a spectral approach and requires the acquisition of a turbine parameter (e.g. torque, thrust, power or root-blade force) in synchronization with an upstream flow velocity measurement. On the frequency range where the causality between these two signals is proven, the transfer function is established using the ratio between the cross-spectral density and the spectral density of the incoming velocity.The linearity is verified using the coherence function, which shows validity for the turbine power in the lowest frequencies only. This transfer function is then used to reconstruct the power fluctuations which is compared to the recorded one for a particular flow condition with bathymetry generated turbulence. The result shows the dependence on the accurate location of the velocity measurement point used for the reconstruction. This point must exactly correspond to the expected turbine location, i.e. where the turbine response needs to be processed. Bearing in mind its limits, the method can be used to predict the loadings of extreme events on the turbine structure and the performance variations corresponding to the unsteady characteristics of a turbulent flow, for a better grid integration.
19
Gebreslassie, Mulualem G., Gavin R. Tabor e Michael R. Belmont. "Numerical simulation of a new type of cross flow tidal turbine using OpenFOAM – Part II: Investigation of turbine-to-turbine interaction". Renewable Energy 50 (febbraio 2013): 1005–13. http://dx.doi.org/10.1016/j.renene.2012.08.064.
20
Gorban’, Alexander N., Alexander M. Gorlov e Valentin M. Silantyev. "Limits of the Turbine Efficiency for Free Fluid Flow". Journal of Energy Resources Technology 123, n. 4 (14 agosto 2001): 311–17. http://dx.doi.org/10.1115/1.1414137.
Abstract (sommario):
An accurate estimate of the theoretical power limit of turbines in free fluid flows is important because of growing interest in the development of wind power and zero-head water power resources. The latter includes the huge kinetic energy of ocean currents, tidal streams, and rivers without dams. Knowledge of turbine efficiency limits helps to optimize design of hydro and wind power farms. An explicitly solvable new mathematical model for estimating the maximum efficiency of turbines in a free (nonducted) fluid is presented. This result can be used for hydropower turbines where construction of dams is impossible (in oceans) or undesirable (in rivers), as well as for wind power farms. The model deals with a finite two-dimensional, partially penetrable plate in an incompressible fluid. It is nearly ideal for two-dimensional propellers and less suitable for three-dimensional cross-flow Darrieus and helical turbines. The most interesting finding of our analysis is that the maximum efficiency of the plane propeller is about 30 percent for free fluids. This is in a sharp contrast to the 60 percent given by the Betz limit, commonly used now for decades. It is shown that the Betz overestimate results from neglecting the curvature of the fluid streams. We also show that the three-dimensional helical turbine is more efficient than the two-dimensional propeller, at least in water applications. Moreover, well-documented tests have shown that the helical turbine has an efficiency of 35 percent, making it preferable for use in free water currents.
21
Pucci, Micol, Stefania Zanforlin, Debora Bellafiore, Stefano Deluca e Georg Umgiesser. "A Double Multiple Stream Tube (DMST) routine for site assessment to select efficient turbine aspect ratios and solidities in real marine environments". E3S Web of Conferences 312 (2021): 08001. http://dx.doi.org/10.1051/e3sconf/202131208001.
Abstract (sommario):
A MATLAB routine, based on a Double Multiple Stream Tube model, developed to quickly predict the performance of cross-flow hydrokinetic turbine, here is presented. The routine evaluate flow data obtained with the open-source marine circulation code SHYFEM. The tool can establish the best locations to place tidal devices taking into account bathymetric constraints and the hydrokinetic potential. Hence, it can be used to decide the best set of geometrical parameters. The geometrical variables of our analysis are turbine frontal area, aspect ratio and solidity. Several sub-models, validated with 3D and 2D CFD simulations, reproduce phenomena such as dynamic stall, fluid dynamic tips losses and the lateral deviation of streamlines approaching the turbine. As a case study, the tool is applied to an area of the northern Adriatic Sea. After having identified some suitable sites to exploit the energy resource, we have compared behaviours of different turbines. The set of geometrical parameters that gives the best performance in terms of power coefficient can vary considering several locations. Conversely, the power production is always greater for turbine with low aspect ratio (for a fixed solidity and area). Indeed, shorter devices benefit from higher hydrokinetic potentials at the top of the water column.
22
Paillard, B., J. A. Astolfi e F. Hauville. "URANSE simulation of an active variable-pitch cross-flow Darrieus tidal turbine: Sinusoidal pitch function investigation". International Journal of Marine Energy 11 (settembre 2015): 9–26. http://dx.doi.org/10.1016/j.ijome.2015.03.001.
23
Borg, Mitchell G., Qing Xiao, Steven Allsop, Atilla Incecik e Christophe Peyrard. "A Numerical Swallowing-Capacity Analysis of a Vacant, Cylindrical, Bi-Directional Tidal Turbine Duct in Aligned & Yawed Flow Conditions". Journal of Marine Science and Engineering 9, n. 2 (10 febbraio 2021): 182. http://dx.doi.org/10.3390/jmse9020182.
Abstract (sommario):
Introducing a duct along the perimeter of a rotor has been acknowledged to augment turbine performance. The outcome causation due to a bi-directional, cylindrical shroud, however, is uncertain. This study analyses the hydrodynamic swallowing capacity of a true-scale, vacant duct for tidal turbine applications in aligned and yawed inlet flow conditions by utilising three-dimensional unsteady computational fluid dynamics. The performance is investigated within free-stream magnitudes of 1 to 7 m.s−1, and a bearing angular range of 0° to 45° with the duct axis. In proportion to the free-stream magnitude, the normalised axial velocity through the duct increases as a result of a diminishment in pressure drag. Within yawed flow, the maximum capacity falls at a bearing of 23.2°, resulting in a performance increase of 4.13% above that at aligned flow conditions. The analysis concludes that the augmentation at yawed flow occurs due to the duct cross-sectional profile lift variation with angle-of-attack. Towards nominal yaw angle, the internal static pressure reduces, permitting a higher mass-flow rate. Beyond the nominal angle-of-attack, flow separation occurs within the duct, increasing pressure drag, thereby reducing the swallowing capacity.
24
Zhao, Muyu, Ying Chen e Jin Jiang. "Hydrodynamics and Wake Flow Analysis of a Floating Twin-Rotor Horizontal Axis Tidal Current Turbine in Roll Motion". Journal of Marine Science and Engineering 11, n. 8 (18 agosto 2023): 1615. http://dx.doi.org/10.3390/jmse11081615.
Abstract (sommario):
The study of hydrodynamic characteristics of floating double-rotor horizontal axis tidal current turbines (FDHATTs) is of great significance for the development of tidal current energy. In this paper, the effect of roll motion on a FDHATT is investigated using the Computational Fluid Dynamics (CFD) method. The analysis was conducted in the CFD software STAR-CCM+ using the Reynolds-averaged Navier–Stokes method. The effects of different roll periods and tip speed ratios on the power coefficient and thrust coefficient of FDHATT were studied, and then the changes in the vorticity field and velocity field of the turbine wake were analyzed by two-dimensional cross-section and Q criterion. The study indicates that roll motion results in a maximum decrease of 30.76% in the average power coefficient and introduces fluctuations in the instantaneous load. Furthermore, roll motion significantly accelerates the recovery of wake velocity. Different combinations of roll periods and tip speed ratios lead to varying degrees of wake velocity recovery. In the optimal combination, at a position 12 times the rotor diameter downstream, roll motion can recover the wake velocity to 92% of the incoming flow velocity. This represents a 23% improvement compared to the case with no roll motion.
25
Allmark, Matthew, Rodrigo Martinez, Stephanie Ordonez-Sanchez, Catherine Lloyd, Tim O’Doherty, Grégory Germain, Benoît Gaurier e Cameron Johnstone. "A Phenomenological Study of Lab-Scale Tidal Turbine Loading under Combined Irregular Wave and Shear Flow Conditions". Journal of Marine Science and Engineering 9, n. 6 (29 maggio 2021): 593. http://dx.doi.org/10.3390/jmse9060593.
Abstract (sommario):
Tidal devices are likely to faced with shear flows and subjected to various wave climates. The paper presents an experimental study of the combined impacts of shear profile and irregular waves on the loading of a 1/20th scale device operating at peak power extraction. The experiments presented were conducted at various depths to facilitate analysis of the effects of the shear flow and wave impact on the device at various positions in the water column. The fluid field was measured at three different upstream positions and at three depths (top, middle and bottom of the rotor) for each experiment; in doing so, data from the device were captured three times. The fluid measurements were of a high quality and were analysed to present the structure flow upstream of the device, which contained velocity and turbulence profiles. The upstream measurement was utilised to understand the development of flow structures in the approach to the device, and the impact of the flow structures measured was confirmed via cross-covariance calculations. The long datasets gathered were used to produce full rotational probability density functions for the blade-root-bending moments for three blades. The spectral characteristics were also considered, and showed that rotor loading quantities are less reactive to smaller scale flow structures.
26
Sentchev, Alexei, Thinh Duc Nguyen, Lucille Furgerot e Pascal Bailly du Bois. "Underway velocity measurements in the Alderney Race: towards a three-dimensional representation of tidal motions". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, n. 2178 (27 luglio 2020): 20190491. http://dx.doi.org/10.1098/rsta.2019.0491.
Abstract (sommario):
The Alderney Race, located northwest of the Cotentin Peninsula (France), is a site with high tidal-stream energy potential. Circulation through the Alderney Race is complex, with current speed exceeding 3 m s −1 at neap tide. Towed acoustic Doppler current profiler (ADCP) measurements and static point velocity measurements were performed in July 2018 focusing on assessment of circulation and vertical structure of tidal currents. Transect surveys revealed peculiar features of local dynamics such as change in location of the tidal jet on ebb and flood flow. The spatial expanse of the tidal jet was quantified and regions with largely sheared or nearly homogeneous velocity distributions were identified on the cross-sections. Velocity profiles acquired along the cross-sections were accurately characterized using a power law. The spatial variability of the power-law exponent α was found to be large and correlated with the tidal conditions. The largest variation in profile shape was observed in the northern sector and assumed to be generated by the current interaction with a bathymetric constriction. The velocity profiles were found to vary from highly sheared on flood flow to nearly homogeneous on ebb flow, with corresponding range of power-law exponent α variation from 6 to 14. In the southern sector, over a relatively smooth bathymetry, the velocity profile shape was accurately approximated using the 1/7 power law with a range of variation of α from 6.5 to 8, with respect to the tidal conditions. To our knowledge, this is the largest field survey done using towed ADCP and the results could represent a significant advance in tidal site characterization and provide advanced information to turbine developers. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race'.
27
NAKASE, Yoshiyuki, Junichiro FUKUTOMI e Yasushi FUKE. "Study of a cross-flow turbine for tidal power generation. 2nd report Effect of the changes of flow passage area on the turbine with symmetrical nozzle shapes." Transactions of the Japan Society of Mechanical Engineers Series B 53, n. 486 (1987): 500–504. http://dx.doi.org/10.1299/kikaib.53.500.
28
Wijaya, Rudi Kusuma, e Iwan Kurniawan. "Study Experimental Darrieus Type-H Water Turbines Using NACA 2415 Standard Hydrofoil Blade". Jurnal Pendidikan Teknik Mesin Undiksha 9, n. 2 (31 agosto 2021): 109–23. http://dx.doi.org/10.23887/jptm.v9i2.29257.
Abstract (sommario):
Telah dilakukan kaji eksperimental turbin air Darrieus tipe-H menggunakan blade hydrofoil standar NACA 2415 untuk mengetahui nilai torsi statik dan dinamik yang dihasilkan turbin air Darrieus tipe-H 3 blade dan 6 blade, pengujian menggunakan water tunnel dimensi 6m x 0.6m x 1m. Variasi tiga blade dan enam blade, dengan diameter turbin 0.44 m x 0.15 m pada turbin luar dan 0.18 x 0.14 m pada turbin bagian dalam, panjang chord 0.10 m dengan variasi sudut serang 0º sampai dengan 360º, variasi kecepatan air pertama 0.3 m/s, variasi kecepatan aliran air kedua 0.65 m/s. Kecepatan air 0.3 m/s enam blade, torsi statik 0.3 Nm, torsi dinamik nya 0.384 Nm, kecepatan air 0,65 m/s torsi dinamik 0.432 Nm dan torsi statik nya 0.384 Nm, pengujian turbin Darrieus tiga blade kecepatan air 0,3 m/s nilai torsi dinamik 0.336 Nm dan dengan kecepatan yang sama torsi statik nya 0.264 Nm. Pada kecepatan air 0.65 m/s nilai torsi dinamik sebesar 0.384 Nm, dan nilai torsi statik 0.336 Nm. Dari data hasil pengukuran tersebut dapat disimpulkan bahwa variasi turbin enam blade memiliki nilai torsi statik dan torsi dinamik yang lebih tinggi dari pada turbin tiga blade, jumlah blade sangat berpengaruh terhadap daya serap energi kinetik air untuk di konversikan menjadi torsi statik maupun torsi dinamik.Kata kunci : Turbin Hydrokinetic, Darrieus, Torsi Statik,Torsi DinamikAn experimental study of the H-type Darrieus water turbine was carried out using a standard NACA 2415 hydrofoil blade to determine the value of static and dynamic torque generated by the 3-blade and 6-blade Darrieus H-type water turbine, testing using a water tunnel dimensions of 6m x 0.6m x 1m. Variation of three blades and six blades, with a turbine diameter of 0.44 mx 0.15 m on the outer turbine and 0.18 x 0.14 m on the inner turbine, chord length 0.10 m with variations in angle of attack 0º to 360º, variation of first water velocity 0.3 m / s second water flow velocity 0.65 m / s. Water velocity 0.3 m / s six blades, static torque 0.3 Nm, dynamic torque 0.384 Nm, water velocity 0.65 m / s dynamic torque 0.432 Nm and static torque 0.384 Nm, Darrieus three blade turbine test water speed 0.3 m / s dynamic torque value of 0.336 Nm and with the same speed its static torque is 0.264 Nm. At 0.65 m / s water velocity, the dynamic torque value is 0.384 Nm, and the static torque value is 0.336 Nm. From the measurement data, it can be concluded that the six-blade turbine variation has a higher value of static torque and dynamic torque than the three-blade turbine, the number of blades greatly influences the absorption of water kinetic energy to be converted into static torque and dynamic torque. Keywords: Hydrokinetic Turbine, Darrieus, static torque, dynamic torqueDAFTAR RUJUKANKirke, B.K. (2011). Tests on ducted and bare helical and straight blade Darrieus hydrokinetic turbines, 36, pp.3013-3022Dominy, R., Lunt, P., Bickerdyke A., Dominy, J. (2007). Self-starting capability of a Darrieus turbine. Proc Inst Mech Eng (IMechE) ePart A: J Power Energy ;221: 111-120Decoste, Josh. (2004). Self-Starting Darrieus Wind Turbine. Department of Mechanical Engineering, Dalhousie University.Febrianto, A., & Santoso, A. (2016). “Analisa Perbandingan Torsi Dan rpm Tipe Darrieus Terhadap Efisiensi Turbin”. Fakultas Teknologi Kelautan, Institut Teknologi Sepuluh Nopember (ITS)Febriyanto, N. (2014). “Studi Perbandingan Karakteristik Airfoil NACA 0012 Dengan NACA 2410 Terhadap Koefisien Lift dan Koefisien Drag Pada Berbagai Variasi Sudut Serang Dengan CFD” Fakultas teknik, Universitas Muhammadiyah SurakartaSaputra, G. (2016). Kaji Eksperimental Turbin Angin Darrieus-H Dengan Bilah Tipe NACA 2415. Universitas Riau, JOM Teknik Mesin vol. 3 No. 1.Hafied, B. (2018). Kaji Eksperimental Torsi Statik Dan Torsi Dinamik Hidrokinetik Turbin Savonius Single Stage Type Bach Tiga Sudu. Tugas Akhir Teknik Mesin. Fakultas Teknik Universitas Riau.Hau, E. (2005). Wind Turbines: Fundamentals, Technologies, Aplication, Economics. Springer. Berlin.Kaprawi. (2011), Pengaruh Geometri Blade Dari Turbin Air Darrieus Terhadap Kinerjany. Prosiding Seminar Nasional AVoER ke-3 PalembangKhan, M. J., Bhuyan, G., Iqbal M. T., & Quaicoe J.E. (2009). Hydrokinetic Energy Conversion Systems and Assessment of Horizontal and Vertical Axis Turbines for River and Tidal: Applications A Technology Status Review. Applied Energy, 86, 1823-1835.Lain, S., & Osario, C. (2010). Simulation and Evaluation of a Sraight Bladed Darrieus Type Cross Flow Marine Turbine. Journal of Scientific & Research, Vol. 69 p.906-912Marizka, L. D. (2010). Analisis Kinerja Turbin Hydrokinetic Poros Vertical Dengan Modifikasi Rotor Savonius L Untuk Optimasi Kinerja Turbin. Tugas Akhir Sains Fisika. FMIPA-Universitas Sebelas Maret.Malge, P. (2015).Analysis of Lift and Drag Forces at Different Azimuth Angle of Innovative Vertical Axis Wind Turbine.International Journal of Energy Engineering 4(5-8).Teja, P., D. (2017). Studi Numerik Turbin Angin Darrieus – Savonius Dengan Penambahan Stage Rotor Darrieus. Institut Teknologi Sepuluh Nopember, Surabaya.Zobaa, A. F., & Bansal, R. C. (2011). Handbook of Renewable Energy Technology. USA: World Scientific Publishing Co. Pte. Ltd.
29
Gebreslassie, Mulualem G., Gavin R. Tabor e Michael R. Belmont. "Numerical simulation of a new type of cross flow tidal turbine using OpenFOAM – Part I: Calibration of energy extraction". Renewable Energy 50 (febbraio 2013): 994–1004. http://dx.doi.org/10.1016/j.renene.2012.08.065.
30
Muhyiddin Mohammed, Shamsul Sarip, Sa’ardin Abdul Aziz e Wan Azani Mustafa. "Systematic Review of Computational Fluid Dynamics Modelling and Simulation Techniques Employed in Vertical Axis Hydrokinetic Turbines". Journal of Advanced Research in Applied Mechanics 117, n. 1 (2 giugno 2024): 51–71. http://dx.doi.org/10.37934/aram.117.1.5171.
Abstract (sommario):
At present, Computational Fluid Dynamics (CFD) is being utilized to explore tidal and hydrokinetic turbine systems, advancing comprehension of turbulent flow phenomena and raising the accuracy of performance predictions for these fluid-driven turbines. Consequently, this utilization of CFD contributes to the optimization of efficiency in these devices. Turbines are subject to variations from the best design point due to the influence of fluctuating flow rates, despite the findings of recent research that have identified the ideal design points. In contrast to conventional literature reviews, systematic analysis offers numerous advantages. The methodological strategy applied in this study entailed cross-referencing the findings obtained from Web of Science (WOS) and Scopus databases to establish the comprehensiveness as well as reliability of researcher data. Improving the review process, elevating the prominence of the field of study, and establishing critical priorities to mitigate research bias are all potential strategies for enhancing the quality of these evaluations. This research divides its findings into three core themes: (1) Performance assessment for practical implications, (2) Numerical analysis for theoretical insights, and (3) Design parameter optimization for engineering relevance. These themes collectively provide a well-rounded examination of the research outcomes across practical, theoretical, and engineering dimensions. Finally, the research findings have the potential to act as a significant point of reference for informing the best design considerations pertaining to vertical axis turbines.
31
Schmitt, Pal, e Desmond Robinson. "Coupled Actuator Line and Finite Element Analysis Tool". OpenFOAM® Journal 2 (2 maggio 2022): 81–93. http://dx.doi.org/10.51560/ofj.v2.51.
Abstract (sommario):
Fluid-dynamic loading of many solid bodies can be simulated using geometry resolving computational fluid dynamics methods, where the body's shape is resolved in the mesh. In some cases though slender bodies, like ropes or cables, spars, turbine blades, foils and lattice structures would require prohibitively high cell counts, since the geometrical features to be resolve are much smaller than the overall domain. Such bodies are usually made up of generic cross sections like round, square or standardised technical profiles like the famous NACA digit series for which good parametrisations of reaction forces to incoming flow exist. Actuator line methods apply inflow dependent reaction forces to the fluid domain, thus allowing the computationally efficient simulation of slender bodies and have been used extensively, for example in wind and tidal turbine simulations. Beam elements representing slender bodies are standard building blocks in structural finite element models. Combining actuator line theory with a finite element beam model allows the efficient simulation of flexible structures under fluid loads, like turbine blades or nettings used in fish farms. This paper presents an implementation of such a coupled model in OpenFOAM based on the existing turbineFoam actuator line model. The underlying numerical method is detailed and first test cases are provided.
32
Sutherland, Duncan, Stephanie Ordonez-Sanchez, Michael R. Belmont, Ian Moon, Jeffrey Steynor, Thomas Davey e Tom Bruce. "Experimental optimisation of power for large arrays of cross-flow tidal turbines". Renewable Energy 116 (febbraio 2018): 685–96. http://dx.doi.org/10.1016/j.renene.2017.10.011.
33
Stringer, R. M., A. J. Hillis e J. Zang. "Numerical investigation of laboratory tested cross-flow tidal turbines and Reynolds number scaling". Renewable Energy 85 (gennaio 2016): 1316–27. http://dx.doi.org/10.1016/j.renene.2015.07.081.
34
Nishino, Takafumi, e Richard H. J. Willden. "Two-scale dynamics of flow past a partial cross-stream array of tidal turbines". Journal of Fluid Mechanics 730 (30 luglio 2013): 220–44. http://dx.doi.org/10.1017/jfm.2013.340.
Abstract (sommario):
AbstractThe characteristics of flow past a partial cross-stream array of (idealized) tidal turbines are investigated both analytically and computationally to understand the mechanisms that determine the limiting performance of partial tidal fences. A two-scale analytical partial tidal fence model reported earlier is further extended by better accounting for the effect of array-scale flow expansion on device-scale dynamics, so that the new model is applicable to short fences (consisting of a small number of devices) as well as to long fences. The new model explains theoretically general trends of the limiting performance of partial tidal fences. The new model is then compared to three-dimensional Reynolds-averaged Navier–Stokes (RANS) computations of flow past an array of various numbers (up to 40) of actuator disks. On the whole, the analytical model agrees well with the RANS computations, suggesting that the two-scale dynamics described in the analytical model predominantly determines the fence performance in the RANS computations as well. The comparison also suggests that the limiting performance of short partial fences depends on how much of device far-wake mixing takes place within the array near-wake region. This factor, however, depends on the structures of the wake and therefore on the type/design of devices to be arrayed.
35
Ridwan, Ridwan. "PERANCANGAN MODEL AIR ALIRAN SILANG (CROSS FLOW TURBINE) DENGAN HEAD 2 m DAN DEBIT 0,03 m3/s". Jurnal Teknik Mesin 3, n. 3 (19 gennaio 2017): 7. http://dx.doi.org/10.22441/jtm.v3i3.1023.
Abstract (sommario):
Pembangkit listrik tenaga mikrohidro merupakan pembangkit listrik skala kecil yang menggunakan air sebagai penggeraknya dan penggerak mula adalah turbin. Sistem pembangkit ini sangat tepat digunakan di pedesaan karena sistem ini mudah dibuat, menghasilkan daya listrik yang cukup besar dan biaya pembuatan yang lebih relatif murah. Atas dasar diatas maka perlu dirancang suatu turbin yang mendukung sistem pembangkit ini, diantaranya adalah Turbin Aliran Silang. Untuk merancang sebuah turbin air agar tidak terjadi kesalahan dalam perancangan (seperti hal-nya biaya pembuatannya) maka dilakukan perancangan prototipenya. Sebuah prototipe Turbin Aliran Silang dirancang dalam kegiatan tugas akhir ini dengan debit (Q) = 0,03 m3/s, head (H) = 2 m dengan efisiensi 0,80. Spesifikasi teknik utama dari hasil perancangan turbin adalah diameter runner (D) = 0,195 m dengan putaran turbin 281,39 rpm daya keluaran efektif sebesar 470,4 W.
36
Jasa, Lie, e I. Putu Ardana. "Disain Turbin Model Nest-Lie Untuk Mikro Hidro". Majalah Ilmiah Teknologi Elektro 17, n. 2 (22 novembre 2018): 393. http://dx.doi.org/10.24843/mite.2018.v17i02.p19.
Abstract (sommario):
Abstract — Air merupakan salah satu sumber energi yang potesinnya besar dan tersebar di seluruh wilayah Indonesia. Masalah utama dari pembangkit tenaga air adalah debit air yang mengalir tidak kontinyu sepanjang tahun. Karakteristik lokasi masing-masing penempatan mikro hidro adalah unik. Sebuah mikro hidro yang ditempatkan pada lokasi tertentu diperlukan turbin yang sesuai dengan karakteristik lokasi yang ada. Dalam penelitian ini dirancang turbin untuk mendapatkan turbin model Nest-Lie jenis baru yang mengakomodir semua parameter lokasi yang ada. Metode yang dilakukan adalah (1). Memanfaatkan data lokasi untuk isiaiasi desain awal, (2). menemukan model matematis turbin, (3). membuat prototipe model untuk diuji di laboratorium, (4). Membuat model turbin yang sebenarnya untuk ujicoba lapangan. Hasil yang didapat dari penelitian ini adalah RPM pada roda turbin Nest-Lie menghasilkan perbedaan yang sangat signifikan, dengan tekanan pada 28 Psi yang terbaca pada menghasilkan RPM berkisar antara 157,2 -231,1 dimana sudut posisi untuk 0o. 5o, 10o, 15o. RPM tertinggi untuk sudut posisi 0o dan dengan pada sudut nozzle 22,5o. dan Sudut nozzle yang menghasilkan RPM tertinggi adalah pada sudut 22,5-25,5 dengan sudut posisi 0o-5o. Tekanan yang dihasilkan pada saluran nozzle bukan merupakan penjumlahan dari tekanan masing-masing, hanya terjadi peningkatan sebesar 27%. Dan RPM mengalami peningkatan sebesar 20%.
Kata Kunci— Mikro hidro, Turbin, Cross flow, Nest-lie
37
Tarmizi, Achmad, e Herry Wardono. "Studi Kelayakan Dan Perancangan Serta Implementasi Turbin Pada Proyek PLTMH Di Kabupaten Sleman Yogyakarta". Jurnal Profesi Insinyur Universitas Lampung 1, n. 2 (1 dicembre 2020): 28–39. http://dx.doi.org/10.23960/jpi.v1n2.48.
Abstract (sommario):
Pemerintah Daerah Kabupaten Sleman akan membangun PLTMH dengan memanfaatkan potensi tenaga air di desa Girikerto yang merupakan salah satu sumber energi terbarukan. Penelitian ini didasarkan pada hasil studi kelayakan yang dilakukan penulis dengan melakukan studi lapangan untuk mengambil data-data dilokasi dengan memperhatikan aspek teknis, ekonomis dan sosial, kemudian dilakukan studi literatur dan analisis data untuk menentukan jenis turbin dan karakteristik yang paling tepat untuk PLTMH dilokasi tersebut. Dari hasil analisis data dan dengan melakukan perhitungan yang teliti serta dengan memperhatikan kondisi lokasi proyek PLTMH tersebut, turbin yang paling tepat untuk digunakan adalah turbin tipe Cross Flow. Turbin ini selain memiliki konstruksi yang sederhana, dapat pula didesain untuk kapasitas yang cukup besar dan lebih mudah dalam proses fabrikasi. Hasil lain yang diperoleh yaitu nilai perbandingan benefit dengan cost sebesar 0,79 (kurang dari 1). Hal ini berarti bahwa pembangunan PLTMH ini dinilai tidak ekonomis, tapi dengan daya yang mampu dihasilkan sebesar 10,58 kW tentunya akan mampu menerangi dan menyuplai listrik (manfaat yang sangat besar) bagi puluhan warga desa Girikerto.
38
Qu, Hengliang, Xueyan Li e Xiaochen Dong. "Numerical Study on Hydrodynamic Performance of a Pitching Hydrofoil with Chordwise and Spanwise Deformation". Journal of Marine Science and Engineering 12, n. 5 (16 maggio 2024): 830. http://dx.doi.org/10.3390/jmse12050830.
Abstract (sommario):
The hydrofoil plays a crucial role in tidal current energy (TCE) devices, such as horizontal-axis turbines (HATs), vertical-axis turbines (VATs), and oscillating hydrofoils. This study delves into the numerical investigation of passive chordwise and spanwise deformations and the hydrodynamic performance of a deformable hydrofoil. Three-dimensional (3D) coupled fluid–structure interaction (FSI) simulations were conducted using the ANSYS Workbench platform, integrating computational fluid dynamics (CFD) and finite element analysis (FEA). The simulation involved a deformable hydrofoil undergoing pitching motion with varying elastic moduli. The study scrutinizes the impact of elastic modulus on hydrofoil deformation, pressure distribution, flow structure, and hydrodynamic performance. Coefficients of lift, drag, torque, as well as their hysteresis areas and intensities, were defined to assess the hydrodynamic performance. The analysis of the correlation between pressure distribution and deformation elucidates the FSI mechanism. Additionally, the study investigated the 3D effects based on the flow structure around the hydrofoil. Discrepancies in pressure distribution along the spanwise direction result from these 3D effects. Consequently, different chordwise deformations of cross-sections along the spanwise direction were observed, contributing to spanwise deformation. The pressure difference between upper and lower surfaces diminished with increasing deformation. Peak values and fluctuations of lift, drag, and torque decreased. This study provides insights for selecting an appropriate elastic modulus for hydrofoils used in TCE devices.
39
Ihsan, Ahmad, Julia Azriana, Oreza Sativa, T. Miftanul Syubb’an, Wahyu Abdillah e Nasruddin Abdullah. "MENYINARI MASA DEPAN: STRATEGI OPTIMALISASI PEMBANGKIT LISTRIK MIKROHIDRO UNTUK KESEJAHTERAAN DESA SELAMAT, ACEH TAMIANG". Jurnal Masyarakat Berdikari dan Berkarya (Mardika) 2, n. 1 (30 marzo 2024): 10–16. http://dx.doi.org/10.55377/mardika.v2i1.9637.
Abstract (sommario):
PLTMH, Pembangkit Listrik Tenaga Mikrohidro, adalah solusi vital untuk meningkatkan ketersediaan listrik di daerah terpencil seperti Desa Selamat, Kecamatan Tenggulun, Kabupaten Aceh Tamiang. Dengan energi listrik yang sangat penting bagi masyarakat di daerah pedalaman dan pegunungan yang belum terjangkau oleh jaringan distribusi PLN, PLTMH memanfaatkan sungai dan aliran irigasi sebagai sumber energi terbarukan. Desa Selamat memiliki potensi hidro yang dapat dimanfaatkan baik untuk irigasi pertanian maupun sebagai pembangkit listrik. Pengembangan potensi sumber daya energi alternatif, seperti PLTMH, menjadi langkah penting mengingat keterbatasan energi listrik yang disediakan oleh PT. PLN (Persero) dan menipisnya cadangan bahan bakar minyak (BBM) dengan harga yang semakin tinggi. Penelitian ini mengkaji tinggi jatuh air dan efisiensi daya PLTMH, serta membahas perencanaan pembangunan dengan tahapan studi kelayakan dan rincian desain teknis. Tujuan perencanaan ini adalah untuk mengetahui pengaruh tinggi jatuh air terhadap putaran turbin Cross Flow, kecepatan turbin, effisiensi generator, serta untuk menghitung Rencana Anggaran Biaya (RAB) dari proyek perencanaan PLTMH. Dengan demikian, pengembangan PLTMH di Desa Selamat tidak hanya akan memenuhi kebutuhan listrik lokal, tetapi juga akan meningkatkan pendapatan asli daerah (PAD) serta membantu warga setempat yang kekurangan listrik
40
Lesmana, I. Putu Dody, Beni Widiawan e Rosa Tri Hertamawati. "Pengembangan Teknologi Energi Terbarukan Terpadu Melalui Pemanfaatan Mikrohidro dan Biogas Komunal Pada Kawasan Tertinggal Desa Gelang Kabupaten Jember". J-Dinamika : Jurnal Pengabdian Masyarakat 7, n. 2 (30 agosto 2022): 275–80. http://dx.doi.org/10.25047/j-dinamika.v7i2.3309.
Abstract (sommario):
Desa Gelang merupakan salah satu desa yang terletak di lereng Gunung Argopuro, Kabupaten Jember. Kondisi geografis Desa Gelang khususnya Dusun Lanasan memiliki perkebunan teh dan kopi seluas ±5.205,245 Ha. Walaupun Dusun Lanasan memiliki agrowisata menarik, tetapi tidak adanya listrik mengganggu aktivitas perekonomian dan mobilitas warganya. Selain itu, warga Dusun Lanasan yang memiliki 32 sapi dan 60 kambing menghasilkan limbah kotoran ±800 Kg per-hari dimana limbah kotoran hanya ditumpuk sehingga terlihat kotor dan menyebarkan bau tidak sedap. Melalui pengabdian masyarakat ini diterapkan solusi mikrohidro dengan memanfaatkan aliran sungai di Dusun Lanasan dan pembuatan biogas komunal. Pelaksanaan kegiatan dimulai dari pengukuran potensi mikrohidro, konstruksi bangunan sipil, pembuatan mikrohidro dengan turbin cross-flow, pembuatan saluran inlet-outlet dan digester biogas, serta instalasi listrik dan biogas. Hasil kegiatan ini dibangun PLTMH Dusun Lanasan yang menghasilkan daya listrik 2800 Watt untuk kebutuhan listrik dari 20 KK dan biogas komunal dari pengolahan limbah ternak mampu menghasilkan 16 m3 biogas per-hari yang telah disalurkan ke dapur-dapur warga Dusun Lanasan dimana mampu menghemat pembelian 2-3 elpiji per-bulannya.
41
Hoerner, Stefan, Shokoofeh Abbaszadeh, Olivier Cleynen, Cyrille Bonamy, Thierry Maître e Dominique Thévenin. "Passive flow control mechanisms with bioinspired flexible blades in cross-flow tidal turbines". Experiments in Fluids 62, n. 5 (22 aprile 2021). http://dx.doi.org/10.1007/s00348-021-03186-8.
Abstract (sommario):
Abstract State-of-the-art technologies for wind and tidal energy exploitation focus mostly on axial turbines. However, cross-flow hydrokinetic tidal turbines possess interesting features, such as higher area-based power density in array installations and shallow water, as well as a generally simpler design. Up to now, the highly unsteady flow conditions and cyclic blade stall have hindered deployment at large scales because of the resulting low single-turbine efficiency and fatigue failure challenges. Concepts exist which overcome these drawbacks by actively controlling the flow, at the cost of increased mechatronical complexity. Here, we propose a bioinspired approach with hyperflexible turbine blades. The rotor naturally adapts to the flow through deformation, reducing flow separation and stall in a passive manner. This results in higher efficiency and increased turbine lifetime through decreased structural loads, without compromising on the simplicity of the design. Graphic abstract
42
Schmitz, Christian, e Peter F. Pelz. "Optimal control of tidal flow". Journal of Fluid Mechanics 962 (4 maggio 2023). http://dx.doi.org/10.1017/jfm.2023.172.
Abstract (sommario):
The tidal flow through a channel connecting two basins with different tidal regimes can be optimally controlled by means of a turbine fence or array to maximise the extracted mechanical power. The paper gives the optimal control strategy as a function of the blockage ratio $\sigma$ , i.e. the ratio of the turbine cross-section to the cross-section of the local passage of a turbine. The results presented are a physically consistent generalisation of the results of Garrett & Cummins (Proc. R. Soc. Lond. A, vol. 461, 2060, pp, 2563–2572), valid only for $\sigma =1$ and turbine efficiency of one, now for arbitrary blockage ratio $0 < \sigma \leqslant 1$ . Published research over the past decade on the same topic has taken the momentum equation and the turbine drag force as a starting point. The new approach presented here, in contrast, takes the energy equation as the starting point and uses the relative volume flow as the control variable. As the work shows, this new approach has three advantages. First, starting with the energy equation allows us to derive an optimal flow control problem resulting in an Euler–Lagrange equation using the physically consistent and experimentally validated actuator disk model for the free surface flow of Pelz et al. (J. Fluid Mech., vol. 889, 2020) in a direct and formal way. The optimal control problem is solved (a) numerically and (b) analytically. In the latter case, the turbine characteristics are approximated by a rational function in the relevant design and operating range. The analytical solution (b) validated against the numerical solution (a) is surprisingly concise and easy to apply in practice, as shown by use cases. Second, instead of the induction factor, we use the volume flow that is the same for all turbines in a cascade, i.e. a row of turbines in the direction of flow, which significantly reduces the complexity of the optimal control task of turbine arrays. Third, we obtain a well-founded energy estimate, whereas previous methods overestimate the energy yield due to inconsistent turbine disc models (for the consistency and valid parameter ranges of different models, also in comparison with experiments, see Pelz et al., J. Fluid Mech., vol. 889, 2020). The results can be used for the conceptual design of turbine arrays, but also for a sound physically realistic and consistent resource assessment of tidal power for a system consisting of two basins, a channel and a turbine fence with $0<\sigma \leqslant 1$ and operated in a complete tidal cycle.
43
Huchet, Marion, Eloi Droniou, Larissa Perez, Bart Vermeulen, Andrew Baldock, Fraser Johnson e Cuan Boake. "Wake characterization of tidal turbines in the Pentland Firth using vessel-mounted ADCP measurements". Proceedings of the European Wave and Tidal Energy Conference 15 (2 settembre 2023). http://dx.doi.org/10.36688/ewtec-2023-456.
Abstract (sommario):
Knowledge of the extension and velocity deficit induced by tidal turbine wakes is crucial for the optimization of tidal farm layouts, as the wake induced by an upstream turbine may substantially affect the power and loadings of a device located downstream. The MeyGen project is the largest planned tidal stream energy project in the world: it aims to develop up to 398 MW of installed power in the Pentland Firth, Scotland, a site with current velocities reaching up to 5 m/s. During Phase 1 of the project, four 1.5 MW turbines were installed, providing a valuable opportunity to investigate turbine wake dynamics in full scale. As part of Phase 2, site characterization campaigns were carried out to plan the deployment of additional turbines, representing 28 MW of tidal power capacity. Hence, the influence of the existing devices on the downstream flow was investigated.
This work introduces the method used for studying wakes downstream tidal turbines using vessel-mounted Acoustic Doppler Current Profiles (ADCP) measurements. During two spring tides, the data was collected using an ADCP Teledyne Workhorse 600 kHz configured for along-beam velocities recording with 1 m resolution, as well as a GNSS Hemisphere Vector V102. The aim of this study was to map the flow downstream the turbines already installed on site, in order to identify and characterize the wake. Cross-flow transect measurements were conducted at various along-flow distances downstream from the devices, and repeated several times for improved accuracy. The cycles of repeated transects were performed both at flood and ebb tides, with the turbine running or switched off to spot potential differences introduced by device operation. Mean flow velocity estimates in the cross-section were obtained from raw data using the location-based velocity solver developed by Vermeulen et al. (2014). The method provides improved flow velocity estimates from vessel-mounted ADCP measurements because it strongly reduces the spatial extent over which flow homogeneity must be assumed, thus decreasing the chances that this assumption will fail. The reduction of the volume across which homogeneity must be achieved may represent a significant advantage for the investigation of tidal turbine wakes. To the authors’ knowledge, this is the first time that this method has been applied to wake characterization in a tidal stream energy site.
Outputs of the analysis include mean velocity magnitude and direction, as well as velocity deficits associated with the wakes. The mean velocity estimates obtained in each cross-section are compared for cases when the turbine was running or switched off. Findings reveal that vessel-mounted ADCP transects, coupled with the location-based methodology for velocity estimation, provide a powerful tool for tidal turbine wake characterization. The final presentation and paper will provide the results of this study.
References:Vermeulen, B., Sassi, M. G., & Hoitink, A. J. F. (2014). Improved flow velocity estimates from moving-boat ADCP measurements. Water Resources Research, 50(5), 4186–4196. https://doi.org/10.1002/2013WR015152
44
Ruiz-Hussmann, Karla, Pierre-Luc Delafin, Cyrille Bonamy, Yves Delannoy, Dominique Thévenin e Stefan Hoerner. "Objective Functions for the Blade Shape Optimisation of a Cross-Flow Tidal Turbine under Constraints". Proceedings of the European Wave and Tidal Energy Conference 15 (2 settembre 2023). http://dx.doi.org/10.36688/ewtec-2023-252.
Abstract (sommario):
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.
45
Tsuru, Wakana, Yoichi Kinoue, Tengen Murakami, Masaki Sakaguchi, Norimasa Shiomi e Manabu Takao. "Design method for a bidirectional ducted tidal turbine based on conventional turbomachinery methods". Advances in Mechanical Engineering 15, n. 6 (giugno 2023). http://dx.doi.org/10.1177/16878132231181066.
Abstract (sommario):
Renewable energy sources include solar, wind, hydro, geothermal and biomass. Furthermore, ocean energy is being rapidly harnessed worldwide. In this study, to establish a suitable design method for various bidirectional ducted tidal turbines, instead of using blade element momentum theory and CFD, which have been used previously, the method used for turbomachinery was used for designing the turbines. A bidirectional turbine optimises the equipment design and reduces manufacturing and maintenance costs. Using the turbine power as the design condition, the difference in the tangential velocity between the front and rear of the turbine was calculated using Euler’s equation, and the blade stagger angle was determined based on the potential flow theory. To incorporate the effect of duct geometry into this design method in the future, the effect on the internal flow of the duct was experimentally investigated using three ducts with different maximum cross-sectional areas. Performance tests showed that the duct geometry had a negligible effect on the flow rate through the turbine. Therefore, the larger the maximum diameter of the duct, the greater the flow rate into the outside of the duct. The pressure difference between front and rear of the turbine and the inflow energy into the duct were different due to the energy conversion as the flow turned outside of the duct. To improve the accuracy of the design method, the effect of flow at the duct inlet and the energy conversion should be incorporated, and a review of the estimation method for the axial velocity ratio and the selection method for the design representative value should be conducted.
46
Peraza, Jezella I., e John K. Horne. "Quantifying conditional probabilities of fish-turbine encounters and impacts". Frontiers in Marine Science 10 (9 novembre 2023). http://dx.doi.org/10.3389/fmars.2023.1270428.
Abstract (sommario):
Tidal turbines are one source of marine renewable energy but development of tidal power is hampered by uncertainties in fish-turbine interaction impacts. Current knowledge gaps exist in efforts to quantify risks, as empirical data and modeling studies have characterized components of fish approach and interaction with turbines, but a comprehensive model that quantifies conditional occurrence probabilities of fish approaching and then interacting with a turbine in sequential steps is lacking. We combined empirical acoustic density measurements of Pacific herring (Clupea pallasii) and when data limited, published probabilities in an impact probability model that includes approach, entrainment, interactions, and avoidance of fish with axial or cross-flow tidal turbines. Interaction impacts include fish collisions with stationary turbine components, blade strikes by rotating blades, and/or a collision followed by a blade strike. Impact probabilities for collision followed by a blade strike were lowest with estimates ranging from 0.0000242 to 0.0678, and highest for blade strike ranging from 0.000261 to 0.40. Maximum probabilities occurred for a cross-flow turbine at night with no active or passive avoidance. Estimates were lowest when probabilities were conditional on sequential events, and when active and passive avoidance was included for an axial-flow turbine during the day. As expected, conditional probabilities were typically lower than analogous independent events and literature values. Estimating impact probabilities for Pacific herring in Admiralty Inlet, Washington, United States for two device types illustrates utilization of existing data and simultaneously identifies data gaps needed to fully calculate empirical-based probabilities for any site-species combination.
47
Bennecke, Timo, Karla Ruiz-Hussmann, Paul Joedecke, Shokoofeh Abbaszadeh, Pierre-Luc Delafin, Christian-Toralf Weber e Stefan Hoerner. "methodology to capture the single blade loads on a cross-flow tidal turbine flume model". Proceedings of the European Wave and Tidal Energy Conference 15 (2 settembre 2023). http://dx.doi.org/10.36688/ewtec-2023-501.
Abstract (sommario):
The OPTIDE project aims to improve the efficiency and durability of Hydro-kinetic cross-flow tidal turbines (CFTT). These turbines are attractive for the exploitation of tidal energy, as the area-based power density of such turbine arrays is higher in comparison to those from horizontal-axis turbines. CFTT also generally feature a simpler 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 can be affected by alternating and pulsating stresses, caused by continuous variations of the angle of attack and hydraulic loads during the rotation. These stresses may lead to structural damage and fatigue-induced material failures. 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 consequence is smoothed peaks of the load alternations and a higher power coefficient CP . The project aims to explore the influence of active blade pitching on CFTTs and to optimize it with numerical and experimental means. Therefore, a lab-scaled three-bladed experimental turbine with embedded pitch actuators is developed. The model will subsequently be tested in the lab flume of the Institute of Fluid Dynamics and Thermodynamics of the Otto-von-Guericke University Magdeburg. Blade forces in tangential and radial components as well as the machine torque and the rotational speed are measured during the experiments. The turbine is equipped with two full-bridges of strain gauges for the detection of the blade loads, from which the structural stress is calculated subsequently. To ensure the turbine model’s mechanical durability, weakly coupled fluid-solid-interaction (FSI) simulations have been performed and will be presented. To this purpose, a 2D flow analysis, employing the open-source CFD toolkit OpenFOAM (v2206), has been coupled with a 3D structural analysis, using the Mechanical module of the commercial software package Ansys Workbench (2020 R2). The FSI simulations show that the current setup only allows for the measurement of the radial blade load component, because the pitching moment at blade level interferes with the measurements as soon as the profile stalls. The measurements are further distorted by secondary force paths from the loads on the other rotor blades. Possible measures for an improved instrumentation strategy on the flume model will be presented and discussed. It is shown that multiple equipment options allow for a decent investigation of the forces on blade level.
48
Chen, Lei, Paul A. J. Bonar, Christopher R. Vogel e Thomas A. A. Adcock. "A Note on the Effects of Local Blockage and Dynamic Tuning on Tidal Turbine Performance". Journal of Offshore Mechanics and Arctic Engineering 143, n. 1 (26 giugno 2020). http://dx.doi.org/10.1115/1.4047357.
Abstract (sommario):
Abstract Numerical simulations are used to explore the potential for local blockage effects and dynamic tuning strategies to enhance the performance of turbines in tidal channels. Full- and partial-width arrays of turbines, modeled using the volume-flux-constrained actuator disc and blade element momentum theories, are embedded within a two-dimensional channel with a naturally low ratio of drag to inertial forces. For steady flow, the local blockage effect observed by varying the cross-stream spacing between the turbines is found to agree very well with the predictions of the two-scale actuator disc theory of Nishino and Willden (2012, “The Efficiency of an Array of Tidal Turbines Partially Blocking a Wide Channel,” J. Fluid Mech., 708, pp. 596–606). For oscillatory flow, however, results show that, consistent with the findings of Bonar et al. (2019, “On the Arrangement of Tidal Turbines in Rough and Oscillatory Channel Flow,” J. Fluid Mech., 865, pp. 790–810), the shorter and more highly blocked arrays produce considerably more power than predicted by two-scale theory. Results also show that, consistent with the findings of Vennell (2016, “An Optimal Tuning Strategy for Tidal Turbines,” Proc. R. Soc. A, 472(2195), p. 20160047), the “dynamic” tuning strategy, in which the tuning of the turbines is varied over the tidal cycle, can only produce significantly more power than a temporally fixed turbine tuning if the array has a large number of turbine rows or a large local blockage ratio. For all cases considered, trends are consistent between the two turbine representations but the effects of local blockage and dynamic tuning are found to be much less significant for the more realistic tidal rotor than for the idealized actuator disc.
49
Jung, Hyun Ju, Ju Hyun Lee, Shin Hyung Rliee, Museok Song e Beom-Soo Hyun. "Unsteady flow around a two-dimensional section of a vertical axis turbine for tidal stream energy conversion". International Journal of Naval Architecture and Ocean Engineering 1, n. 2 (1 gennaio 2009). http://dx.doi.org/10.2478/jnaoe-2013-0008.
Abstract (sommario):
ABSTRACTThe two-dimensional unsteady flow around a vertical axis turbine for tidal stream energy' conversion was investigated using a computational fluid dynamics tool solving the Reynolds-Averaged Navier-Stokes equations. The geometry' of the turbine blade section was NACA653-01S airfoil. The computational analysis was done at several different angles of attack and the results were compared with the corresponding experimental data for validation and calibration. Simulations were then carried out for the two-dimensional cross section of a vertical axis turbine. The simulation results demonstrated the usefulness of the method for the typical unsteady flows around vertical axis turbines. The optimum turbine efficiency was achieved for carefully selected combinations of the number of blades and tip speed ratios.
50
Ouro, Pablo, Peter Stansby, Alasdair Macleod, Tim Stallard e Hannah Mullings. "High-fidelity modelling of a six-turbine tidal array in the Shetlands". Proceedings of the European Wave and Tidal Energy Conference 15 (2 settembre 2023). http://dx.doi.org/10.36688/ewtec-2023-442.
Abstract (sommario):
Micro-siting tidal stream turbines in a confined seabed area requires a extensive understanding of the flow dynamics over the water column at turbine deployment locations so that operating conditions are assessed, wake effects can be estimated to infer the energy yield [1], or bathymetry effects can be quantified. Tidal currents have the advantage of being highly predictable and mostly bidirectional but the uneven bathymetry found at most of sites introduces a high variability to the flow conditions within relatively short distances. Considering future tidal turbine arrays will comprise dozens of devices, deploying ADCPs at each turbine position would be very expensive or very time consuming, outlining the need for accurate modelling tools to be used as digital twins in micro-siting. Shallow-water models are widely adopted in preliminary design of tidal arrays but fail to capture the three dimensional nature of the flow and predict deflected wakes whose streamwise length is also over-predicted [2]. Thus, eddy-resolving method are required to fully capture the turbulence from the free-stream flow, induced by turbines and from bathymetry. \\
This study provides a real-project application of the state-of-the-art large-eddy simulation (LES) code DOFAS (Digital Offshore Farms Simulator) [3] to the six 100kW-turbine array deployed by NOVA Innovation Ltd. in the Shetlands, UK [4]. The bathymetry data has been obtained from EMODnet database with the velocity profiles set at the inlet condition of both ebb and flood tides imported from Macleod et al. (2019) [4]. The deployment site is characterised by steep slopes with a maximum depth of 45 m at the cross-section where turbines are located. The bathymetry has a downwards slope when the flow goes in the ebb tide direction whilst upstream during flood tide. The tidal rose indicated a slight deviation of about 20$^{\circ}$ between ebb and flood directions. The turbines have a diameter ($D$) of 9 m attached to a 10 m long hub whose diameter is 1 m. Three array configurations have been studied: (i) single row of three turbines, (ii) two rows of turbines spaced 8$D$, and (iii) two rows of turbines spaced 12$D$. The computational domain extends over 600 m by 300 m in the horizontal plane yielding 540 million cells, requiring 32,500 CPU hours to compute 30 min of physical time.\\
Results show that bathymetry effects at this site play a larger role when designing the location of the secondary row of turbines compared to wake effects from upstream turbines. During the ebb tide, the increase in water depth reduces the wake recovery far downstream so that the array with 12$D$ row spacing has a lower performance than the 8$D$ one with approx. 30\% decrease in energy yield. Conversely, the uphill shape of the bathymetry during the flood enables a fast wake recovery so that the downstream row experiences almost no energy yield loss due to wakes.