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Stavropoulou, C., Goude, A., Katsidoniotaki, E. & Göteman, M. (2023). Fast time-domain model for the preliminary design of a wave power farm. Renewable energy, 219
Open this publication in new window or tab >>Fast time-domain model for the preliminary design of a wave power farm
2023 (English)In: Renewable energy, Vol. 219Article in journal (Refereed) Published
Abstract [en]

This study presents a novel, fast time-domain model developed for an array of interacting point-absorber wave energy converters. The model is validated using experimental wave tank data. The point-absorbers, based on Uppsala University’s design, are arranged in a symmetric grid and interact with scattered and radiated waves while constrained to the heave motion. The model employs linear potential flow theory to solve the hydrodynamic coefficients in the frequency domain and employs Cummins’ formulation to solve the equations of motion in the time domain. Modeling an array of wave energy converters in the time domain yields a system of integro-differential equations, featuring convolution terms in the excitation and radiation forces. This implies that past waves radiated by the body continue to impact future dynamics. Irregular long-crested waves, generated from the Bretschneider spectrum, serve as the incident waves for the study. The model’s accuracy in capturing the dynamics and power absorption of the farm is demonstrated through validation against experimental data from a 1:10 scaled prototype of a six-point-absorber array. Despite inherent differences between the experimental and numerical set-ups, the model accurately represents the farm’s behavior. Furthermore, an efficiency test reveals that the numerical scheme approximates the performance of wave power farms comprising 6, 12, 24, 48, and 96 interacting devices within a maximum computational time of 20 s. Overall, this research presents a novel and accurate time-domain model for analyzing an array of point-absorber wave energy converters. The model’s ability to capture the dynamics and power absorption, along with its efficiency in simulating larger wave power farms, make it a valuable tool for the preliminary design stage.

Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-514825 (URN)10.1016/j.renene.2023.119482 (DOI)001106919000001 ()
Available from: 2023-10-23 Created: 2023-10-23 Last updated: 2024-01-03Bibliographically approved
Andersson, E., Bernhoff, H. & Goude, A. (2023). Vortex filament method 3D analysis of design parameters for counter-rotating axis floating tilted turbine. In: Tande, J. O. G.; Kvamsdal, T.; Muskulus, M. (Ed.), EERA DeepWind conference 2023: . Paper presented at EERA DeepWind Conference / 20th Deep Sea Offshore Wind R and D Conference, January 18-20, 2023, SINTEF, Trondheim, Norway. Institute of Physics Publishing (IOPP), Article ID 012001.
Open this publication in new window or tab >>Vortex filament method 3D analysis of design parameters for counter-rotating axis floating tilted turbine
2023 (English)In: EERA DeepWind conference 2023 / [ed] Tande, J. O. G.; Kvamsdal, T.; Muskulus, M., Institute of Physics Publishing (IOPP), 2023, article id 012001Conference paper, Published paper (Refereed)
Abstract [en]

The Counter-Rotating Axis Floating Tilted turbine (CRAFT) is a new design for floating off-shore wind power, which utilizes a low center of gravity and allows the tower to tilt to mitigate costs for platforming.

In this study, 3D simulations of the CRAFT have been performed to investigate the effect from the tower's tilt angle on the aerodynamics of the turbine using a vortex filament method. Due to lack of empirical data of the CRAFT, the method has been benchmark tested against a previous project on a vertical axis wind turbine.

Using this method, the blades' twist angle has been set to achieve good lift-to-drag ratio along the entire blade. Furthermore, the blades' chord length has been determined for optimal Tip Speed Ratio (TSR) 6 when the tower is tilted 30 degrees from vertical position.

The CRAFT has been simulated vertically and tilted 15°, 30° and 45°, for TSRs ranging between 4 and 9. The power coefficients (CP) and normal forces have been determined, and velocity plots are presented to show how the near-wake develops.

The results from this study serves as a basis for further development and design of the CRAFT.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2023
Series
Journal of Physics Conference Series, ISSN 1742-6588, E-ISSN 1742-6596 ; 2626
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-523974 (URN)10.1088/1742-6596/2626/1/012001 (DOI)001147057400001 ()
Conference
EERA DeepWind Conference / 20th Deep Sea Offshore Wind R and D Conference, January 18-20, 2023, SINTEF, Trondheim, Norway
Available from: 2024-02-27 Created: 2024-02-27 Last updated: 2024-02-27Bibliographically approved
Aihara, A., Mendoza, V., Goude, A. & Bernhoff, H. (2022). A numerical study of strut and tower influence on the performance of vertical axis wind turbines using computational fluid dynamics simulation. Wind Energy, 25(5), 897-913
Open this publication in new window or tab >>A numerical study of strut and tower influence on the performance of vertical axis wind turbines using computational fluid dynamics simulation
2022 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 25, no 5, p. 897-913Article in journal (Refereed) Published
Abstract [en]

This paper presents the influence of the strut and the tower on the aerodynamic force of the blade for the vertical axis wind turbine (VAWT). It has been known that struts degrade the performance of VAWTs due to the inherent drag losses. In this study, three-dimensional Reynolds-averaged Navier-Stokes simulations have been conducted to investigate the effect of the strut and the tower on the flow pattern around the rotor region, the blade force distribution, and the rotor performance. A comparison has been made for three different cases where only the blade; both the blade and the strut; and all of the blade, the strut, and the tower are considered. A 12-kW three-bladed H-rotor VAWT has been studied for tip speed ratio of 4.16. This ratio is relatively high for this turbine, so the influence of the strut is expected to be crucial. The numerical model has been validated first for a single pitching blade and full VAWTs. The simulations show distinguished differences in the force distribution along the blade between two cases with and without struts. Since the wake from the struts interacts with the blades, the tangential force is reduced especially in the downwind side when the struts are considered. The calculated power coefficient is decreased by 43 %, which shows the importance of modeling the strut effect properly for accurate prediction of the turbine performance. The simulations also indicate that including the tower does not yield significant difference in the force distribution and the rotor power.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
aerodynamics, CFD, RANS, strut, vertical axis wind turbine (VAWT)
National Category
Energy Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-483934 (URN)10.1002/we.2704 (DOI)000746829500001 ()
Funder
Swedish Research Council, 2019/3-383Swedish Research Council, 2020/5-360
Available from: 2022-09-14 Created: 2022-09-14 Last updated: 2022-09-14Bibliographically approved
Aihara, A., Mendoza, V., Goude, A. & Bernhoff, H. (2022). Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine. Energies, 15(7), Article ID 2361.
Open this publication in new window or tab >>Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine
2022 (English)In: Energies, E-ISSN 1996-1073, Vol. 15, no 7, article id 2361Article in journal (Refereed) Published
Abstract [en]

This paper compares three different numerical models to evaluate their accuracy for predicting the performance of an H-rotor vertical-axis wind turbine (VAWT) considering the influence of struts. The strut of VAWTs is one factor that makes the flow feature around the turbine more complex and thus influences the rotor performance. The focus of this study is placed on analyzing how accurately three different numerical approaches are able to reproduce the force distribution and the resulting power, taking the strut effect into account. For the 12 kW straight-bladed VAWT, the blade force is simulated at three tip speed ratios by the full computational fluid dynamics (CFD) model based on the Reynolds-averaged Navier-Stokes (RANS) equations, the actuator line model (ALM), and the vortex model. The results show that all the models do not indicate a significant influence of the struts in the total force over one revolution at low tip speed ratio. However, at middle and high tip speed ratio, the RANS model reproduces the significant decrease of the total tangential force that is caused due to the strut. Additionally, the RANS and vortex models present a clear influence of the struts in the force distribution along the blade at all three tip speed ratios investigated. The prediction by the ALM does not show such distinctive features of the strut impact. The RANS model is superior to the other two models for predicting the power coefficient considering the strut effect, especially at high tip speed ratio.

Place, publisher, year, edition, pages
MDPI, 2022
Keywords
vertical-axis wind turbine, CFD, RANS, actuator line model, vortex method
National Category
Fluid Mechanics and Acoustics Energy Engineering
Identifiers
urn:nbn:se:uu:diva-473670 (URN)10.3390/en15072361 (DOI)000780599400001 ()
Funder
Swedish Research Council, 2021/5-336
Available from: 2022-05-02 Created: 2022-05-02 Last updated: 2023-08-28Bibliographically approved
Aihara, A., Karl, B., Goude, A. & Bernhoff, H. (2021). Aeroacoustic noise prediction of a vertical axis wind turbine using Large Eddy Simulation. International Journal of Aeroacoustics, 20(8), 959-978
Open this publication in new window or tab >>Aeroacoustic noise prediction of a vertical axis wind turbine using Large Eddy Simulation
2021 (English)In: International Journal of Aeroacoustics, ISSN 1475-472X, E-ISSN 2048-4003, Vol. 20, no 8, p. 959-978Article in journal (Other academic) Published
Abstract [en]

This study investigates the numerical prediction for the aerodynamic noise of the vertical axis wind turbine using large eddy simulation and the acoustic analogy. Low noise designs are required especially in residential areas, and sound level generated by the wind turbine is therefore important to estimate. In this paper, the incompressible flow field around the 12 kW straight-bladed vertical axis wind turbine with the rotor diameter of 6.5 m is solved, and the sound propagation is calculated based on the Ffowcs Williams and Hawkings acoustic analogy. The sound pressure for the turbine operating at high tip speed ratio is predicted, and it is validated by comparing with measurement. The measured spectra of the sound pressure observed at several azimuth angles show the broadband characteristics, and the prediction is able to reproduce the shape of these spectra. While previous works studying small-scaled vertical axis wind turbines found that the thickness noise is the dominant sound source, the loading noise can be considered to be a main contribution to the total sound for this turbine. The simulation also indicates that the received noise level is higher when the blade moves in the downwind than in the upwind side.

Place, publisher, year, edition, pages
Sage PublicationsSAGE Publications, 2021
Keywords
Vertical axis wind turbine, acoustics, aerodynamic noise, CFD, LES
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-426037 (URN)10.1177/1475472X211055179 (DOI)000721550900001 ()
Funder
Swedish National Infrastructure for Computing (SNIC)Swedish Research Council, 2020/5-321
Available from: 2020-11-23 Created: 2020-11-23 Last updated: 2024-01-15Bibliographically approved
Nguyen, M.-T., Balduzzi, F. & Goude, A. (2021). Effect of pitch angle on power and hydrodynamics of a vertical axis turbine. Ocean Engineering, 238, Article ID 109335.
Open this publication in new window or tab >>Effect of pitch angle on power and hydrodynamics of a vertical axis turbine
2021 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 238, article id 109335Article in journal (Refereed) Published
Abstract [en]

The use of vertical-axis turbines in marine-current applications for electric energy generation is still in early developments, and one of the key factors for assessing the applicability of such technology is the power coefficient. To contribute towards the highly competitive market of renewable energy conversions, the turbine system requires good outcomes in terms of energy yield. In this scenario, one of the main challenges regarding the design process to improve the blade performance is to find the best trade-off between the maximization of the power output and the minimization of the structural loadings. In the current work, the influence of blade pitch angles on the hydrodynamics of a vertical-axis five-blade water turbine has been studied. The pitch angles from - 5 degrees to +5 degrees were investigated using Computational Fluid Dynamics (CFD). The simulations were validated against experimental data for the power coefficient collected in a river. Overall, a good agreement was found in terms of computed power between simulations and experiments for a wide range of tip speed ratios. The CFD model was proven to be suitable for exploratory analyses and an optimized design was found, providing a 2.3% higher power coefficient by adopting a pitch angle of +2 degrees compared to the zero-referenced pitch angle. Besides validating with the experiment, the CFD simulations were compared with the results of a vortex model. The effect of different pitch angles on the performance prediction and on the blade and turbine loadings was also discussed. It is becoming vital to develop an understanding of the complex interaction of vertical-axis turbines, especially in tidal-current areas where there is a lack of detailed experimental data.

Place, publisher, year, edition, pages
ElsevierPERGAMON-ELSEVIER SCIENCE LTD, 2021
Keywords
Vertical-axis marine-current turbine, Pitch-angle optimization, Power coefficient, Normal force, Tangential force, Hydrodynamics, CFD
National Category
Energy Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-456923 (URN)10.1016/j.oceaneng.2021.109335 (DOI)000696708900004 ()
Funder
Swedish Research Council, 2018-05973StandUpSwedish National Infrastructure for Computing (SNIC)
Available from: 2021-11-01 Created: 2021-11-01 Last updated: 2024-01-15Bibliographically approved
Aihara, A., Goude, A. & Bernhoff, H. (2021). Numerical prediction of noise generated from airfoil in stall using LES and acoustic analogy. Noise & Vibration Worldwide, 52(10), 295-305
Open this publication in new window or tab >>Numerical prediction of noise generated from airfoil in stall using LES and acoustic analogy
2021 (English)In: Noise & Vibration Worldwide, ISSN 0957-4565, E-ISSN 2048-4062, Vol. 52, no 10, p. 295-305Article in journal (Other academic) Published
Abstract [en]

This article presents the aerodynamic noise prediction of a NACA 0012 airfoil in stall region using Large Eddy Simulation and the acoustic analogy. While most numerical studies focus on noise for an airfoil at a low angle of attack, prediction of stalled noise has been made less sufficiently. In this study, the noise of a stalled airfoil is calculated using the spanwise correction where the total noise is estimated from the sound source of the simulated span section based on the coherence of turbulent flow structure. It is studied for the airfoil at the chord-based Reynolds number of 4.8 × 105 and the Mach number of 0.2 with the angle of attack of 15.6° where the airfoil is expected to be under stall condition. An incompressible flow is resolved to simulate the sound source region, and Curle’s acoustic analogy is used to solve the sound propagation. The predicted spectrum of the sound pressure level observed at 1.2 m from the trailing edge of the airfoil is validated by comparing measurement data, and the results show that the simulation is able to capture the dominant frequency of the tonal peak. However, while the measured spectrum is more broadband, the predicted spectrum has the tonal character around the primary frequency. This difference can be considered to arise due to insufficient mesh resolution.

Place, publisher, year, edition, pages
Sage Publications, 2021
Keywords
Acoustics, noise; airfoil, computational fluid dynamics, LES, Curle’s acoustic analogy
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-426035 (URN)10.1177/09574565211030706 (DOI)
Available from: 2020-11-23 Created: 2020-11-23 Last updated: 2023-03-13Bibliographically approved
Nguyen, M.-T., Balduzzi, F., Bianchini, A., Ferrara, G. & Goude, A. (2020). Evaluation of the unsteady aerodynamic forces acting on a vertical-axis turbine by means of numerical simulations and open site experiments. Journal of Wind Engineering and Industrial Aerodynamics, 198, Article ID 104093.
Open this publication in new window or tab >>Evaluation of the unsteady aerodynamic forces acting on a vertical-axis turbine by means of numerical simulations and open site experiments
Show others...
2020 (English)In: Journal of Wind Engineering and Industrial Aerodynamics, ISSN 0167-6105, E-ISSN 1872-8197, Vol. 198, article id 104093Article in journal (Refereed) Published
Abstract [en]

An increasing number of vertical-axis wind turbine prototypes have reached the step in which the theoretically predicted performance needs to be validated in order to move to the next steps of a real commercial project. This step often faces the significant challenges posed by their airfoil aerodynamics that are more complex than those of conventional horizontal-axis wind turbines, and it has also to deal with the lack of fundamental experimental data for robust validation. In this context, an accurate prediction of the real turbine operation is important and the use of computational fluid dynamics (CFD) is imposing itself as the most suitable tool to characterize the unsteady phenomena that are difficult to detect by means of experimental measurements. In the current work, two-dimensional numerical simulations of an H-type three-blade Darrieus turbine have been performed in a wide range of tip-speed ratios (TSRs) from TSR = 1.8 to TSR = 5.0. Unsteady CFD simulations were compared with unique experimental data collected in the field in terms of normal aerodynamic forces acing on the blades during the revolution. Generally, nice agreement was found between simulations and experiments, especially at medium-high tip-speed ratios. The influence of operating conditions on the performance prediction capability of the numerical model was also discussed. This is one of the key points of study since the lack of detailed experimental data often makes numerical analyses doubtful or scarcely effective. Finally, the simulation results were exploited in order to analyze the phenomena occurring during the revolution and to correlate them with the experimental findings.

Place, publisher, year, edition, pages
ELSEVIER, 2020
Keywords
CFD, Darrieus, Wind turbine, Tangential force, Normal force, Unsteady aerodynamics
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-407518 (URN)10.1016/j.jweia.2020.104093 (DOI)000515136800008 ()
Funder
StandUp
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-03-25Bibliographically approved
Aihara, A., Goude, A. & Bernhoff, H. (2020). LES prediction for acoustic noise of airfoil at high angle of attack. In: : . Paper presented at AIAA Scitech 2020 Forum.
Open this publication in new window or tab >>LES prediction for acoustic noise of airfoil at high angle of attack
2020 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-426027 (URN)10.2514/6.2020-1723 (DOI)
Conference
AIAA Scitech 2020 Forum
Available from: 2020-11-23 Created: 2020-11-23 Last updated: 2021-12-28
Mendoza, V. & Goude, A. (2020). Validation of Actuator Line and Vortex Models using Normal Forces Measurements of a Straight-Bladed Vertical Axis Wind Turbine. Energies, 13(3), Article ID 511.
Open this publication in new window or tab >>Validation of Actuator Line and Vortex Models using Normal Forces Measurements of a Straight-Bladed Vertical Axis Wind Turbine
2020 (English)In: Energies, E-ISSN 1996-1073, Vol. 13, no 3, article id 511Article in journal (Refereed) Published
Abstract [en]

Vertical Axis Wind Turbines (VAWTs) are characterized by complex and unsteady flow patterns resulting in considerable challenges for both numerical simulations and measurements describing the phenomena involved. In this study, a 3D Actuator Line Model (ALM) is compared to a 2D and a 3D Vortex Model, and they are validated using the normal forces measurements on a blade of an operating 12 kW VAWT, which is located in an open site in the north of Uppsala, Sweden. First, the coefficient power ( Cp ) curve of the device has been simulated and compared against the experimental one. Then, a wide range of operational conditions for different tip speed ratios (TSRs), with λ = 1.84, 2.55, 3.06, 3.44, 4.09 and 4.57 were investigated. The results showed descent agreement with the experimental data for both models in terms of the trend and magnitudes. On one side, a slight improvement for representing the normal forces was achieved by the ALM, while the vortex code performs better in the simulation of the Cp curve. Similarities and discrepancies between numerical and experimental results are discussed.

Keywords
vertical axis wind turbines, actuator line model, vortex method, dynamic stall model
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:uu:diva-348689 (URN)10.3390/en13030511 (DOI)000522489000005 ()
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2023-08-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6975-1588

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