List of publications:
2024
Forslund, Johan; Mendoza, Victor; Goude, Anders
Impact of Blade Pitch Angle on Turbine Performance of a Vertical Axis Current Turbine Journal Article Forthcoming
In: Ocean Engineering, Forthcoming.
@article{R16,
title = {Impact of Blade Pitch Angle on Turbine Performance of a Vertical Axis Current Turbine},
author = {Johan Forslund and Victor Mendoza and Anders Goude},
year = {2024},
date = {2024-03-18},
urldate = {2024-03-18},
journal = {Ocean Engineering},
abstract = {This paper presents experimental data and numerical simulation results on the influence of blade pitch angle on the power capture performance of a vertical axis current turbine. Experiments have been conducted at 1.42 m/s with a turbine in a river for blade pitch angles 0° and +3° (the angle is defined as the leading edge of the blade rotating outwards, perpendicular to and in the opposite direction of the turbine axis). Two numerical models, a vortex model and an actuator line model, have been used to simulate the turbine in the same conditions (1.42 m/s and 0°,+3°). Both the experimental and simulation results show that 0° gives a higher power capture power than +3°. In addition to 0°,+3°, the simulation models were used to simulate the performance for an extended range of pitch angles, -3° to +3° using a fixed tip-speed-ratio with a step size of 1°. The simulations show that +1° gives the highest value of the power coefficient, increasing the average power capture by up to 0.6%. The results show that for vertical axis marine current turbines the performance can be improved by increasing the pitch angle 1° in the positive direction, which is different from wind turbines where literature shows a negative pitch angle can increase the average power capture of the turbine.},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
This paper presents experimental data and numerical simulation results on the influence of blade pitch angle on the power capture performance of a vertical axis current turbine. Experiments have been conducted at 1.42 m/s with a turbine in a river for blade pitch angles 0° and +3° (the angle is defined as the leading edge of the blade rotating outwards, perpendicular to and in the opposite direction of the turbine axis). Two numerical models, a vortex model and an actuator line model, have been used to simulate the turbine in the same conditions (1.42 m/s and 0°,+3°). Both the experimental and simulation results show that 0° gives a higher power capture power than +3°. In addition to 0°,+3°, the simulation models were used to simulate the performance for an extended range of pitch angles, -3° to +3° using a fixed tip-speed-ratio with a step size of 1°. The simulations show that +1° gives the highest value of the power coefficient, increasing the average power capture by up to 0.6%. The results show that for vertical axis marine current turbines the performance can be improved by increasing the pitch angle 1° in the positive direction, which is different from wind turbines where literature shows a negative pitch angle can increase the average power capture of the turbine.
2023
Mendoza, Victor; Katsidoniotaki, Eirini; Florentiades, Markos; Fraga, Jorge Dot; Dyachuk, Eduard
Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors Journal Article
In: Wind Energy, vol. 26, no. 6, pp. 512-537, 2023.
Abstract | Links | Dimensions
@article{R15,
title = {Aerodynamic performance of a dual turbine concept characterized by a relatively close distance between rotors},
author = {Victor Mendoza and Eirini Katsidoniotaki and Markos Florentiades and Jorge Dot Fraga and Eduard Dyachuk},
url = {http://onlinelibrary.wiley.com/doi/abs/10.1002/we.2813},
doi = {https://doi.org/10.1002/we.2813},
year = {2023},
date = {2023-03-14},
urldate = {2023-03-14},
journal = {Wind Energy},
volume = {26},
number = {6},
pages = {512-537},
abstract = {In this work a closely-spaced dual turbine concept is studied. The distance between the two side-by-side hubs is 1.05D, where D is the rotor diameter. This configuration has a potential benefit for offshore wind developments in which power density can be maximized. The main goal is to evaluate the overall aerodynamic performance, blade loads and wake structure of a reference wind turbine generator operating within this dual turbine configuration, and to compare the effects against those for the typical single turbine configuration. For this purpose, an actuator line model has been employed together with the large eddy simulation approach for predicting the turbulence effects. This model, was implemented by using the open-source computational fluid dynamics toolbox OpenFOAM. Results show a better performance for the dual turbine concept. Under same operating conditions, the aerodynamic power of each turbine within the dual concept is higher than the power of the stand alone turbine, particularly at lower operating wind speeds (approximately 2% to 3% of extra power per turbine). Comparison between the two configurations shows similar character of the tangential and normal forces acting on the blades in terms of magnitude and fluctuation, eliminating potential concerns regarding fatigue and blade design. The largest difference in the tangential and normal root bending moments are approximately 3% and 2%, respectively, between single and dual turbine configurations. Finally, wake recovery analysis shows a downwind velocity deficit that is not enhanced streamwise in the dual turbine configuration with no considerable difference after 7D.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this work a closely-spaced dual turbine concept is studied. The distance between the two side-by-side hubs is 1.05D, where D is the rotor diameter. This configuration has a potential benefit for offshore wind developments in which power density can be maximized. The main goal is to evaluate the overall aerodynamic performance, blade loads and wake structure of a reference wind turbine generator operating within this dual turbine configuration, and to compare the effects against those for the typical single turbine configuration. For this purpose, an actuator line model has been employed together with the large eddy simulation approach for predicting the turbulence effects. This model, was implemented by using the open-source computational fluid dynamics toolbox OpenFOAM. Results show a better performance for the dual turbine concept. Under same operating conditions, the aerodynamic power of each turbine within the dual concept is higher than the power of the stand alone turbine, particularly at lower operating wind speeds (approximately 2% to 3% of extra power per turbine). Comparison between the two configurations shows similar character of the tangential and normal forces acting on the blades in terms of magnitude and fluctuation, eliminating potential concerns regarding fatigue and blade design. The largest difference in the tangential and normal root bending moments are approximately 3% and 2%, respectively, between single and dual turbine configurations. Finally, wake recovery analysis shows a downwind velocity deficit that is not enhanced streamwise in the dual turbine configuration with no considerable difference after 7D.
2022
Aihara, Aya; Mendoza, Victor; Goude, Anders; Bernhoff, Hans
Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine Journal Article
In: Energies, vol. 15, no. 7, pp. 2361, 2022, ISSN: 1996-1073.
Abstract | Links | Dimensions
@article{R13,
title = {Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine},
author = {Aya Aihara and Victor Mendoza and Anders Goude and Hans Bernhoff},
url = {https://www.mdpi.com/1996-1073/15/7/2361},
doi = {10.3390/en15072361},
issn = {1996-1073},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Energies},
volume = {15},
number = {7},
pages = {2361},
abstract = {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.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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.
Aihara, Aya; Mendoza, Victor; Goude, Anders; Bernhoff, Hans
A numerical study of strut and tower influence on the performance of vertical axis wind turbines using computational fluid dynamics simulation Journal Article
In: Wind Energy, vol. 25, no. 5, pp. 897-913, 2022.
Abstract | Links | Dimensions
@article{R12,
title = {A numerical study of strut and tower influence on the performance of vertical axis wind turbines using computational fluid dynamics simulation},
author = {Aya Aihara and Victor Mendoza and Anders Goude and Hans Bernhoff},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/we.2704},
doi = {10.1002/we.2704},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Wind Energy},
volume = {25},
number = {5},
pages = {897-913},
publisher = {Wiley Online Library},
abstract = {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.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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.
2021
Goude, Anders; Mendoza, Victor
Computational methods for vertical axis wind turbines Book Chapter
In: Small Wind and Hydrokinetic Turbines, pp. 71-107, Institution of Engineering and Technology, 2021, ISBN: 9781839530715.
Abstract | Links | Dimensions
@inbook{R14,
title = {Computational methods for vertical axis wind turbines},
author = {Anders Goude and Victor Mendoza},
url = {https://digital-library.theiet.org/content/books/10.1049/pbpo169e_ch4},
doi = {10.1049/PBPO169E_ch4},
isbn = {9781839530715},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
booktitle = {Small Wind and Hydrokinetic Turbines},
pages = {71-107},
publisher = {Institution of Engineering and Technology},
series = {Energy Engineering},
abstract = {There are two major types of vertical axis wind turbines (VAWTs): the Savonius rotor, which is based on the drag force and the Darrieus rotor, which is based on the lift force. The vertical axis turbine has the option to be modeled in two-dimensional (2D), which offer significant speed improvements and can give good approximations of the turbine forces, but cannot handle all interactions within the turbine and are less suitable for wake modeling. The Savonius rotor is commonly modeled with traditional computational fluid dynamics (CFD) software, as flow separation is crucial to its operation. While CFD models with resolved boundary layers also can be applied to the Darrieus, it is computationally demanding and simplified models, where the blades are modeled by external force models, are commonly applied. The most simplified model is the streamtube model, which uses a very simplified stationary model for the flow through the turbine. A more advanced approach is the actuator cylinder model, where the stationary flow is modeled through Euler's equation, giving a more realistic flow field. If time-dependent solutions are desired, there are the options to use either the actuator line model (ALM) or the vortex method, where the ALMs typically are implemented within traditional CFD solvers, while the vortex method often is implemented as a Lagrangian method that uses the vorticity as discretization parameter. The simplified models are primary useful for turbines with a high tip speed ratio, while the deep stall that can occur at a low tip speed ratio often requires traditional CFD solvers that resolve the boundary layers.},
keywords = {},
pubstate = {published},
tppubtype = {inbook}
}
There are two major types of vertical axis wind turbines (VAWTs): the Savonius rotor, which is based on the drag force and the Darrieus rotor, which is based on the lift force. The vertical axis turbine has the option to be modeled in two-dimensional (2D), which offer significant speed improvements and can give good approximations of the turbine forces, but cannot handle all interactions within the turbine and are less suitable for wake modeling. The Savonius rotor is commonly modeled with traditional computational fluid dynamics (CFD) software, as flow separation is crucial to its operation. While CFD models with resolved boundary layers also can be applied to the Darrieus, it is computationally demanding and simplified models, where the blades are modeled by external force models, are commonly applied. The most simplified model is the streamtube model, which uses a very simplified stationary model for the flow through the turbine. A more advanced approach is the actuator cylinder model, where the stationary flow is modeled through Euler's equation, giving a more realistic flow field. If time-dependent solutions are desired, there are the options to use either the actuator line model (ALM) or the vortex method, where the ALMs typically are implemented within traditional CFD solvers, while the vortex method often is implemented as a Lagrangian method that uses the vorticity as discretization parameter. The simplified models are primary useful for turbines with a high tip speed ratio, while the deep stall that can occur at a low tip speed ratio often requires traditional CFD solvers that resolve the boundary layers.
2020
Mendoza, Victor; Katsidoniotaki, Eirini; Bernhoff, Hans
Numerical Study of a Novel Concept for Manufacturing Savonius Turbines with Twisted Blades Journal Article
In: Energies, vol. 13, no. 8, pp. 1874, 2020, ISSN: 1996-1073.
Abstract | Links | Dimensions
@article{R11,
title = {Numerical Study of a Novel Concept for Manufacturing Savonius Turbines with Twisted Blades},
author = {Victor Mendoza and Eirini Katsidoniotaki and Hans Bernhoff},
url = {https://www.mdpi.com/1996-1073/13/8/1874},
doi = {10.3390/en13081874},
issn = {1996-1073},
year = {2020},
date = {2020-01-01},
urldate = {2020-01-01},
journal = {Energies},
volume = {13},
number = {8},
pages = {1874},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {This work presents a numerical study of the aerodynamic performance and the resulting flow field of two novel Savonius wind turbines with twisted blades. The novelty relies on the blade manufacturing process which is characterized by a ‘twisted cut’ through the central axis of a hollow cylinder (tube), followed by a partial twisted cut in the range of 90°. This approach does not require any expensive fabrication process such as blade molding and/or 3D prints, and, therefore, it can potentially mitigate the production costs. The main goal is to investigate the operational parameters and the overall performance of the presented devices, which are currently being operated in atmospheric conditions. For this purpose, three-dimensional simulations have been performed using the open-source CFD library OpenFOAM in order to solve the governing equations and for characterizing the main phenomena involved in the flow pattern. The Reynolds-averaged Navier-Stokes (RANS) approach together with the k − ω SST model were employed to reproduce the flow turbulence effects. This model is validated using wind tunnel measurements of the power ( C P ) and torque ( C M ) coefficients from a straight blade Savonius turbine. Unsteady simulations of the two turbine prototypes were investigated at different tip speed ratio TSR ( λ ) by varying the rotational speed of the rotor while keeping constant the free stream (rated) velocity V ∞ . The results were compared against the Savonius turbine employed for validating the model. Aerodynamic loads and general wake structure were studied at the optimal operational conditions as well. For the same turbine configurations, the new blade geometry improved the performance by 20-25% (at its optimal TSR), compared to the conventional straight blade Savonius rotor, as well as the reducing torque fluctuation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This work presents a numerical study of the aerodynamic performance and the resulting flow field of two novel Savonius wind turbines with twisted blades. The novelty relies on the blade manufacturing process which is characterized by a ‘twisted cut’ through the central axis of a hollow cylinder (tube), followed by a partial twisted cut in the range of 90°. This approach does not require any expensive fabrication process such as blade molding and/or 3D prints, and, therefore, it can potentially mitigate the production costs. The main goal is to investigate the operational parameters and the overall performance of the presented devices, which are currently being operated in atmospheric conditions. For this purpose, three-dimensional simulations have been performed using the open-source CFD library OpenFOAM in order to solve the governing equations and for characterizing the main phenomena involved in the flow pattern. The Reynolds-averaged Navier–Stokes (RANS) approach together with the k − ω SST model were employed to reproduce the flow turbulence effects. This model is validated using wind tunnel measurements of the power ( C P ) and torque ( C M ) coefficients from a straight blade Savonius turbine. Unsteady simulations of the two turbine prototypes were investigated at different tip speed ratio TSR ( λ ) by varying the rotational speed of the rotor while keeping constant the free stream (rated) velocity V ∞ . The results were compared against the Savonius turbine employed for validating the model. Aerodynamic loads and general wake structure were studied at the optimal operational conditions as well. For the same turbine configurations, the new blade geometry improved the performance by 20–25% (at its optimal TSR), compared to the conventional straight blade Savonius rotor, as well as the reducing torque fluctuation.
Mendoza, Victor; Goude, Anders
Validation of Actuator Line and Vortex Models using Normal Forces Measurements of a Straight-Bladed Vertical Axis Wind Turbine Journal Article
In: Energies, vol. 13, no. 3, pp. 511, 2020, ISSN: 1996-1073.
Abstract | Links | Dimensions
@article{R10,
title = {Validation of Actuator Line and Vortex Models using Normal Forces Measurements of a Straight-Bladed Vertical Axis Wind Turbine},
author = {Victor Mendoza and Anders Goude},
url = {https://www.mdpi.com/1996-1073/13/3/511},
doi = {10.3390/en13030511},
issn = {1996-1073},
year = {2020},
date = {2020-01-01},
urldate = {2020-01-01},
journal = {Energies},
volume = {13},
number = {3},
pages = {511},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {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 ( C P ) 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 C P curve. Similarities and discrepancies between numerical and experimental results are discussed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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 ( C P ) 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 C P curve. Similarities and discrepancies between numerical and experimental results are discussed.
2019
Mendoza, Victor; Goude, Anders
Improving farm efficiency of interacting vertical-axis wind turbines through wake deflection using pitched struts Journal Article
In: Wind Energy, vol. 22, no. 4, pp. 538–546, 2019.
Abstract | Links | Dimensions
@article{R1,
title = {Improving farm efficiency of interacting vertical-axis wind turbines through wake deflection using pitched struts},
author = {Victor Mendoza and Anders Goude},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/we.2305},
doi = {10.1002/we.2305},
year = {2019},
date = {2019-01-01},
urldate = {2019-01-01},
journal = {Wind Energy},
volume = {22},
number = {4},
pages = {538--546},
publisher = {Wiley Online Library},
abstract = {This work presents a numerical study of the obtained performance and the resulting flow field between two interacting large scale vertical-axis wind turbines (VAWTs), under the influence of a deflected wake through the struts pitching of the upwind turbine. The configuration consists of two VAWTs aligned in the direction of the incoming flow in which a wide range of fixed struts pitching angles in the upwind turbine have been investigated. The main goal is to evaluate the influence of the wake deflection on the turbines performance while they are operating at their optimal tip speed ratio (TSR), and to reproduce the most relevant phenomena involved in the flow pattern of the interacting wake. Arrangements with cross-stream offsets have also been tested for quantifying the contribution of this modification into the overall performance. For this purpose, an actuator line model (ALM) has been implemented using the open-source CFD library OpenFOAM in order to solve the governing equations and to calculate the resulting flow. The Large eddy simulation (LES) approach is considered to reproduce the turbulence flow effects. A preliminary study to identify the optimal TSR of the interacting downwind turbine has been investigated.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This work presents a numerical study of the obtained performance and the resulting flow field between two interacting large scale vertical-axis wind turbines (VAWTs), under the influence of a deflected wake through the struts pitching of the upwind turbine. The configuration consists of two VAWTs aligned in the direction of the incoming flow in which a wide range of fixed struts pitching angles in the upwind turbine have been investigated. The main goal is to evaluate the influence of the wake deflection on the turbines performance while they are operating at their optimal tip speed ratio (TSR), and to reproduce the most relevant phenomena involved in the flow pattern of the interacting wake. Arrangements with cross-stream offsets have also been tested for quantifying the contribution of this modification into the overall performance. For this purpose, an actuator line model (ALM) has been implemented using the open-source CFD library OpenFOAM in order to solve the governing equations and to calculate the resulting flow. The Large eddy simulation (LES) approach is considered to reproduce the turbulence flow effects. A preliminary study to identify the optimal TSR of the interacting downwind turbine has been investigated.
Mendoza, Victor; Chaudhari, Ashvinkumar; Goude, Anders
Performance and wake comparison of horizontal and vertical axis wind turbines under varying surface roughness conditions Journal Article
In: Wind Energy, vol. 22, no. 4, pp. 458–472, 2019.
Abstract | Links | Dimensions
@article{R2,
title = {Performance and wake comparison of horizontal and vertical axis wind turbines under varying surface roughness conditions},
author = {Victor Mendoza and Ashvinkumar Chaudhari and Anders Goude},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/we.2299},
doi = {10.1002/we.2299},
year = {2019},
date = {2019-01-01},
urldate = {2019-01-01},
journal = {Wind Energy},
volume = {22},
number = {4},
pages = {458--472},
publisher = {Wiley Online Library},
abstract = {A numerical study of both a horizontal axis wind turbine (HAWT) and a vertical axis wind turbine (VAWT) with similar size and power rating is presented. These large scale turbines have been tested when operating stand-alone at their optimal tip speed ratio (TSR) within a neutrally stratified atmospheric boundary layer (ABL). The impact of three different surface roughness lengths on the turbine performance is studied for the both turbines. The turbines performance, the response to the variation in the surface roughness of terrain, and the most relevant phenomena involved on the resulting wake were investigated. The main goal was to evaluate the differences and similarities of these two different types of turbine when they operate under the same atmospheric flow conditions. An actuator line model (ALM) was used together with the large eddy simulation (LES) approach for predicting wake effects, and it was implemented using the open-source computational fluid dynamics (CFD) library OpenFOAM to solve the governing equations and to compute the resulting flow fields. This model was first validated using wind tunnel measurements of power coefficients and wake of interacting HAWTs, and then employed to study the wake structure of both full scale turbines. A preliminary study test comparing the forces on a VAWT blades against measurements was also investigated. These obtained results showed a better performance and shorter wake (faster recovery) for an HAWT compared with a VAWT for the same atmospheric conditions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A numerical study of both a horizontal axis wind turbine (HAWT) and a vertical axis wind turbine (VAWT) with similar size and power rating is presented. These large scale turbines have been tested when operating stand-alone at their optimal tip speed ratio (TSR) within a neutrally stratified atmospheric boundary layer (ABL). The impact of three different surface roughness lengths on the turbine performance is studied for the both turbines. The turbines performance, the response to the variation in the surface roughness of terrain, and the most relevant phenomena involved on the resulting wake were investigated. The main goal was to evaluate the differences and similarities of these two different types of turbine when they operate under the same atmospheric flow conditions. An actuator line model (ALM) was used together with the large eddy simulation (LES) approach for predicting wake effects, and it was implemented using the open-source computational fluid dynamics (CFD) library OpenFOAM to solve the governing equations and to compute the resulting flow fields. This model was first validated using wind tunnel measurements of power coefficients and wake of interacting HAWTs, and then employed to study the wake structure of both full scale turbines. A preliminary study test comparing the forces on a VAWT blades against measurements was also investigated. These obtained results showed a better performance and shorter wake (faster recovery) for an HAWT compared with a VAWT for the same atmospheric conditions.
Mendoza, Victor; Bachant, Peter; Ferreira, Carlos; Goude, Anders
Near-wake flow simulation of a vertical axis turbine using an actuator line model Journal Article
In: Wind Energy, vol. 22, no. 2, pp. 171–188, 2019.
Abstract | Links | Dimensions
@article{R3,
title = {Near-wake flow simulation of a vertical axis turbine using an actuator line model},
author = {Victor Mendoza and Peter Bachant and Carlos Ferreira and Anders Goude},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/we.2277},
doi = {10.1002/we.2277},
year = {2019},
date = {2019-01-01},
urldate = {2019-01-01},
journal = {Wind Energy},
volume = {22},
number = {2},
pages = {171--188},
publisher = {Wiley Online Library},
abstract = {In the present work, the near-wake generated for a vertical axis wind turbine (VAWT) was simulated using an actuator line model (ALM) in order to validate and evaluate its accuracy. The sensitivity of the model to the variation of the spatial and temporal discretization was studied and showed a bigger response to the variation in the mesh size as compared with the temporal discretization. The large eddy simulation (LES) approach was used to predict the turbulence effects. The performance of Smagorinsky, dynamic k-equation, and dynamic Lagrangian turbulence models was tested, showing very little relevant differences between them. Generally, predicted results agree well with experimental data for velocity and vorticity fields in representative sections. The presented ALM was able to characterize the main phenomena involved in the flow pattern using a relatively low computational cost without stability concerns, identified the general wake structure (qualitatively and quantitatively), and the contribution from the blade tips and motion on it. Additionally, the effects of the tower and struts were investigated with respect to the overall structure of the wake, showing no significant modification. Similarities and discrepancies between numerical and experimental results are discussed. The obtained results from the various simulations carried out here can be used as a practical reference guideline for choosing parameters in VAWTs simulations using the ALM.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In the present work, the near-wake generated for a vertical axis wind turbine (VAWT) was simulated using an actuator line model (ALM) in order to validate and evaluate its accuracy. The sensitivity of the model to the variation of the spatial and temporal discretization was studied and showed a bigger response to the variation in the mesh size as compared with the temporal discretization. The large eddy simulation (LES) approach was used to predict the turbulence effects. The performance of Smagorinsky, dynamic k-equation, and dynamic Lagrangian turbulence models was tested, showing very little relevant differences between them. Generally, predicted results agree well with experimental data for velocity and vorticity fields in representative sections. The presented ALM was able to characterize the main phenomena involved in the flow pattern using a relatively low computational cost without stability concerns, identified the general wake structure (qualitatively and quantitatively), and the contribution from the blade tips and motion on it. Additionally, the effects of the tower and struts were investigated with respect to the overall structure of the wake, showing no significant modification. Similarities and discrepancies between numerical and experimental results are discussed. The obtained results from the various simulations carried out here can be used as a practical reference guideline for choosing parameters in VAWTs simulations using the ALM.
2017
Mendoza, Victor; Goude, Anders
Wake flow simulation of a vertical axis wind turbine under the influence of wind shear Proceedings Article
In: Journal of Physics: Conference Series, pp. 012031, IOP Publishing, 2017.
Abstract | Links | Dimensions
@inproceedings{R5,
title = {Wake flow simulation of a vertical axis wind turbine under the influence of wind shear},
author = {Victor Mendoza and Anders Goude},
url = {https://dx.doi.org/10.1088/1742-6596/854/1/012031},
doi = {10.1088/1742-6596/854/1/012031},
year = {2017},
date = {2017-01-01},
urldate = {2017-01-01},
booktitle = {Journal of Physics: Conference Series},
volume = {854},
number = {1},
pages = {012031},
publisher = {IOP Publishing},
abstract = {The current trend of the wind energy industry aims for large scale turbines installed in wind farms. This brings a renewed interest in vertical axis wind turbines (VAWTs) since they have several advantages over the traditional Horizontal Axis Wind Tubines (HAWTs) for mitigating the new challenges. However, operating VAWTs are characterized by complex aerodynamics phenomena, presenting considerable challenges for modeling tools. An accurate and reliable simulation tool for predicting the interaction between the obtained wake of an operating VAWT and the flow in atmospheric open sites is fundamental for optimizing the design and location of wind energy facility projects. The present work studies the wake produced by a VAWT and how it is affected by the surface roughness of the terrain, without considering the effects of the ambient turbulence intensity. This study was carried out using an actuator line model (ALM), and it was implemented using the open-source CFD library OpenFOAM to solve the governing equations and to compute the resulting flow fields. An operational H-shaped VAWT model was tested, for which experimental activity has been performed at an open site north of Uppsala-Sweden. Different terrains with similar inflow velocities have been evaluated. Simulated velocity and vorticity of representative sections have been analyzed. Numerical results were validated using normal forces measurements, showing reasonable agreement.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The current trend of the wind energy industry aims for large scale turbines installed in wind farms. This brings a renewed interest in vertical axis wind turbines (VAWTs) since they have several advantages over the traditional Horizontal Axis Wind Tubines (HAWTs) for mitigating the new challenges. However, operating VAWTs are characterized by complex aerodynamics phenomena, presenting considerable challenges for modeling tools. An accurate and reliable simulation tool for predicting the interaction between the obtained wake of an operating VAWT and the flow in atmospheric open sites is fundamental for optimizing the design and location of wind energy facility projects. The present work studies the wake produced by a VAWT and how it is affected by the surface roughness of the terrain, without considering the effects of the ambient turbulence intensity. This study was carried out using an actuator line model (ALM), and it was implemented using the open-source CFD library OpenFOAM to solve the governing equations and to compute the resulting flow fields. An operational H-shaped VAWT model was tested, for which experimental activity has been performed at an open site north of Uppsala-Sweden. Different terrains with similar inflow velocities have been evaluated. Simulated velocity and vorticity of representative sections have been analyzed. Numerical results were validated using normal forces measurements, showing reasonable agreement.
2016
Mendoza, Victor; Bachant, Peter; Wosnik, Martin; Goude, Anders
Validation of an actuator line model coupled to a dynamic stall model for pitching motions characteristic to vertical axis turbines Proceedings Article
In: Journal of physics: Conference series, pp. 022043, IOP Publishing, 2016.
Abstract | Links | Dimensions
@inproceedings{R6,
title = {Validation of an actuator line model coupled to a dynamic stall model for pitching motions characteristic to vertical axis turbines},
author = {Victor Mendoza and Peter Bachant and Martin Wosnik and Anders Goude},
url = {https://dx.doi.org/10.1088/1742-6596/753/2/022043},
doi = {10.1088/1742-6596/753/2/022043},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
booktitle = {Journal of physics: Conference series},
volume = {753},
number = {2},
pages = {022043},
publisher = {IOP Publishing},
abstract = {Vertical axis wind turbines (VAWT) can be used to extract renewable energy from wind flows. A simpler design, low cost of maintenance, and the ability to accept flow from all directions perpendicular to the rotor axis are some of the most important advantages over conventional horizontal axis wind turbines (HAWT). However, VAWT encounter complex and unsteady fluid dynamics, which present significant modeling challenges. One of the most relevant phenomena is dynamic stall, which is caused by the unsteady variation of angle of attack throughout the blade rotation, and is the focus of the present study. Dynamic stall is usually used as a passive control for VAWT operating conditions, hence the importance of predicting its effects. In this study, a coupled model is implemented with the open-source CFD toolbox OpenFOAM for solving the Navier-Stokes equations, where an actuator line model and dynamic stall model are used to compute the blade loading and body force. Force coefficients obtained from the model are validated with experimental data of pitching airfoil in similar operating conditions as an H-rotor type VAWT. Numerical results show reasonable agreement with experimental data for pitching motion.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Vertical axis wind turbines (VAWT) can be used to extract renewable energy from wind flows. A simpler design, low cost of maintenance, and the ability to accept flow from all directions perpendicular to the rotor axis are some of the most important advantages over conventional horizontal axis wind turbines (HAWT). However, VAWT encounter complex and unsteady fluid dynamics, which present significant modeling challenges. One of the most relevant phenomena is dynamic stall, which is caused by the unsteady variation of angle of attack throughout the blade rotation, and is the focus of the present study. Dynamic stall is usually used as a passive control for VAWT operating conditions, hence the importance of predicting its effects. In this study, a coupled model is implemented with the open-source CFD toolbox OpenFOAM for solving the Navier-Stokes equations, where an actuator line model and dynamic stall model are used to compute the blade loading and body force. Force coefficients obtained from the model are validated with experimental data of pitching airfoil in similar operating conditions as an H-rotor type VAWT. Numerical results show reasonable agreement with experimental data for pitching motion.
Parra-Santos, M Teresa; Perez, Ruben; Mendoza, Victor; Rodriguez, Miguel A; Castro, Francisco
Influence of swirl number on semi-confined flames Journal Article
In: International Journal of Applied Mathematics, Electronics and Computers, vol. 4, no. 3, pp. 65–67, 2016, ISSN: 2147-8228.
Abstract | Links | Dimensions
@article{R7,
title = {Influence of swirl number on semi-confined flames},
author = {M Teresa Parra-Santos and Ruben Perez and Victor Mendoza and Miguel A Rodriguez and Francisco Castro},
url = {https://dergipark.org.tr/en/pub/ijamec/issue/24462/259238},
doi = {10.18100/ijamec.69979},
issn = {2147-8228},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
journal = {International Journal of Applied Mathematics, Electronics and Computers},
volume = {4},
number = {3},
pages = {65--67},
abstract = {Stoichiometric methane air swirling flame has been modelled using RANS equations and a simplified mechanisms of reaction. The reaction zone is strongly affected by the swirl intensity. The higher the swirl number is, the narrower the reaction zone is. The thermodynamic state of reaction products matches well that of equilibrium state at constant pressure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Stoichiometric methane air swirling flame has been modelled using RANS equations and a simplified mechanisms of reaction. The reaction zone is strongly affected by the swirl intensity. The higher the swirl number is, the narrower the reaction zone is. The thermodynamic state of reaction products matches well that of equilibrium state at constant pressure.
2015
Parra-Santos, MT; Mendoza, Victor; Szasz, R; Gutkowski, AN; Castro-Ruiz, F
Influence of flow swirling on the aerothermodynamic behaviour of flames Journal Article
In: Combustion, Explosion, and Shock Waves, vol. 51, no. 4, pp. 424–430, 2015, ISSN: 1573-8345.
Abstract | Links | Dimensions
@article{R8,
title = {Influence of flow swirling on the aerothermodynamic behaviour of flames},
author = {MT Parra-Santos and Victor Mendoza and R Szasz and AN Gutkowski and F Castro-Ruiz},
url = {https://doi.org/10.1134/S0010508215040048},
doi = {10.1134/S0010508215040048},
issn = {1573-8345},
year = {2015},
date = {2015-01-01},
urldate = {2015-01-01},
journal = {Combustion, Explosion, and Shock Waves},
volume = {51},
number = {4},
pages = {424--430},
publisher = {Springer},
abstract = {The present work focuses on the numerical simulation of diffusive flames in a confined high-swirl burner. Navier–Stokes equations expressed for a time-dependent, compressible, and three-dimensional flow with finite-rate kinetics are solved for lean methane/air mixtures. A simplified mechanism is used to model the combustion. Non-reactive and reactive cases are contrasted for a swirl number of 0.95. Three flames for swirl numbers of 0, 0.6, and 0.95 are analyzed. In swirling flows, the inner recirculation zone is mainly composed of reaction products, which help in ignition of the incoming fuel. Moreover, the forward stagnation point plays an important role, leading to an azimuthal deflection of the flame front.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The present work focuses on the numerical simulation of diffusive flames in a confined high-swirl burner. Navier–Stokes equations expressed for a time-dependent, compressible, and three-dimensional flow with finite-rate kinetics are solved for lean methane/air mixtures. A simplified mechanism is used to model the combustion. Non-reactive and reactive cases are contrasted for a swirl number of 0.95. Three flames for swirl numbers of 0, 0.6, and 0.95 are analyzed. In swirling flows, the inner recirculation zone is mainly composed of reaction products, which help in ignition of the incoming fuel. Moreover, the forward stagnation point plays an important role, leading to an azimuthal deflection of the flame front.
2013
Parra, Teresa; Szasz, R. Z.; Duwig, C.; Pérez, R.; Mendoza, Victor; Castro, F.
Acoustic Instabilities on Swirling Flames Journal Article
In: International Journal of Mechanical Engineering, vol. 7, no. 9, pp. 1836 - 1839, 2013, ISSN: 1307-6892.
Abstract | Links | Dimensions
@article{R9,
title = {Acoustic Instabilities on Swirling Flames},
author = {Teresa Parra and R. Z. Szasz and C. Duwig and R. Pérez and Victor Mendoza and F. Castro},
url = {https://publications.waset.org/16734/acoustic-instabilities-on-swirling-flames},
doi = {10.5281/zenodo.1087838},
issn = {1307-6892},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
journal = {International Journal of Mechanical Engineering},
volume = {7},
number = {9},
pages = {1836 - 1839},
abstract = {The POD makes possible to reduce the complete high-dimensional acoustic field to a low-dimensional subspace where different modes are identified and let reconstruct in a simple way a high percentage of the variance of the field.
Rotating modes are instabilities which are commonly observed in swirling flows. Such modes can appear under both cold and reacting conditions but that they have different sources: while the cold flow rotating mode is essentially hydrodynamic and corresponds to the wellknown PVC (precessing vortex core) observed in many swirled unconfined flows, the rotating structure observed for the reacting case inside the combustion chamber might be not hydrodynamically but acoustically controlled. The two transverse acoustic modes of the combustion chamber couple and create a rotating motion of the flame which leads to a self-sustained turning mode which has the features of a classical PVC but a very different source (acoustics and not hydrodynamics).},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The POD makes possible to reduce the complete high-dimensional acoustic field to a low-dimensional subspace where different modes are identified and let reconstruct in a simple way a high percentage of the variance of the field.
Rotating modes are instabilities which are commonly observed in swirling flows. Such modes can appear under both cold and reacting conditions but that they have different sources: while the cold flow rotating mode is essentially hydrodynamic and corresponds to the wellknown PVC (precessing vortex core) observed in many swirled unconfined flows, the rotating structure observed for the reacting case inside the combustion chamber might be not hydrodynamically but acoustically controlled. The two transverse acoustic modes of the combustion chamber couple and create a rotating motion of the flame which leads to a self-sustained turning mode which has the features of a classical PVC but a very different source (acoustics and not hydrodynamics).
Rotating modes are instabilities which are commonly observed in swirling flows. Such modes can appear under both cold and reacting conditions but that they have different sources: while the cold flow rotating mode is essentially hydrodynamic and corresponds to the wellknown PVC (precessing vortex core) observed in many swirled unconfined flows, the rotating structure observed for the reacting case inside the combustion chamber might be not hydrodynamically but acoustically controlled. The two transverse acoustic modes of the combustion chamber couple and create a rotating motion of the flame which leads to a self-sustained turning mode which has the features of a classical PVC but a very different source (acoustics and not hydrodynamics).