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  • 1.
    Breton, Simon-Philippe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Olivares-Espinosa, H.
    Masson, C.
    Dufresne, L.
    Comparative CFD study of the effect of the presence of downstream turbines on upstream ones using a rotational speed control system2014In: Science of Making Torque from Wind 2012, 2014, Vol. 555Conference paper (Refereed)
    Abstract [en]

    The effect of a downstream turbine on the production of a turbine located upstream of the latter is studied in this work. This is done through the use of two CFD simulation codes, namely OpenFOAM and EllipSys3D, which solve the Navier-Stokes equations in their incompressible form using a finite volume approach. In both EllipSys3D and Open Foam, the LES (Large Eddy Simulation) technique is used for modelling turbulence. The wind turbine rotors are modelled as actuator disks whose loading is determined through the use of tabulated airfoil data by applying the blade-element method. A generator torque controller is used in both simulation methods to ensure that the simulated turbines adapt, in terms of rotational velocity, to the inflow conditions they are submited to. Results from both simulation codes, although they differ slightly, show that the downstream turbine affects the upstream one when the spacing between the turbines is small. This is also suggested to be the case looking at measurements performed at the Lillgrund offshore wind farm, whose turbines are located unusually close to each other. However, for distances used in today's typical wind farms, this effect is shown by our calculations not to be significant.

  • 2.
    Breton, Simon-Philippe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Olivares-Espinosa, Hugo
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Masson, Christian
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Dufresne, Louis
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Study Of The Influence Of Atmospheric turbulence On The Asymptotic wake Deficit In A very Long Line Of Wind Turbines2013In: Proceedings of the 2013 International Conference on Aerodynamics of Offshore Wind Energy Systems and Wakes (ICOWES 2013), Denmark, 2013, p. 420-434Conference paper (Refereed)
    Abstract [en]

    The influence of atmospheric turbulence on the development of the flow along a long row of wind turbines is studied, in search for an asymptotic wake deficit state. Calculations are performed using EllipSys3D, a CFD code that solves the Navier-Stokes equations in their incompressible form using a finite volume approach. In this code, the Large Eddy Simulation technique is used for modelling turbulence, and the wind turbine rotors are represented as actuator disks whose loading is determined through the use of tabulated airfoil data by applying the blade-element method.

    Ten turbines are located along a row and separated from each other by seven rotor diameters, which is representative of the distance used in today’s offshore wind farms. Turbulence is pregenerated with the Mann model, with imposed turbulent levels of 4.5 and 8.9%. The turbines are in this study isolated from their environment, as no effect from the ground is modeled. This makes the proposed study of the asymptotic wake state behavior easier. Analysis of the characteristics of the flow as a function of the position along the row of turbines is performed in terms of turbulence intensity, mean velocity, and power spectra of the velocity fluctuations. Power production along the row of turbines is also used as an indicator.

    Calculations are performed below rated power, where a generator torque controller implemented in EllipSys3D renders it possible for the turbines to adapt to the inlet conditions in which they operate.

    The results obtained for the turbulence intensity, power and mean velocity as a function of downstream distance show that an asymptotic wake state seems close to be reached near the end of the 10 turbine row. They also show a certain dependency on the imposed level of turbulence. Uncertainties obtained in the power spectra of the velocity fluctuations suggest that further investigation is necessary.

  • 3.
    Eriksson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Environment and Climate Change Canada.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Impact of Wind Veer and the Coriolis Force for an Idealized Farm to Farm Interaction Case2019In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 5, article id 922Article in journal (Refereed)
    Abstract [en]

    The impact of the Coriolis force on the long distance wake behind wind farms is investigated using Large Eddy Simulations (LES) combined with a Forced Boundary Layer (FBL) technique. When using the FBL technique any mean wind shear and turbulent fluctuations can be added with body forces. The wind shear can also include the mean wind veer due to the Coriolis force. The variation of the Coriolis force due to local deviations from the mean profile, e.g., from wakes, is not taken into account in the FBL. This can be corrected for with an extra source term in the equations, hereon defined as the Coriolis correction. For a row of 4 turbines it is shown that the inclusion of the wind veer turns the wake to the right, while including the Coriolis correction turns it to the left. When including both wind veer and Coriolis correction the impact of wind veer dominates. For an idealized farm to farm interaction case, two farms of 4 * 4 turbines with 6 km in between, it can be seen that when including wind veer and the Coriolis correction a approximately 3% increase in the relative production for a full wake direction can be seen and only a slightly smaller increase can be seen when including only wind veer. The results indicate that FBL can be used for studies of long distance wakes without including a Coriolis correction but efforts need to be taken to use a wind shear with a correct mean wind veer.

  • 4.
    Eriksson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Mikkelsen, R.
    Hansen, K. S.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Analysis of long distance wakes of Horns Rev I using actuator disc approach2014In: Science of Making Torque from Wind 2012, 2014Conference paper (Refereed)
    Abstract [en]

    The wake recovery behind the Horns Rev wind farm is analysed to investigate the applicability of Large Eddy Simulations (LES) in combination with an actuator disc method (ACD) for farm to farm interaction studies. Periodic boundary conditions on the lateral boundaries are used to model the wind farm (as infinitely wide), using only two columns of turbines. The meteorological conditions of the site are taken into account by introducing wind shear and pre-generated synthetic turbulence to the simulation domain using body forces. Simulations are carried out to study the power production and the velocity deficit in the farm wake. The results are compared to the actual power production as well as to wind measurements at 2 km and 6 km behind the wind farm. The simulated power production inside the farm shows an overall good correlation with the real production, but is slightly overpredicted in the most downstream rows. The simulations overpredict the wake recovery, namely the wind velocity, at long distances behind the farm. Further studies are needed before the presented method can be applied for the simulation of long distance wakes. Suggested parameters to be studied are the development of the turbulence downstream in the domain and the impact of the grid resolution.

  • 5.
    Eriksson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Analysis of long distance wakes behind a row of turbines – a parameter study2014In: Science of Making Torque from Wind, 2014, p. 012152-Conference paper (Refereed)
    Abstract [en]

    Large Eddy Simulations (LES) of the long distance wake behind a row of 10 turbines are conducted to predict wake recovery. The Navier-Stokes solver EllipSys3D is used in combination with the actuator disc concept. Neutral atmospheric conditions are assumed in combination with synthetic turbulence using the Mann method. Both the wind shear profile and turbulence are introduced into the flow field using body forces. Previous simulations using the same simulation method to model the Horns Rev wind farm showed a higher wake recovery at long distances compared to measurements. The current study investigates further the sensitivity to parameters such as the grid resolution, Reynolds number, the turbulence characteristics as well as the impact of using different internal turbine spacings. The clearest impact on the recovery behind the farm could be seen from the background turbulence. The impact of the wind shear on the turbulence level in the domain needs further studies. A lower turbulence level gives lower wake recovery as expected. A lower wake recovery can also be seen for a higher grid resolution. The Reynolds number, apart from when using a very low value, has a small impact on the result. The variation of the internal spacing is seen to have a relatively minor impact on the farm wake recovery.

  • 6.
    Eriksson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Large-eddy simulations of wind farm production and long distance wakes2015In: Wake Conference 2015, 2015, p. 012022-, article id 012022Conference paper (Refereed)
    Abstract [en]

    The future development of offshore wind power will include many wind farms built in the same areas. It is known that wind farms produce long distance wakes, which means that we will see more occasions of farm to farm interaction, namely one wind farm operating in the wake of another wind farm. This study investigates how to perform accurate power predictions on large wind farms and how to assess the long distance wakes generated by these farms. The focus of this paper is the production's and wake's sensitivity to the extension of the grid as well as the turbulence when using Large-eddy simulations (LES) with pregenerated Mann turbulence. The aim is to determine an optimal grid which minimizes blockage effects and ensures constant resolution in the entire wake region at the lowest computational cost. The simulations are first performed in the absence of wind turbines in order to assess how the atmospheric turbulence and wind profile are evolving downstream (up to 12,000 m behind the position where the turbulence is imposed). In the second step, 10 turbines are added in the domain (using an actuator disc method) and their production is analyzed alongside the mean velocities in the domain. The blockage effects are tested using grids with different vertical extents. An equidistant region is used in order to ensure high resolution in the wake region. The importance of covering the entire wake structure inside the equidistant region is analyzed by decreasing the size of this region. In this step, the importance of the lateral size of the Mann turbulence box is also analyzed. In the results it can be seen that the flow is acceptably preserved through the empty domain if a larger turbulence box is used. The relative production is increased (due to blockage effects) for the last turbines using a smaller vertical domain, increased for a lower or narrower equidistant region (due to the smearing of the wake in the stretched area) and decreased when using a smaller turbulence box (due to decreased inmixing) The long distance wake behind the row is most impacted by the use of a smaller turbulence box, while the other simulation setups have less influence on these results. In summary, the results show the importance of having relatively large extensions of the domain, large extensions of the equidistant region and especially large extensions of the turbulence box.

  • 7.
    Martinen, Silke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Carlén, Ingemar
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Analysis of the effect of curtailment on power and fatigue loads of two aligned wind turbines using an actuator disc approach2014In: Science of Making Torque from Wind, 2014, p. 012182-Conference paper (Refereed)
    Abstract [en]

    To study the effects of curtailment on both power production and fatigue loading, actuator disc (ACD) simulations of two turbines aligned in the wind direction are performed with the EllipSys3D code developed at DTU/Risø. Blade forces, extracted along a line that rotates in the rotor plane with the rotational velocity of the respective turbine, are used to calculate flapwise bending moments. After applying a rainflow counting algorithm an equivalent moment is calculated. Power curtailment is introduced by changing the pitch angle of the first turbine. Evaluation is made with regards to load reduction at the second turbine and to total production loss compared to the situation without any curtailment. The aeroelastic code Vidyn, developed by Teknikgruppen (Ganander [20]), is used to validate the above-mentioned ACD-based load calculation method. For this purpose, the EllipSys3D simulations are also performed without the second turbine and time series of cross sectional velocity fields are extracted at positions corresponding to the placement of the downstream turbine tested above. These fields are later used as an input for the simulations performed with Vidyn. The results from Vidyn and the results based on the ACD blade forces show similar trends. Fatigue loads at the downwind turbine are clearly decreasing as the blade pitch angle of the upstream turbine is increasing. The achievable amount of fatigue load reduction depends on the level of the imposed pre- generated turbulence as well as the spacing between the turbines. The presented method is intended for further development of wind park optimization strategies.

  • 8.
    Nilsson, Karl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Sørensen, Jens Nørkær
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Airfoil data sensitivity analysis for actuator disc simulations used in wind turbine applications2014In: Science of Making Torque from Wind, 2014, p. 012135-Conference paper (Refereed)
    Abstract [en]

    To analyse the sensitivity of blade geometry and airfoil characteristics on the prediction of performance characteristics of wind farms, large-eddy simulations using an actuator disc (ACD) method are performed for three different blade/airfoil configurations. The aim of the study is to determine how the mean characteristics of wake flow, mean power production and thrust depend on the choice of airfoil data and blade geometry. In order to simulate realistic conditions, pre-generated turbulence and wind shear are imposed in the computational domain. Using three different turbulence intensities and varying the spacing between the turbines, the flow around 4-8 aligned turbines is simulated. The analysis is based on normalized mean streamwise velocity, turbulence intensity, relative mean power production and thrust. From the computations it can be concluded that the actual airfoil characteristics and blade geometry only are of importance at very low inflow turbulence. At realistic turbulence conditions for an atmospheric boundary layer the specific blade characteristics play an minor role on power performance and the resulting wake characteristics. The results therefore give a hint that the choice of airfoil data in ACD simulations is not crucial if the intention of the simulations is to compute mean wake characteristics using a turbulent inflow.

  • 9.
    Nilsson, Karl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Mikkelsen, Robert
    Technical University of Denmark.
    Hansen, K.S.
    Technical University of Denmark.
    Sørensen, Jens Nørkær
    Technical University of Denmark.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Henningson, D.
    Technical University of Denmark.
    Large-eddy simulations of the Lillgrund wind farm2015In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 18, no 3, p. 449-467Article in journal (Refereed)
    Abstract [en]

    The power production of the Lillgrund wind farm is determined numerically using large-eddy simulations and compared with measurements. In order to simulate realistic atmospheric conditions, pre-generated turbulence and wind shear are imposed in the computational domain. The atmospheric conditions are determined from data extracted from a met mast, which was erected prior to the establishment of the farm. In order to allocate most of the computational power to the simulations of the wake flow, the turbines are modeled using an actuator disc method where the discs are imposed in the computational domain as body forces which for every time step are calculated from tabulated airfoil data. A study of the influence of imposed upstream ambient turbulence is performed and shows that higher levels of turbulence results in slightly increased total power production and that it is of great importance to include ambient turbulence in the simulations. By introducing ambient atmospheric turbulence, the simulations compare very well with measurements at the studied inflow angles. A final study aiming at increasing the farm production by curtailing the power output of the front row turbines and thus letting more kinetic energy pass downstream is performed. The results, however, show that manipulating only the front row turbines has no positive effect on the farm production, and therefore, more complex curtailment strategies are needed to be tested.

  • 10.
    Nilsson, Karl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Shen, Wen Z.
    Sorensen, Jens N.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Validation of the actuator line method using near wake measurements of the MEXICO rotor2015In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 18, no 3, p. 499-514Article in journal (Refereed)
    Abstract [en]

    The purpose of the present work is to validate the capability of the actuator line method to compute vortex structures in the near wake behind the MEXICO experimental wind turbine rotor. In the MEXICO project/MexNext Annex, particle image velocimetry measurements have made it possible to determine the exact position of each tip vortex core in a plane parallel to the flow direction. Determining center positions of the vortex cores makes it possible to determine the trajectory of the tip vortices, and thus the wake expansion in space, for the analyzed tip speed ratios. The corresponding cases, in terms of tip speed ratios, have been simulated by large-eddy simulations using a Navier-Stokes code combined with the actuator line method. The flow field is analyzed in terms of wake expansion, vortex core radius, circulation and axial and radial velocity distributions. Generally, the actuator line method generates significantly larger vortex cores than in the experimental cases, but predicts the expansion, the circulation and the velocity distributions with satisfying results. Additionally, the simulation and experimental data are used to test three different techniques to compute the average axial induction in the wake flow. These techniques are based on the helical pitch of the tip vortex structure, 1D momentum theory and wake expansion combined with mass conservation. The results from the different methods vary quite much, especially at high values of . Copyright (c) 2014 John Wiley & Sons, Ltd.

  • 11.
    Nilsson, Karl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Soares, José
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Energy transition Gotland: Renewable resources and system effects2018Report (Other academic)
  • 12.
    Olivares-Espinosa, Hugo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Ecole Technol Super, Dept Mech Engn, 1100 Notre Dame Ouest, Montreal, PQ H3C 1K3, Canada.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Nergica, 70 Rue Bolduc, Gaspe, PQ G4X 1G2, Canada.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Masson, Christian
    Ecole Technol Super, Dept Mech Engn, 1100 Notre Dame Ouest, Montreal, PQ H3C 1K3, Canada.
    Dufresne, Louis
    Ecole Technol Super, Dept Mech Engn, 1100 Notre Dame Ouest, Montreal, PQ H3C 1K3, Canada.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Assessment of Turbulence Modelling in the Wake of an Actuator Disk with a Decaying Turbulence Inflow2018In: Applied Sciences, E-ISSN 2076-3417, Vol. 8, no 9, article id 1530Article in journal (Refereed)
    Abstract [en]

    The characteristics of the turbulence field in the wake produced by a wind turbine model are studied. To this aim, a methodology is developed and applied to replicate wake measurements obtained in a decaying homogeneous turbulence inflow produced by a wind tunnel. In this method, a synthetic turbulence field is generated to be employed as an inflow of Large-Eddy Simulations performed to model the flow development of the decaying turbulence as well as the wake flow behind an actuator disk. The implementation is carried out on the OpenFOAM platform, resembling a well-documented procedure used for wake flow simulations. The proposed methodology is validated by comparing with experimental results, for two levels of turbulence at inflow and disks with two different porosities. It is found that mean velocities and turbulent kinetic energy behind the disk are well estimated. The development of turbulence lengthscales behind the disk resembles what is observed in the free flow, predicting the ambient turbulence lengthscales to dominate across the wake, with little effect of shear from the wake envelope. However, observations of the power spectra confirm that shear yields a boost to the turbulence energy within the wake noticeable only in the low turbulence case. The results obtained show that the present implementation can successfully be used in the modelling and analysis of turbulence in wake flows.

  • 13.
    Olivares-Espinosa, Hugo
    et al.
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Masson, Christian
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Dufresne, Louis
    École de technologie supérieure, Department of Mechanical Engineering, Montréal, Canada.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Characterization of wind turbine wakes in a non-sheared turbulent flow2013In: Proceedings of the 2013 International Conference on Aerodynamics of Offshore Wind Energy Systems and Wakes (ICOWES2013), Denmark, 2013, p. 435-449Conference paper (Refereed)
    Abstract [en]

    The characteristics of the turbulence field in wakes produced by horizontal-axis wind turbines under a uniform inflow are studied. To this aim, LES simulations of a rotor subjected to different types of inflow are performed with OpenFOAM. Two different Actuator Disk (AD) models for the rotor are implemented with the goal of assessing their capabilities to reproduce the turbulence characteristics of the wake: a uniformly loaded rotor and an AD model based on the blade element theory that employs tabulated airfoil data to calculate the distribution of forces over the disk as well as the geometry and other physical parameters from a conceptual 5 MW offshore wind turbine. The latter AD implementation makes use of a control system to adjust the rotational velocity of the rotor to the conditions of the wind flow.

    The turbulent wakes produced by the two AD models are analyzed over three different inflow conditions: laminar and two turbulent inflows of intensities 3.2 % and 6.7 % measured at the location of the rotor when the turbine is not present. The turbulence is pre-generated using the Mann model, that produces turbulent fields with the same second order statistics of the atmospheric turbulence. The turbulence is introduced in the computational domain at a position ahead of the rotor instead of at the inlet, to minimize its decay as it is convected downstream in the domain.

    A study of the turbulence evolution in the absence of the rotor reveals a discrepancy between the values of the turbulence intensity of the pre-generated field when it is measured before and after it has been introduced in the computational domain. This in turn suggests a numerical issue caused by imposing a turbulent velocity field in the flow. However, once the turbulence is introduced, it is found to exhibit a very small decay as the flow moves downstream.

    The simulations of the turbulent wake show differences in the turbulence characteristics of the near wake of each AD model. We also observe a dissimilar behaviour of the turbulence intensity along the wake for the different inflow conditions which difficult the task of determining a conclusive trend. Nonetheless, the results show that the turbulence characteristics in the far wake are nearly independent of the AD model or the inflow turbulence characteristics.

    This new implementation of the AD techniques and the use of the Mann method in OpenFOAM can be also proved useful in the future when comparing with the results of similar studies for which other CFD platforms are used.

  • 14.
    Simisiroglou, Nikolaos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. WindSim AS, Fjordgaten 15, N-3125 Tonsberg, Norway.
    Karatsioris, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Breton, Simon-Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Ivanell, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    The actuator disc concept in PHOENICS2016In: Energy Procedia / [ed] Tande, JOG; Kvamsdal, T; Muskulus, M, 2016, Vol. 94, p. 269-277Conference paper (Refereed)
    Abstract [en]

    This study presents two models to simulate a wind turbine. This is done by employing the 1D momentum actuator disc theory in PHOENICS, a general purpose computational fluid dynamics software. To test the general applicability of these models, single wind turbine simulations are conducted using eight different wind turbine models from two manufacturers. The simulations are performed by imposing sheared inflow with hub height wind speeds ranging from 3 m/s up to 25 m/s. A range of computational parameters are investigated, including the resolution of the domain, the thickness of the actuator disc and the iterative convergence criteria. To investigate the wake development produced by these methods, a comparison study is performed with the more complex large-eddy simulation software EllipSys3D using an actuator disc approach for validation purposes. The resulting wind turbine thrust and power outputs from PHOENICS are compared with the experimental power curves and thrust values provided by the manufacturers for each wind turbine. The results show that actuator disc methods are able to provide a reasonable estimation of the conventional wind turbine power and thrust output with low computational effort. Moreover, the results from the preliminary comparison of the wake produced from these two rotor models compare well with the wake produced by the actuator disc in EllipSys3D.

  • 15.
    Sopher, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Juhlin, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Levendal, Tegan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Erlstrom, Mikael
    Geol Survey Sweden SGU, Kiliansgatan 10, S-22350 Lund, Sweden;Lund Univ, Dept Geol, Solvegatan 12, S-22362 Lund, Sweden.
    Nilsson, Karl
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Da Silva Soares, José Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Evaluation of the subsurface compressed air energy storage (CAES) potential on Gotland, Sweden2019In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 78, no 6, article id 197Article in journal (Refereed)
    Abstract [en]

    Wind energy is an important field of development for the island of Gotland, Sweden, especially since the island has set targets to generate 100% of its energy from renewable sources by 2025. Due to the variability of wind conditions, energy storage will be an important technology to facilitate the continued development of wind energy on Gotland and ensure a stable and secure supply of electricity. In this study, the feasibility of utilizing the Middle Cambrian Faludden sandstone reservoir on Gotland for Compressed Air Energy Storage (CAES) is assessed. Firstly, a characterization of the sandstone beneath Gotland is presented, which includes detailed maps of reservoir thickness and top reservoir structure. Analysis of this information shows that the properties of the Faludden sandstone and associated cap rock appear favorable for the application of CAES. Seven structural closures are identified below the eastern and southern parts of Gotland, which could potentially be utilized for CAES. Scoping estimates of the energy storage capacity and flow rate for these closures within the Faludden sandstone show that industrial scale CAES could be possible on Gotland.

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