Room:
Diesel Hall
Topic:
B. Wind, wakes, turbulence and wind farms
Form of presentation:
Oral
Duration:
120 Minutes
Chaired by: J. Meyers, J. Peinke
10:30
Shear layer approximation of Navier-Stokes steady equations for non-axisymmetric wind turbine wakes: Description and preliminary verification
Davide Trabucchi | ForWind - University of Oldenburg | Germany
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Authors:
Davide Trabucchi | ForWind - University of Oldenburg | Germany
Lukas Vollmer | Germany
Martin Kühn | Germany
The number of turbines installed in offshore wind farms has strongly increased in the last years and at the same time the need for more precise estimation of the wind farm efficiency. For this reason, the wind energy community could benefit from more accurate models for multiple wakes. Existing engineering models can only simulate single wakes, which are superimposed if they are interacting in a wind farm. This method is a practical solution, but it is not fully supported by a physical background. The limitation to single wakes is given by the assumption that the wake is axisymmetric. In this paper we propose an alternative model which is based on the existing engineering wake models, but is extended to simulate also non-axisymmetric wakes. Two application cases were addressed. First, we proved that for axisymmetric wakes the new model is equivalent to a commonly used engineering model. Then, we evaluated the improvements of the new model for the simulation of a non-axisymmetric wake.
10:50
3D Lagrangian VPM: simulations of the near-wake of an actuator disc and Horizontal Axis Wind Turbine
Tom Berdowski | TU Delft | Netherlands
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Authors:
Tom Berdowski | TU Delft | Netherlands
Carlos Ferreira | Netherlands
Jens Walther | Netherlands
The application of a 3-dimensional Lagrangian vortex particle method, coupled to a fast multipole method, has been assessed for modelling the near-wake of an axisymmetrical actuator disc and 3-bladed horizontal axis wind turbine with prescribed circulation from the MEXICO experiment. Simulations with the actuator disc showed a close agreement with theoretical, numerical, and experimental results from literature regarding wake expansion, velocity deficit, induction factor, and shear layer stability. Simulations with the 3-bladed turbine demonstrated that a purely 3-dimensional flow representation is challenging to model with particles. The manifestation of local complex flow structures of highly stretched vortices made the simulation unstable, which was successfully counteracted by the application of a particle strength exchange scheme. The axial and radial velocity profile over the near-wake showed a close agreement with results from the MEXICO experiment.
11:10
Vortex Particle-Mesh simulations of Vertical Axis Wind Turbine flows: from the blade aerodynamics to the very far wake
Prof. Philippe Chatelain | Université catholique de Louvain | Belgium
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Authors:
Prof. Philippe Chatelain | Université catholique de Louvain | Belgium
Matthieu Duponcheel | Belgium
Denis-Gabriel Caprace | Belgium
Yves Marichal | Belgium
Grégoire Winckelmans | Belgium
Thierry Maeder | Belgium
A Vortex Particle-Mesh (VPM) method with immersed lifting lines has been developed and validated. Based on the vorticity-velocity formulation of the Navier-Stokes equations, it combines the advantages of a particle method and of a mesh-based approach. The immersed lifting lines handle the creation of vorticity from the blade elements and its early development. LES of Vertical Axis Wind Turbine (VAWT) flows are performed. The complex wake development is captured in details and over very long distances: from the blades to the near wake coherent vortices, then through the transitional ones to the fully developed turbulent far wake (beyond 10 rotor diameters). The statistics and topology of the mean flow are studied. The computational sizes also allow insights into the detailed unsteady vortex dynamics, including some unexpected topological flow features.
11:30
Validation of actuator disc approach using model scaled wind turbines
Nikolaos Simisiroglou | Uppsala University | Sweden
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Authors:
Nikolaos Simisiroglou | Uppsala University | Sweden
Sasan Sarmast | Sweden
Simon Philippe Breton | Sweden
Stefan Ivanell | Sweden
In this study two wind turbine setups are investigated numerically: (a) the flow around a single model wind turbine and (b) the wake interaction between two in-line model wind turbines. This is done by using Reynolds averaged Navier-Stokes (RANS) and an actuator disc (ACD) technique in the computational fluid dynamics code PHOENICS. The computations are conducted for the design condition of the rotors using four different turbulence closure models. The computed axial velocity field as well as the turbulent kinetic energy are compared with PIV measurements. For the two model wind turbine setup, the thrust and power coefficient are also computed and compared with measurements. The results show that this RANS ACD method is able to predict the overall behaviour of the flow with low computational effort and that the turbulence closure model has a direct effect on the predicted wake development.
11:50
Validation of actuator line and disc techniques using the New MEXICO measurements
Dr. Sasan Sarmast | Uppsala University Campus Gotland | Sweden
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Authors:
Dr. Sasan Sarmast | Uppsala University Campus Gotland | Sweden
Wen Zhong Shen | Sweden
Stefan Ivanell | Sweden
Robert Flemming Mikkelsen | Sweden
Simon-Philippe Breton | Sweden
Actuator line and disc techniques are employed to analyse the wake obtained in the New MEXICO wind turbine experiment. Three flow configurations in axial flow condition are simulated and both computed loads and velocity fields around the rotor are compared with detailed PIV measurements. The comparisons show that the computed loadings are generally in agreement with the measurements under the rotor's design condition. Both actuator approaches under-predicted the loading in the inboard part of blade in stall condition as only 2D airfoil data were used in the simulations. The predicted wake velocities generally agree well with the PIV measurements. In the experiment, PIV measurements are also provided close to the hub and nacelle. To study the effect of hub and nacelle, numerical simulations are performed both in the presence and absence of the hub geometry. This study shows that the large hub used in the experiment has only small effects on overall wake behaviour.
12:10
Using High-Fidelity Computational Fluid Dynamics to Help Design a Wind Turbine Wake Measurement Experiment
Dr. Matthew Churchfield | National Renewable Energy Laboratory | United States
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Authors:
Dr. Matthew Churchfield | National Renewable Energy Laboratory | United States
Andrew Scholbrock | United States
Thomas Herges | United States
Torben Mikkelsen | United States
Mikael Sjöholm | United States
We describe the process of using large-eddy simulations of wind turbine wake flow to help design a wake measurement campaign. The main goal of the experiment is to measure wakes and wake deflection that result from intentional yaw misalignment under a variety of atmospheric conditions at the Scaled Wind Farm Technology facility operated by Sandia National Laboratories in Lubbock, Texas. Prior simulation studies have shown that wake deflection may be used for wind-plant control that maximizes plant power output. In this study, simulations are performed to characterize wake deflection and general behavior before the experiment is performed to ensure better upfront planning. Beyond characterizing the expected wake behavior, we also use the large-eddy simulation to test a virtual version of the lidar we plan to use to measure the wake and better understand our lidar scan strategy options. This work is an excellent example of a "simulation-in-the-loop" measurement campaign.