Room:
Prandtl Hall
Topic:
F. Measurement, monitoring and experimental techniques
Form of presentation:
Oral
Duration:
120 Minutes
Chaired by: M. Kühn, J. Mann
13:30
Improving lidar turbulence estimates for wind energy
Dr. Jennifer Newman | NREL | United States
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Authors:
Dr. Jennifer Newman | NREL | United States
Andrew Clifton | United States
Matthew Churchfield | United States
Petra Klein | United States
Remote sensing devices (e.g., lidars) are quickly becoming a cost-effective and reliable alternative to meteorological towers for wind energy applications. While lidars can measure mean wind speeds accurately, these devices measure different values of turbulence intensity (TI) than an instrument on a tower. In response to these issues, a lidar TI error reduction model was recently developed for commercially available lidars. The TI error model first applies physics-based corrections to the lidar measurements, then uses machine learning techniques to further reduce errors in lidar TI estimates. The model was tested at two sites in the Southern Plains where vertically profiling lidars were collocated with meteorological towers. Results indicate that the model works well under stable conditions but cannot fully mitigate the effects of variance contamination under unstable conditions. In order to understand how variance contamination affects lidar TI estimates, a new set of equations was derived in previous work to characterize the actual variance measured by a lidar. Terms in these equations were quantified using a lidar simulator and modeled wind field, and the new equations were then implemented into the TI error model.
13:50
Analysis of wind coherency in the longitudinal direction using turbine mounted lidar
Dr. Samuel Davoust | GE Global Research | Germany
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Authors:
Dr. Samuel Davoust | GE Global Research | Germany
Dominic von Terzi | Germany
We examine wind coherency using measurements of longitudinal wind speed obtained using a single beam from a pulsed turbine mounted lidar over three sites. The effect of different atmospheric conditions is evaluated. We measured the increased coherency decay with frequency when turbulence intensity increases, and the increased 0Hz coherency limit when integral length-scale increases. A correction was applied for artificial coherency decrease due to lidar measurement effects. Results display encouraging similarities with a computational study carried out by Large Eddy Simulation.
14:10
Demonstration of synchronised scanning lidar measurements of 2D velocity fields in a boundary-layer wind tunnel
Marijn van Dooren | Carl von Ossietzky University of Oldenburg | Germany
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Authors:
Marijn van Dooren | Carl von Ossietzky University of Oldenburg | Germany
Martin Kühn | Germany
Vlaho Petrovíc | Germany
Marc Bromm | Germany
Carlo Bottasso | Germany
Filippo Campagnolo | Germany
Mikael Sjöholm | Germany
Nikolas Angelou | Germany
Torben Mikkelsen | Germany
Alessandro Croce | Germany
Alberto Zasso | Germany
This paper combines the research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dual- Lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot wire probe measurements commonly used in wind tunnels to validate the methodology. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed. The research campaign revealed a high potential for using short-range WindScanner Lidar for accurately measuring small scale flow structures inside a boundary-layer wind tunnel.
14:30
Open Access Wind Tunnel Measurements of a Downwind Free Yawing Wind Turbine
Dr. David Verelst | DTU Wind Energy | Denmark
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Authors:
Dr. David Verelst | DTU Wind Energy | Denmark
Torben Larsen | Denmark
Jan-Willem van Wingerden | Denmark
A series of free yawing wind tunnel experiments was held in the Open Jet Facility (OJF) of the TU Delft. The turbine has three blades in a downwind configuration and is optionally free to yaw. Different rotor configurations are tested, such as blade flexibility and sweep. This paper gives a brief overview of the measurement setup and challenges, and continues with presenting some key results. This wind tunnel campaign has shown that a three bladed downwind wind turbine can operate in a stable fashion under a minimal yaw error. Finally, a description of how to obtain this open access dataset, including the post-processing scripts and procedures, is made available via a publicly accessible website.
14:50
Wind tunnel study of the power output spectrum in a micro-wind farm
Juliaan Bossuyt | KU Leuven | Belgium
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Authors:
Juliaan Bossuyt | KU Leuven | Belgium
Michael F. Howland | Belgium
Charles Meneveau | Belgium
Johan Meyers | Belgium
Instrumented small-scale porous disc models are used to study the spectrum of a surrogate for the power output in a micro wind farm with 100 models of wind turbines. The power spectrum of individual porous disk models in the first row of the wind farm show the expected 5/3 power law at higher frequencies. Downstream models measure an increased variance due to wake effects. Conversely, the power spectrum of the sum of the power over the entire wind farm shows a peak at the turbine-to-turbine travel frequency between the model turbines, and a near 5/3 power law region at a much wider range of lower frequencies, confirming previous LES results. Comparison with the spectrum that would result when assuming that the signals are uncorrelated, highlights the strong effects of correlations and anti-correlations in the fluctuations at various frequencies.
15:10
Momentum considerations on the New MEXICO experiment
Herman Snel | ECN | Netherlands
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Authors:
Herman Snel | ECN | Netherlands
Parra Edgar Andres | Netherlands
Koen Boorsma | Netherlands
Gerard Schepers
The investigation regards axial and angular momentum considerations combining detailed loads from pressure sensors and the flow field mapped with particle image velocimetry (PIV) techniques. For this end, the study implements important results leaning on experimental data from wind tunnel measurements of the New MEXICO project. The measurements, taken on a fully instrumented rotor, were carried out in the German Dutch Wind tunnel Organisation (DNW) testing the MEXICO rotor in the open section. The work revisits the so-called momentum theory, showing that to a good extent the integral thrust and torque on the rotor correspond to the momentum balance of the global flow field using the general momentum equations. Likewise, the sectional forces combined with the local induced velocities are found to plausibly obey the annular streamtube theory, albeit some limitations in the axial momentum seem more apparent at higher inductions.