Abstract
Abstract. Light detection and ranging (lidar) systems have gained a great importance in today's wake characteristic measurements. The aim of this measurement campaign is to track the wake meandering and in a further step to validate the wind speed deficit in the meandering frame of reference (MFR) and in the fixed frame of reference using nacelle-mounted lidar measurements. Additionally, a comparison of the measured and the modeled wake degradation in the MFR was conducted. The simulations were done with two different versions of the dynamic wake meandering (DWM) model. These versions differ only in the description of the quasi-steady wake deficit. Based on the findings from the lidar measurements, the impact of the ambient turbulence intensity on the eddy viscosity definition in the quasi-steady deficit has been investigated and, subsequently, an improved correlation function has been determined, resulting in very good conformity between the new model and the measurements.
Highlights
Wake calculation of neighboring wind turbines is a key aspect of every wind farm development
In the analysis presented here, only results from a horizontal line scan are analyzed, so that no vertical meandering is eliminated from the wind speed deficit, and the deficit’s depth is less pronounced in comparison to the real meandering frame of reference (MFR)
The measured wind speed deficit in the HMFR is consecutively compared to the dynamic wake meandering (DWM) model, which is based on the assumption that the wake behaves as a passive tracer in the turbulent wind field
Summary
Wake calculation of neighboring wind turbines is a key aspect of every wind farm development. The DWM model is based on the assumption that the wake behaves as a passive tracer, which means the wake itself is deflected in the vertical and horizontal directions (Larsen et al, 2008b) The combination of this deflection and the shape of the wind speed deficit leads to an increased turbulence at a fixed position downstream. Particular focus is put on the investigation of the wind speed deficit’s shape in the MFR and the degradation of the wind speed deficit in the downstream direction The latter can be captured very well with the used nacelle-mounted pulsed scanning lidar systems due to the fact that it measures simultaneously in different downstream distances. Based on the outlined measurement results, a recalibration of the defined degradation of the wind speed deficit in the DWM model is proposed in Sect.
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