A Two-Day Case Study: Comparison of Turbulence Data from an Unmanned Aircraft System with a Model Chain for Complex Terrain

Kjell Zum Berge,Moritz Mauz,Jens Bange,Asmae El Bahlouli,Patrick Letzgus,Daniel Leukauf,Hermann Knaus,Bram Van Kesteren,Andreas Platis,Martin Schoen

doi:10.1007/s10546-021-00608-2

Abstract

The airborne measurement platform MASC-3 (Multi-Purpose Airborne Sensor Carrier) is used for measurements over a forested escarpment in the Swabian Alps to evaluate the wind field. Data from flight legs between 20 and 200 m above the ground on two consecutive days with uphill (westerly) flow in September 2018 are analyzed. In the lowest 140 m above the ground a speed-up is found with increased turbulence and changes in wind direction directly over the escarpment, whereas in the lowest 20 to 50 m above the ground a deceleration of the flow is measured. Additionally, simulation results from a numerical model chain based on the Weather Research and Forecasting (WRF) model and an OpenFOAM (Open Source Field Operation and Manipulation) model, developed for complex terrain, are compared to the data captured by MASC-3. The models and measurements compare well for the mean wind speed and inclination angle.

Highlights

In 2019, wind energy production covered 15% of the electricity demand for all 28 European Union member states (WindEurope 2019)
Simulation results from a numerical model chain based on the Weather Research and Forecasting (WRF) model and an OpenFOAM (Open Source Field Operation and Manipulation) model, developed for complex terrain, are compared to the data captured by MASC-3
The unmanned aircraft system (UAS) MASC-3 was used to conduct measurements on two consecutive days in September 2018 over the WINSENT test site. Data from these flights were compared to numerical simulations of two stages of fidelity and the measured wind field was analyzed regarding its impact on the future wind turbines

Summary

Introduction

In 2019, wind energy production covered 15% of the electricity demand for all 28 European Union member states (WindEurope 2019). Due to the increasing numbers of wind turbines erected, the wind-energy research focus is shifting from flat terrain and offshore locations towards complex topography Orographic effects, such as channeling or the acceleration of near-surface flow, can lead to local increases in wind speed (Wagenbrenner et al 2016) and improvement in wind resource (Clifton et al 2014). The flow is influenced by the heterogeneous orography, leading to higher levels of turbulence in the lower atmospheric boundary layer (ABL), wind shear, and a less predictable behaviour. These features rapidly change the wind field in both space and time (Wildmann et al 2017). This makes a UAS especially useful for measurements in complex terrain, as it captures the phenomena over certain areas of an escarpment or other complex structures

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