University of Tübingen, Center for Applied Geoscience Environmental Physics, Hölderlinstr. 12, 72074 Tübingen
Abstract. The Weather Research and Forecasting (WRF) Model has been coupled with a URANS Model to simulate the passage of a cold front over the WINSENT site, a wind energy test-site under development. It is located on a hill near a steep, forested terrain edge. A high spatial resolution is necessary to simulate the flow over this complex site accurately for which reason the WRF model is run at high resolution in LES mode coupled to a URANS model with an even higher resolution. A forest parametrization is implemented in both models to account for the drag caused by the trees. The main result is that the WRF model without forest parametrization overestimates the wind speed in the lowest 100 m above ground on average by about 3 ms−1. Introducing the forest parametrization reduces the bias considerably, but overcompensates the error at 45 m above ground, leading to a small negative bias. The URANS model further improves the flow simulation and provides a nearly bias free simulation compared to observation. Observations are taken with a 100-m high met-mast at five different levels. In addition, wind measurements taken with an Unmanned Aircraft System provide data along a cross-section that intersects the terrain edge.
How to cite. Leukauf, D., El-Bahlouli, A., zum Berge, K., Schön, M., Knaus, H., and Bange, J.: The impact of a forest parametrization on coupled WRF-CFD
simulations during the passage of a cold front over the WINSENT
test-site, Wind Energ. Sci. Discuss. [preprint], https://doi.org/10.5194/wes-2019-68, 2019.
Hilltops are in principle favorable locations for wind turbines due to the increased mean wind speed that can be found over hills. However, the more complex terrain leads to more complex flow conditions and increased turbulence. Numerical simulations are required to understand the flow conditions at sites in hilly terrain. A numerical simulation of the passage of a cold front over the site shows that increased drag caused by the nearby forests must be included in the model.
Hilltops are in principle favorable locations for wind turbines due to the increased mean wind...