Comparison of CFD Simulation to UAS Measurements for Wind Flows in Complex Terrain: Application to the WINSENT Test Site

Bahlouli, Asmae El; Rautenberg, Alexander; Schön, Martin; Berge, Kjell zum; Bange, Jens; Knaus, Hermann

doi:10.3390/en12101992

Cited by 11 publications

(10 citation statements)

References 33 publications

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“…In the current study, the wind flow is simulated using the software OpenFOAM v6. An unsteady Reynolds Averaged Navier-Stokes (URANS) approach, necessary for the investigation of non-stationary flow features, was considered [34,35]. The governing equations for mass, momentum, and potential temperature, under the Boussinesq approximation, are written relative to a hydrostatic state (index h) in a Cartesian coordinate system as:…”

Section: Numerical Modelmentioning

confidence: 99%

Validating CFD Predictions of Flow over an Escarpment Using Ground-Based and Airborne Measurement Devices

et al. 2020

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Micrometeorological observations from a tower, an eddy-covariance (EC) station and an unmanned aircraft system (UAS) at the WINSENT test-site are used to validate a computational fluid dynamics (CFD) model, driven by a mesoscale model. The observation site is characterised by a forested escarpment in a complex terrain. A two-day measurement campaign with a flow almost perpendicular to the escarpment is analysed. The first day is dominated by high wind speeds, while, on the second one, calm wind conditions are present. Despite some minor differences, the flow structure, analysed in terms of horizontal wind speeds, wind direction and inclination angles shows similarities for both days. A real-time strategy is used for the CFD validation with the UAS measurement, where the model follows spatially and temporally the aircraft. This strategy has proved to be successful. Stability indices such as the potential temperature and the bulk Richardson number are calculated to diagnose atmospheric boundary layer (ABL) characteristics up to the highest flight level. The calculated bulk Richardson values indicate a dynamically unstable region behind the escarpment and near the ground for both days. At higher altitudes, the ABL is returning to a near neutral state. The same characteristics are found in the model but only for the first day. The second day, where shear instabilities are more dominant, is not well simulated. UAS proves its great value for sensing the flow over complex terrains at high altitudes and we demonstrate the usefulness of UAS for validating and improving models.

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Section: Numerical Modelmentioning

confidence: 99%

Validating CFD Predictions of Flow over an Escarpment Using Ground-Based and Airborne Measurement Devices

et al. 2020

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“…Black areas in the high-elevation portion of the study area (top-to-central portion of the plot network) are associated with landscape depressions that regularly fill with water. The red arrows indicate the prevailing wind direction on the windward and high-elevation ridge of the study area, modelled with the CFD wind-flow simulator [43]. Figure 7 illustrates the performance of the GP-generated model using the training ( Figure 7A) and validation ( Figure 7B) data sets.…”

Section: The Principles Of the Gpmentioning

confidence: 99%

A Semi-empirical Approach Based on Genetic Programming for the Study of Biophysical Controls on Diameter-Growth of Fagus orientalis in Northern Iran

et al. 2019

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This paper examines the possible ecological controls on the diameter increment of oriental beech (Fagus orientalis Lipsky) in a high altitude forest in northern Iran. The main objectives of the study are computer-generated abiotic surfaces and associated plot estimates of (i) growing-season-cumulated potential solar radiation, (ii) seasonal air temperature, (iii) topographic wetness index in representing soil water distribution, and (iv) wind velocity generated from the simulation of fluid-flow dynamics in complex terrain. Plot estimates of the tree growth are based on averaged plot measurements of diameter at breast height increment during a growing period of nine years (2003–2012). Biotic variables related to the tree diameter increment involve averaged 2003 tree diameter and basal area measured in individual forest plots. In the modelling data (144 plots), the assemblage of modelled and observed site variables explained 75% of the variance in plot-level diameter increment. In the validation data (32 plots), the degree of explained variance was 77%. Mean tree diameter at breast height showed the strongest correlation with diameter increment, explaining 32% of the variation between-plot, followed by the configuration of topography and re-distribution of surface water (19.5%) and plot basal area (16.9%). On average, localised estimates of solar radiation and wind velocity potentially contribute to about 20% of the control on plot-level mean increment in oriental beech of the area. The results of the genetic programming showed that controlling the stand basal area and tree size by thinning and/or selective harvesting can have a favourable impact on the future distribution of mean diameter in oriental beech.

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“…The OpenFOAM toolbox includes open source C++ libraries released under the general public license (GPL). An unsteady Reynolds Averaged Navier-Stokes approach under the Boussinesq approximation, was considered (El Bahlouli et al, 2019). For the turbulence closure, a modified k − model is applied.…”

Section: Openfoam Model Setup and Configurationmentioning

confidence: 99%

The impact of a forest parametrization on coupled WRF-CFD simulations during the passage of a cold front over the WINSENT test-site

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El-Bahlouli

Berge³

et al. 2019

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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.

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Comparison of CFD Simulation to UAS Measurements for Wind Flows in Complex Terrain: Application to the WINSENT Test Site

Cited by 11 publications

References 33 publications

Validating CFD Predictions of Flow over an Escarpment Using Ground-Based and Airborne Measurement Devices

Validating CFD Predictions of Flow over an Escarpment Using Ground-Based and Airborne Measurement Devices

A Semi-empirical Approach Based on Genetic Programming for the Study of Biophysical Controls on Diameter-Growth of Fagus orientalis in Northern Iran

The impact of a forest parametrization on coupled WRF-CFD simulations during the passage of a cold front over the WINSENT test-site

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