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

Abstract

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.

Application of a Small Unmanned Aerial System to Measure Ammonia Emissions from a Pilot Amine-CO2 Capture System

“…Possible interesting efforts in this field could also include numerical simulations to compare with present or new measured results. Particularly, the recent development of computational fluid dynamics (CFD) numerical simulations can contribute to improve the analysis of pollutant emissions and their spread [41,42]. Finally, this work also serves as an example for future applications of sUAS to monitor pollution emissions-i.e., in the case of agriculture and ammonia contributed by livestock or from rice paddies.…”

Urban Atmospheric Boundary-Layer Structure in Complex Topography: An Empirical 3D Case Study for Stuttgart, Germany

“…A comparison was made between the empirical outcomes and a recently completed model simulation that matches the area in this study (see, e.g., Bahlouli et al, 2020;Zum Berge et al, 2021) and follows the approach by Talbot et al (2012). A summary of the model configuration has been included in the supplementary material (see Supplementary Section S1.3).…”

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

“…The present study analyzes the undisturbed wind field before the installation of wind turbines at and around the test site. It also compares the UAS measurements with data from a numerical-model chain developed by our project partners, consisting of the mesoscale Weather Research and Forecasting (WRF) model and the meso-microscale URANS (Unsteady Reynolds-Averaged Navier-Stokes) model OpenFOAM (Open Source Field Operation and Manipulation;El-Bahlouli et al 2019, 2020.…”