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Towards steady neutral and stably stratified ABL model

: Hillmann, Nina; Kassem, Hassan

Fulltext urn:nbn:de:0011-n-5345100 (262 KByte PDF)
MD5 Fingerprint: 804ef75c76a35327637b0d5f6755c147
Created on: 19.2.2019

Uppsala Universitet, Earth Sciences Department:
SOWE 2018, 6th Symposium on OpenFOAM in Wind Energy 2018 : June 13-14, 2018, Visby
Visby, 2018
5 pp.
Symposium on OpenFOAM in Wind Energy (SOWE) <6, 2018, Visby>
Conference Paper, Electronic Publication
Fraunhofer IWES ()

A steady state single column OpenFOAM model for neutral and stably stratified ABL flow is presented which is a tool of significant importance for wind energy industry. For site assessment applications, where simulating the entire wind rose and stability rose is essential to evaluate the wind potential of a certain location, unsteady CFD models are computationally expensive. Achieving steady state simulations of thermally stratified atmospheric boundary layer is challenging due to the transient nature of the problem. Primarily only a quasi-steady state is reachable for stable stratification and a discontinuity at the top of the boundary layer due the limited-length turbulence model leads to mesh sensitivity. Based on Monin-Obukhov-length and geostrophic wind values, the maximum turbulence mixing length is adjusted. Additionally, extra source terms have been added to the turbulence model governing equations to maintain a minimum level of turbulence within the ABL. This leads to a constant boundary layer height and smoothed velocity profiles. A good agreement with the experimental data is reached for neutral stratification and the solver is validated against LES data for stable stratification.