Repository: Freie Universit├Ąt Berlin, Math Department

TurbEFA: an interdisciplinary effort to investigate the turbulent flow across a forest clearing

Queck, R. and Bernhofer, C. and Bienert, A. and Eipper, T. and Goldberg, V. and Harmansa, S. and Hildebrand, V. and Maas, H.-G and Schlegel, F. and Stiller, J. (2014) TurbEFA: an interdisciplinary effort to investigate the turbulent flow across a forest clearing. Meteorologische Zeitschrift, 1 .



the atmosphere within turbulence closure models is mainly limited by a realistic three-dimensional (3D) representation of the vegetation architecture. Within this contribution we present a method to record the 3D vegetation structure and to use this information to derive model parameters that are suitable for numerical flow models. A mixed conifer forest stand around a clearing was scanned and represented by a dense 3D point cloud applying a terrestrial laser scanner. Thus, the plant area density (PAD) with a resolution of one cubic meter was provided for analysis and for numerical simulations. Multi-level high-frequency wind velocity measurements were recorded simultaneously by 27 ultrasonic anemometers on 4 towers for a period of one year. The relationship between wind speed, Reynolds stress and PAD was investigated and a parametrization of the drag coefficient CD by the PAD is suggested. The derived 3D vegetation model and a simpler model (based on classical forest assessments of the site) were applied in a boundary layer model (BLM) and in large-eddy simulations (LES). The spatial development of the turbulent flow over the clearing is further demonstrated by the results of a wind tunnel experiment. The project showed, that the simulation results were improved significantly by the usage of realistic vegetation models. 3D simulations are necessary to depict the influence of heterogeneous canopies on the turbulent flow. Whereas we found limits for the mapping of the vegetation structure within the wind tunnel, there is a considerable potential for numerical simulations. The field measurements and the LES gave new insight into the turbulent flow in the vicinity and across the clearing. The results show that the zones of intensive turbulence development can not be restricted to the locations found in previous studies with more idealized canopies.

Item Type:Article
Uncontrolled Keywords:Boundary layer model, drag coefficient; large eddy simulation, vegetation parametrization, wind field measurements, terrestrial laser scanning, wind tunnel
Subjects:Mathematical and Computer Sciences > Mathematics > Applied Mathematics
ID Code:1484
Deposited By: Ulrike Eickers
Deposited On:20 Jan 2015 14:41
Last Modified:03 Mar 2017 14:41

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