Einsatz eines diagnostischen Strömungsmodelles zur Beschreibung der Strömung im Wald
Einsatz eines diagnostischen Strömungsmodelles zur Beschreibung der Strömung im Wald
In the first part of this paper aspects are introduced which influence the current in a canopylayer, for example temperature, solar radiation, humidity, wind velocity and wind direction.Due to the different influences of these parameters in the domain of the tree top andtree trunk both mechanically...
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Personal Name(s): | Manfrahs, Claudia (Corresponding author) |
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Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2000
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Physical Description: |
VI, 99 p. |
Document Type: |
Report Book |
Research Program: |
Addenda |
Series Title: |
Berichte des Forschungszentrums Jülich
3807 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
In the first part of this paper aspects are introduced which influence the current in a canopylayer, for example temperature, solar radiation, humidity, wind velocity and wind direction.Due to the different influences of these parameters in the domain of the tree top andtree trunk both mechanically and thermally induced turbulence is produced. Furthermore,a summary is given of existing models capable of computing the wind fields inside acanopy layer. An approach towards calculating these currents is introduced starting fromthe theory of the flow inside a forest. In the following chapter the location and data arepresented. The latter are interpreted on the basis of the weather situation and presentedgraphically. The results are also used for the initialization of the MCF model and for validatingthe results of theMCFsimulations. In Chapter Four prognostic and diagnostic flowmodels are compared and attention focused on the differences between the two kinds of modelling. The MCF model, further developed at the University of Cologne, is given as anexample of a diagnostic flow model. The equations used for the initialization are shown.The theory of computinga current over horizontal homogeneous ground is no longer validfor reproducing the wind field inside a canopy, because the roughness elements are so largethat the flow goes through them, not over them. For that reason themomentum transfer isno longer constant with heightbut increases with decreasing height above ground. Cionco(1965) and Su et al. (1998) pointed out that the vertical wind profile inside a canopy can beexpressed by an exponential function. This function is implemented in the MCF model tocalculate the wind velocity inside a forest. Furthermore, measurements near the ground expandedthe initialization so that wind direction and also wind velocity are considered. Theadvantage of this addition is that several effects can be considered, for example a reductionof the wind velocity near the forest edge, which could not be explained by the previoustheory of initialization alone.In Chapter Five the modelling area and the modifications to the MCF are shownstep bystep, and the implemented modifications are tested. Finally, in Chapter Six the results o£the simulations with different modifications are shownand interpreted both for an individualcase and also for a timeseries of simulations. One result of the paper is that the windfield in canopies can be described at all altitudes by an exponential wind profile, which isof great interest for applications on the microscale. Nevertheless, the examinations showthat the results must be modified, for example, to provide a meaningful simulation of highwind speed inside a forest. |