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| Titel |
Flow adjustment inside homogeneous canopies after a leading edge - An analytical approach backed by LES |
| VerfasserIn |
Konstantin Kröniger, Tirtha Banerjee, Frederik De Roo, Matthias Mauder |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138913
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| Publikation (Nr.) |
 EGU/EGU2017-2054.pdf |
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| Zusammenfassung |
| A two-dimensional analytical model for describing the mean flow inside a vegetation canopy
after a leading edge in neutral conditions was developed and tested by means of large eddy
simulations (LES) employing the LES code PALM. The analytical model is able to predict
the mean flow in the region directly after the canopy edge, the adjustment region, where
one-dimensional canopy models fail due to the sharp change in roughness. The derivation of
the adjustment region model is based on an analytic solution of the two-dimensional
Reynolds averaged Navier-Stokes equation in neutral conditions for a canopy with constant
plant area density (PAD). The main assumptions for solving the governing equations
are separability of the velocity components concerning the spatial variables and
the neglection of the Reynolds stress tensor gradients. These two assumptions are
verified by means of LES. To determine the emerging model parameters, a fitting
scheme is simultaneously applied to the velocity and pressure data of a reference LES
simulation. Furthermore a sensitivity analysis of the adjustment region model, equipped
with the previously calculated parameters, is performed varying the three relevant
length scales, the canopy height (h), the canopy length and the adjustment length
(Lc), in additional LES. Even if the model parameters are, in general, functions of
h∕Lc, it was found out that the model is capable of predicting the flow quantities
in various cases, while using constant parameters. Finally, the adjustment region
model is combined with the one-dimensional model of Massman [Boundary-Layer
Meteorol., 83(3):407-421, 1997], which is applicable for the interior of the canopy, to
attain an analytical model capable of describing the mean flow for the full canopy
domain. |
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