Averaging procedures for flow within vegetation canopies

Most one-dimensional models of flow within vegetation canopies are based on horizontally averaged flow variables. This paper formalizes the horizontal averaging operation. Two averaging schemes are considered: 1) pure horizontal averaging at a single instant and 2) time averaging followed by horizon...

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Bibliographic Details
Published in:Boundary-layer meteorology 1982-01, Vol.22 (1), p.79-90
Main Authors: Raupach, M. R., Shaw, R. H.
Format: Article
Language:English
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Summary:Most one-dimensional models of flow within vegetation canopies are based on horizontally averaged flow variables. This paper formalizes the horizontal averaging operation. Two averaging schemes are considered: 1) pure horizontal averaging at a single instant and 2) time averaging followed by horizontal averaging. These schemes produce different forms for the mean and turbulent kinetic energy balances, especially for the wake production term describing the transfer of energy from large-scale motion to wake turbulence by form drag. The differences are due primarily to the appearance, in the covariances produced by the second scheme, of dispersive components arising from the spatial correlation of time-averaged flow variables. The two schemes are shown to coincide if these dispersive fluxes vanish.
ISSN:0006-8314
1573-1472
DOI:10.1007/BF00128057