Boundary-Layer Meteorology

, Volume 149, Issue 1, pp 43–63

How to Parametrize Urban-Canopy Drag to Reproduce Wind-Direction Effects Within the Canopy

Article

DOI: 10.1007/s10546-013-9833-y

Cite this article as:
Santiago, J.L., Coceal, O. & Martilli, A. Boundary-Layer Meteorol (2013) 149: 43. doi:10.1007/s10546-013-9833-y

Abstract

The mean wind direction within an urban canopy changes with height when the incoming flow is not orthogonal to obstacle faces. This wind-turning effect is induced by complex processes and its modelling in urban-canopy (UC) parametrizations is difficult. Here we focus on the analysis of the spatially-averaged flow properties over an aligned array of cubes and their variation with incoming wind direction. For this purpose, Reynolds-averaged Navier–Stokes simulations previously compared, for a reduced number of incident wind directions, against direct numerical simulation results are used. The drag formulation of a UC parametrization is modified and different drag coefficients are tested in order to reproduce the wind-turning effect within the canopy for oblique wind directions. The simulations carried out for a UC parametrization in one-dimensional mode indicate that a height-dependent drag coefficient is needed to capture this effect.

Keywords

Direct numerical simulations (DNS) Drag coefficients  Reynolds-averaged Navier–Stokes (RANS) Urban-canopy parametrization Wind direction 

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Atmospheric Pollution Division, Environmental DepartmentCIEMATMadridSpain
  2. 2.Department of Meteorology, National Centre for Atmospheric Science (NCAS)University of ReadingReadingUK

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