How to Parametrize Urban-Canopy Drag to Reproduce Wind-Direction Effects Within the Canopy |
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| Authors: | J L Santiago O Coceal A Martilli |
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| Institution: | 1. Atmospheric Pollution Division, Environmental Department, CIEMAT, Avda. Complutense 40, Ed. 3, 28040, Madrid, Spain
2. Department of Meteorology, National Centre for Atmospheric Science (NCAS), University of Reading, P.O. Box 243, Reading, RG6 6BB, UK
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| 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. |
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