Large-eddy simulation of the urban boundary layer using drag-porosity modeling
Résumé
This work details the assessment of the performance of the drag-porosity model implemented in ARPS
(Advanced Regional Prediction System) atmospheric Large-Eddy Simulation (LES) solver for simulating the
atmospheric boundary layer developing over the urban canopy with comparison with literature. The flow
within and above an idealized urban canopy consisting of a staggered array of cubes with various packing
densities modeled with the drag-porosity approach immersed into a neutral, Coriolis-free atmospheric boundary
layer at high Reynolds is investigated. Besides one-points statistics, particular interest was given to the ability of
the model to reproduce the turbulent coherent structures and their characteristic scales. A detailed analysis of
one-point statistics, one- and two-dimensional spectra and two-point correlation functions revealed the presence
of typical structures and features found in wall-bounded turbulent flows (two-scale behavior in the roughness
sublayer, ejections, sweeps, self-similar wall-attached large scale streaky motions, canopy-independent very
large scale motions). Further investigation to identify the interaction mechanisms between large and small
scales based on spectral filtering highlighted an interaction mechanism that resembles an amplitude modulation
process, as observed in literature on wall-bounded flows. These findings therefore show that the proposed
approach is able to reproduce all the key features of the flow developing over urban terrain.
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