Boundary-Layer Meteorology

, Volume 126, Issue 3, pp 365–388

# Flow in a Street Canyon for any External Wind Direction

• Lionel Soulhac
• Richard J. Perkins
• Pietro Salizzoni
Original Paper

## Abstract

An analytical model has been developed for the flow along a street canyon (of height H and width W), generated by an external wind blowing at any angle relative to the axis of the street. Initially, we consider the special case of a wind blowing parallel to the street. The interior of the street is decomposed into three regions, and the flow within each region is assumed to depend only on the external wind and the distance to the closest solid boundary. This decomposition leads to two different flow regimes: one for narrow streets (H/W > 1/2) and one for wide streets (H/W < 1/2). The theoretical model agrees well with results obtained from numerical simulations using a Reynolds-Averaged Navier–Stokes model. We then generalize the model to the case of arbitrary wind direction. Numerical solutions show that the streamlines of the mean flow in the street have a spiral form, and for most angles of incidence, the mass flux along the street scales on the component of the external wind resolved parallel to the street. We use this result to generalize the model derived for wind blowing parallel to the street, and the results from this model agree well with the numerical simulations. The model that has been developed can be evaluated rapidly using only very modest computing power, so it is suitable for use as an operational tool.

## Keywords

Numerical modelling Street canyon Urban canopy flow

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## Authors and Affiliations

• Lionel Soulhac
• 1
• Richard J. Perkins
• 1
• Pietro Salizzoni
• 1
• 2
1. 1.Laboratoire de Mécanique des Fluides et d’Acoustique, UMR CNRS 5509University of Lyon – Ecole Centrale de Lyon, INSA Lyon, Université Claude Bernard Lyon IEcullyFrance
2. 2.DIASP Politecnico di TorinoTorinoItaly