Measurements and Computations of Flow in an Urban Street System

Abstract

We present results from laboratory and computational experiments on the

Are Urban-Canopy Velocity Profiles Exponential?

“…) along alternate rows in the figure. At right plan view of DIPLOS array of h × 2h × h cuboids (Castro et al 2016) directions and in a half-channel with H = 4h, have also been reported (Claus et al 2012); grid sizes were typically Δ = h/25 over the canopy height. A 'random height' extension of the case of the staggered cube array with λ p = 0.25 was that initially studied experimentally by Cheng and Castro (2002) and subsequently computationally by Xie et al (2008) .…”

“…For the present work, data from the two sets of boundary-layer simulations (Cheng and Porte-Agel 2015; were spatially averaged only within the fully developed region downstream. A final set of data is that reported by Castro et al (2016) who, as part of a wider dispersion project (DIPLOS-http://www.diplos.org), used a channel-flow LES for a square array of rectangular obstacles of size 2h × 1h × 1h spaced apart by 1h ( Fig. 1) In discussing the canopy region results presented below, possible differences arising from different domain sizes or outer flow conditions (e.g.…”

“…1) In discussing the canopy region results presented below, possible differences arising from different domain sizes or outer flow conditions (e.g. whether of boundary-layer or channel type) are generally assumed to be small, in line with Castro et al (2016). We address the influences of Reynolds number, resolution and (in LES cases) subgrid model where appropriate.…”

“…Within the canopy these are extrinsic spatial averages-i.e. averages over the total volume, rather than the fluid volume only, (2006); LC (black, blue, red, purple), Leonardi and Castro (2010); CXFRCHHC (green), Castro et al (2016); BCTB (black), Branford et al (2011); CP-A (green), Cheng and Porte-Agel (2016) which would yield intrinsic averages. Böhm et al (2013) outline the differences between these two averaging methods and the topic has recently been explored more fully by Xie and Fuka (2017, in press).…”

“…An aligned array of cubes, similarly, yields rather higher canopy velocities because of the uninterrupted streets. Note, incidentally, that the drag of the staggered array is higher than that of the aligned array and highest for θ = 45 • , because λ f is highest for that case and there are no uninterrupted streets of any width in the flow direction (Castro et al 2016).…”