Twin test 4 of TWEET-IE project: Scale effects on the flow in an urban street canyon. PTV data from wind tunnel experiments at NTUA and TU Delft.

The present data refers to a twin test, as part of the TWEET-IE project (TWEET-IE : Twin Wind tunnels for Energy and the EnvironmenT - Innovations and Excellence, HORIZON-WIDERA-2021-ACCESS-03-01 / PR# 101079125), carried out in the wind tunnels of the Technical University of Delft (TU Delft) and the National Technical University of Athens (NTUA), using measurement equipment mainly provided by TU Delft. An investigation of the scale effects on flow in the urban environment is carried out. More specifically, this urban environment is a series of five consecutive street canyons perpendicular to the approaching flow, simulating the urban fabric, since the street canyon geometry is usually considered as a fundamental component of contemporary cities. The examined canyon was the fourth one with respect to the direction of the approaching flow. The effect of vegetation (hedges at the pedestrian level or roof greening) on the flow is also examined throughout this study. In the wind tunnel of the National Technical University of Athens, all the former cases were investigated for two different values of ambient turbulence intensity corresponding to two distinct experimental configurations (i.e. with and without a passive grid). The study at NTUA was performed with a 3D-3C Robotic Particle Tracking Velocimetry (3D-PTV) System and at TU Delft with a 3D-3C Volumetric PTV system. Both systems can be categorised as volumetric methods. Additionally, surface pressure measurements were conducted in both wind tunnels whereas hot-film anemometry was employed in NTUA’s wind tunnel to supplement the PTV-extracted dataset. Apart from insight into the application itself, the twin test results provide an opportunity to analyse the effects of the different wind tunnel (WT) configurations (i.e. closed-loop WT vs. open jet WT) on Reynolds number sensitivity.