Simulation of air pollution abatement in deep street canyon

1. Simulation of air pollution abatement in deep street canyon Marina De Giovanni1, Gabriele Curci2, Cesare Darisalisburgo1, Alessandro Avveduto1, Lorenzo Pace1, Franco Gianmaria2, Alessio Monaco2, Giuseppe Spanto3, Paolo Tripodi1,3 1S.P.In - Società Progetti Innovativi, Nucleo Industriale Bazzano, L’Aquila, Italy 2CETEMPS, Dept. of Physical and Chemical Sciences, University of L’Aquila, L’Aquila, Italy 3IsTECH – Innovation in Sciences & Technologies, Via Mar della Cina 304, Rome, Italy e-mail: marina.degiovanni@spintecnologia.com • MOTIVATION • Indoor and outdoor pollution has caused 3.3 millions death worldwide in 2012 (WHO, 2013). The risk for human health increase with increasing level of exposure to particulate matter and other air pollutants (IARC, 2013) • The common approach to tackle the pollution problem is emission reduction. In this work, we start to test a new approach: removal of air pollutants close to their sources by a network of Air Pollution Absorber • Rows of tall buildings create a peculiar urban habitat, known as deep street canyon, where traffic emissions are trapped by the limited dispersal into the free atmosphere. We simulate the effect of our idea into one such environment • CONCLUSIONS • We simulate the cleansing of an idealized street canyon by Computational Fluid Dynamics (CFD) method • The mass transfer process between the bottom of the canyon and the above atmosphere is driven by the presence of a vortex induced by the above-roofs wind • We simulate the effect of an additional removal term at road level to mimic the effect of a pollutant removal wet scrubber • The presence of the scrubber has the potential of reducing the cleansing time scale of the canyon and, as a consequence, the exposure at pedestrian level CFD 2D Simulation IdealizedDeep Street Canyon Average pollutant concentration in street canyon • The tracer concentration in the street canyon is halved after 700 seconds, in the base case without the scrubber (APA in the legend) • When a scrubber with an efficiency of 95% is simulated into the canyon, the cleansing time decreases to 220 s • With scrubberefficiencies of 10, 30 and 40% the cleasing time decrease to 550, 470, and 400 s, respectively • Height H: 18m • Width W: 6m • Velocity inlet (above-roof wind): 2 m/s • Number of grid points: 10,000 of which 5,000 in the canyon • We use the k-ε model RNG (re-normalizedgrouptheory) turbulentclosuremethod • Tracerinitialcondition: 10 ppmhomogeneousthrougout the domain • (Figure from Murena et al., 2005) Street Canyon • Tracer concentration field • Above-roof “clean” air enters the canyon on the upwind side, while “dirty” air exits the canyon from the downwind side • The presence of the scrubber (here with efficiency of 40%) creates an additional sink at the bottom of the canyon, accelerating the cleansing process of the canyon • The plume of “scrubbed” air is transported by the vortex toward the downwind walkside and buildings • Velocity vector field • Above-roof wind enters the canyon on the upwind side, inducing a vortex • The vortex is slowed down by friction, thus velocity decreases toward the bottom of the canyon Tracer concentration after 200 sec NO Scrubber YES Scrubber Tracer concentration after 1000sec NO scrubber YES Scrubber Tracer concentration after 500 sec NO Scrubber YES Scrubber Applied results on Via del Corso - Rome References • IARC (2013), Outdoor air pollution a leading environmental cause of cancer deaths, Press release n. 221, 17 October 2013 • Murena et al. (2011), Mass transfer velocity and momentum vertical exchange in simulated deep street canyon, Boundary Layer Meteorology, 140, pp. 125-142 • WHO (2013), Air quality and health, Fact sheet N°313, Updated September 2011