Rise of Buoyant Emissions from Low-Level Sources in the Presence of Upstream and Downstream Obstacles

Pournazeri, Sam; Princevac, Marko; Venkatram, Akula

doi:10.1007/s10546-012-9717-6

Cited by 6 publications

(2 citation statements)

References 44 publications

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“…This technique gives us averaged plume behavior, which is used to understand dispersion under different flow conditions and sound barrier configurations. More details on flow visualization can be found in Pournazeri et al (2012a). Simulating flow and dispersion in such a laboratory facility requires utilizing correct scaling techniques.…”

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Sound wall barriers: Near roadway dispersion under neutrally stratified boundary layer

Pournazeri

Princevac

2015

Transportation Research Part D: Transport and Environment

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a b s t r a c tWith the passage of California Senate Bill 375, which motivates infill development near transit hubs, there is the potential to increase vehicle congestion in residential communities and increase in human exposure to toxic mobile source pollutants. Among all the mitigation strategies that protect near roadway residents from health-affecting vehicular emissions (e.g. separating sensitive receptors from high traffic roadways), this paper discusses the impact of sound wall barriers (SBs) in reducing the air pollution exposure of nearby residents. To date, there have been some studies done to understand the impact of these structures on dispersion of vehicular emissions; however, no definitive conclusion has been drawn yet. The main objective of this paper is to provide more information and details on flow and dispersion affected by barriers through a systematic laboratory simulation of plume dispersion using a water channel. Three sets of experiments were conducted: (1) plume visualizations, (2) plume concentration measurements, and (3) flow velocity measurements. Results from this study shows that the deployment of sound barriers induces a recirculating flow over the roadway which transports the surface released emissions to the upwind side of the roadway, and then shifts the plume upward through an induced updraft motion. Plume visualizations clearly demonstrate that the presence of SBs induce significant vertical mixing and updraft motion on the roadway which increases the initial plume dilution and plume height and consequently results in reduced downwind ground level concentrations. Although different SB configurations result in different localized flow patterns, the dispersion pattern does not change significantly after several SB heights downwind of the roadway.Ó 2015 Elsevier Ltd. All rights reserved. IntroductionNumerous epidemiological studies have shown that long-term exposure to outdoor air pollution increases the risk of respiratory diseases, birth defects, premature mortality, cardiovascular disease, and cancer (Dockery and Pope, 1994;Harrison et al., 1999;Wilhelm and Ritz, 2003;Peters et al., 2004;Jerrett et al., 2005;McConnell et al., 2006). Houston et al. (2006) showed that more than 24,000 childcare centers in California are within 200 m of highly trafficked roadways with more than 50,000 vehicles per day. A statistical analysis has shown that children diagnosed with asthma are more likely to live within 500 m of major roadways (Edwards et al., 1994).

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confidence: 99%

Sound wall barriers: Near roadway dispersion under neutrally stratified boundary layer

Pournazeri

Princevac

2015

Transportation Research Part D: Transport and Environment

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“…Equation (5) yields the analytical expression, In the modified model, the decrease of concentrations depends on the lateral spread, y , which is a function of building dimensions in the urban canopy and is modelled through Equation (3). Plume rise is also calculated through the numerical plume rise model explained in Pournazeri et al (2012b), where the effect of surrounding buildings as well as the effect of ambient turbulence is taken into account. Figure 13 shows a comparison of equation 6with concentrations observed in the water tank.…”

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confidence: 99%

Dispersion of buoyant emissions from low level sources in urban areas: water channel modelling

Pournazeri

Schulte

Tan

et al. 2013

IJEP

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A laboratory study was done to investigate dispersion of buoyant emissions from near surface sources in urban areas. Ground level concentrations under different surrounding building geometries were measured using a newly developed system based on laser induced fluorescence. In the presence of upstream buildings AERMOD (AMS/U.S. EPA regulatory dispersion model) is unable to explain concentrations close to the source. Plume visualisations and velocity measurements show that upstream buildings induce low velocity and a highly turbulent region near the stack, which increases the plume rise and induces rapid vertical mixing. Also, the urban canopy imposes a length scale on the horizontal turbulence, causing the plume to spread laterally with the square root of distance (~x 1/2) rather than linearly as occurs in open terrain. A Gaussian-based dispersion model which accounts for these effects performs substantially better in predicting ground level concentrations associated with buoyant emissions from distributed power generators in urban areas.

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Air Circulation in Urban Areas

Bernardino

Palusci

Pini

et al. 2021

Urban Microclimate Modelling for Comfort and Energy Studies

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Rise of Buoyant Emissions from Low-Level Sources in the Presence of Upstream and Downstream Obstacles

Cited by 6 publications

References 44 publications

Sound wall barriers: Near roadway dispersion under neutrally stratified boundary layer

Sound wall barriers: Near roadway dispersion under neutrally stratified boundary layer

Dispersion of buoyant emissions from low level sources in urban areas: water channel modelling

Air Circulation in Urban Areas

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