Skyscraper rooftop tracer concentration observations in Manhattan and comparisons with urban dispersion models

Hanna, Steven R.; Chang, Jimmy

doi:10.1016/j.atmosenv.2015.01.051

Cited by 11 publications

(9 citation statements)

References 14 publications

(23 reference statements)

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“…In particular, high‐rise buildings modify flow and pollutant dispersion significantly. Wind‐tunnel experiments (Heist et al ., , ) and observation studies in real urban areas (Gowardhan et al ., ; Nelson et al ., ; Hanna and Chang, ) revealed that updraughts occurring behind high‐rise buildings transport pollutants upward. Moreover, vortices generated continuously on both sides of high‐rise buildings, a phenomenon known as vortex shedding, propagate downstream of the high‐rise buildings and affect flow and pollutant dispersion.…”

Section: Introductionmentioning

confidence: 99%

“…According to Rossi and Iaccarino (), periodic fluctuations of pollutant concentration occur in the wake region due to vortex streets, and they affect turbulent fluxes of pollutant in the streamwise, spanwise and vertical directions. Nonetheless, there has been little study on pollutant dispersion behind high‐rise buildings in real urban areas where other buildings affect flow around high‐rise buildings (Hanna and Chang, ; Kwak et al ., ). Therefore, it is worth investigating turbulent flow and pollutant dispersion behind high‐rise buildings in real urban areas.…”

Section: Introductionmentioning

confidence: 99%

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Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Han

Park

Baik

et al. 2017

Quart J Royal Meteoro Soc

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Understanding turbulent flow and pollutant dispersion in urban areas is one of the important problems in urban meteorology and environmental fluid mechanics. In this study, we examine turbulent flow and pollutant dispersion in a densely built‐up area in Seoul, South Korea, using the parallelized large‐eddy simulation model (PALM). In particular, we focus on vortex streets and associated pollutant dispersion behind high‐rise buildings. The turbulence recycling method is used to produce inflow profiles. Vortices are generated near the high‐rise buildings and propagate downstream forming vortex streets behind the high‐rise buildings. To investigate characteristics of the vortex streets, spectral and correlation analyses are performed. The spectral analysis reveals that vortices have a non‐dimensional vortex shedding frequency of 0.1–0.2, and this periodicity is weakened due to the influence of other buildings. The correlation analysis shows that vortices appear frequently in regions of negative pressure perturbation. The vertical turbulent momentum fluxes induced by ejections and sweeps largely contribute to the total vertical turbulent momentum flux downstream of the high‐rise buildings. Especially, ejections in the wake region are stronger compared to other regions because ejections are induced by vortices near the top of the high‐rise buildings. It is found that pollutant dispersion is interrupted by both low‐rise and high‐rise buildings. Strong updraughts behind the high‐rise buildings transport pollutant upward and increase the mean pollutant concentration at upper levels. Vortices forming the vortex streets play a role in pollutant mixing in such a way that the vortices eject air of high pollutant concentration from the wake region behind the high‐rise buildings and entrain air of low pollutant concentration into the wake region. The mixing by vortices is verified by the correlation between vorticity and pollutant concentration.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Han

Park

Baik

et al. 2017

Quart J Royal Meteoro Soc

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“…Off-axis, the concentration in the plume falls away as a function of the turbulent properties of the atmosphere. Many dispersion models exist to quantify the horizontal and vertical dispersion of a plume in urban environments including Micro Swift Spray and QUIC (Hanna and Chang 2015) but a simple approximation can be made using a Gaussian plume model from a single point (Sutton 1953),…”

Section: Flow Dispersion Modelsmentioning

confidence: 99%

Urban Tracer Dispersion and Infiltration into Buildings Over a 2-km Scale

Matthews

Wright

Martin

et al. 2020

Boundary-Layer Meteorol

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Field experiments were undertaken in the summer of 2015 in Manchester, UK, to investigate the dispersion behaviour and infiltration into buildings of gas-phase pollutants over horizontal distances of 1-5 km. Inert cyclic perfluorocarbon tracers were released for 15 min at either one or three release points and samples taken in locations indoors and outdoors up to 2 km downwind. Background measurements of these cyclic perfluorocarbons range between 5.6 and 12.6 parts per quadrillion (ppq). On most occasions, tracer concentrations are higher on the sixth floor than at ground level. Tracer concentrations persist in the least well-ventilated rooms after concentrations return to background levels outdoors. The highest tracer concentrations, 329 ppq above background, occur at dawn on 23 July from a sixth-floor sampling position during thermally stable conditions. At low wind speeds, tracer is detected upwind of the prevailing wind direction; on 24 July, tracer is detected to the northwest of the release point for north-northeast wind direction. A simple street network model does not predict tracer concentrations at low wind speeds over the km scales in this investigation due to tracer likely escaping the urban canopy. Predictions from a simple correlation model overestimate concentrations originating from distant sources, which is believed to be due to infiltration into buildings along the journey from source to receptor. A Gaussian plume model predicts the highest tracer concentrations for most receptor points on 23 July when the lowest Obukhov length of-26 m was measured, agreeing with tracer measurements.

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“…Atmospherics -Atmospherics is a key component in determining radionuclide dispersion, thus a separate module is dedicated to handling its accurate representation (Platt et al 2014;Singh et al 2015;Hanna and Chang 2015). Atmospherics, particularly turbulence, may adversely impact helicopter pilot performance with increased weight with respect to the velocity and altitude parameters of the helicopter .…”

Section: Component Analysis Of the Conceptual Modelmentioning

confidence: 99%

“…Also outside NRC, M&S has a long history in DoD that may support nuclear disaster mitigation scenarios (Hollenbach and Alexander 1997). Hazard Prediction and Assessment Capability (HPAC) is a widely used tool (Chang et al 2005;Platt et al 2014;Hanna and Chang 2015;Singh et al 2015) licensed by the Defense Threat Reduction Agency. HPAC "assists in emergency response to hazardous agent releases.…”

Section: Introductionmentioning

confidence: 99%

A Systems-Of-Systems Conceptual Model and Live Virtual Constructive Simulation Framework for Improved Nuclear Disaster Emergency Preparedness, Response, and Mitigation

Davis

Proctor

Shageer

2016

Journal of Homeland Security and Emergency Management

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Nuclear disasters have severe and far-reaching consequences. Emergency managers and first responders from utility owners to local, state, and federal civil authorities and the Department of Defense (DoD) must be well prepared in order to rapidly mitigate the disaster and protect the public and environment from spreading damage. Given the high risks, modeling and simulation (M&S) plays a significant role in planning and training for the spectrum of derivate scenarios. Existing reactor models are largely legacy, stove-piped designs lacking interoperability between themselves and other M&S tools for emergency preparedness system evaluation and training. Unmanned systems present a growing area of technology promising significant improvement in response and mitigation. To bridge the gap between current and future models, we propose a conceptual model (CM) for integrating live, virtual, and constructive (LVC) models with nuclear disaster and mitigation models utilizing a system-ofsystems (SoS) approach. The CM offers to synergistically enhance current reactor and dispersion simulations with intervening avatar and agent simulations. The SoS approach advances life cycle stages including concept exploration, system design, engineering, training, and mission rehearsal. Component subsystems of the CM are described along with an explanation of input/output requirements. A notional implementation is described. Finally, applications to analysis and training, an evaluation of the CM based on recently proposed criteria found in the literature, and suggestions for future research are discussed.

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Skyscraper rooftop tracer concentration observations in Manhattan and comparisons with urban dispersion models

Cited by 11 publications

References 14 publications

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Urban Tracer Dispersion and Infiltration into Buildings Over a 2-km Scale

A Systems-Of-Systems Conceptual Model and Live Virtual Constructive Simulation Framework for Improved Nuclear Disaster Emergency Preparedness, Response, and Mitigation

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