An Investigation of the Correlation between Pollutant Dispersion and Wind Environment: Evaluation of Static Wind Speed

Low airflow or poor outdoor ventilation around building blocks can negatively influence pollutant dispersion in the surroundings and indoor air quality, and increase the risks of airborne transmission of infectious diseases. However, there have been few studies addressing the wind environment, thermal comfort and other concerns at the pedestrian level. Buildings with a lift-up design may have a number of impacts on the pedestrian-level wind and thermal environments. Three building configurations that resulted in the lowest wind speed zones were identified from a previous study. A 3.5 m high open ground floor was added to each of the three configurations, and scale models of the three designs were studied in a wind tunnel to assess their influences on airflow and ventilation around the buildings. Undesirable areas of low wind speed leading to poor air ventilation and, on the other side of extreme, areas of discomfort due to strong wind conditions were both identified, and their practical implications are discussed.

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Characteristics of the Wind Environment above Bridge Deck near the Pylon Zone and Wind Barrier Arrangement Criteria

Applied Sciences ◽

10.3390/app10041437 ◽

2020 ◽

Vol 10 (4) ◽

pp. 1437 ◽

Cited By ~ 1

Author(s):

Dalei Wang ◽

Yiquan Zhang ◽

Mengjin Sun ◽

Airong Chen

Keyword(s):

Wind Speed ◽

Evaluation Method ◽

Bridge Deck ◽

Sudden Change ◽

Safety Evaluation ◽

Longitudinal Direction ◽

Optimal Arrangement ◽

Wind Environment ◽

Wind Barrier ◽

Sutong Bridge

Due to the complex arrangement of structural components in the vicinity of bridge pylon zones, the wind environment above bridge decks is very complicated. A sudden change in wind speed exerts an adverse effect on vehicle control stability. In order to investigate the characteristics of the flow field in the vicinity of the bridge pylon, the wind environment near an inverted Y-shaped pylon is studied by experimental and numerical methods. From the flow visualization and the wind speed measurement in the wind tunnel and the numerical simulation created using Fluent software, specific patterns of the direction and magnitude of wind speed at a range of vehicle height above the bridge deck near the pylon zone were observed along the longitudinal direction. This distribution pattern of the wind environment can effectively guide the wind barrier arrangement near the bridge pylon zone. Combined with the two safety evaluation indicators proposed in this paper, the optimal arrangement scheme of wind barriers in the bridge pylon zone of Sutong Bridge is determined. This paper deepens the understanding of the wind environment near the pylon zone and proposes an evaluation method for the wind environment near the pylon zone, which can serve as the basis for wind barrier arrangement in similar research projects.

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Analysis of the Wind Environment to Improve the Thermal Comfort in the Colonnade Space of a Qilou Street Based on the Relative Warmth Index

Sustainability ◽

10.3390/su11164402 ◽

2019 ◽

Vol 11 (16) ◽

pp. 4402 ◽

Cited By ~ 1

Author(s):

Xianfeng Huang ◽

Zhen Lu ◽

Zhixiang Zhuang

Keyword(s):

Wind Speed ◽

Thermal Comfort ◽

Architectural Design ◽

Thermal Environment ◽

Transitional Space ◽

Wind Environment ◽

Warmth Index ◽

Research Findings ◽

Building Components ◽

Computational Fluid Dynamics Cfd

By analyzing measurements of the thermal environment of a qilou (arcade building) street, this study used the relative warmth index (RWI) to evaluate the thermal comfort in the colonnade space of a qilou. The analysis of the influence of the temperature, humidity, and wind speed on the thermal comfort in the colonnade space of a qilou street was conducted, and it was shown that the ambient wind speed had a strong influence on the RWI, indicating that a proper increase in the wind speed positively affected thermal comfort in this space. Then, this study also analyzed the effects of different forms of qilou streets on the wind environment by employing computational fluid dynamics (CFD) and summarized the architectural design measures that can improve the thermal comfort, including adopting back chamfer, street gaps, and the appropriate sizing of building components. It was concluded that the wind environment of a qilou could be optimized in terms of these measures, and the average RWI value decreased by 0.06, effectively enhancing the thermal comfort in the colonnade space. The research findings are applicable toward designing a thermally comfortable environment in the transitional space.

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Strategy on Improving Lateral Driving Stability of the Automobiles Passing by the Vicinity of A-Shaped Pylon of Zhengxin Yellow River Highway-Railway Bridge in Cross Wind

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.1827 ◽

2011 ◽

Vol 250-253 ◽

pp. 1827-1833

Author(s):

Da Lei Wang ◽

Ai Rong Chen ◽

Hui Lin Ai

Keyword(s):

Wind Speed ◽

Yellow River ◽

Driving Safety ◽

Medium Size ◽

Railway Bridge ◽

Complex Flow ◽

Wind Environment ◽

Wind Barrier ◽

Set Up ◽

Driving Stability

Problem of lateral driving stability of the automobiles passing by the vicinity of pylons of cable-supported bridges in condition of strong cross wind exists obviously because of the alternative wind environment above the deck due to complex flow fluid around the pylon and the deck. Based on numerical wind tunnel technology, the numerical simulation investigation of alternating wind environment above the girder near A-shaped pylon for main span of the steel truss girder cable-stayed bridge of Zhengxin Yellow River Highway-railway Bridge is carried out, considering wind barrier set up on the deck or not. The result shows that the original program has significant effect on wind speed amplification and mutation near the pylon domain in cross wind. Further investigation on wind barrier set up on both sides of the girder section or near the A-shaped pylon along the bridge gives that wind barrier near the A-shaped pylon is useful for reducing wind speed above the leeward deck near the pylon and weakening its mutation. Deeply, taken a medium-size commercial bus as an example, lateral driving stability of the automobiles passing by the leeward lane near A-shaped pylon is discussed through the dynamic response simulation of the vehicle controlled by ideal-driver under cross wind. The results confirms again that the wind barrier near the A-shaped pylon is good for driving safety of vehicles passing by the leeward lanes in vicinity of A-shaped pylon. In all, above work provides technical support for the final implementation of the wind barrier as an engineering measure.

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Consistency of mean wind speed in pedestrian wind environment analyses: Mathematical consideration and a case study using large-eddy simulation

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/j.jweia.2017.11.021 ◽

2018 ◽

Vol 173 ◽

pp. 91-99 ◽

Cited By ~ 10

Author(s):

Hideki Kikumoto ◽

Ryozo Ooka ◽

Mengtao Han ◽

Keigo Nakajima

Keyword(s):

Wind Speed ◽

Large Eddy Simulation ◽

Wind Environment ◽

Eddy Simulation ◽

Large Eddy ◽

Mean Wind Speed

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Pollutant dispersion simulation for low wind speed condition by the ILS method

Atmospheric Environment ◽

10.1016/j.atmosenv.2005.07.007 ◽

2005 ◽

Vol 39 (34) ◽

pp. 6282-6288 ◽

Cited By ~ 16

Author(s):

Jonas C. Carvalho ◽

Marco Túllio M.B. de Vilhena

Keyword(s):

Wind Speed ◽

Pollutant Dispersion ◽

Speed Condition ◽

Low Wind Speed

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Effects of building aspect ratio, diurnal heating scenario, and wind speed on reactive pollutant dispersion in urban street canyons

Journal of Environmental Sciences ◽

10.1016/s1001-0742(11)60971-6 ◽

2012 ◽

Vol 24 (12) ◽

pp. 2091-2103 ◽

Cited By ~ 22

Author(s):

Nelson Y.O. Tong ◽

Dennis Y.C. Leung

Keyword(s):

Wind Speed ◽

Aspect Ratio ◽

Pollutant Dispersion ◽

Street Canyons ◽

Urban Street ◽

Urban Street Canyons ◽

Reactive Pollutant

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Wind Environment Simulation Accuracy in Traditional Villages with Complex Layouts Based on CFD

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18168644 ◽

2021 ◽

Vol 18 (16) ◽

pp. 8644

Author(s):

Xingbo Yao ◽

Shuo Han ◽

Bart Dewancker

Keyword(s):

Steady State ◽

Wind Speed ◽

Turbulence Intensity ◽

Simulated Data ◽

Wind Environment ◽

Complex Building ◽

Environment Simulation ◽

Ventilation Performance ◽

Steady State Simulation ◽

The Village

Using wind speed, wind direction, and turbulence intensity values as evaluation indicators, the ventilation performance of villages with complex building layouts was studied. We used the SKE, RNG, and RKE solvers in CFD-3D steady-state Reynolds-averaged Navier–Stokes (RANS) to simulate the wind environment of a village. The findings show that for the simulation of rural wind environments with complex building layouts, steady-state simulation solvers need to be evaluated in detail to verify their accuracy. In this study, a village with a complex architectural layout in Southern Shaanxi, China, was taken as the research object, and three steady-state simulation solvers were used to evaluate the ventilation performance of the village. The simulated data were compared with the measured data to find the most suitable solver for this kind of village wind environment simulation. The results show that for the simulation of the village wind environment with a complex building layout, the RNG simulation results have the lowest reliability among the three steady-state solvers. The reliability of wind speed distribution and turbulence intensity distribution are 0.7881 and 0.2473, respectively. However, the wind speed and turbulence intensity values obtained by the SKE solver are the closest to the measured values, which are 0.8625 and 0.9088, respectively. Therefore, for villages with complex building layouts, the SKE solver should be the first choice for simulating wind environment distribution. When using the RNG solver, the overall turbulence intensity value obtained is higher than the measured value. The average deviation between the simulated data and SKE and RKE at a height of 1.7 m is 42.61%. The main reason for this is that RNG overestimates the vortices and underestimates the airflow rate in the building intervals.

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On the Impact of Trees on Ventilation in a Real Street in Pamplona, Spain

Atmosphere ◽

10.3390/atmos10110697 ◽

2019 ◽

Vol 10 (11) ◽

pp. 697 ◽

Cited By ~ 4

Author(s):

Jose-Luis Santiago ◽

Riccardo Buccolieri ◽

Esther Rivas ◽

Beatriz Sanchez ◽

Alberto Martilli ◽

...

Keyword(s):

Wind Speed ◽

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Wind Velocity ◽

Flow Direction ◽

Pollutant Dispersion ◽

Average Concentration ◽

Pollutant Concentration ◽

Prevailing Wind Direction ◽

The Impact

This paper is devoted to the quantification of changes in ventilation of a real neighborhood located in Pamplona, Spain, due to the presence of street trees Pollutant dispersion in this urban zone was previously studied by means of computational fluid dynamic (CFD) simulations. In the present work, that research is extended to analyze the ventilation in the whole neighborhood and in a tree-free street. Several scenarios are investigated including new trees in the tree-free street, and different leaf area density (LAD) in the whole neighborhood. Changes between the scenarios are evaluated through changes in average concentration, wind speed, flow rates and total pollutant fluxes. Additionally, wind flow patterns and the vertical profiles of flow properties (e.g., wind velocity, turbulent kinetic energy) and concentration, horizontally-averaged over one particular street, are analyzed. The approach-flow direction is almost perpendicular to the street under study (prevailing wind direction is only deviated 4º from the perpendicular direction). For these conditions, as LAD increases, average concentration in the whole neighborhood increases due to the decrease of wind speed. On the other hand, the inclusion of trees in the street produces an increase of averaged pollutant concentration only within this street, in particular for the scenario with the highest LAD value. In fact, the new trees in the street analyzed with the highest LAD value notably change the ventilation producing an increase of total pollutant fluxes inward the street. Additionally, pollutant dispersion within the street is also influenced by the reduction of the wind velocity along the street axis and the decrease of turbulent kinetic energy within the vegetation canopy caused by the new trees. Therefore, the inclusion of new trees in a tree-free street should be done by considering ventilation changes and traffic emissions should be consequently controlled in order to keep pollutant concentration within healthy levels.

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Urban Flow and Dispersion Simulation Using a CFD Model Coupled to a Mesoscale Model

Journal of Applied Meteorology and Climatology ◽

10.1175/2009jamc2066.1 ◽

2009 ◽

Vol 48 (8) ◽

pp. 1667-1681 ◽

Cited By ~ 65

Author(s):

Jong-Jin Baik ◽

Seung-Bu Park ◽

Jae-Jin Kim

Keyword(s):

Wind Speed ◽

Boundary Conditions ◽

Mesoscale Model ◽

Model Simulation ◽

Pollutant Dispersion ◽

Time Dependent ◽

Cfd Model ◽

Ambient Wind ◽

Mm5 Model ◽

Urban Flow

Abstract Flow and pollutant dispersion in a densely built-up area of Seoul, Korea, are numerically examined using a computational fluid dynamics (CFD) model coupled to a mesoscale model [fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)]. The CFD model used is a Reynolds-averaged Navier–Stokes equations model with the renormalization group k − ɛ turbulence model. A one-way nesting method is employed in this study. MM5-simulated data are linearly interpolated in time and space to provide time-dependent boundary conditions for the CFD model integration. In the MM5 simulation, four one-way nested computational domains are considered, and the innermost domain with a horizontal grid size of 1 km covers the Seoul metropolitan area and its adjacent areas, including a part of the Yellow Sea. The NCEP final analysis data are used as initial and boundary conditions for MM5. MM5 is integrated for 48 h starting from 0300 LST 1 June 2004 and the coupled CFD–MM5 model is integrated for 24 h starting from 0300 LST 2 June 2004. During the two-day period, a high-pressure system was dominant over the Korean peninsula, with clear conditions and weak synoptic winds. MM5 simulates local circulations characterized by sea breezes and mountain/valley winds. MM5-simulated synoptic weather and near-surface temperatures and winds are well matched with the observed ones. Results from the coupled CFD–MM5 model simulation show that the flow in the presence of real building clusters can change significantly as the ambient wind speed and direction change. Diurnally varying local circulations mainly cause changes in ambient wind speed and direction in the present simulation. Some characteristic flows—such as the double-eddy circulation, channeling flow, and vertical recirculation vortex—are simulated. Pollutant dispersion pattern and the degree of lateral pollutant dispersion are shown to be complicated in the presence of real building clusters and under varying ambient wind speed and direction. This study suggests that because of the sensitive dependency of urban flow and pollutant dispersion on variations in ambient wind, time-dependent boundary conditions should be used to better simulate or predict them when the ambient wind varies over the period of CFD model simulation.

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