scholarly journals Study of Heavy Gas Pollutants’ Dispersion in Street Canyon Terrain

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1754
Author(s):  
Xiaoye Nie ◽  
Yuyan Fan ◽  
Hong Gao ◽  
Qiang Lin
Keyword(s):  
Wind Speed ◽  
Aspect Ratio ◽  
Flow Field ◽  
Street Canyon ◽  
Relative Concentration ◽  
Windward Side ◽  
Street Canyons ◽  
Gas Dispersion ◽  
Wind Speeds ◽  
Heavy Gas

This study focused on heavy gas dispersion under the terrain conditions of street canyons. The effects of street aspect ratio and height ratio were investigated, and the influence of environmental wind speed in the typical ideal street canyon terrain was explored. The results indicated that the surrounding flow field distributions in street terrains were dominated by higher buildings. In addition, when the building height was held constant, the flow field was affected by the joint influence of the two isolated buildings. The interception effect of the street canyon on upstream pollutants declined with the decrease in the street canyon’s aspect ratio. In addition, when the height ratios were different, a large quantity of upstream pollutants accumulated on the windward side of higher buildings. The relative concentration per unit area inside the canyon was affected by the air circulation inside and outside the canyon and the size of the dispersion space. The increase in the environmental wind speed promotes the entry of pollutants into the street while aggravating the overall dispersion of the pollutants. Therefore, the emergence of the most unsafe wind speeds caused most of the pollutants to gather in the street canyons.

scholarly journals A GLOBAL RELATION OF FIRE SMOKE RE-CIRCULATION BEHAVIOUR IN URBAN STREET CANYONS

2015 ◽  
Vol 21 (4) ◽  
pp. 459-469 ◽  
Author(s):  
Longhua Hu ◽  
Xiaochun Zhang ◽  
Wei Zhu ◽  
Zhi Ning ◽  
Fei Tang
Keyword(s):  
Aspect Ratio ◽  
Froude Number ◽  
Wind Velocity ◽  
Street Canyon ◽  
Inertial Force ◽  
Wind Flow ◽  
Street Canyons ◽  
Global Parameter ◽  
Urban Street ◽  
Fire Smoke

Street canyon, formed by buildings along two sides of a road, is an important and ubiquitous architectural element in the metropolises. When a fire occurs in an urban street canyon, a critical serious phenomenon is found to happen where the uprising fire smoke is re-circulated back into the base of the street canyon by the wind flow beyond a critical velocity. Theoretical analysis is derived based on Froude number (Fr), by balancing the inertial force of the wind flow to the buoyancy strength of the fire smoke. It is found that the critical re-circulation wind velocity is proportional to an integrated global parameter . Large Eddy Simulations (LES) are carried out by Fire Dynamics Simulator (FDS). The critical Froude number (Fr) is found to be about 0.7~0.8. The simulation results are well collapsed by the generalized theoretical relation. It is further revealed that the non-dimensional critical re-circulation wind velocity . against aspect ratio of street canyons in the skimming flow pattern (W/H < 1.43) falls into two behavioural regimes, where it firstly increases then remains constant with the increase in street canyon aspect ratio (W/H) with a turning point at W/H = 1. A global non-dimensional relation is finally achieved for the critical re-circulation wind velocity (u), fire heat release rate (Q) and its height (H) to the top of the street canyon as well as the street canyon aspect ratio (W/H).

Development and Validation of a Thermodynamic Model for Predicting Traffic-Related Pollutants Dispersion in Urban Street Canyons under Low Wind Speed Conditions

2012 ◽  
Vol 157-158 ◽  
pp. 710-713
Author(s):  
Guo Hua Gao ◽  
Jing Liu ◽  
Fei Ma ◽  
Wei Dong Luo
Keyword(s):  
Wind Speed ◽  
Thermodynamic Model ◽  
Street Canyon ◽  
Pollutant Dispersion ◽  
Shielding Effect ◽  
Street Canyons ◽  
Urban Street ◽  
Low Wind Speed ◽  
Urban Street Canyons ◽  
Pollutants Dispersion

To study the thermal effects on pollutant dispersion in the street canyon, a thermodynamic model is developed in this paper to predict surface temperature in street canyon environment, which can offer boundary conditions for CFD model. This model considered the shielding effect of buildings on solar radiation, the multi-reflection of radiation between building surfaces and the road. Furthermore, sensible heat exchange between the canyon space and the overlaying atmosphere was also modeled based on the classical theory of dynamics of atmospheric boundary layer. The reliability of this model is validated through a field measurement. Based on the thermodynamic model, a coupled calculation method is presented to predict traffic-related pollutants dispersion in urban street canyons under low wind speed conditions.

scholarly journals Influence of Wind and Humidity on Foraging Behavior of Olfactory Mesopredators

2011 ◽  
Vol 125 (2) ◽  
pp. 132 ◽  
Author(s):  
Rebekah E. Ruzicka ◽  
Michael R. Conover
Keyword(s):  
Wind Speed ◽  
Foraging Behavior ◽  
Wind Direction ◽  
Weather Conditions ◽  
Windward Side ◽  
Red Foxes ◽  
Predator Species ◽  
Wind Speeds ◽  
Mammalian Predators ◽  
Striped Skunks

Many mammalian predators rely on scents to locate prey and weather conditions that affect an odor plume (i.e., scents suspended in air) or depositional odor (i.e., scents laid on the ground) should affect predator foraging behavior. We predicted that wind speed, wind direction, and humidity would influence the foraging behavior of olfactory mesopredators. We tested these predictions by conducting spotlight surveys for foraging Red Foxes (Vulpes vulpes), Striped Skunks (Mephitis mephitis), and Raccoons (Procyon lotor) along the dike surrounding Willard Bay Reservoir in Willard, Utah, from August 2008 to August 2009. We recorded predator species, locations, numbers, and weather conditions at the time each predator was observed. While humidity had no effect on foraging, wind speed and direction were significant predictors of a predator's nightly foraging activity, with most predators observed when wind speeds were 2 to 4 m/s and winds were blowing perpendicularly over the dike the dike rather than parallel to the dike. Wind speed and direction also influenced where predators foraged on the dike, with predators being more likely to forage on the windward side of the dike when wind speeds were high enough to cause turbulence. We detected differences among predator species in their response to wind speed: Raccoons were more active than Striped Skunks and Red Foxes when the wind was calm and blowing parallel to the dike. Overall, our results indicate that these predator species alter their foraging behavior based on wind speed and wind direction. By foraging when winds were light and blowing perpendicularly over the dike, predators could likely enhance their ability to locate food using olfaction.

scholarly journals The Numerical Simulation of Uplifted Street Canyon On Flow Field Structure And Pollutant Diffusion

2021 ◽  
Author(s):  
Mengru Sun ◽  
Yuqing Song ◽  
Changfa Tao ◽  
Xiaoping Liu ◽  
Quanli Wang ◽  
...  
Keyword(s):  
Flow Field ◽  
Street Canyon ◽  
Concentration Distribution ◽  
Field Structure ◽  
Pollutant Concentration ◽  
Windward Side ◽  
Leeward Side ◽  
Building Height ◽  
Lift Height ◽  
Pollutant Concentration Distribution

Abstract The flow field structure, pollutant concentration distribution and dimensionless concentration evolution of uplifted street canyon has been analyzed in this study. Different from the ideal street canyon, the pollutant concentration distribution of the uplifting street canyon is higher at the bottom, lower at the top, higher at the windward side and lower at the leeward side. The total pollutant concentration (TPC) generally decreases with the increase of leeward building lifting height while the lift height increases with the same total building height or the total building height increases with increase in the lifting height. It is beneficial to the pollutant emission of in street canyon. On the contrary, the TPC increases when the total building height increases with the same lift height. The main reason is that the vertical length of the vortex increases, which is more difficult for pollutants to be discharged from the street canyon.

The effect of the cooling on a dry storage cask for spent nuclear fuel by different wind speed

2020 ◽  
Author(s):  
LinYing Cheng ◽  
Chi-Ming Lai
Keyword(s):  
Wind Speed ◽  
Nuclear Fuel ◽  
Thermal Performance ◽  
Spent Nuclear Fuel ◽  
Cfd Simulation ◽  
Temperature Drop ◽  
Windward Side ◽  
Thermal Buoyancy ◽  
Wind Speeds ◽  
Dry Storage

<p>In this study, we considered different the wind speeds affects the thermal performance when the dry storage cask for spent nuclear fuel , which used NAC- MAGNASTOR cask of system, and placed outdoors. We Ddiscuss the dry storage cask for spent nuclear fuel cooling by the thermal buoyancy ventilation of cask. Firstly, Compare the experimental data of low-speed wind tunnel experiments with the result of from a commercial software PHOENICS CFD (Computational Fluid Dynamics) for heat flow analysis, and confirm the reliability of the CFD simulation results of the software. Then we used the software to simulate higher wind speeds to understand the thermal performance of the cask for spent nuclear fuel by various wind speeds. With external wind speed is was more much faster, channel airflow of the cask hads increased, especially upper channel airflow of the cask and near steel cylindrical. The temperature of the windward side of the cask hads also been significantly reduced, The lee side hads a slower wind speed and a smaller temperature drop, and generates an eddy below the lee side, which helpeds to dissipate .heat,. However, as the wind speed gradually increases, the lee side changed to a downdraft, and the temperature drop was also slowed down. It is noticeable that the situation may occur when a typhoon comes.</p>

Effects of building aspect ratio and wind speed on air temperatures in urban-like street canyons

2010 ◽  
Vol 45 (1) ◽  
pp. 176-188 ◽  
Author(s):  
Rizwan Ahmed Memon ◽  
Dennis Y.C. Leung ◽  
Chun-Ho Liu
Keyword(s):  
Wind Speed ◽  
Aspect Ratio ◽  
Street Canyons ◽  
Air Temperatures

scholarly journals Effect of Environmental Wind on Performance of a 600MW Direct Air-cooled Unit Based on FLUENT

2019 ◽  
Vol 118 ◽  
pp. 02019
Author(s):  
Junfeng Xu ◽  
Taoying Wang ◽  
Minmin Zhao
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Flow Field ◽  
Wind Direction ◽  
Heat Transfer Performance ◽  
Air Flow ◽  
Transfer Efficiency ◽  
Windward Side ◽  
Transfer Performance ◽  
Heat Transfer Efficiency

The external flow field of a 600MW air-cooled unit is numerically simulated based on FLUENT. The distribution law of air flow field of air-cooled unit under different wind speed and wind direction conditions is studied. The influence of wind speed and wind direction on the heat transfer performance of air-cooled unit is analyzed. Predict the exhaust pressure of direct air-cooled unit under the influence of environmental wind. The results show that in the +X direction environmental wind, the first row of air-cooled unit on the windward side is prone to backflow; in the +Y direction environmental wind, the first row of air-cooled unit on the windward side is prone to hot air recirculation. As the wind speed increases, the heat transfer efficiency of the air-cooled unit decreases. The dominant wind direction (WNW) environmental wind has the least impact on the heat transfer efficiency, and the furnace wind (+Y direction wind) has the greatest influence on the heat transfer efficiency. To improve the heat transfer performance of the air-cooled unit under windy conditions, it is necessary to narrow the range of the negative pressure zone below the air-cooled unit and increase the cooling air flow rate of the air-cooled unit.

Numerical Simulation of Traffic Emissions in Urban Street Canyon

2010 ◽  
Vol 168-170 ◽  
pp. 1548-1551
Author(s):  
Peng Wang ◽  
Dai Qing Zhao ◽  
Guo Tian Cai ◽  
Cui Ping Liao
Keyword(s):  
Wind Speed ◽  
Street Canyon ◽  
Pollutant Emissions ◽  
Turbulent Model ◽  
Urban Street Canyon ◽  
Vehicle Exhaust ◽  
Wind Tunnel Experiments ◽  
Street Canyons ◽  
Urban Street ◽  
Street Width

Dispersion of gaseous pollutant emissions in different street canyons was studied using two dimensional sections of canyon models airflow. Effects of building size, street width wind velocity and different turbulent model on the pollutant transport were examined. Depending on wind speed, building height, and street width, it was found that large recirculation regions in canyons may form. Under certain conditions, gaseous pollutants emitted from vehicle exhaust may trap inside the street canyon. It was shown that the amount of pollutants in street canyons reduces when the wind speed increases. The simulation results were compared with the available wind tunnel experiments and favorable agreement was found.

SHAPING OF AN AUTONOMOUS POWER SYSTEM FOR GUARANTEED POWER SUPPLY WITH THE PREDOMINANCE WIND ENERGY

2018 ◽  
pp. 28-50
Author(s):  
S. G. Ignatiev ◽  
S. V. Kiseleva
Keyword(s):  
Energy Storage ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Diesel Generator ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Optimization of the autonomous wind-diesel plants composition and of their power for guaranteed energy supply, despite the long history of research, the diversity of approaches and methods, is an urgent problem. In this paper, a detailed analysis of the wind energy characteristics is proposed to shape an autonomous power system for a guaranteed power supply with predominance wind energy. The analysis was carried out on the basis of wind speed measurements in the south of the European part of Russia during 8 months at different heights with a discreteness of 10 minutes. As a result, we have obtained a sequence of average daily wind speeds and the sequences constructed by arbitrary variations in the distribution of average daily wind speeds in this interval. These sequences have been used to calculate energy balances in systems (wind turbines + diesel generator + consumer with constant and limited daily energy demand) and (wind turbines + diesel generator + consumer with constant and limited daily energy demand + energy storage). In order to maximize the use of wind energy, the wind turbine integrally for the period in question is assumed to produce the required amount of energy. For the generality of consideration, we have introduced the relative values of the required energy, relative energy produced by the wind turbine and the diesel generator and relative storage capacity by normalizing them to the swept area of the wind wheel. The paper shows the effect of the average wind speed over the period on the energy characteristics of the system (wind turbine + diesel generator + consumer). It was found that the wind turbine energy produced, wind turbine energy used by the consumer, fuel consumption, and fuel economy depend (close to cubic dependence) upon the specified average wind speed. It was found that, for the same system with a limited amount of required energy and high average wind speed over the period, the wind turbines with lower generator power and smaller wind wheel radius use wind energy more efficiently than the wind turbines with higher generator power and larger wind wheel radius at less average wind speed. For the system (wind turbine + diesel generator + energy storage + consumer) with increasing average speed for a given amount of energy required, which in general is covered by the energy production of wind turbines for the period, the maximum size capacity of the storage device decreases. With decreasing the energy storage capacity, the influence of the random nature of the change in wind speed decreases, and at some values of the relative capacity, it can be neglected.

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