A Numerical Study on Airflow and Particle Dispersion within an Urban Street Canyon with Different Wedge-Shaped Roofs

2013 ◽  
Vol 869-870 ◽  
pp. 213-217
Author(s):  
Yakup Parida ◽  
Wen Rong He ◽  
Zhong Hua Zhou ◽  
Deng Feng Fu
Keyword(s):  
Street Canyon ◽  
Stokes Equations ◽  
Numerical Study ◽  
Distribution Patterns ◽  
Particle Dispersion ◽  
Atmospheric Environment ◽  
Navier Stokes ◽  
Urban Street Canyon ◽  
Urban Street ◽  
Pollution Levels

This work presents a numerical study on airflow and particle dispersion within an urban street canyon with different wedge-shaped roof. A two-dimensional computational fluid dynamics (CFD) model for evaluating the airflow and particles dispersion within a street canyon was built up, which was based on the incompressible Reynolds Averaged Navier-Stokes equations, turbulence model and the particles transportation equation. It is revealed that: (1) particles dispersion inside an urban street canyon is mostly dominated by the in-canyon wind flow; (2) different wedge-shaped roof configurations causes a variety of particles distribution patterns; (3) air pollution levels are much higher in the step-down canyons relative to the step-up canyons; (4) the simulated result of FLUENT is reasonable, and the prospect of applying FLUENT to study atmospheric environment is very well. Key words: CFD; street canyon; particle dispersion; numerical simulation

scholarly journals Wind-field and pollution-dispersion simulation in a street canyon in Helsinki with ADREA-HF code

2013 ◽  
Vol 8 (3) ◽  
pp. 272-276
Keyword(s):  
Complex Terrain ◽  
Street Canyon ◽  
Eddy Viscosity ◽  
Local Scale ◽  
Navier Stokes ◽  
Urban Street Canyon ◽  
Pollution Dispersion ◽  
Urban Street ◽  
Eddy Viscosity Model ◽  
Computational Fluid Dynamics Cfd

ADREA-HF, which is a Computational Fluid Dynamics (CFD) code, is utilised in order to numerically study the flow and concentration fields within a street-canyon area. The selected site is Runeberg Str., a typical urban street canyon with an aspect ratio of approximately 1:1 in Helsinki, Finland. The ADREA-HF model is a transient, non-hydrostatic, dense transport code, especially developed for dispersion modelling of buoyant or passive gases over complex terrain in local scale. It solves the 3D unsteady Reynolds Averaged Navier-Stokes (RANS) equations treating complex multi-building domains with a porosity formulation. For modelling turbulence a one-equation eddy-viscosity model is used. The numerical results illustrate the flow and concentration fields within the canyon and also show the influence of the detailed geometry, such as, that of the street junction situated at the northern end of the canyon, and that of the boulevard at the southern end.

scholarly journals AERODYNAMIC EFFECTS OF POLLUTION CONCENTRATIONS IN URBAN STREET CANYON USING TWO PASSIVE CONTROL METHODS: CROSSING UNDER BUILDING AND LOW BOUNDARY WALL

2019 ◽  
pp. 13-22
Author(s):  
Faddia Baghlad ◽  
Benouada Douaiba ◽  
Abbes Azzi
Keyword(s):  
Air Quality ◽  
Urban Areas ◽  
Street Canyon ◽  
Sulfur Hexafluoride ◽  
Passive Control ◽  
Stokes Equations ◽  
Control Methods ◽  
Urban Street Canyon ◽  
Urban Street ◽  
Pollution Concentrations

The present work, focused on the Atmospheric boundary-layer airflows and their interactions with obstacles, particularly in relation to urban air quality, therefore two passive control methods are represented in barriers solid LBWs (Low Boundary Walls) and crossings under building, in order to investigate the dynamic impacts in the center urban canyon road. These passive control solutions are designed for reducing the concentrations airflows polluted necessary, while a correct air quality in the urban areas. For these reasons, the passageways under building and LBWs models have been performed with a two dimensional numerical ANSYS-CFX code, rendering it ideal for examining the concentration distribution within street canyons of H1/H2 = 0.5-1-1.5 and the dynamics effects of pollution concentrations of vehicle emissions of sulfur hexafluoride (SF6), which it is taken as a tracer gas within the symmetrical urban street canyon. However the Reynolds-averaged Navier–Stokes equations and the k-ɛ turbulence model are applied in order to close the equations system. The results achieved are evidence about the diminishing of the pollutant concentrations normalized in in the leeward and windward of the urban street canyon

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

scholarly journals Experimental and Numerical Study on Water Filling and Air Expelling Process in a Pipe with Multiple Air Valves under Water Slow Filling Condition

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2511
Author(s):  
Jintao Liu ◽  
Di Xu ◽  
Shaohui Zhang ◽  
Meijian Bai
Keyword(s):  
Numerical Model ◽  
Stokes Equations ◽  
Numerical Study ◽  
Practical Method ◽  
Navier Stokes ◽  
Physical Processes ◽  
Two Phase ◽  
Saint Venant Equations ◽  
Water Filling ◽  
Air Valve

This paper investigates the physical processes involved in the water filling and air expelling process of a pipe with multiple air valves under water slow filling condition, and develops a fully coupledwater–air two-phase stratified numerical model for simulating the process. In this model, the Saint-Venant equations and the Vertical Average Navier–Stokes equations (VANS) are respectively applied to describe the water and air in pipe, and the air valve model is introduced into the VANS equations of air as the source term. The finite-volume method and implicit dual time-stepping method (IDTS) with two-order accuracy are simultaneously used to solve this numerical model to realize the full coupling between water and air movement. Then, the model is validated by using the experimental data of the pressure evolution in pipe and the air velocity evolution of air valves, which respectively characterize the water filling and air expelling process. The results show that the model performs well in capturing the physical processes, and a reasonable agreement is obtained between numerical and experimental results. This agreement demonstrates that the proposed model in this paper offers a practical method for simulating water filling and air expelling process in a pipe with multiple air valves under water slow filling condition.

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