177,193 research outputs found
Optimisation of Modelling Methods for Traffic Pollution in Streets. TRAPOS
No full textThe TRAPOS (Optimisation of Modelling Methods for Traffic Pollution in Streets) Project was a European Research Network that had two main objectives:
1) To contribute to scientific achievements in the development and improvement of modelling tools used for the prediction of traffic pollution in urban streets through co-operative work.
2) To promote training-through-research, especially of young researchers, within the framework of high quality trans-national collaborative research projects
The project was in the framework of the European Commission’s Training and Mobility of Researchers Programme (TMR), was co-ordinated by the Danish National Environmental Research Institute (NERI) and ran from November 1997 until April 2001. This summary and available CD has been distributed to some researchers in Europe. Several of them suggested that others may be interested in the project and that led to this note and contact points.
The Network's participants represented universities, public research organisations and commercial consulting companies from several European countries (Denmark, France, Germany, Greece, Switzerland, the Netherlands and the United Kingdom). Their fields of research covered several different aspects of air pollution modelling, such as: laboratory wind tunnel modelling, field measurements, dispersion modelling including computational fluid dynamics and the regulatory applications of models. The work within the TRAPOS Network was closely connected with many other European projects and research activities conducted by the participants. The interdisciplinary character of the co-operation among the participants represented diverse experience and working methods and this led to efficient utilisation of the results and scientific achievements.
Traffic pollution modelling is a very broad area and, to narrow the scope of the work within the Network, some principal research areas were identified as priorities:
• the traffic created turbulence and its influence on dispersion of pollutants in the street,
• the influence of thermal effects on flow modification within street canyons with special regard to low wind speed conditions,
• the sensitivity of the flow and turbulence characteristics to the architecture of the street and its surroundings,
• the fast chemical processes with special regard to NO-NO2 conversion,
• the dispersion and transformation processes of Respirable Suspended Particulate (RSP) matter.
Making use of the existing facilities and expertise of the participants, the activities contributing to the research objectives were:
• field measurements and analyses of data,
• laboratory (wind tunnel) measurements,
• model evaluation and inter-comparison.
The models in use within TRAPOS covered both simpler, parameterised models and more advanced Computational Fluid Dynamics (CFD) models. Synergy in the work with different types of models ensured scientific quality and the practical applicability of the results.
Field measurements and wind-tunnel data were used for evaluation and improvement of mathematical models. Wind-tunnel models were also tested against data from field measurements. Results from CFD models were used to improve parameterisation of simpler semi-empirical models. Design of new field experiments and also wind-tunnel measurements were guided by results from mathematical modelling.
In order to facilitate the joint work a number of Working Groups were created to focus on each of several activities of the Network. These Working Groups, which were led by the young researchers, accepted the main responsibility for the organisation of the work within TRAPOS. Especially dedicated web-sites, with presentation of the results and conclusions, were established by these groups (http://www.dmu.dk/AtmosphericEnvironment/trapos/wg.htm).
Based on the achievements and conclusions provided by the Working Groups a CD was put together for distribution. This included:
Chapter 1 deals with the processes influencing dispersion in a street environment. Theoretical and experimental studies of these processes were the main subject of TRAPOS. Beside the more traditional aspects, such as the influence of the street architecture on the dispersion conditions, this chapter covers also some special phenomena, which have not been studied in such details previously. These include traffic produced turbulence and effects of surface heating.
Presentation and discussion of the different tools used within traffic pollution modelling is given in Chapter 2. This chapter covers the use of laboratory wind tunnels and the use of CFD modelling. An extensive CFD model evaluation study was conducted within TRAPOS. The data used for this evaluation study originated mainly from systematic wind tunnel experiments but field data were also used.
In Chapter 3 the application and evaluation of different modelling methodologies for a practical traffic pollution study is presented. This study, the so-called "Podbielski exercise", was initiated and conducted by German institutions but with a very active participation of TRAPOS.
A summary and overview of the TRAPOS Network and its achievements is given in Chapter 4.
The achievements of the TRAPOS project were frequently presented at several major Air Pollution conferences and published in the open literature. In March 2001 the Third International Conference on Urban Air Quality was held in Loutraki, Greece. This conference provided an excellent opportunity to present some the results of the Network to a broader community. The Extended Abstracts of presentations given by TRAPOS participants at this Conference are attached to this publication as Chapter 5.
The reference list of all papers published during TRAPOS is given in Chapter 6.
The Appendices provide organisational details of the Participants and the list of the Young Visiting Researchers employed by the network
Flow and Pollutant Dispersion in Street Canyons using FLUENT and ADMS-URBAN
No full textThis paper is devoted to the study of flow within a small building arrangement and pollutant dispersion in street canyons starting from the simplest case of dispersion from a simple traffic source. Flow results from the commercial computational fluid dynamics (CFD) code FLUENT are validated against wind tunnel data (CEDVAL). Dispersion results from FLUENT are analysed using the well-validated atmos pheric dispersion model ADMS-Urban. The k∈-∈ε turbulence model and the advection-diffusion (AD) method are used for the CFD simulations. Sensitivity of dispersion results to wind direction within street canyons of aspect ratio equal to 1 is investigated. The analysis shows that the CFD model well reproduces the wind tunnel flow measurements and compares adequately with ADMS-Urban dispersion predictions for a simple traffic source by using a slightly modified k∈-∈ε model. It is found that a Schmidt number of 0.4 is the most appropriate number for the simulation of a simple traffic source and in street canyons except for the case when the wind direction is perpendicular to the street canyon axis. For this last case a Schmidt number equal to 0.04 gives the best agreement with ADMS-Urban. Overall the modified k∈-∈ε turbulence model may be accurate for the simulation of pollutant dispersion in street canyons provided that an appropriate choice for coefficients in the turbulence model and the Schmidt number in the diffusion model are made
Urban Texture Analysis with image processing techniques: winds and dispersion
No full textThe focus is the analysis Of urban Digital Elevation Models (DEMs) with image processing techniques. A brief review of existing methods to derive sky view factors, building energy consumption and space syntax shows how well established parameters that relate to airflow and dispersion (Such as the height-to-width of urban canyons and the aerodynamic roughness length) can be calculated. Other measures of urban directionality and periodicity, inspired by traditional image processing, are also introduced, such as the Radon, Hough and Fourier transforms and the variance plot. Analyses of three case Study sites in London, Toulouse and Berlin are compared, showing considerable variation in the chosen parameters, Results Suggest that the DEM format is an extremely versatile tool to investigate the urban intermediate scale, allowing analyses that Would be very difficult Or impossible to carry Out using traditional vectorial models
Sustainable development of Heathrow airport: model intercomparison study
No full textAir quality modelling near airports has received attention due to the impact of emissions from aircrafts near ground level. This work is part of the model inter-comparison study undertaken for the Department of Transport in connection with air quality near Heathrow Airport. Results formed part of a submission to the UK government in July 2006. The Emissions and Dispersion Modelling System (EDMS) was used. Our contribution required the setting up and running of EDMS for Heathrow Airport and its surroundings to simulate the year 2002. NOX, NO2 and PM10 were chosen for the study; these being of particular concern
Analysis of cfd and gaussian-type model simulations of flow andpollutant dispersion in various urban configurations
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Simulations of pollutant dispersion within idealised urban-type geometries using CFD and integral models
No full textUntil recently, urban air quality modelling has been based on operational models of an integral nature. The use
of computational fluid dynamics (CFD) models to address the same problems is increasing rapidly. Operational models
e.g. OSPM, AERMOD, ADMS-Urban have undergone many comprehensive formal evaluations as to their ‘‘fitness for
purpose’’ while CFD models do not have such an evaluation record in the urban air quality context. This paper looks at
the application of both approaches to common problems. In particular, pollutant dispersion from point and line sources in
the simplest neutral atmospheric boundary layer and line sources placed within different regular building geometries is
studied with the CFD code FLUENT and the atmospheric dispersion model ADMS-Urban. Both the effect of street
canyons of different aspect ratios and various obstacle array configurations consisting of cubical buildings are investigated.
The standard k2 turbulence model and the advection–diffusion (AD) method (in contrast to the Lagrangian particle
tracking method) are used for the CFD simulations. Results from the two approaches are compared. Overall CFD
simulations with the appropriate choice of coefficients produce similar concentration fields to those predicted by the
integral approach. However, some quantitative differences are observed. These differences can be explained by
investigating the role of the Schmidt number in the CFD simulations. A further interpretation of the differences between the two approaches is given by quantifying the exchange velocities linked to the mass fluxes between the in-canopy and above-canopy layers
Transfer processes in a simulated urban street canyon using morphological parameters from DEM analysis
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