Dispersion of localised releases in a street network (DIPLOS)

Lead Research Organisation: University of Southampton
Department Name: Faculty of Engineering & the Environment


The security threat level from international terrorism, introduced by the UK Security Service, has been classified as either "severe" or "critical" for much of its six-year history, and currently remains as "substantial" (source: MI5 web site). Part of the risk posed by terrorist threats involves potential releases of air-borne chemical, biological, radiological or nuclear (CBRN) material into highly populated urbanised areas. Smoke from industrial accidents within or in the vicinity of urban areas also pose risks to health and can cause widespread disruption to businesses, public services and residents. The Buncefield depot fire of 2005 resulted in the evacuation of hundreds of homes and closure of more than 200 schools and public buildings for two days; consequences would have been much more severe if prevailing meteorological conditions had promoted mixing or entrainment of the smoke plume into the urban canopy.

In both these scenarios it is crucial to be able to model, quickly and reliably, dispersion from localised sources through an urban street network in the short range, where the threat to human health is greatest. However, this is precisely where current operational models are least reliable because our understanding and ability to model short-range dispersion processes is limited. The contribution that DIPLOS will make is: (i) to fill in the gaps in fundamental knowledge and understanding of key dispersion processes, (ii) to enable those processes to be parametrized for use in operational models, and (iii) to implement them into an operational model, evaluate the improvement and apply the model to a case study in central London.

Most of the existing research on urban dispersion has focused on air quality aspects, with sources being extensive and distributed in space. Scientifically, the proposed research is novel in focusing on localized releases within urban areas, and on dispersion processes at short range. Through a combination of fundamental studies using wind tunnel experiments and high resolution supercomputer simulations, extensive data analysis and development of theoretical and numerical models, DIPLOS will contribute to addressing this difficult and important problem from both a scientific research and a practical, operational perspective.


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Description The character of the scalar dispersion from a localized source in an array of rectangular buildings strongly depends on the position of the source relative to the street network and the wind direction.

In the simulated case with wind direction 0°, where the scalar source lies in a street perpendicular to the mean flow, the scalar is transported above the canopy by the recirculation in the street canyon. The streamwise scalar flux above the canopy is then larger than the corresponding flux below the roof level. The vertical concentration variance sz at the plume centreline is larger than 1H and is increasing with the distance from the source.

The asymmetry of the experimental results and a computational sensitivity study showed that a small change of the wind direction between 1° and 3° can strongly affect the plume shape. We should take into account such uncertainties into the quick prediction models.
When the scalar source is located in the street parallel to the mean wind direction, as in the simulated 90° case, the scalar is advected by the mean flow inside the street and transported upwards by turbulence and by recirculating flow in the spanwise streets. The streamwise scalar flux within the canopy is larger than the corresponding flux above and the sz at the plume centreline is smaller than 1H within the simulated domain.
Exploitation Route The obtained knowledge will be shared through publication, conferences/workshops etc; also through partnership with others.
Sectors Aerospace, Defence and Marine,Energy,Environment,Security and Diplomacy

Description 1. The developed approaches have been used in the DSTL part-time phd project 'Modelling the production and transport of vapour from explosives in an indoor environment considering effects of mechanical and natural ventilation'. The project is conducted by DSTL employee Mr Tim Foat under Dr ZT Xie's supervision. 2. The developed technology has been used in Wessex Petroleum Limited (WP), and has successfully approved WP Fuel Solutions' new concept - a more effective bottom filtration pipework for fuel tanks. 3. The research output resulted in a new research project ( Air Quality Around Tall Buildings in London) with industry company RWDI funded by London City Council, 2018-19.
Sector Aerospace, Defence and Marine,Energy,Environment
Impact Types Policy & public services

Description ARCHER eCSE 
Organisation Engineering and Physical Sciences Research Council (EPSRC)
Department ARCHER Service
Country United Kingdom 
Sector Academic/University 
PI Contribution the developed code will be made accessible to the ARCHER community.
Collaborator Contribution technique support, etc.
Impact to come.
Description Newton Research Collaboration Programme 14/03/2017-14/03/2018 with Brazilian partners 
Organisation Federal University of Espírito Santo
Country Brazil 
Sector Academic/University 
PI Contribution The collaboration between UFES in Brazil and the University of Southampton in the UK will allow for partaking LES, DNS and wind tunnel experimental data obtained in a previous project developed by the University of Southampton with UK partners. It will also allow for sharing knowledge and experience already gained by both teams about the methodologies involved in using turbulence models. Turbulence modelling is a big challenge, enhancing the knowledge of LES and DNS will certainly help the UK engineering community. The UK Met Office, DSTL and NCAS (National Centre for Atmospheric Science) are the partners of the DIPLOS project for which the Applicant is the Southampton PI. These partners will attend the final DIPLOS workshop in Mar/2017 in Southampton. Contribution from the co-Applicant's team will benefit to these partners. In addition, the Applicant is a member of NCAS, a committee member of the UK Wind Engineering Society and is currently supported by DSTL through a few Phd student projects. The proposed project will be beneficial to all of these collaborations.
Collaborator Contribution The co-Applicant's team will test the Applicant's recently developed tool - a Numerical Environmental Wind Tunnel Of Newtonian fluid (NEWTON) for a wider range of applications, such as thermal stratification effects. Brazil has several research funding agencies which, in time, can be used to fund further research on the topic. In addition, the Supercomputing Centre for Industrial Innovation (YEMOJA), which is the largest in Latin America, is fully accessible to the Brazilian research group including academic visitors.
Impact The two teams will publish 5 journal and conference papers. These will have impacts for the international engineering community and the general public.
Start Year 2007
Description Supervising a DSTL employee as a Part-Time PhD student in Southampton 
Organisation Defence Science & Technology Laboratory (DSTL)
Country United Kingdom 
Sector Public 
PI Contribution The title of the part-time phd research of DSTL is 'Modelling the production and transport of vapour from explosives in an indoor environment considering effects of mechanical and natural ventilation'. The phd student Tim Foat has successfully passed his first milestone viva. My research team provides expertise, and computer resources.
Collaborator Contribution Tim Foat in turn inputs industry drivers, reported conf papers with Southampton as co-institution, and is writing joint papers with Southampton.
Impact A joint conference paper (DSTL+ Southampton) was reported in the 68th Annual Meeting of the APS Division of Fluid Dynamics. http://meetings.aps.org/Meeting/DFD15/Event/255644
Start Year 2014
Description co-supervising a phd student in Eindhoven University of Technology 
Organisation Eindhoven University of Technology
Country Netherlands 
Sector Academic/University 
PI Contribution co-supervising a phd student in Eindhoven University of Technology
Collaborator Contribution In turn the partner will co-publish paper with me, provide experimental data etc.
Impact To come
Start Year 2006
Description collaboration with DSTL 
Organisation Defence Science & Technology Laboratory (DSTL)
Country United Kingdom 
Sector Public 
PI Contribution The university of Southampton will provide 50% of two phd studentships (and other relevant support), which will be co-supervised with DSTL.
Collaborator Contribution DSTL ill provide 50% of two phd studentships.
Impact this collaboration has just started and we are recruiting the phd students.
Start Year 2014