Features

SIRANERISK is an atmospheric pollution modelling software for urban environments, designed to address hazardous substances (CBRN-type threats).

SIRANERISK can handle unsteady emission conditions and time-varying meteorology. It is particularly suited to hazardous substances (CBRN-type), although any type of species can be considered. The characteristic spatial scale of the software is the neighbourhood scale (study domain ranging from a few hundred metres to a few kilometres). It allows the description of pollutant concentrations in an area mainly composed of streets lined with buildings. SIRANERISK covers a spatial scale between the street scale, where the focus is on pollutant distribution within a single street, and the city scale, where it is no longer possible to explicitly model the effect of each building. It therefore provides a three-dimensional mapping of the impact of a hazardous release at neighbourhood scale. From a temporal point of view, SIRANERISK is suited to characteristic time scales ranging from about one minute to a few hours.

SIRANERISK is not strictly speaking a meteorological flow model. The analysis of flow processes above a city (Soulhac, 2004) makes it possible to distinguish two regions characterised by significantly different phenomena:

• The urban canopy, defined approximately as the region below roof level, in which the highly complex flow is characterised by confinement between buildings and the presence of many recirculation zones.
• The external atmosphere, i.e. the region above roof level. In this region, the flow is dominated by the atmospheric boundary layer and by the influence of terrain. Open areas without buildings are also included in the "external atmosphere".

In SIRANERISK, the wind field in the external atmosphere is computed by its meteorological preprocessor. Meteorological inputs provided by the user determine the structure of the wind field. It may be horizontally uniform over the entire domain with variation only in the vertical direction, or defined on a 3D spatial grid. The wind field inside the urban canopy is then computed by SIRANERISK based on the external flow.

The SIRANERISK software is a computational code developed in the C programming language. It is available on different operating systems (Windows, Linux).

SIRANERISK is not limited by computational constraints in terms of the number of sources, streets, or domain size. Only the limits of physical validity restrict the application of the software to domains of about twenty kilometres.

SIRANERISK currently operates without a graphical user interface, using input and output data files, as described in the user documentation.

The SIRANERISK software has been validated through comparison with detailed numerical simulations, wind tunnel experiments, and field experiments.

This work has resulted in numerous scientific publications.