CFD air quality control study – Issy underground RER station construction site
CFD air quality control study - Issy underground RER station construction site
Year
2024
Customer
Location
Paris
Typology
Air & Wind
EOLIOS ingénierie's mission: CFD and aeraulic simulation expertise
EOLIOS engineers, experts in aeraulics for underground environments
EOLIOS engineers are experts in the analysis and control of aeraulic phenomena in confined and underground environments, particularly in the context of complex worksites.
This expertise is put to work in the interests of air quality and worker safety, based on a rigorous methodology combining site audits and high-fidelity numerical simulations. Analysis enables us to anticipate local phenomena of stagnation or propagation of pollutants, likely to affect working conditions, while taking into account the technical and operational constraints of the worksite.
EOLIOS is a leader in aeraulic and thermal CFD simulation. Our studies are based on feedback from measurement campaigns in real conditions and from a hundred or so simulated sites around the world.
Airflow study and air quality on the Issy RER station site
Anticipate and control aeraulic risks in an underground environment during the construction phase
The construction phase of an underground rail infrastructure represents a major challenge in terms of air quality. In the absence of definitive ventilation systems, enclosed spaces are subject to complex aeraulic phenomena, highly dependent on site configuration, temporary openings and meteorological conditions.
In this context, EOLIOS Ingénierie worked on the Issy RER station site to analyze air movements, identify risk areas and propose appropriate solutions to guarantee a healthier and safer working environment.
Limited natural ventilation
Construction work (cutting, welding, etc.) generates fine dust and pollutants that can accumulate in poorly ventilated areas. If air flows are not controlled, these pollutants can spread to other levels of the station, degrading air quality for workers.
The EOLIOS team carried out an on-site aeraulic audit, including smoke tests, to visualize air inlets and outlets, as well as the main flow trends between the different levels of the station.
Identify sources of pollution and critical areas with an audit
Construction work (cutting, welding, etc.) generates fine dust and pollutants that can accumulate in poorly ventilated areas. If air flows are not controlled, these pollutants can spread to other levels of the station, degrading air quality for workers.
The EOLIOS team carried out an on-site aeraulic audit, including smoke tests, to visualize air inlets and outlets, as well as the main flow trends between the different levels of the station.
CFD modeling and study of Issy RER station
CFD modeling adapted to the construction phase
Construction work (cutting, welding, etc.) generates fine dust and pollutants that can accumulate in poorly ventilated areas. If air flows are not controlled, these pollutants can spread to other levels of the station, degrading air quality for workers.
The EOLIOS team carried out an on-site aeraulic audit, including smoke tests, to visualize air inlets and outlets, as well as the main flow trends between the different levels of the station.
This approach makes it possible to take account of the severe geometric constraints and changing nature of the structure, while maintaining a coherent overall view of air flows.
Study of different ways of optimizing site ventilation
To assess the influence of technical choices and temporary layouts, several operating configurations were simulated: the existing configuration, the configuration with partitions and then an optimized configuration with supply ducts.
These configurations represent different modes of site ventilation, ranging from a situation dominated by natural ventilation to scenarios incorporating supply ducts.
By comparing these scenarios, we can identify which configurations are most conducive to air renewal, and which generate air imbalances, with flows that are too low, poorly distributed or insufficiently directed towards areas occupied by workers.
Analysis of velocity fields and air mixing in the station as a function of optimizations
Comparative scenario analysis - a structured method for optimizing solutions
CFD simulations were used to analyze the distribution of air velocities throughout the volumes. Some zones show low velocities and little structure, reflecting limited mixing and a reduced capacity to evacuate pollutants generated by site activities.
Conversely, other configurations favor more continuous and evenly distributed circulation, with more homogeneous flows between levels, limiting the formation of stagnant zones and improving the distribution of fresh air in sensitive areas.
The aeraulic study was carried out in three stages, starting with the initial state of the site and then assessing the impact of two alternative configurations.
Theinitial state, with natural ventilation only, constitutes the reference scenario. Analyses reveal that air movement is generally weak and unstructured: while levels close to the surface benefit from relative renewal, the situation deteriorates significantly at depth. The lower levels have very low velocities and a high air age, generating marked stagnation zones, particularly under the platforms. This configuration makes it impossible to guarantee satisfactory air quality during the construction phase.
An initial optimization, involving the introduction of temporary partitions at platform and vertical circulation levels, proved counterproductive. Far from improving the situation, this partitioning limits exchanges between volumes and impedes vertical air circulation, accentuating the confinement of lower levels. Simulations show an increase in the average age of the air in several zones, including previously better-ventilated volumes, with stagnation zones more extensive and pronounced than in the initial configuration.
The second configuration, with fresh air supplied by forced ventilation, delivers significantly better results. Mixing improves in the targeted zones, stagnation is reduced andair renewal becomes more efficient in depth. When supplies are positioned as close as possible to critical areas, the improvement becomes significant and extends to larger volumes. This configuration has been selected as the most appropriate to ensure safe working conditions during the construction phase.
Average air age as a key indicator of ventilation quality
In addition to velocities, the study is based on an analysis of theaverage age of the air, a particularly relevant indicator during the construction phase. This indicator can be used to assess the freshness of the air in each zone.
The results highlight significant contrasts between areas of low air age, benefiting from satisfactory renewal, and areas of high air age, revealing inadequate ventilation and an increased risk of pollutant accumulation. These zones are mainly located under the platforms and in certain parts of the lower levels.
A clear reading of the action priorities for the site
Recommendations tailored to each project
The aeraulic study carried out on the Issy RER station site enabled us to precisely identify the air circulation mechanisms and highlight the limits of natural ventilation during the construction phase.
The results of the study illustrate :
- Natural ventilation alone is insufficient during the construction phase,
- Certain configurations aggravate confinement phenomena,
- Targeted air supply can improve the situation locally,
- A strategy adapted to critical areas is essential to guarantee satisfactory air quality.
The CFD thus enabled us to prioritize problems, identify the most effective levers for improvement, and formulate recommendations tailored to the site’s operational constraints.
Find out more:
Video summary of the study
Summary of the study
EOLIOS Ingénierie carried out a complete aeraulic study to assess air quality and ensure safe working conditions during the construction phase of the Issy RER station. Given the absence of definitive ventilation systems and the depth of the underground levels, the engineers combined a site audit with smoke tests and high-fidelity CFD digital simulations. Three configurations were analyzed and compared: natural ventilation alone, temporary partitioning of the platforms, andfresh air supply via forced ventilation. The results showed that natural ventilation is insufficient during the construction phase, and that partitioning worsens confinement phenomena in the lower levels. The only way to reduce stagnation zones and significantly improve air renewal is to introducetargeted air supplies. This study enabled us to rank the risks and formulate concrete operational recommendations, adapted to the evolving constraints of the site.
Video summary of the mission
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