Theoretical modelling of gas flow and filtering of particulates in cracks in containment barriers, and comparison with other theoretical and empirical studies

Following earlier publication of a model of crack flow and filtering based on a 2-D crack representation, the model has now been improved and submitted to validation by comparison with data from a number of other theoretical and experimental studies. This process has led to improved understanding of gas flow and filtering in real crack geometry and reinforced expectations that the model predictions of barrier filtering capacity will be conservative for realistic containment conditions. Our analysis also indicates that, because of drag effects related to the existence of reduced aperture sites, the viscosity limited flow cannot be approximated by the plane Poiseuille model. As a result, theoretical models employing this assumption over-predict measured flow rates by around an order of magnitude. The narrowing of the flow stream at these reduced aperture sites is also found to be a factor which significantly boosts the filtering of particles. As a result of these investigations, there is a strong possibility that we have now identified all essential elements required for a detailed description of aerosol transport through cracks via the laminar flow of a non-condensible carrier gas.

► Gas flow and particulate filtering in cracks is modelled theoretically and compared with a number of other studies.
► Reveals importance of reduced aperture sites which directly result from the geometry of meandering flow path.
► These sites appear to restrict flow rate to around an order of magnitude lower than predicted by the plane Poiseuille model.
► Reduced aperture sites also boost filtering capacity beyond the predictions of the theoretical model.
► The proposed theoretical model is likely to be conservative for realistic containment conditions.