DEM filtration modelling for granular materials: Comparative analysis of dry and wet approaches

A detailed study comparing two - dry and wet - numerical approaches to model filtration processes at stake in actual granular filters is presented using the discrete element method (DEM). In the first approach, the migration of fines is provided by gravitational forces, while in the second, hydrodynamic forces induce their movement. Numerical filtration tests were performed on granular filters involving materials with different gradings and porosities. The study demonstrated that the wet filtration approach generates higher tortuosity due to the possibility for fines to deviate from direct paths towards more open sideways. It leads to a lower coefficient of retention for the filter than if it were characterised using a dry filtration approach. However, the intensity of this feature greatly depends on the grading and the porosity of the granular filter. Finally, an enhanced dry filtration model designated as the equivalent cyclic wet filtration model is presented, which better mimics the results obtained through the preferable wet filtration model compared to the original dry filtration model. This new model constitutes a valuable alternative tool for studies of filtration properties in granular materials.

Automated summary

This study compares two numerical approaches, dry and wet, for modeling filtration processes in granular filters using the discrete element method. The wet filtration approach generates higher tortuosity and lower retention coefficient compared to the dry filtration approach, depending on the grading and porosity of the filter. An enhanced dry filtration model is also proposed, which mimics the results of the wet filtration model more accurately.