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Non-expert summaryIce-pigging is a cleaning method in which a dense slurry (to be removed) is pushed along a channel (often a pipe, but more complex geometries can also be cleaned by this method) by an upstream solid-liquid thick ice slurry. The authors use the commercial CFD code FLUENT to evaluate a numerical model of this multiphase (solid-liquid) material undergoing pipe flow. In this coupled Eulerian-Eulerian description the two phases are treated separately as continuous phases coupled by pressure and interphase forces. They validate their model against experimental data from literature and report the predicted ice volume fraction, wall shear stress and melting rate. The results show strong inhomogeneity in the solid content (ice volume fraction).
Non-expert summaryThe removal of biofilms by sloughing is a natural phenomenon in biofilm dynamics. Three hypothetical mechanisms of detachment were incorporated into a 3D model of biofilm development. The model integrated processes of substrate utilization, substrate diffusion, growth, cell advection, and detachment in a cellular automata framework. The three detachment mechanisms analyzed represented various physical and biological influences hypothesized to affect biofilm detachment; fluid shear removing protruding material; removal linked to local nutrient availability; and erosion. The detachment mechanisms demonstrated diverse behaviors with respect to the four analysis criteria. The results show that detachment is a critical determinant of biofilm structure and of the dynamics of biofilm accumulation and loss.
Non-expert summaryThe structure of many biofilms results in a surface layer which does not detach readily and a growing layer that detaches (sloughs) off more readily. The authors present a general method for describing biomass detachment in a multidimensional biofilm modelling framework. Biomass losses from processes acting on the entire surface of the biofilm, such as erosion, are modelled, and discrete detachment events, i.e. sloughing, are implicitly derived from the simulations. This methodology for biomass detachment was integrated with multidimensional (2D and 3D) particle-based multispecies biofilm models by using the level set method. Application of the method is demonstrated by looking at the trends in biofilm structure and activity over time in two case studies: I - a simple model considering uniform biomass; II - a model discriminating biomass composition in heterotrophic active mass, extracellular polymeric substances (EPS) and inert mass.