Rafał Przekop

Lattice-Boltzmann approach for description of the structure of deposited particulate matter in fibrous filters

Abstract The rational design of filtration process should be based on reliable predictions of the dependence on the effluent concentration and on the pressure drop variations with time for a given set of the operating conditions, i.e. particle concentration and size, filter packing density, size of filter element, gas velocity, etc. The pattern of filling of the internal space with the porous structure of fibrous filters strongly influences the behavior of the filter at the stage of non-steady-state filtration. The cellular automata probabilistic model extended to the lattice-Boltzmann approach was used for description of the local structures of deposited particles forming clusters on the surface of a single fibre of the filter. The fractal dimension of deposited structure and its local porosity were calculated for the Peclet number ranging from 0.5 to10. The results of calculations show that deposits, for which diffusion is a controlling mechanism of deposition, have higher fractal dimension, are strongly branched and are distributed around the filter fibre. Deposits obtained for the conditions related to the higher Peclet numbers are situated at the front of the fibre and are more regular than those obtained for diffusion-controlled deposition. The pressure drop of the aerosol flow through a loaded fibre increases more rapidly, during loading, for diffusion-controlled deposition than that for the higher contribution of convection during the deposition process.

Deposition and Filtration of Nanoparticles in the Composites of Nano- and Microsized Fibers

Filtration of aerosol particles using composites of nano- and microsized fibrous structures is a promising method of effective separation of nanoparticles from gases. The multiscale physical system describing the flow pattern and particles deposition in it requires other than a continuous approach for the process analysis. The lattice-Boltzmann method was used for the calculation of deposition efficiency on nanosized particles for the system consisting of two nano- and microsized fibers. The proposed method allows to calculate the deposition efficiency of nanoparticles on both fibers for a very wide range of Knudsen numbers in the case of each nanofiber considering molecular, slip, and continuous flow patterns. The nanofiber is a significant attractor for collecting particles as an element of multiscale fibers of the filtration composite. The results of particle deposition efficiency calculated for the microfiber, using proposed method, are similar to those obtained from the classical continuum approach (Filippova and Hanel 1997; Przekop et al. 2003). The proposed model was extended to calculate the performance of bilayer filter structures consisting of a nanofibrous front layer and a microfibrous backing layer of the filter. Filtration efficiency, pressure drop and quality factors for uniform and non-uniform distributions of nanofibers in the front filter layer were calculated for a wide range of Knudsen and Peclet numbers.

Energy-Balanced Oscillatory Model for Description of Particles Deposition and Re-Entrainment on Fiber Collector

The pattern of filling of the internal space in fibrous filters strongly influences the behavior of the filter at the stage of nonsteady-state deep bed filtration. The model of single-fiber loading with deposited particles, including the resuspension effect, is presented. Structures of deposited charged particles from the range of diameters 0.01–10 μm deposited on the electret fiber of diameter 30 μm were calculated. Results of calculations indicate that the distribution of deposits around the fiber depend on particle size. Fractal dimension and local porosity of deposits depend on the predominant mechanism of deposition. The incorporation of the resuspension effect into the deposition models shows significant differences of the geometry of dendrites in comparison with the case of model in which resuspension was neglected.

Non-steady-state aerosol filtration in nanostructured fibrous media

The filtration of aerosol particles using composites of nano- and microsized fibrous structures is a promising method for the effective separation of nanoparticles from gases. A multi-scale physical system describing the flow pattern and particle deposition at a non-steady-state condition requires an advanced method of modelling. The combination of lattice Boltzmann and Brownian dynamics was used for analysis of the particle deposition pattern in a fibrous system. The dendritic structures of deposits for neutral and charged fibres and particles are present. The efficiency of deposition, deposit morphology, porosity and fractal dimension were calculated for a selected operational condition of the process.

Modeling of erythrocytes transport in blood capillaries using spring – Based model combined with lattice-Boltzmann approach

The microstructural model of Red Blood Cells (RBCs) behavior was proposed. The erythrocyte is treated as elastic object, which is denoted by network of virtual particles connected by elastic springs. The modeled RBC is submerged in plasma modeled by lattice Boltzmann fluid, which allow incorporating fluid – structure interactions. The simulations of RBCs behavior during flow between two parallel plates and wall impact were performed.The microstructural model of Red Blood Cells (RBCs) behavior was proposed. The erythrocyte is treated as elastic object, which is denoted by network of virtual particles connected by elastic springs. The modeled RBC is submerged in plasma modeled by lattice Boltzmann fluid, which allow incorporating fluid – structure interactions. The simulations of RBCs behavior during flow between two parallel plates and wall impact were performed.

Effect of work of adhesion on deep bed filtration process

Collection of aerosol particles in the particular steps of the technology of their production, and purification of the air at the workplace and atmospheric environment, requires the efficient method of separation of particulate matter from the carrier gas. There are many papers published in last few years in which the deposition of particles on fibrous collectors is considered, Most of them assume that collisions between particle and collector surface is 100% effective. In this work we study the influence of particles and fiber properties on the deposition efficiency. For the purpose of this work the lattice-Boltzmann model describes fluid dynamics, while the solid particle motion is modeled by the Brownian dynamics. The interactions between particles and surface are modelled using energy balanced oscillatory model. The work of adhesion was estimated using Atomic Force Microscopy.