جستجوی مقالات مرتبط با کلیدواژه "particle deposition" در نشریات گروه "مکانیک"

The numerical modeling of particle deposition in industrial problems is essential due to domination on intricate details of this phenomenon. In the present study, suggestions for properly using the governing equations and conditions have been presented. Modeling particle deposition phenomenon is generally divided into the Lagrangian and Eulerian approaches. Eulerian approaches are used to model particles deposition when the volumetric ratio is higher than 10−3 and The Lagrangian approaches are used for the volumetric ratio of particles less than 10−3 . The Drift Flux method is more common among the Eulerian approaches than others. In Lagrangian approaches, if the particles are small (in Nano size), and the volumetric ratio of particles is less than 10−6 due to the greater Van der Waals force between the particles and deposition place, the condition of the sticky wall is invoked. Furthermore, with increasing the size of the particles, the possibility of rebounding after their collision should be investigated. Moreover, if the flow rate is high, the possibility of particles detachment from the deposited layer should be considered. Also, the temperature affects particles deposition. Increasing temperature changes the phase of the particles, and as a result, they settle when they hit the surface.

In this paper the Multi Relaxation Time Lattice Boltzmann Method in conjunction with the Large Eddy Simulation model was used to study the particle deposition in a room  with various diameters (10nm-10µm)and the effect of buoyancy, drag and Brownian forces to particle deposition on the different walls of the room has been investigated.  The sub-grid scale turbulence effects were simulated through a shear-improved Smagorinsky model. To simulate the particle deposition in the room, the particle injection process was initiated with 144 particles injected uniformly at the inlet with the same velocity as the airflow at every 0.05s; particle injection was stopped after 30s. Therefore, a total of 86400 particles were injected into the room. The present simulation results for the airflow showed good agreement with the experimental data and the earlier numerical results. The simulated results for particle dispersion and deposition showed that the numbers of deposited particles on the walls increases by augmentation of the time. When the particle injection started the concentration in the inlet jet region is more than other zones and that increases in the region far from the inlet by time. Present results will be interesting for designing air condition systems in the office and hospitals rooms.

Phenomenon of dispersion and deposition of nano- and micro-particles in turbulent flows been focused in the past decades. In this paper, particle dispersion and deposition in gas-particle two-phase turbulent flow inside a two-dimensional channel with rectangular artificial roughness is studied using an Eulerian–Lagrangian method. The RSM turbulence model with enhanced wall treatment was used to simulate the anisotropic turbulent gas phase flow. The gas phase flow predictions were validated by comparing the results with available experimental data for a fully developed asymmetric turbulent channel flow. In discrete phase, Lagrangian approach was applied for particle tracking. The Lagrangian equation of particle motion includes drag, gravity, Saffman lift, and Brownian forces. The particle phase simulation results were validated by comparing the present work with available equations and valid data for a gas particles turbulent flow inside a two-dimensional smooth channel. The gas phase simulation results show that by increasing the artificial roughness height, a recirculation region which is created in the space between two ribs, becomes larger. The particle phase results show that the rate of deposition in the channel with artificial roughness is a function of gravity force and flow pattern in the space between two ribs. The rate of deposition for small particle is affected significantly by gas flow pattern in the space between two ribs. However for large particles the gravity force is more dominant.