جستجوی مقالات مرتبط با کلیدواژه « lattice Boltzmann method » در نشریات گروه « فنی و مهندسی »

In this research, by using the combined lattice Boltzmann and smooth profile method, for power law non-Newtonian fluidized bed, the effect of changing the geometric and fluid on the expansion behavior of the bed has been studied. Investigations have been carried out for 7 different geometries and 4 Newtonian and non-Newtonian fluids with a power law index of 0.8 to 1. The results of the bed with Newtonian fluid show more porosity than the bed with non-Newtonian fluid. Also, increasing the index of the power law caused an increase in the porosity of the bed, and the porosity of the non-Newtonian bed decreased with an increase in the density of solid particles and the initial height of the bed. Investigating the porosity ratio in the non-Newtonian bed showed that with the increase in the diameter of the solid particles, this ratio decreases and increases with the increase in the diameter of the fluid bed. In addition, comparing the results of the bed with carboxymethyl cellulose 0.1% solution as fluid showed that the effect of reducing the particle diameter in the bed, to increase the porosity ratio is 2 times more than the effect of increasing the diameter of the bed. Finally, the output of the model showed that the porosity ratio for the bed containing solid particles with different diameters is lower than the bed containing particles with equal diameters.

In this article, the simulation methods of multiphase flow in the presence of surfactants are classified into 3 categories based on Navier-Stokes, distribution function, and based on intermolecular forces, and each one is described separately. Navier-Stokes-based methods fall into two categories: interface tracking methods and interface capture methods. Methods based on intermolecular forces act as particle-based methods with a Lagrangian perspective in dealing with the flow field. The widely used models in the methods based on the distribution function are also introduced at the end. A wide range of numerical methods has put many choices in front of researchers. Knowing and understanding the capabilities and details of these methods will help to select the most appropriate numerical method and obtain reliable and cost-effective results according to the hardware facilities.

In the present study, the entropy generated due to the conjugate heat transfer of the hybrid nanofluid inside the K-shaped chamber under magnetic field and uniform heat absorption/generation is investigated. The simulation was performed by writing computer code in Fortran language using the lattice Boltzmann method. Variations in Rayleigh number, volumetric fraction of nanoparticles, Hartmann number, heat absorption/generation coefficient, thermal conductivity ratio, chamber aspect ratio and type of magnetic field applied have been evaluated as the main variables of this study. The findings showed that the flow strength, heat transfer rate and entropy produced could be reduced by applying a magnetic field. A lower reduction of the average Nusselt number is achieved by non-uniform application of a magnetic field. Increasing the heat absorption/generation coefficient due to increasing the set temperature leads to decreasing the mean Nusselt number, which this influence increases with increasing the Hartmann number. Addition of nanoparticles to the base fluid in which the conduction of the phenomenon is predominant, increases the rate of heat transfer. Heat transfer is a function of the ratio of thermal conductivity and Rayleigh number that increasing these two parameters increases the convection effects, and in this case, the effect of increasing the Hartmann number is more pronounced. Increasing the chamber aspect ratio leads to a decline in the mean Nusselt number and entropy production, but the effect of adding nanoparticles is greater in this case. Entropy production decreases with increasing Hartmann number and increases with Rayleigh number and heat absorption/generation coefficient.

Sand production, which is a critical phenomenon in the oil and gas well walls, is numerically investigated in this research. The main goal is to study the particulate mechanism of sand ‎‎production in unbonded assemblies and examine the effects of stress level and pressure drawdown on the ‎model. Discrete Element Method (DEM) in combination with the Lattice-Boltzmann Method (LBM) is selected to simulate the fluid flow ‎through porous media. The Immersed Moving ‎Boundary method is used to couple the DEM and LBM methods. After developing a computer ‎program, a 2D model of sand production is simulated under radial flow. The simulation results show that as the confining stress ‎increases, the number of produced particles and sand production rate increases. After the initiation of sand production, the sanding rate decreases in all models ‎due to the formation of sand arches around the central hole. These sand arches are weak and ‎usually unstable, and after the collapse of every arch, the new arch is formed and replaces the ‎previous one with a larger diameter. The results also show that the pressure drawdown has a negligible effect on sand production at low stress levels. However, at high stress levels, the increase of pressure drawdown significantly increases the number of produced particles (a 50% increase in pressure led to more than twice produced particles). It is also found that the 2D coupled DEM-LBM is a ‎promising tool to predict the mechanism that governs sand production and its main influencing ‎factors‎.