Sharif Digital Repository

In the present study, a high-order accurate numerical solution of steady incompressible slip flow and heat transfer in 2D microchannels is presented. The numerical method used is an alternating direction implicit operator scheme which is efficiently implemented to solve the incompressible Navier-Stokes equations in the primitive variables formulation using the artificial compressibility method. To stabilize the numerical solution, numerical filters are used. The present methodology considers the solution of the Navier-Stokes equations with¬ employing different slip boundary condition¬¬ (Maxwell,¬ ¬¬Hyperbolic tangent function of Knudsen number¬ and Beskok slip models)¬ ¬¬on the wall to model... 

Understanding the flow of liquids and particularly water in nanochannels is important for scientific and technological applications, such as for filtration and drug delivery. In this study, we perform molecular dynamics simulations to investigate the transfer of single-file water molecules across straight or nonstraight single-walled carbon nanotubes (SWCNTs). In contrast with the macroscopic scenario, the nonstraight nanostructure can increase the water permeation. Remarkably, compared with the straight SWCNT, the nonstraight SWCNT with the minimal bending angle of 30° in the simulations can enhance the water transport up to 3.9 times. Also increasing length and diameter of carbon nanotubes... 

Due to important applications and benefits of mass transfer in engineering and especially in nano-scales engineering, nano-science researchers have focused on this field. Considerably, in classical fluid dynamics applications, the fluid can be transported using differential pressure gradient. But the classical methods require moving components, which are usually expensive and not applicable in nano-sizes. To avoid these problems in nano-size transportation, we can use electro-osmotic process to perform mass transfer in low transfer rates. In electro-osmotic process, we can move electrolyte solvent with the aid of an external electrical field. Due to importance of this process in... 

In the recent two decades Lattice Boltzmann method has been introduced as a class of computational fluid dynamic methods for fluid simulation. In this method instead of solving Navier-Stocks equation, Boltzmann equation is solved to simulate the flow of a fluid. This method originally was developed based on uniform grids which makes lattice Boltzmann a time consuming technique. This feature already exists in the case of simulation of fluid flow in porous media. To eliminate this limitation some research has been done on methods to formulate lattice Boltzmann on unstructured grids. On the basis of this research a method on non-uniform grids has been selected. Here using object oriented... 

In this work solid circulation pattern in 2-D gas-solid fluidized beds has been investigated carefully. In this regard TFM approach was used. In addition KTGF was applied along with Gidaspow drag model. A commercial CFD software (ANSYS FLUENT 15.0) was used to simulate the hydrodynamics of the bed. Effects of a number of operating and design parameters on the solid circulation pattern were examined in detail. These parameters were gas velocity, restitution coefficient, pressure, solid density, temperature and vertical plates. The simulation results were validated against experimental data reported in the literature. Furthermore, the solid vertical velocity was investigated carefully