Sharif Digital Repository

In this research, the spectral difference lattice Boltzmann method (SDLBM) is developed and applied for an accurate simulation of two-dimensional (2D) inviscid and viscous compressible flows on the structured and unstructured meshes. The compressible form of the discrete Boltzmann-BGK equation is used in which multiple particle speeds have to be employed to correctly model the compressibility in a thermal fluid. Here, the 2D compressible Lattice Boltzmann (LB) model proposed by Watari is used. The spectral difference (SD) method is implemented for the solution of the LB equation in which the particle distribution functions are stored at the solution points while the fluxes are calculated... 

In the present study, the computation of the viscous compressible flow over two-dimensional geometries is performed by using the immersed boundary method and applying a second-order finite volume scheme. For the solution of the governing equations, a uniform Cartesian grid that is not coincident with the body surface is used and the boundary conditions on the wall are satisfied by the ghost-cell immersed boundary method. The spatial discretization of the fluid equations is carried out using the second-order central difference finite volume scheme and the time integration is performed by applying the fourth-order Runge-Kutta method. To stabilize the solution algorithm and reduce unwanted... 

In this study, the viscous compressible flow is simulated over two-dimensional geometries by using the immersed boundary method and applying a high-order accurate numerical scheme. A fourth-order compact finite-difference scheme is used to accurately discretize the spatial derivative terms of the governing equations and the time integration is performed by the fourth-order Runge–Kutta scheme. To regularize the numerical solution and eliminate spurious modes due to unresolved scales, nonlinearities and inaccuracies in implementing boundary conditions, high-order low-pass compact filters are applied. A uniform Cartesian grid that is not coincident with the body surface is used and the boundary... 

In this study, an accurate numerical solution of the two-dimensional incompressible viscous flows is performed by using the spectral difference method on structured grids. The system of equations to be solved here is the preconditioned incompressible Navier-Stokes equations in the primitive variable formulation with the artificial compressibility approach. In the spectral difference method, two sets of the structured points, namely, “solution points” and “flux points” are defined in each cell for supporting the reconstruction of desirable order of accuracy. Here, the formulation of the spectral difference method is derived and the representative form of the solution and flux points for... 

In this study, 2-D compressible viscous and inviscid flows are simulated by using a finite volume Lattice Boltzmann method. Two different models, namely, the Qu model and Watari model are employed for compressible flows simulations. The first model includes 13 discrete velocity vectors and 2 energy levels in which the Maxwellian function is replaced with a simple function for describing the distribution function that is suitable for inviscid flow simulations. The second model is a thermal multi-velocity model with isotropic tensors up to seventh rank that is suitable for compressible viscous and inviscid flow simulations with arbitrary specific heats ratio. In both the models, lattice... 

The aim of this research is to model the separation and transport of multi-component gas mixture through a nanoporous membrane by using pore network models (PNM).
The first part of this project represents the membrane simulating by means of the PNM. A three-dimensional network is used to represent the membrane’s pore space and it consists of two parts; pore and throat. The pores are the main parts of the network and their diameter is characterized according to the pore size distribution of the membrane. Every throat connects two pores and the number of throats which is connected to each pore is named "coordination number". Using a variety size of pores and throats leads to production of...