Sharif Digital Repository

In this study,thecut-cells method is developed for simulating two-dimensional, inviscid, compressible flows with immersed boundaries. A finite volume method based on the second-order accurate central-difference scheme and the Runge-Kutta time stepping scheme is used. The key aspects that require to be considered in thedevelopment of such a solver are implementation of boundary conditions on the immersed boundaries and correct discretizing the governing equations in those cells cut by the boundaries. An appropriate interpolation procedure is applied to preserve the second-order spatial accuracy of the solver. The solution procedure is validated vs. well documented test problems for a wide... 

In this study, bulk viscosity of suspensions is predicted using numerical simulation.The elaborated numerical method consists of the lattice Boltzmann (LB) method for fluid matrix simulation and the immersed boundary (IB) method for solid boundary implementation. In order to successfully implement the IB method in the frame-work of the LB method, two important challenges, which are body force modeling in the LB method and numerical velocity slip on solid boundaries, are discussed. As a first challenge, body force modeling in the LB method is studied by using a uni-fied framework which has been devised in this study. Using this unified framework,firstly, errors of different body force... 

In this work, a new methodology for modeling the whole lung using porous media is presented. Dealing with the details of the proposed method establishes the need for some tools. Proposed method combines data extraction from lung images to identify large airways, porosity and porous region boundaries. Combining some sequential images, change in properties with time could be obtained. To obtain behavior of this porous media with respect to flow, a method based on the classification of bifurcations and gas exchange areas and pore scale modeling of these classes is proposed. All these require a specifically designed numerical tool. Development of this tool is the subject of the next parts of... 

Taghizadeh Manzari, M. (In this work, a modified Smoothed Particle Hydrodynamics (SPH) method, with a new moving solid boundary treatment approach, is utilized to simulate the particulateflow problems. The renormalized first and second derivative schemes which lead tothe consistency of the method, are also used along with a modification to the continuityequation which prevents the spurious pressure oscillations. The proposed methodis validated by solving benchmark problems of solid body motion in channel flows.There is a good agreement between the obtained results and those reported in theliterature. The convergence of solutions for different domain discretizations is alsoassessed. In order... 

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 thesis, an Incompressible SPH (ISPH) method is used to simulate suspensions. A suspension is assumed to be a mixture of solid particles in a Newtonian fluid. First, renormalization tensors are applied to the discretized equations of SPH method. This leads to a higher accuracy in this method. It should be noted that the projection method is used for ISPH. After that, the Immersed Boundary Method (IBM) is used to model and simulate the presence of solid particles in fluid flow. Some modifications were necessary to use IBM with Lagrangian approach. Then, some benchmark problems are solved to validate the presented method. The main objective of the present thesis is simulation of... 

In this study, the dynamics of microparticles in a straight microchannel in the presence of an inhomogeneous oscillating electric field have been simulated by the immersed boundary method in combination with the lattice Boltzmann Navier-Stokes solver and the lattice Boltzmann method for solving the Poisson equation. The effect of the electric field on the location and number of particle equilibrium positions have been examined. In the absence of the electric field, circular particles will migrate to two stable equilibrium positions. The site of these equilibrium positions depends on the particle size and the fluid flow rate and is independent of the particle density. In the case of negative... 

Two-dimensional incompressible flow analysis is one the most important applied issues in engineering and applied science field. Numerical solution of governing equations of flow requires exact computational grid generation.In complex geometries, generation of the grid which is coincident to the body is very difficult and time consuming. Immersed boundary method is an appropriate superseded method of body conformal grid generation in flow field numerical solution. In this method a grid which is not coincidentto bodyis generated and flow field properties are modified on points adjacent to the boundary of the object (Ghost Cell Method) to satisfy boundary conditions.
The purpose of this... 

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...