Sharif Digital Repository

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... 

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 the present work, the deformation and collapse of a single cavitating bubble near solid boundaries is simulated by solving the preconditioned, homogenous, multiphaseNavier-Stokes equations. Up to now, all studies in the literature performed by the volume of fluid (VOF)approach to capture the bubble surface have been based on the pressure-based category in which the flow variables are calculated through solving the Poisson equation. Here, the density-based category is applied and the solution methodology is based on the artificial compressibility approach. The compressible form of the Navier-Stokes equations is applied inside the bubble and the liquid phase is assumed to be incompressible.... 

In the current study, the numerical simulation of the turbulent cavitating flows is performed by solving the preconditioned, homogenous, multiphase Navier-Stokes equations. For the turbulence modeling, the standard two-equation k-ϵ model is used. The baseline differential equations system is comprised of the mixture volume, mixture momentum and constituent volume fraction equations together with two equations for the turbulence kinetic energy k and the turbulence energy dissipation rate ϵ. For the calculation of the eddy viscosity near the wall boundary, appropriate turbulence damping functions are applied to modify the source terms of the ϵ equation. The system of governing equations is... 

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...