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    Comparison between triangular and hexagonal modeling of a hexagonal-structured reactor core using box method

    , Article Annals of Nuclear Energy ; Volume 38, Issue 2-3 , February–March , 2011 , Pages 371-378 ; 03064549 (ISSN) Malmir, H ; Moghaddam, N. M ; Zahedinejad, E ; Sharif University of Technology
    2011
    Abstract
    A hexagonal-structured reactor core (e.g. VVER-type) is mostly modeled by structured triangular and hexagonal mesh zones. Although both the triangular and hexagonal models give good approximations over the neutronic calculation of the core, there are some differences between them that seem necessary to be clarified. For this purpose, the neutronic calculations of a hexagonal-structured reactor core have to be performed using the structured triangular and hexagonal meshes based on box method of discretisation and then the results of two models should be benchmarked in different cases. In this paper, the box method of discretisation is derived for triangular and hexagonal meshes. Then, two 2-D... 

    Numerical simulation of three-dimensional interfacial flows

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 17, Issue 4 , 2007 , Pages 384-404 ; 09615539 (ISSN) Jahanbakhsh, E ; Panahi, R ; Seif, M. S ; Sharif University of Technology
    2007
    Abstract
    Purpose - This study aims to present compatible computational fluid dynamics procedure for calculation of incompressible three-dimensional time-dependent flow with complicated free surface deformation. A computer software is developed and validated using a variety of academic test cases. Design/methodology/approach - Two fluids are modeled as a single continuum with a fluid property jump at the interface by solving a scalar transport equation for volume fraction. In conjunction, the conservation equations for mass and momentum are solved using fractional step method. Here, a finite volume discretisation and colocated arrangement are used. Findings - The developed code results in accurate... 

    Development of a 2-D 2-group neutron noise simulator for hexagonal geometries

    , Article Annals of Nuclear Energy ; Volume 37, Issue 8 , 2010 , Pages 1089-1100 ; 03064549 (ISSN) Malmir, H ; Vosoughi, N ; Zahedinejad, E ; Sharif University of Technology
    Abstract
    In this paper, the development of a neutron noise simulator for hexagonal-structured reactor cores using both the forward and the adjoint methods is reported. The spatial discretisation of both 2-D 2-group static and dynamic equations is based on a developed box-scheme finite difference method for hexagonal mesh boxes. Using the power iteration method for the static calculations, the 2-group neutron flux and its adjoint with the corresponding eigenvalues are obtained by the developed static simulator. The results are then benchmarked against the well-known CITATION computer code. The dynamic calculations are performed in the frequency domain which leads to discarding of the time... 

    Development of a Finite Volume Numerical Method by Overlapping Grids

    , M.Sc. Thesis Sharif University of Technology Masoudi, Ali (Author) ; Seif, Mohammad Saeed (Supervisor) ; Nouri Borujerdi, Ali (Supervisor)
    Abstract
    A finite volume algorithm to assess hydrodynamic aspects of a rigid and up to three degrees of freedom marine structure in the context of transient two-phase flow o viscous incompressible fluids is presented. Different components of the algorithm are selected just after a complete review of all probable choices. Using a collocated arrangement to save data, a fractional step method is applied to satisfy Navier-Stokes and continuity equations, as an appropriate choice in transient flows. Also, a volume fraction transport equation is solved to capture large and complex deformations of the interface between two phases. So, an effective fluid is introduced by combining two immiscible phases in... 

    Localization of a noise source in VVER-1000 reactor core using neutron noise analysis methods

    , Article International Conference on Nuclear Engineering, Proceedings, ICONE, 17 May 2010 through 21 May 2010 ; Volume 2 , May , 2010 ; 9780791849309 (ISBN) Malmir, H ; Vosoughi, N ; Zahedinejad, E ; Nuclear Engineering Division ; Sharif University of Technology
    2010
    Abstract
    In this paper, localization of a noise source from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The boxscheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. The dynamic state is assumed in the frequency domain which leads to discarding of the time disrcetisation. The developed 2-D 2- group neutron noise simulator calculates... 

    Towards simulation of 3D nonlinear high-speed vessels motion

    , Article Ocean Engineering ; Volume 36, Issue 3-4 , 2009 , Pages 256-265 ; 00298018 (ISSN) Panahi, R ; Jahanbakhsh, E ; Seif, M. S ; Sharif University of Technology
    2009
    Abstract
    A numerical simulation algorithm based on the finite volume discretisation is presented for analyzing ship motions. The algorithm employs a fractional step method to deal with the coupling between the pressure and velocity fields. The free surface capturing is fulfilled by using a volume of fluid method in which the interface between the liquid (water) and gas (air) phases are computed by solving a scalar transport equation for the volume fraction of the liquid phase. The computed velocity field is employed to evaluate the acting forces and moments on the vessel. Using the strategy of boundary-fitted body-attached mesh and calculating all six degrees-of-freedom of motion in each time step,...