Search for: free-surfaces
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    Modeling the effect of mould wall roughness on the melt flow simulation in casting process

    , Article Applied Mathematical Modelling ; Volume 28, Issue 11 , 2004 , Pages 933-956 ; 0307904X (ISSN) Mirbagheri, S. M. H ; Dadashzadeh, M ; Serajzadeh, S ; Taheri, A. K ; Davami, P ; Sharif University of Technology
    In this investigation a computational model has been developed which includes heat and mass transfer as well as effects of backpressure, and mould wall friction for the simulation of incompressible flow with free surfaces in mould cavity filling. The simulation of flow with free surfaces is based on the SOLA-VOF numerical algorithm, utilizing the finite difference method. The solid and free boundary conditions have been modified and a new algorithm has been developed to calculate the effect of cavity pressure and wall-slip ratio, during mould filling. In this algorithm, the effect of wall-slip ratio on filling pattern has been modeled with an experimental function. In order to verify the... 

    Simulation of melt flow in coated mould cavity in the casting process

    , Article Journal of Materials Processing Technology ; Volume 142, Issue 2 , 2003 , Pages 493-507 ; 09240136 (ISSN) Mirbagheri, S. M. H ; Esmaeileian, H ; Serajzadeh, S ; Varahram, N ; Davami, P ; Sharif University of Technology
    In this investigation, simulation of the 3D flow of incompressible molten metal in a mould cavity has been carried out. A code has been developed to include heat transfer and permeability of coating utilizing the finite difference method (FDM). To achieve this, solid and free boundary conditions have been modified and a new algorithm has been proposed to calculate the effect of coating permeability during mould filling. In this algorithm, the effect of coating permeability on the filling pattern has been modelled and compared with an experiment. The modelling of molten metal flow and the location of free surfaces has been simulated based on the SOLution Algorithm-Volume Of Fraction... 

    Modeling Multiphase Fluid Flow Using SPH

    , M.Sc. Thesis Sharif University of Technology Safdari Shadloo, Mostafa (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method for simulation of fluid flow. Movable particles are used to interpolate fluid properties instead of fixed Eulerian grids in this method. By essence, the aforesaid particles are movable points which carry the fluid properties such as temperature, enthalpy, density, etc. these variables can also be the stress, strain or the rheological properties of the fluid. Thus, this method needs no grids and the fluid properties are calculated using an interpolation mechanism which classifies this method as meshless. A computational code is designed using SPH for the simulation of multiphase flows. Usage of the Lagrangian formulation has made it... 

    Transient free-surface seepage in three-dimensional general anisotropic media by BEM

    , Article Engineering Analysis with Boundary Elements ; Vol. 46, issue , 2014 , p. 51-66 Rafiezadeh, K ; Ataie-Ashtiani, B ; Sharif University of Technology
    Kinematic boundary condition is usually used when dealing with transient free-surface flow problems in isotropic media. When dealing with anisotropic problems, a transformation can transform the anisotropic media to an equivalent isotropic media for seepage analysis, but the kinematic boundary condition cannot be used directly in the transformed media. A generalization of the kinematic boundary condition along any arbitrary direction is derived for use in the transformed domain for general three-dimensional anisotropic problems. A boundary element method for solving transient free-surface seepage problems is developed and the treatment of the proposed kinematic boundary condition in the... 

    Investigation of free surface flow generated by a planing flat plate using smoothed particle hydrodynamics method and FLOW3D simulations

    , Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 227, Issue 2 , 2013 , Pages 125-135 ; 14750902 (ISSN) Ghadimi, P ; Dashtimanesh, A ; Farsi, M ; Najafi, S ; Sharif University of Technology
    In this article, smoothed particle hydrodynamics method is applied in order to study the free surface flow generated by two-dimensional planing flat plate. For this purpose, a two-dimensional smoothed particle hydrodynamics code is developed and validated by the well-known dam breaking problem. Four trim angles and three different velocities are considered to perform a parametric study to examine their physical effects. The obtained results from smoothed particle hydrodynamics are compared against the corresponding Reynolds-averaged Navier Stokes solutions. It is observed that at lower velocities, there exists a good agreement between the smoothed particle hydrodynamics and Reynolds-averaged... 

    Interaction of two spark-generated bubbles near a confined free surface

    , Article Theoretical and Computational Fluid Dynamics ; Volume 30, Issue 3 , 2016 , Pages 185-209 ; 09354964 (ISSN) Saleki Haselghoubi, N ; Shervani Tabar, M. T ; Taeibi Rahni, M ; Dadvand, A ; Sharif University of Technology
    Springer New York LLC 
    In this paper, the oscillation of two spark-generated bubbles placed on a vertical column in close proximity to a confined free surface is considered. The confined free surface is accorded by the top opening of different configurations. These configurations include (i) a centrally perforated horizontal flat plate (θ = 90∘), (ii) vertically placed cylinder (θ = 0∘) and (iii) nozzle (θ > 0∘). The main objective of the present work is to study the effects of key parameters such as the nozzle geometry, the locations of the energy input (i.e., initial position of the bubbles with respect to each other and relative to the free surface) on the dynamics of the two bubbles and the free surface. It... 

    Comparing sloshing phenomena in a rectangular container with and without a porous medium using explicit nonlinear 2-D BEM-FDM

    , Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 93-101 ; 10263098 (ISSN) Abbaspour, M ; Ghodsi Hassanabad, M ; Sharif University of Technology
    The sloshing phenomena in a partially filled tank can affect its stability. Modifications of tank instability due to the movement of the tank carrier, are key design points for the stability of a carrier. Even though the sloshing phenomenon has already been investigated using the BEM-FDM technique, the research in this paper covers this phenomenon in a porous media, which is new in 2-D coordinates. For this purpose, a Laplace equation has been used for potential flow, and kinematic and dynamic boundary conditions have been applied to the free surface. Also, a formulation has been developed for a free surface in porous media. BEM has been used for solving the governing equation and FDM... 

    Flow field analysis around the ship fin stabilizer including free surface

    , Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 31 May 2009 through 5 June 2009, Honolulu, HI ; Volume 4, Issue PART A , 2009 , Pages 603-608 ; 9780791843444 (ISBN) Hoseini Dadmarzi, F ; Ghassemi, H ; Ghadimi, P ; Ommani, B ; Sharif University of Technology
    Fin stabilizers are very important device for controlling the ship roll motion against the external moments due to wave. This paper presents numerical results for flow field simulation and the hydrodynamic performance of fin stabilizer attached to a ship hull with free surface effects. Combination of CFD and RANS method has been used for this study. The fin is nonrectangular NACA0015 profile section with a finite aspect ratio. The numerical results include pressure distributions and flow field around the fin which are used to calculate lift coefficients and free surface elevation as the main interest. Some results are compared with available experimental and numerical data in literature and... 

    3-D simulation of mold filling with κ-ε turbulence modeling

    , Article Proceedings of the 14th IASTED International Conference on Applied Simulation and Modelling, Benalmadena, 15 June 2005 through 17 June 2005 ; 2005 , Pages 437-442 ; 0889864691 (ISBN) Shahinfar, S ; Babaei, R ; Asgary, K ; Davami, P ; Hamza M. H ; Sharif University of Technology
    In this work the SOLA-VOF method was used to solve the Navier-Stokes equations and track the free surface. For modeling the turbulence phenomena in the mold filling κ-ε model was used. In this method solving domain was discreted to three regions includes: laminar sub layer, boundary layer and internal region. The simulation results were shown to be in a good agreement with the experimental results  

    3D computer simulation of melt flow and heat transfer in the lost foam casting process

    , Article International Journal for Numerical Methods in Engineering ; Volume 58, Issue 5 , 2003 , Pages 723-748 ; 00295981 (ISSN) Mirbagheri, S. M. H ; Varahram, N ; Davami, P ; Sharif University of Technology
    A new mathematical model has been developed to simulate mould filling in the lost foam casting process, using the finite difference method. The simulation of molten flow and track of free surfaces is based on the SOLA-VOF numerical technique. An algorithm was developed to calculate the gas pressure of the evaporated foam during the mould filling. The effect of backpressure on the filling behaviour was modelled with an experimental function by adding three-dimensions 3DVOF functions. In order to verify the computational results, a thin grey iron plate was poured into a transparent mould. Cavity filling, foam depolymerization and gap formation were recorded with a 16mm high-speed camera. A... 

    Simulation of mould filling in lost foam casting process

    , Article International Journal of Cast Metals Research ; Volume 16, Issue 6 , 2003 , Pages 554-565 ; 13640461 (ISSN) Mirbagheri, S. M. H ; Ashuri, H ; Varahram, N ; Davami, P ; Sharif University of Technology
    Maney Publishing  2003
    In this investigation, an algorithm was developed to calculate the gas pressure at the melt/foam interface (gap) owing to degraded foam during mould filling in the lost foam casting process (LFC). The effect of back-pressure on mould filling was modelled using a new experimental function by the addition of a three-dimensional volume of fluid (3D-VOF) function. The molten flow and free surface were simulated using the solution algorithm-VOF (SOLA-VOF) numerical technique. To simulate the three-dimensional incompressible flow in the LFC, the pressure boundary conditions, heat transfer and foam gas pressure effect were modified. Finally, in order to verify the computational results of... 

    Numerical simulation of free-surface waves and wave induced separation

    , Article Scientia Iranica ; Volume 15, Issue 3 , 2008 , Pages 323-331 ; 10263098 (ISSN) Sadathosseini, S. H ; Mousaviraad, S. M ; Firoozabadi, B ; Ahmadi, G ; Sharif University of Technology
    Sharif University of Technology  2008
    The present study is concerned with the numerical simulation of free-surface waves and wave induced separation in the presence of an intrusion. The results of several simulations are reported. The first study was performed for a NACA0024 surface piercing hydrofoil over a range of several Froude numbers (0.19, 0.37, 0.55), along with wave breaking at Fr = 1.0 The NACA0024 foil was of particular interest, as it almost has no separation at large depths; thus the effect of the free-surface wave and the wave induced separation could be studied. Free- surface waves and wave induced separation results were evaluated and compared with both the available experimental data and the previous numerical... 

    An incompressible SPH method for simulation of unsteady viscoelastic free-surface flows

    , Article International Journal of Non-Linear Mechanics ; Volume 42, Issue 10 , 2007 , Pages 1210-1223 ; 00207462 (ISSN) Rafiee, A ; Manzari, M. T ; Hosseini, M ; Sharif University of Technology
    In this paper, an incompressible smoothed particle hydrodynamics (SPH) method is presented to solve unsteady free-surface flows. Both Newtonian and viscoelastic fluids are considered. In the case of viscoelastic fluids, both the Maxwell and Oldroyd-B models are investigated. The proposed SPH method uses a Poisson pressure equation to satisfy the incompressibility constraints. The solution algorithm is an explicit predictor-corrector scheme and employs an adaptive smoothing length based on density variations. To alleviate the numerical difficulties encountered when fluid is highly stretched, an artificial stress term is incorporated into the momentum equation which reduces the risk of... 

    3-D FEM analysis of plastic behavior inside MMC composites considering damage theory

    , Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 3 , 2006 , Pages 1759-1768 Abedian, A ; Farahpour, H ; Sharif University of Technology
    Curran Associates Inc  2006
    The delamination phenomenon has been studied in macroscopic scale by different approaches. Here, using micro-mechanical models, it is tried to find the possible relationship between the problem and the stress fields around a fiber. Using the ideas and the results on the free surface cracking of unidirectional composite, the FEM model is developed. The model verification is done by comparing the results by the results obtained in presence of damaged incorporated by the damage theory. Here, on the free surfaces fiber/matrix debonding is applied as a composite damage and the results show a good agreement with the available results  

    Numerical modeling of flow over a dam spillway

    , Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 1 SYMPOSIA , 2006 , Pages 343-349 ; 0791847500 (ISBN); 9780791847503 (ISBN) Saeedpanah, I ; Shayanfar, M ; Jabbari, E ; Mohammadi, M. H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Free surface flows are frequently encountered in hydraulic engineering problems including water jets, weirs and around gates. An iterative solution to the incompressible two-dimensional vertical steady Navier-Stokes equations, comprising momentum and continuity equations, is used to solve for the priori unknown free surface, the velocity and the pressure fields. The entire water body is covered by a unstructured finite element grid which is locally refined. The dynamic boundary condition is imposed for the free surface where the pressure vanishes. This procedure is done continuously until the normal velocities components vanish. To overcome numerical errors and oscillations encountering in... 

    A stable moving-particle semi-implicit method for free surface flows

    , Article Fluid Dynamics Research ; Volume 38, Issue 4 , 2006 , Pages 241-256 ; 01695983 (ISSN) Ataie Ashtiani, B ; Farhadi, L ; Sharif University of Technology
    In this paper, a mesh-less numerical approach is utilized to solve Euler's equation that is the governing equation of the irrotational flow of ideal fluids. A fractional step method of discritization is applied which consists to split each time step in two steps. This numerical method is based on moving-particle semi-implicit method (MPS) for simulating incompressible inviscid flows with free surfaces. The motion of each particle is calculated through interactions with neighboring particles covered with the kernel function. There are limitations for getting a stable solution by MPS method. In this paper, various kernel functions are considered and applied to improve the stability of MPS... 

    Numerical study on the oscillation of a transient bubble near a confined free surface for droplet generation

    , Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , p. 449-472 Saleki-Haselghoubi, N ; Shervani-Tabar, M.T ; Taeibi-Rahni, M ; Dadvand, A ; Sharif University of Technology
    In the present work, the oscillation of a spark-created bubble near a confined water-air interface and the ensuing droplet generation and ejection are studied numerically using the boundary element method. The interface is accorded by the top opening of either one of the following symmetrical configurations, which are distinguished by the value of angle between their vertical symmetry axis and lateral wall (i.e., θ): (i) a centrally perforated horizontal flat plate (θ = 90°) and (ii) vertically placed cylinder (θ = 0°), nozzle (θ > 0°) and diffuser (θ < 0°). Furthermore, the influences of the effective parameters such as the strength parameter (i.e., the intensity of local energy input), the... 

    A dislocation-based model considering free surface theory through HPT process: Nano-structured Ni

    , Article Scientia Iranica ; Volume 17, Issue 1 F , 2010 , Pages 52-59 ; 10263098 (ISSN) Hosseini, E ; Kazeminezhad, M ; Sharif University of Technology
    In this study, a dislocation-based model is presented for investigating the evolution of micro structure and mechanical properties of thin films during a wide range of straining. The model is applied to the High Pressure Torsion (HPT) process of thin nickel disks that provides valuable information on the evolution of material parameters during deformation. The model considers a free surface theory for thin films and can explain the size effect phenomenon in agreement with previous reported trends in literature  

    Reduced order modeling of liquid sloshing in 3D tanks using boundary element method

    , Article Engineering Analysis with Boundary Elements ; Volume 33, Issue 6 , 2009 , Pages 750-761 ; 09557997 (ISSN) Dehghani Firouzabadi, R ; Haddadpour, H ; Ghasemi, M ; Sharif University of Technology
    This paper presents the application of reduced order modeling technique for investigation of liquid sloshing in three-dimensional tanks. The governing equations of sloshing are written using a boundary element formulation for incompressible potential flow. Then, the governing equations are reduced to a more efficient form that is represented only in terms of the velocity potential on the liquid free surface. This particular form is employed for eigen-analysis of fluid motion and the sloshing frequencies and mode shapes are determined. Then, the sloshing frequencies and the corresponding right- and left-eigenvectors are used along the modal analysis technique to find a reduced order model... 

    Modified incompressible SPH method for simulating free surface problems

    , Article Fluid Dynamics Research ; Volume 40, Issue 9 , 2008 , Pages 637-661 ; 01695983 (ISSN) Ataie Ashtiani, B ; Shobeyri, G ; Farhadi, L ; Sharif University of Technology
    An incompressible smoothed particle hydrodynamics (I-SPH) formulation is presented to simulate free surface incompressible fluid problems. The governing equations are mass and momentum conservation that are solved in a Lagrangian form using a two-step fractional method. In the first step, velocity field is computed without enforcing incompressibility. In the second step, a Poisson equation of pressure is used to satisfy incompressibility condition. The source term in the Poisson equation for the pressure is approximated, based on the SPH continuity equation, by an interpolation summation involving the relative velocities between a reference particle and its neighboring particles. A new form...