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    A numerical study on fluid flow and acoustic characteristics of a supersonic impinging jet using vorticity confinement

    , Article Acta Acustica united with Acustica ; Volume 105, Issue 6 , 2019 , Pages 1127-1136 ; 16101928 (ISSN) Sadri, M ; Hejranfar, K ; Ebrahimi, M ; Sharif University of Technology
    S. Hirzel Verlag GmbH  2019
    Abstract
    The objective of this work is to numerically study the fluid flow and acoustic field of a supersonic impinging jet by applying the vorticity confinement (VC) method. For this aim, the three-dimensional compressible Navier-Stokes equations with the incorporation of the VC method are considered and the resulting system of equations is solved by using the sixth-order compact finite-difference scheme. To eliminate the numerical instability, a low-pass high-order filter is used. The nonreflective boundary conditions are applied for all the free boundaries and the radiated sound field is obtained by the Kirchhoff surface integration. Comparisons of the present results with the experimental data... 

    Tuning the dispersion of reactive solute by steady and oscillatory electroosmotic-Poiseuille flows in polyelectrolyte-grafted micro/nanotubes

    , Article Journal of Fluid Mechanics ; 2019 , Pages 73-112 ; 00221120 (ISSN) Reshadi, M ; Saidi, M. H ; Sharif University of Technology
    Cambridge University Press  2019
    Abstract
    This paper extends the analysis of solute dispersion in electrohydrodynamic flows to the case of band broadening in polyelectrolyte-grafted (soft) capillaries by accounting for the effects of ion partitioning, irreversible catalytic reaction and pulsatile flow actuation. In the Debye-Hückel limit, we present the benchmark solutions of electric potential and velocity distribution pertinent to steady and oscillatory mixed electroosmotic-pressure-driven flows in soft capillaries. Afterwards, the mathematical models of band broadening based on the Taylor-Aris theory and generalized dispersion method are presented to investigate the late-time asymptotic state and all-time evolution of... 

    A numerical study on fluid flow and acoustic characteristics of a supersonic impinging jet using vorticity confinement

    , Article Acta Acustica united with Acustica ; Volume 105, Issue 6 , 2019 , Pages 1127-1136 ; 16101928 (ISSN) Sadri, M ; Hejranfar, K ; Ebrahimi, M ; Sharif University of Technology
    S. Hirzel Verlag GmbH  2019
    Abstract
    The objective of this work is to numerically study the fluid flow and acoustic field of a supersonic impinging jet by applying the vorticity confinement (VC) method. For this aim, the three-dimensional compressible Navier-Stokes equations with the incorporation of the VC method are considered and the resulting system of equations is solved by using the sixth-order compact finite-difference scheme. To eliminate the numerical instability, a low-pass high-order filter is used. The nonreflective boundary conditions are applied for all the free boundaries and the radiated sound field is obtained by the Kirchhoff surface integration. Comparisons of the present results with the experimental data... 

    Exponential stabilization of flexural sway vibration of gantry crane via boundary control method

    , Article JVC/Journal of Vibration and Control ; Volume 26, Issue 1-2 , 2020 , Pages 36-55 Entessari, F ; Najafi Ardekany, A ; Alasty, A ; Sharif University of Technology
    SAGE Publications Inc  2020
    Abstract
    This paper aims to develop a boundary control solution for complicated gantry crane coupled motions. In addition to the large angle sway motion, the crane cable has a flexural transverse vibration. The Hamilton principle has been utilized to derive the governing partial differential equations of motion. The control objectives which are sought include: moving the payload to the desired position; reducing the payload swing with large sway angle; and finally suppressing the cable transverse vibrations in the presence of boundary disturbances simultaneously. These simultaneous boundary control objectives make the problem challenging. The proposed control approach is based on the original... 

    Influence of river cross-section data resolution on flood inundation modeling: Case study of Kashkan river basin in western Iran

    , Article Journal of Hydrology ; Volume 584 , 2020 Geravand, F ; Hosseini, S. M ; Ataie Ashtiani, B ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this study, a coupling of a hydrologic and hydraulic model was utilized to assess the impacts of river geometry data resolution on the flood inundation characteristics in a data-scarce environment. Hydrological modeling incorporates soil conservation service curve-number (SCS-CN) and the geomorphologic based instantaneous unit hydrograph model (GIUH) to compute the direct runoff hydrograph in Kashkan river basin located in western Iran. 1D HEC-Geo-RAS model was used and performed to simulate inundation extent of 100-yr floods (~1800 m3/s) along 40 km reach of Kashkan river with a ground survey of river cross-section (2000 cross-sections, each including 500 data-points). The effect of... 

    Insights into the pore-scale mechanisms of formation damage induced by drilling fluid and its control by silica nanoparticles

    , Article Energy and Fuels ; Volume 34, Issue 6 , 20 May , 2020 , Pages 6904-6919 Mohammadi, M ; Mahani, H ; Sharif University of Technology
    American Chemical Society  2020
    Abstract
    The formation damage (FD) caused by the invasion of drilling fluid severely affects reservoir performance during production. Most of the published research studies which address this type of FD have been carried out at the core or field scale. Thus, the main aim of the paper is to investigate the pore-scale mechanisms of FD induced by drilling fluids and their control with silica nanoparticles (NPs) using a microfluidic approach. The proper identification of the mechanisms of FD can lead to the proper selection of NP type and concentration as well as a suitable method to remediate FD. The micromodel was designed in a way to closely simulate the cross-flow at the wellbore surface. A... 

    Dynamic modeling of the turning process of slip-cast fused silica ceramics using the discrete element method

    , Article Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture ; Volume 234, Issue 3 , 2020 , Pages 629-640 Roostai, H ; Movahhedy, M. R ; Sharif University of Technology
    SAGE Publications Ltd  2020
    Abstract
    Simulation of brittle regime machining of materials (such as ceramics) is often difficult because of the complex material removal mechanisms involved. In this study, the discrete element method is used to simulate the dynamic process for machining of slip-cast fused silica ceramics. Flat-joint contact model is exploited to model contacts between particles in synthetic discrete element method models. This contact model is suitable for modeling of brittle materials with high ratios (higher than 10) of unconfined compressive strength to tensile strength. The discrete element method has the ability to simulate initiation, propagation, and coalescence of cracks leading to chip formation in the... 

    Improved advection algorithm of computational modeling of free surface flow using structured grids

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 195, Issue 7-8 , 2006 , Pages 775-795 ; 00457825 (ISSN) Babaei, R ; Abdollahi, J ; Homayonifar, P ; Varahram, N ; Davami, P ; Sharif University of Technology
    2006
    Abstract
    In the present study a finite difference method has been developed to model the transient fluid flow and heat transfer. A single fluid has been selected for modeling of mold filling and The SOLA-VOF 3D technique was modified to increase the accuracy of simulation of filling phenomena for shape castings. The model was then evaluated with the experimental methods. Refereeing to the experimental and simulation results a good consistency and the accuracy of the suggested model are confirmed. © 2005 Published by Elsevier B.V  

    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
    2010
    Abstract
    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... 

    CFD-DEM simulation of the hole cleaning process in a deviated well drilling: the effects of particle shape

    , Article Particuology ; Volume 25 , 2016 , Pages 72-82 ; 16742001 (ISSN) Akhshik, S ; Behzad, M ; Rajabi, M ; Sharif University of Technology
    Abstract
    We investigate the effect of particle shape on the transportation mechanism in well-drilling using a three-dimensional model that couples computational fluid dynamics (CFD) with the discrete element method (DEM). This numerical method allows us to incorporate the fluid-particle interactions (drag force, contact force, Saffman lift force, Magnus lift force, buoyancy force) using momentum exchange and the non-Newtonian behavior of the fluid. The interactions of particle-particle, particle-wall, and particle-drill pipe are taken into account with the Hertz-Mindlin model. We compare the transport of spheres with non-spherical particles (non-smooth sphere, disc, and cubic) constructed via the... 

    Pure axial flow of viscoelastic fluids in rectangular microchannels under combined effects of electro-osmosis and hydrodynamics

    , Article Theoretical and Computational Fluid Dynamics ; Volume 32, Issue 1 , 2018 ; 09354964 (ISSN) Reshadi, M ; Saidi, M. H ; Ebrahimi, A ; Sharif University of Technology
    Springer New York LLC  2018
    Abstract
    This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid... 

    Optimal riser design in sand casting process by topology optimization with SIMP method I: poisson approximation of nonlinear heat transfer equation

    , Article Structural and Multidisciplinary Optimization ; Volume 36, Issue 2 , 25 January , 2008 , Pages 193-202 ; 1615147X (ISSN) Tavakoli, R ; Davami, P ; Sharif University of Technology
    2008
    Abstract
    The optimal design of a casting feeding system is considered. The problem is formulated as the volume constrained topology optimization and is solved with the finite element analysis, explicit design sensitivity, and numerical optimization. In contrast to the traditional topology optimization where the objective function is defined on the design space, in the presented method, the design space is a subset of the complement of the objective function space. To accelerate optimization procedure, the nonlinear unsteady heat transfer equation is approximated with a Poisson-like equation. The feasibility of the presented method is supported with illustrative examples. © 2007 Springer-Verlag