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Experimental and numerical investigation of radial flow compressor volute shape effects in characteristics and circumferential pressure non-uniformity
, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1753-1764 ; 10263098 (ISSN) ; Hajilouy Benisi, A ; Movahhedy, M. R ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
In this article, the effects of volute cross section shape and centroid profile of a radial ow compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and ow parameters at the inlet and outlet of the compressor. The three-dimensional ow field model of the compressor was obtained numerically solving Navier-Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement. Modification of a volute was performed by introducing a shape factor for volute cross section geometry....
Influence of the angle of incident shock wave on mixing of transverse hydrogen micro-jets in supersonic crossflow
, Article International Journal of Hydrogen Energy ; Volume 40, Issue 30 , August , 2015 , Pages 9590-9601 ; 03603199 (ISSN) ; Jahanian, O ; Mokhtari, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
A three-dimensional numerical study has been performed to investigate the influence of angle of shock waves on sonic transverse Hydrogen micro-jets subjected to a supersonic crossflow. This study focuses on mixing of the Hydrogen jet in a Mach 4.0 crossflow with a global equivalence ratio of 0.5. Flow structure and fuel/air mixing mechanism were investigated numerically. Parametric studies were conducted on the angle of shock wave by using the Reynolds-averaged Navier-Stokes equations with Menter's Shear Stress Transport turbulence model. Complex jet interactions were found in the downstream region with a variety of flow features depending upon the angle of shock incident. These flow...
Hydrodynamic and electrochemical modeling of vanadium redox flow battery
, Article Mechanics and Industry ; Volume 16, Issue 2 , 2015 ; 22577777 (ISSN) ; Elyasi, S ; Mollazadeh, M ; Sharif University of Technology
EDP Sciences
2015
Abstract
Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demonstrated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation,...
Implementation of PISO algorithm for simulating unsteady cavitating flows
, Article Ocean Engineering ; Volume 37, Issue 14-15 , 2010 , Pages 1321-1336 ; 00298018 (ISSN) ; Asnaghi, A ; Jahanbakhsh, E ; Sharif University of Technology
Abstract
The present study focuses on the implementation of PISO algorithm to simulate cavitating flows. For simulation of unsteady behaviors of cavitation which have practical applications, the development of unsteady PISO algorithm based on the non-conservative approach is investigated. The effects of mixture compressibility are considered to improve accuracy of simulations. For multi-phase simulation, single-fluid Navier-Stokes equations, along with the volume fraction transport equation, are employed. The bubble dynamics model is utilized to simulate phase change. To prove capabilities of the developed PISO algorithm to simulate cavitating flows, unsteady simulation of cavitation around NACA0015...
The uncertainties of continuum-based cfd solvers to perform microscale hot-wire anemometer simulations in flow fields close to transitional regime
, Article ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer, MNHMT 2016, 4 January 2016 through 6 January 2016 ; Volume 2 , 2016 ; 9780791849668 (ISBN) ; Ghorbani, M. R ; Darbandi, H ; Heat Transfer Division ; Sharif University of Technology
American Society of Mechanical Engineers
2016
Abstract
In this study, we simulate the flow and heat transfer during hot-wire anemometry and investigate its thermal behavior and physics using the Computational Fluid Dynamics (CFD) tool. In this regard, we use the finite-volume method and solve the compressible Navier-Stokes equations numerically in slightly non-continuum flow fields. We do not use any slip flow model to include the transitional flow physics in our simulations. Using the CFD method, we simulate the flow over hot-wire and evaluate the uncertainty of CFD in thermal simulation of hot-wire in low transitional flow regimes. The domain sizes and the mesh distributions are carefully chosen to avoid boundary condition error appearances....
A truly incompressible smoothed particle hydrodynamics based on artificial compressibility method
, Article Computer Physics Communications ; Volume 210s , 2017 , Pages 10-28 ; 00104655 (ISSN) ; Hejranfar, K ; Sharif University of Technology
Abstract
In the present study, a truly incompressible smoothed particle hydrodynamics based on the artificial compressibility method for simulating steady and unsteady incompressible flows is proposed and assessed. The incompressible Navier–Stokes equations in the primitive variables formulation using the artificial compressibility method proposed by Chorin in the Eulerian reference frame are written in a Lagrangian reference frame to provide an appropriate incompressible SPH algorithm. The proposed SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of time-accurate analysis of unsteady flows. The advantage of the Artificial Compressibility-based...
Prediction of fluid flow and acoustic field of a supersonic jet using vorticity confinement
, Article Journal of the Acoustical Society of America ; Volume 144, Issue 3 , 2018 , Pages 1521-1527 ; 00014966 (ISSN) ; Hejranfar, K ; Ebrahimi, M ; Sharif University of Technology
Acoustical Society of America
2018
Abstract
In this study, the numerical simulation of the fluid flow and acoustic field of a supersonic jet is performed by using high-order discretization and the vorticity confinement (VC) method on coarse grids. The three-dimensional Navier-Stokes equations are considered in the generalized curvilinear coordinate system and the high-order compact finite-difference scheme is applied for the space discretization, and the time integration is performed by the fourth-order Runge-Kutta scheme. A low-pass high-order filter is applied to stabilize the numerical solution. The non-reflecting boundary conditions are adopted for all the free boundaries, and the Kirchhoff surface integration is utilized to...
Pore-level influence of micro-fracture parameters on visco-capillary behavior of two-phase displacements in porous media
, Article Advances in Water Resources ; Volume 113 , 2018 , Pages 260-271 ; 03091708 (ISSN) ; Akhlaghi Amiri, H. A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this work, coupled Cahn–Hilliard phase field and Navier–Stokes equations were solved using finite element method to address the effects of micro-fracture and its characterizations on water-oil displacements in a heterogeneous porous medium. Sensitivity studies at a wide range of viscosity ratios (M) and capillary numbers (Ca), and the resultant log Ca–log M stability phase diagram, revealed that in both media, with/without fracture, the three regimes of viscous fingering, capillary fingering and stable displacement similarly occur. However, presence of the fracture caused water channeling phenomenon which resulted in reduction of the number of active fingers and hence the final oil...
Simulation of incompressible multiphase flows using the artificial compressibility method
, Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 2 , 2018 ; 08888116 (ISSN); 9780791851562 (ISBN) ; Hejranfar, K ; Fluids Engineering Division ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
The Eulerian methods are susceptible to generate the nonphysical spurious currents in the multiphase flow simulations near the interfaces. This paper presents a new Eulerian method to accurately simulate the velocity fields, especially near the multiphase flow interfaces and prevents the numerical results from generating the nonphysical currents. A Eulerian central difference finite-volume scheme equipped with the suitable numerical dissipation terms is used to simulate incompressible multiphase flows. The interface is captured by Flux Corrected Transport-Volume of Fluid method (FCT-VOF). Increasing the accuracy near the sharp gradients, such as interface, the conservative form of...
Computational simulation of marangoni convection under microgravity condition
, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 513-524 ; 10263098 (ISSN) ; Taeibi Rahni, M ; Asadi, B ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
In this work, the rising of a single bubble in a quiescent liquid under microgravity condition was simulated. In addition to general studies of microgravity effects, the initiation of hydrodynamic convection, solely due to the variations of interface curvature (surface tension force) and thus the generation of shearing forces at the interfaces, was also studied. Then, the variation of surface tension due to the temperature gradient (Marangoni convection), which can initiate the onset of convection even in the absence of buoyancy, was studied. The related unsteady incompressible full Navier-Stokes equations were solved using a finite difference method with a structured staggered grid. The...
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) ; 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...
An improved Mesh Adaption and Refinement approach to Cavitation Simulation (MARCS) of propellers
, Article Ocean Engineering ; Volume 171 , 2019 , Pages 139-150 ; 00298018 (ISSN) ; Atlar, M ; Khorasanchi, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents the improvements of cavitation modelling for marine propellers particularly developing tip vortex cavitation. The main purpose of the study is to devise a new approach for modelling tip vortex cavitation using Computational Fluid Dynamics (CFD) methods with commercial software, STAR-CCM+. The INSEAN E779A model propeller was used for this study as a benchmark propeller. Utilizing this propeller, firstly, validation studies were conducted in non-cavitating conditions together with grid and time step uncertainty studies. Then, the cavitation was simulated on the propeller using a numerical cavitation model, which is known as the Schnerr–Sauer model, based on the...
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) ; 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...
Dynamics and stability analysis of rotating cylindrical shells in annular fluid medium
, Article International Journal of Structural Stability and Dynamics ; Volume 20, Issue 8 , 2020 ; Firouz Abadi, R. D ; Rahmanian, M ; Sharif University of Technology
World Scientific
2020
Abstract
Stability and dynamics of rotating coaxial cylindrical shells conveying incompressible and inviscid fluid are investigated. The interior shell is assumed to be flexible while the exterior cylinder is rigid. Using Sander's-Koiter theory assumptions and following Hamilton's principle, governing equations of motion are determined in their integral form. Employing the extended Galerkin method of solution, the integral equations of motion are projected to their equivalent system of algebraic equations. Fluid equations are fundamentally based on the linearized inviscid Navier-Stokes equations. Impermeability condition on the fluid and structure interface as well as the zero radial velocity...
A high-order nodal discontinuous Galerkin method to solve preconditioned multiphase Euler/Navier-Stokes equations for inviscid/viscous cavitating flows
, Article International Journal for Numerical Methods in Fluids ; Volume 92, Issue 5 , 2020 , Pages 478-508 ; Hejranfar, K ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
In this study, a high-order accurate numerical method is applied and examined for the simulation of the inviscid/viscous cavitating flows by solving the preconditioned multiphase Euler/Navier-Stokes equations on triangle elements. The formulation used here is based on the homogeneous equilibrium model considering the continuity and momentum equations together with the transport equation for the vapor phase with applying appropriate mass transfer terms for calculating the evaporation/condensation of the liquid/vapor phase. The spatial derivative terms in the resulting system of equations are discretized by the nodal discontinuous Galerkin method (NDGM) and an implicit dual-time stepping...
Impact of trim on added resistance of KRISO container ship (KCS) in head waves: An experimental and numerical study
, Article Ocean Engineering ; Volume 211 , 2020 ; Khorasanchi, M ; Day, S ; Turan, O ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, added resistance and motion responses of KRISO Container Ship (KCS) were evaluated experimentally and numerically in six different trim angles. A series of towing tank experiments were performed for six different trim angles at design speed in calm water and regular head waves. The ship motions and added resistance were measured for several wavelength conditions considering short and long wave ranges with wave steepness of 1/60. Next, computations of the towed model in calm water and waves were performed using Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD and 3-D potential methods. Effects of trim angles on added resistance were analysed and results concerning the...
Investigations of supersonic flow around a long axisymmetric body
, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 534-544 ; 10263098 (ISSN) ; Farahani, M ; Soltani, M. R ; Taeibi Rahni, M ; Sharif University of Technology
2009
Abstract
In this work, a supersonic turbulent flow over a long axisymmetric body was investigated, both experimentally and computationally. The experimental study consisted of a series of wind tunnel tests for the flow over an ogive-cylinder body at a Mach number of 1.6 and at a Reynolds number of 8 × 10 6, at angles of attack between -2 and 6 degrees. It included the surface static pressure and the boundary layer profile measurements. Further, the flow around the model was visualized using a Schlieren technique. All tests were conducted in the trisonic wind tunnel of the Qadr Research Center (QRC). Also, the same flow at zero angle of attack was computationally simulated using a multi-block grid...
Interface Feedback Control Stabilization of a Nonlinear Fluid–Structure Interaction
, M.Sc. Thesis Sharif University of Technology ; Hesaraki, Mahmud (Supervisor)
Abstract
In this thesis, We consider a model of a fluid–structure interaction defined on a bounded domain Ω ⊆ R2, that describes a body of elasticity interacting with a fluid. Ω is a bounded simply connected domain, consisting of two open sub-domains Ωs and Ωf .Ωf is the exterior domain with non-overlapping boundaries Γf and Γs, so that ∂Ωs = Γs. Ωs is an interior domain with boundary Γs.Ωs is occupied by an elastic body while Ωf is filled with a fluid.The interaction between the elastic body and the fluid takes place at the interface Γs.The dynamics of the fluid is described by the Navier–Stokes equation and the dynamics of the elastic body is described by an elasto-dynamic system of wave equations....
Existence and Uniqueness of Solutions to a Fluidstructure Model Coupling the Navier-Stokes Equations and the Lame System
, M.Sc. Thesis Sharif University of Technology ; Hesaraki, Mahmoud (Supervisor)
Abstract
In this thesis, we consider a system containing fluid equations, structure equations, and equations of these two materials’ common interface in three dimensions and on the regular domains. We suppose that the solid which is described by the Lamé system of linear elasticity, moves inside an incompressible viscous fluid in three dimensions, and the fluid obeys the incompressible Navier-Stokes equations in a time-dependent domain. At the fluid–solid interface, natural conditions are imposed, continuity of the velocities and of the Cauchy stress forces. The fluid and the solid are coupled through these conditions. By this interaction, the fluid deforms the boundary of the solid which in turn...
Modeling the Forces Acting on NASA's Probe B Satellite, Using Space-Time Fluid Analogy
, M.Sc. Thesis Sharif University of Technology ; Taeibi Rahni, Mohamad (Supervisor)
Abstract
The purpose of this thesis is to study the analogy of space-time fluid flow around Earth and to investigate the hydrodynamic forces caused by this fluid on NASA's Probe B satellite. According to recent research, Einstein's and Navier-Stokes equations are the same. The properties of space-time fluid, including equation of state, compressibility, viscosity, flow field around Earth, and the hydrodynamic forces entering Probe B satellite, are unknown. There are two views about the viscosity of space-time fluid. Spherical mass of the three-dimensional spherical sink and the nature of the sphere located in the probe satellite without a spherical solid particle It are considered within this flow....