Mustafa Tutar - Profile on Academia.edu (original) (raw)

Papers by Mustafa Tutar

Research paper thumbnail of Multi-Objective Design Optimization of a New Engine Intake Electromagnetic Wave Blocker in a Straight Subsonic Duct Configuration

Multi-Objective Design Optimization of a New Engine Intake Electromagnetic Wave Blocker in a Straight Subsonic Duct Configuration

Research paper thumbnail of Sustainability in the vegetable food supply chain - overview of the results of the project SUNNIVA

Sustainability in the vegetable food supply chain - overview of the results of the project SUNNIVA

International audienc

Research paper thumbnail of 液体食品のための相反撹はん殺菌システムの最適振動速度の決定:実験的検証と計算論的アプローチ【Powered by NICT】

液体食品のための相反撹はん殺菌システムの最適振動速度の決定:実験的検証と計算論的アプローチ【Powered by NICT】

Food and Bioproducts Processing, 2016

Research paper thumbnail of 3-D Computational Modelling of Process Condition Effects on Polymer Injection Molding

International Polymer Processing, 2009

Three-dimensional (3-D) computational modeling approach of mold insert injection molding is devel... more Three-dimensional (3-D) computational modeling approach of mold insert injection molding is developed to build a more robust and complete simulation solution of polymer melt flow in a mold cavity considering the effects of process conditions on non-isothermal, viscous, compressible and non-Newtonian flow behavior. The changes in viscosity and density in the polymer melt flow are successfully modeled within a volume of fluid (VOF) method coupled with a finite volume approach to generate more realistic melt flow physics during filling stage of injection molding under different process conditions. The Pressure Implicit with Splitting Operators (PISO) pressure-velocity coupling algorithm is employed to enable higher degree of approximate relation between corrections for pressure and velocity, and a comprehensive high-resolution differencing scheme (CICSAM) is successfully utilized to capture moving interfaces. The present developed numerical approach is verified for a box shape mold ins...

Research paper thumbnail of Modeling of Effect of Inflow Turbulence Data on Large Eddy Simulation of Circular Cylinder Flows

Modeling of Effect of Inflow Turbulence Data on Large Eddy Simulation of Circular Cylinder Flows

Journal of Fluids Engineering, 2006

A random flow generation (RFG) algorithm for a previously established large eddy simulation (LES)... more A random flow generation (RFG) algorithm for a previously established large eddy simulation (LES) code is successfully incorporated into a finite element fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the three-dimensional (3D) LES computations of viscous incompressible turbulent flow over a nominally two-dimensional (2D) circular cylinder at Reynolds number of 140,000. The effect of generated turbulent inflow boundary conditions on the near wake flow and the shear layer and on the prediction of integral flow parameters is studied based on long time average results. Because the near-wall region cannot be resolved for high Reynolds number flows, no-slip velocity boundary function is used, but wall effects are taken into consideration with a near-wall modeling methodology that comprises the no-slip function with a modified form of van Driest damping approach to reduce the subgrid length scale in the vicinity of the cylinder wall. Simulatio...

Research paper thumbnail of Large eddy simulation of wind flow around parallel buildings with varying configurations

Fluid Dynamics Research, Dec 1, 2002

The paper presents numerical calculations of turbulent wind ow conditions around two parallel bui... more The paper presents numerical calculations of turbulent wind ow conditions around two parallel buildings with di erent wind directions and building arrangements. The numerical simulations are carried out with the RNG sub-grid scale model following an initial test case for a single building conÿguration with the time averaged and ÿltered Navier-Stokes equations based turbulence models. A comparison with the experimental data indicates that the present RNG sub-grid scale model gives much better results than other turbulence models tested to predict the time-dependent atmospheric ow ÿeld. This model is further extended to analyse the wind e ects between buildings by considering di erent building geometry, wind ow direction and passage width. All numerical simulations are carried out by using the ÿnite volume method (FVM). The simulation results show that the present sub-grid scale model with the FVM is rather promising to study the wind e ects on buildings and can overcome the disadvantages of conventional Reynolds averaged Navier-Stokes equations based turbulence models.

Research paper thumbnail of Computational Modeling of Wind Flow Around a Group of Buildings

Computational Modeling of Wind Flow Around a Group of Buildings

International Journal of Computational Fluid Dynamics, 2004

In the present paper attention is focused on applications of computational flow modeling for the ... more In the present paper attention is focused on applications of computational flow modeling for the evaluation of wind effects around a single building, between two parallel buildings and around a collection of buildings by using Reynolds averaged Navier-Stokes (RANS) equations based turbulence models, namely the standard k-ε turbulence model and the RNG k-ε turbulence model and the large eddy simulation

Research paper thumbnail of Computational Study of the Effect of Governing Parameters on a Polymer Injection Molding Process for Single-Cavity and Multicavity Mold Systems

Computational Study of the Effect of Governing Parameters on a Polymer Injection Molding Process for Single-Cavity and Multicavity Mold Systems

Journal of Manufacturing Science and Engineering-transactions of The Asme, Dec 22, 2009

In the present study a more complete numerical solution approach using parallel computing technol... more In the present study a more complete numerical solution approach using parallel computing technology is provided for the three-dimensional modeling of mold insert polymer injection molding process by considering the effects of phase-change and compressibility for non-Newtonian fluid flow conditions. A volume of fluid (VOF) method coupled with a finite volume approach is used to simulate the mold-filling stage of the injection molding process. The variations in viscosity and density in the polymer melt flow are successfully resolved in the present VOF method to more accurately represent the rheological behavior of the polymer melt flow during the mold filling. A comprehensive high-resolution differencing scheme (compressive interface capturing scheme for arbitrary meshes or CICSAM) is successfully utilized to capture moving interfaces and the pressure-implicit with splitting operators pressure-velocity coupling algorithm is employed to enable a higher degree of approximate relation between corrections for pressure and velocity. The capabilities of the proposed numerical methodology in modeling real molding flow conditions are verified through quantitative and qualitative comparisons with other simulation programs and the data obtained from the experimental study conducted. The present numerical results are also compared with each other for a polypropylene female threaded adaptor pipe fitting model with a metallic insert for varying governing process conditions/parameters to assess the modeling constraints and enhancements of the present numerical procedure and the effects of these conditions to optimize the polymer melt flow for mold insert polymer injection molding process. The numerical results suggest that the present numerical solution approach can be used with a confidence for further studies of optimization of design of mold insert polymer injection molding processes.

Research paper thumbnail of Computational modelling of two-phase flow around a savonius type wave energy converter in a two- dimensional numerical wave tank

MARINE V : proceedings of the V International Conference on Computational Methods in Marine Engineering, 2013

In the present study, the main objective is to develop a finite volume method (FVM) based numeric... more In the present study, the main objective is to develop a finite volume method (FVM) based numerical modelling approach incorporated with a Volume of fluid (VOF) method to investigate the effect of wave on the performance of Savonius rotor in a twodimensional numerical wave tank (NWT). A Savonius rotor, whose rotational axis is normal to the direction of wave generation, is introduced to computationally investigate flow around the rotor structure at selected wave height conditions. The geometry of the blades is such that wave motion produces a positive force on the rotor and is constructed using CAD software. Followed by importing the orthogonal mesh domain constructed in FLOW-3D software environment, defined in Cartesian coordinates, into the finite volume environment of FLOW-3D for fluid flow analysis. A body-fixed reference system ("body system"), introduced for the rotor, and the space reference system ("space system") is employed to scrutinize a twodimensional unsteady turbulent flow around the rotor structure. At each time step equations of motion are solved for the rotor under coupled motion with consideration of hydraulic, gravitational and control forces. The flow simulations are then performed using Reynoldsaveraged Navier-Stokes (RANS) based two-equation RNG k- turbulence model with dynamically computed turbulent length scale, under the assumption of incompressible, viscous, and transient two-phase turbulent flow conditions. From the numerical results obtained and validated against the theoretical data obtained from the no-rotor flow condition, it can be concluded that the flow characteristics is strongly dependent upon differing wave propagation conditions and energy conversion rate can be increased with a proper combination of selected wave height and frequency for the investigated parametric value range. Flow visualization, which is represented by qualitative contours of velocity vector field also show different flow patterns at different wave height conditions.

Research paper thumbnail of Optimized CFD modelling and validation of radiation section of an industrial top-fired steam methane reforming furnace

Computers & Chemical Engineering, 2021

The present study proposes an optimized computational fluid dynamics (CFD) modelling framework to... more The present study proposes an optimized computational fluid dynamics (CFD) modelling framework to provide a complete and accurate representation of combustion and heat transfer phenomena in the radiation section of an industrial top-fired steam methane reforming (SMR) furnace containing 64 reforming tubes, 30 burners and 3 flue-gas tunnels. The framework combines fully-coupled appropriate furnace-side models with a 1-D reforming process-side model. Experimental measurements are conducted in terms of outlet temperatures at the flue-gas tunnels, point-wise temperature distributions at the panel walls, and inside the reforming tube collectors which are placed at the refinery plant of Petronor. The final results are compared with the experimental data for validation purpose. The proposed fully coupled 3-D CFD modeling framework, which utilizes a detailed chemical-kinetic combustion mechanism, reproduces well basic flow features including pre-mixed combustion process, downward movement of flue-gas in association with large recirculation zones, radiative heat transfer to the reforming tubes, composition profiles along the reaction core of the reforming tubes, temperature non-uniformities, and fluctuating characteristics of heat flux. The reported non-uniform heat and temperature distributions might be optimized by means of the operating parameters in order to avoid a negative impact on furnace balancing and performance.

Research paper thumbnail of Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

Wind and Structures, 2007

ABSTRACT

Research paper thumbnail of Computational modelling of inflow turbulence effects on transitional flow in a highly transonic linear turbine

Computational modelling of inflow turbulence effects on transitional flow in a highly transonic linear turbine

International Journal of Numerical Methods for Heat & Fluid Flow, 2012

PurposeThe purpose of this paper is to numerically study inflow turbulence effects on the transit... more PurposeThe purpose of this paper is to numerically study inflow turbulence effects on the transitional flow in a high pressure linear transonic turbine at the design incidence.Design/methodology/approachThe three‐dimensional (3‐D) compressible turbulent flow in a turbine inlet guide vane is simulated using a finite volume based fluid solver coupled with dynamic large eddy simulation (LES) computations to investigate the effects of varying inflow turbulence length scale and the turbulence intensity on the aero‐thermal flow characteristics and the laminar‐turbulent transition phenomena. The computational analyses are extended to very high exit Reynolds number flow conditions to further study the effect of high exit Reynolds numbers on the transitional behavior of the present flow around the inlet guide vane cascades of the turbine. The calculations are performed with varying degree of inflow turbulence intensity values ranging from 0.8 to 6 percent and the inflow turbulence length sca...

Research paper thumbnail of Numerical correlation for the pressure drop in Stirling engine heat exchangers

International Journal of Thermal Sciences, 2015

New correlation equations, to be valid for the pressure drop and heat exchange calculation under ... more New correlation equations, to be valid for the pressure drop and heat exchange calculation under the developing transitional reciprocating flow encountered in Stirling heat exchangers are numerically derived. Reynolds-Averaged NaviereStokes (RANS) equations based turbulence models are used to analyse laminar to turbulent reciprocating flow, focussing on the onset of turbulence and transitional reciprocating flow regime. The relative performance of four turbulence models in more accurately capturing the characteristics of the flow of interest is assessed in relation to overcoming the problems identified in previous numerical studies. The simulation results are compared with published and wellknown experimental data for reciprocating pipe flows, indicating that the effects of the turbulence anisotropy need to be taken into account in order to accurately predict the laminar to turbulent transition. The anisotropic Reynolds stress turbulence model is selected as a best choice among the tested turbulence models for analysis of this transitory phenomenon based on the comparative qualitative and quantitative results. This model is used to evaluate the heat transfer and pressure drop and propose new correlations considering the working and dimensional characteristics of Stirling heat exchangers: 100 Re u 600, A 0 600, b cri > 761 and 40 L/D 120. These correlation equations reduce the unsteady 2D behaviour in reciprocating pipe flow into a manageable form that can be incorporated into Stirling engine performance codes. It is believed that the validated numerical model can be used with confidence for studying the transitional reciprocating flow and the obtained correlations, can be applied as a cost effective solution for the development of Stirling engine heat exchangers.

Research paper thumbnail of Application of Differing Forcing Function Models on the Flow Past an Oscillating Cylinder in a Uniform Low Reynolds Number Flow

Application of Differing Forcing Function Models on the Flow Past an Oscillating Cylinder in a Uniform Low Reynolds Number Flow

Advances in Computational Heat Transfer. Proceedings of the International Symposium, 1997

A Computational Fluid Dynamics (CFD) model is presented for the uniform viscous two dimensional f... more A Computational Fluid Dynamics (CFD) model is presented for the uniform viscous two dimensional flow past an oscillating cylinder at low Reynolds number. Numerical simulations are made to study the effect of differing forced induced oscillation mechanisms with a large range of cylinder forcing frequencies. In the first case sinusoidal velocity slip boundary conditions are adopted for the cylinder surface to simulate cylinder oscillation. The implication suggests that no modification or additional term need to be added to the Navier-Stokes equations. In the second case this time extra body force terms which are assumed to account for velocity effects due to cylinder movement are included in the Navier~ Stokes equations with the imposition of same boundary conditions. Drag and lift coefficients are extracted from present numerical results and other detailed computations of these coefficients are made at a Reynolds number of 80 and an amplitude-to diameter ratio 0.14. The results are found to be in agreement with each other at low force driving frequencies below and near lock­ in. However, differences are found at higher frequencies above lock-in. Agreement are also found with experimental results at some frequency ranges.

Research paper thumbnail of Experimental and numerical flow investigation of Stirling engine regenerator

Energy, 2014

This paper presents both preliminary experimental and numerical studies of pressure drop and heat... more This paper presents both preliminary experimental and numerical studies of pressure drop and heat transfer characteristics of Stirling engine regenerators. A test bench is designed and manufactured for testing different regenerators under oscillating flow conditions, while three-dimensional (3-D) numerical simulations are performed to numerically characterize the pressure drop phenomena through a wound woven wire matrix regenerator under different porosity and flow boundary conditions. The test bench operating condition range is initially determined based on the performance of the commercial, well-known Stirling engine called WhisperGen™. This oscillating flow test bench is essentially a symmetrical design, which allows two regenerator samples to be tested simultaneously under the same inflow conditions. The oscillating flow is generated by means of a linear motor which moves a piston in an oscillatory motion. Both the frequency and the stroke of the piston are modified to achieve different test conditions. In the numerical study, use of a FVM (finite volume method) based CFD (computational fluid dynamics) approach for different configurations of small volume matrices leads to a derivation of a twocoefficient based friction factor correlation equation, which could be later implemented in an equivalent porous media with a confidence for future regenerator flow and heat transfer analysis.

Research paper thumbnail of The Computational Modeling of Transitional Flow through a Transonic Linear Turbine: Comparative Performance of Various Turbulence Models

The Computational Modeling of Transitional Flow through a Transonic Linear Turbine: Comparative Performance of Various Turbulence Models

Numerical Heat Transfer, Part A: Applications, 2010

Aero-thermal characteristics of transitional flow through a highly loaded transonic linear turbin... more Aero-thermal characteristics of transitional flow through a highly loaded transonic linear turbine are studied at the design incidence using computational methods. The three-dimensional compressible turbulent flow through a turbine inlet guide vane is simulated using finite-volume method-based fluid flow solutions using both Reynolds-averaged Navier Stokes (RANS) equations-based turbulence models, and a dynamic large eddy simulation (LES) approach which is based

Research paper thumbnail of A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

Journal of Polymer Engineering, 2013

The combined effects of solidification and viscous dissipation on the hydrodynamic and thermal be... more The combined effects of solidification and viscous dissipation on the hydrodynamic and thermal behavior of polymer melt flow during the injection process in a straight plane channel of constant cross section are numerically studied by considering the shear-rate and temperature-dependent viscosity and transient-phase change behavior. A numerical finite volume method, in conjunction with a modified form of the Cross constitutive equation to account for shear rate, temperature-dependent viscosity changes and a slightly modified form of the method proposed by Voller and Prakash to account for solidification of the liquid phase, is used and a validation with an analytical solution is presented for viscous heating effects. The hydrodynamic and solidified layers growth under the influence of a transient phase-change process and viscous dissipation, are analyzed for a commercial polymer melt flow, polypropylene (PP) for different parametric conditions namely, inflow velocity, polymer inject...

Research paper thumbnail of Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Energy Conversion and Management, 2014

ABSTRACT

Research paper thumbnail of Numerical study of the pressure drop phenomena in wound woven wire matrix of a Stirling regenerator

Energy Conversion and Management, 2013

Friction pressure drop correlation equations are derived from a numerical study by characterizing... more Friction pressure drop correlation equations are derived from a numerical study by characterizing the pressure drop phenomena through porous medium of both types namely stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. First, a finite volume method (FVM) based numerical approach is used and validated against well known experimentally obtained empirical correlations for a misaligned stacked woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The friction pressure drop correlation equation derived from the numerical results corresponds well with the experimentally obtained correlations with less than 5% deviation. Once the numerical approach is validated, the study is further extended to characterize the pressure drop phenomena in a wound woven wire matrix model of a Stirling engine regenerator for a diameter range from 0.080 to 0.110 mm and a porosity range from 0.472 to 0.638 within the same Reynolds number range. Thus, the new correlation equations are derived from this numerical study for different flow configurations of the Stirling engine regenerator. The results indicate flow nature and complex geometry dependent friction pressure drop characteristics within the present Stirling engine regenerator system. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and woven Stirling engine efficiency in the above specified ranges.

Research paper thumbnail of Computational Modeling of the Effects of Viscous Dissipation on Polymer Melt Flow Behavior During Injection Molding Process in Plane Channels

Journal of Manufacturing Science and Engineering, 2013

The present finite volume method based fluid flow solutions investigate the boundary-layer flow a... more The present finite volume method based fluid flow solutions investigate the boundary-layer flow and heat transfer characteristics of polymer melt flow in a rectangular plane channel in the presence of the effect of viscous dissipation and heat transfer by considering the viscosity and density variations in the flow. For different inflow velocity boundary conditions and the injection polymer melt temperatures, the viscous dissipation effects on the velocity and temperature distributions are studied extensively to analyze the degree of interactions of thermal flow field dominated by the viscous heating and momentum diffusion mechanism with varying boundary conditions. The modified forms of Cross constitutive equation and Tait equation of state are adopted for the representation of viscosity variations and density change, respectively, in the polymer melt flow. These models together with the viscous dissipation terms are successfully incorporated into the finite volume method based flu...

Research paper thumbnail of Multi-Objective Design Optimization of a New Engine Intake Electromagnetic Wave Blocker in a Straight Subsonic Duct Configuration

Multi-Objective Design Optimization of a New Engine Intake Electromagnetic Wave Blocker in a Straight Subsonic Duct Configuration

Research paper thumbnail of Sustainability in the vegetable food supply chain - overview of the results of the project SUNNIVA

Sustainability in the vegetable food supply chain - overview of the results of the project SUNNIVA

International audienc

Research paper thumbnail of 液体食品のための相反撹はん殺菌システムの最適振動速度の決定:実験的検証と計算論的アプローチ【Powered by NICT】

液体食品のための相反撹はん殺菌システムの最適振動速度の決定:実験的検証と計算論的アプローチ【Powered by NICT】

Food and Bioproducts Processing, 2016

Research paper thumbnail of 3-D Computational Modelling of Process Condition Effects on Polymer Injection Molding

International Polymer Processing, 2009

Three-dimensional (3-D) computational modeling approach of mold insert injection molding is devel... more Three-dimensional (3-D) computational modeling approach of mold insert injection molding is developed to build a more robust and complete simulation solution of polymer melt flow in a mold cavity considering the effects of process conditions on non-isothermal, viscous, compressible and non-Newtonian flow behavior. The changes in viscosity and density in the polymer melt flow are successfully modeled within a volume of fluid (VOF) method coupled with a finite volume approach to generate more realistic melt flow physics during filling stage of injection molding under different process conditions. The Pressure Implicit with Splitting Operators (PISO) pressure-velocity coupling algorithm is employed to enable higher degree of approximate relation between corrections for pressure and velocity, and a comprehensive high-resolution differencing scheme (CICSAM) is successfully utilized to capture moving interfaces. The present developed numerical approach is verified for a box shape mold ins...

Research paper thumbnail of Modeling of Effect of Inflow Turbulence Data on Large Eddy Simulation of Circular Cylinder Flows

Modeling of Effect of Inflow Turbulence Data on Large Eddy Simulation of Circular Cylinder Flows

Journal of Fluids Engineering, 2006

A random flow generation (RFG) algorithm for a previously established large eddy simulation (LES)... more A random flow generation (RFG) algorithm for a previously established large eddy simulation (LES) code is successfully incorporated into a finite element fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the three-dimensional (3D) LES computations of viscous incompressible turbulent flow over a nominally two-dimensional (2D) circular cylinder at Reynolds number of 140,000. The effect of generated turbulent inflow boundary conditions on the near wake flow and the shear layer and on the prediction of integral flow parameters is studied based on long time average results. Because the near-wall region cannot be resolved for high Reynolds number flows, no-slip velocity boundary function is used, but wall effects are taken into consideration with a near-wall modeling methodology that comprises the no-slip function with a modified form of van Driest damping approach to reduce the subgrid length scale in the vicinity of the cylinder wall. Simulatio...

Research paper thumbnail of Large eddy simulation of wind flow around parallel buildings with varying configurations

Fluid Dynamics Research, Dec 1, 2002

The paper presents numerical calculations of turbulent wind ow conditions around two parallel bui... more The paper presents numerical calculations of turbulent wind ow conditions around two parallel buildings with di erent wind directions and building arrangements. The numerical simulations are carried out with the RNG sub-grid scale model following an initial test case for a single building conÿguration with the time averaged and ÿltered Navier-Stokes equations based turbulence models. A comparison with the experimental data indicates that the present RNG sub-grid scale model gives much better results than other turbulence models tested to predict the time-dependent atmospheric ow ÿeld. This model is further extended to analyse the wind e ects between buildings by considering di erent building geometry, wind ow direction and passage width. All numerical simulations are carried out by using the ÿnite volume method (FVM). The simulation results show that the present sub-grid scale model with the FVM is rather promising to study the wind e ects on buildings and can overcome the disadvantages of conventional Reynolds averaged Navier-Stokes equations based turbulence models.

Research paper thumbnail of Computational Modeling of Wind Flow Around a Group of Buildings

Computational Modeling of Wind Flow Around a Group of Buildings

International Journal of Computational Fluid Dynamics, 2004

In the present paper attention is focused on applications of computational flow modeling for the ... more In the present paper attention is focused on applications of computational flow modeling for the evaluation of wind effects around a single building, between two parallel buildings and around a collection of buildings by using Reynolds averaged Navier-Stokes (RANS) equations based turbulence models, namely the standard k-ε turbulence model and the RNG k-ε turbulence model and the large eddy simulation

Research paper thumbnail of Computational Study of the Effect of Governing Parameters on a Polymer Injection Molding Process for Single-Cavity and Multicavity Mold Systems

Computational Study of the Effect of Governing Parameters on a Polymer Injection Molding Process for Single-Cavity and Multicavity Mold Systems

Journal of Manufacturing Science and Engineering-transactions of The Asme, Dec 22, 2009

In the present study a more complete numerical solution approach using parallel computing technol... more In the present study a more complete numerical solution approach using parallel computing technology is provided for the three-dimensional modeling of mold insert polymer injection molding process by considering the effects of phase-change and compressibility for non-Newtonian fluid flow conditions. A volume of fluid (VOF) method coupled with a finite volume approach is used to simulate the mold-filling stage of the injection molding process. The variations in viscosity and density in the polymer melt flow are successfully resolved in the present VOF method to more accurately represent the rheological behavior of the polymer melt flow during the mold filling. A comprehensive high-resolution differencing scheme (compressive interface capturing scheme for arbitrary meshes or CICSAM) is successfully utilized to capture moving interfaces and the pressure-implicit with splitting operators pressure-velocity coupling algorithm is employed to enable a higher degree of approximate relation between corrections for pressure and velocity. The capabilities of the proposed numerical methodology in modeling real molding flow conditions are verified through quantitative and qualitative comparisons with other simulation programs and the data obtained from the experimental study conducted. The present numerical results are also compared with each other for a polypropylene female threaded adaptor pipe fitting model with a metallic insert for varying governing process conditions/parameters to assess the modeling constraints and enhancements of the present numerical procedure and the effects of these conditions to optimize the polymer melt flow for mold insert polymer injection molding process. The numerical results suggest that the present numerical solution approach can be used with a confidence for further studies of optimization of design of mold insert polymer injection molding processes.

Research paper thumbnail of Computational modelling of two-phase flow around a savonius type wave energy converter in a two- dimensional numerical wave tank

MARINE V : proceedings of the V International Conference on Computational Methods in Marine Engineering, 2013

In the present study, the main objective is to develop a finite volume method (FVM) based numeric... more In the present study, the main objective is to develop a finite volume method (FVM) based numerical modelling approach incorporated with a Volume of fluid (VOF) method to investigate the effect of wave on the performance of Savonius rotor in a twodimensional numerical wave tank (NWT). A Savonius rotor, whose rotational axis is normal to the direction of wave generation, is introduced to computationally investigate flow around the rotor structure at selected wave height conditions. The geometry of the blades is such that wave motion produces a positive force on the rotor and is constructed using CAD software. Followed by importing the orthogonal mesh domain constructed in FLOW-3D software environment, defined in Cartesian coordinates, into the finite volume environment of FLOW-3D for fluid flow analysis. A body-fixed reference system ("body system"), introduced for the rotor, and the space reference system ("space system") is employed to scrutinize a twodimensional unsteady turbulent flow around the rotor structure. At each time step equations of motion are solved for the rotor under coupled motion with consideration of hydraulic, gravitational and control forces. The flow simulations are then performed using Reynoldsaveraged Navier-Stokes (RANS) based two-equation RNG k- turbulence model with dynamically computed turbulent length scale, under the assumption of incompressible, viscous, and transient two-phase turbulent flow conditions. From the numerical results obtained and validated against the theoretical data obtained from the no-rotor flow condition, it can be concluded that the flow characteristics is strongly dependent upon differing wave propagation conditions and energy conversion rate can be increased with a proper combination of selected wave height and frequency for the investigated parametric value range. Flow visualization, which is represented by qualitative contours of velocity vector field also show different flow patterns at different wave height conditions.

Research paper thumbnail of Optimized CFD modelling and validation of radiation section of an industrial top-fired steam methane reforming furnace

Computers & Chemical Engineering, 2021

The present study proposes an optimized computational fluid dynamics (CFD) modelling framework to... more The present study proposes an optimized computational fluid dynamics (CFD) modelling framework to provide a complete and accurate representation of combustion and heat transfer phenomena in the radiation section of an industrial top-fired steam methane reforming (SMR) furnace containing 64 reforming tubes, 30 burners and 3 flue-gas tunnels. The framework combines fully-coupled appropriate furnace-side models with a 1-D reforming process-side model. Experimental measurements are conducted in terms of outlet temperatures at the flue-gas tunnels, point-wise temperature distributions at the panel walls, and inside the reforming tube collectors which are placed at the refinery plant of Petronor. The final results are compared with the experimental data for validation purpose. The proposed fully coupled 3-D CFD modeling framework, which utilizes a detailed chemical-kinetic combustion mechanism, reproduces well basic flow features including pre-mixed combustion process, downward movement of flue-gas in association with large recirculation zones, radiative heat transfer to the reforming tubes, composition profiles along the reaction core of the reforming tubes, temperature non-uniformities, and fluctuating characteristics of heat flux. The reported non-uniform heat and temperature distributions might be optimized by means of the operating parameters in order to avoid a negative impact on furnace balancing and performance.

Research paper thumbnail of Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

Wind and Structures, 2007

ABSTRACT

Research paper thumbnail of Computational modelling of inflow turbulence effects on transitional flow in a highly transonic linear turbine

Computational modelling of inflow turbulence effects on transitional flow in a highly transonic linear turbine

International Journal of Numerical Methods for Heat & Fluid Flow, 2012

PurposeThe purpose of this paper is to numerically study inflow turbulence effects on the transit... more PurposeThe purpose of this paper is to numerically study inflow turbulence effects on the transitional flow in a high pressure linear transonic turbine at the design incidence.Design/methodology/approachThe three‐dimensional (3‐D) compressible turbulent flow in a turbine inlet guide vane is simulated using a finite volume based fluid solver coupled with dynamic large eddy simulation (LES) computations to investigate the effects of varying inflow turbulence length scale and the turbulence intensity on the aero‐thermal flow characteristics and the laminar‐turbulent transition phenomena. The computational analyses are extended to very high exit Reynolds number flow conditions to further study the effect of high exit Reynolds numbers on the transitional behavior of the present flow around the inlet guide vane cascades of the turbine. The calculations are performed with varying degree of inflow turbulence intensity values ranging from 0.8 to 6 percent and the inflow turbulence length sca...

Research paper thumbnail of Numerical correlation for the pressure drop in Stirling engine heat exchangers

International Journal of Thermal Sciences, 2015

New correlation equations, to be valid for the pressure drop and heat exchange calculation under ... more New correlation equations, to be valid for the pressure drop and heat exchange calculation under the developing transitional reciprocating flow encountered in Stirling heat exchangers are numerically derived. Reynolds-Averaged NaviereStokes (RANS) equations based turbulence models are used to analyse laminar to turbulent reciprocating flow, focussing on the onset of turbulence and transitional reciprocating flow regime. The relative performance of four turbulence models in more accurately capturing the characteristics of the flow of interest is assessed in relation to overcoming the problems identified in previous numerical studies. The simulation results are compared with published and wellknown experimental data for reciprocating pipe flows, indicating that the effects of the turbulence anisotropy need to be taken into account in order to accurately predict the laminar to turbulent transition. The anisotropic Reynolds stress turbulence model is selected as a best choice among the tested turbulence models for analysis of this transitory phenomenon based on the comparative qualitative and quantitative results. This model is used to evaluate the heat transfer and pressure drop and propose new correlations considering the working and dimensional characteristics of Stirling heat exchangers: 100 Re u 600, A 0 600, b cri > 761 and 40 L/D 120. These correlation equations reduce the unsteady 2D behaviour in reciprocating pipe flow into a manageable form that can be incorporated into Stirling engine performance codes. It is believed that the validated numerical model can be used with confidence for studying the transitional reciprocating flow and the obtained correlations, can be applied as a cost effective solution for the development of Stirling engine heat exchangers.

Research paper thumbnail of Application of Differing Forcing Function Models on the Flow Past an Oscillating Cylinder in a Uniform Low Reynolds Number Flow

Application of Differing Forcing Function Models on the Flow Past an Oscillating Cylinder in a Uniform Low Reynolds Number Flow

Advances in Computational Heat Transfer. Proceedings of the International Symposium, 1997

A Computational Fluid Dynamics (CFD) model is presented for the uniform viscous two dimensional f... more A Computational Fluid Dynamics (CFD) model is presented for the uniform viscous two dimensional flow past an oscillating cylinder at low Reynolds number. Numerical simulations are made to study the effect of differing forced induced oscillation mechanisms with a large range of cylinder forcing frequencies. In the first case sinusoidal velocity slip boundary conditions are adopted for the cylinder surface to simulate cylinder oscillation. The implication suggests that no modification or additional term need to be added to the Navier-Stokes equations. In the second case this time extra body force terms which are assumed to account for velocity effects due to cylinder movement are included in the Navier~ Stokes equations with the imposition of same boundary conditions. Drag and lift coefficients are extracted from present numerical results and other detailed computations of these coefficients are made at a Reynolds number of 80 and an amplitude-to diameter ratio 0.14. The results are found to be in agreement with each other at low force driving frequencies below and near lock­ in. However, differences are found at higher frequencies above lock-in. Agreement are also found with experimental results at some frequency ranges.

Research paper thumbnail of Experimental and numerical flow investigation of Stirling engine regenerator

Energy, 2014

This paper presents both preliminary experimental and numerical studies of pressure drop and heat... more This paper presents both preliminary experimental and numerical studies of pressure drop and heat transfer characteristics of Stirling engine regenerators. A test bench is designed and manufactured for testing different regenerators under oscillating flow conditions, while three-dimensional (3-D) numerical simulations are performed to numerically characterize the pressure drop phenomena through a wound woven wire matrix regenerator under different porosity and flow boundary conditions. The test bench operating condition range is initially determined based on the performance of the commercial, well-known Stirling engine called WhisperGen™. This oscillating flow test bench is essentially a symmetrical design, which allows two regenerator samples to be tested simultaneously under the same inflow conditions. The oscillating flow is generated by means of a linear motor which moves a piston in an oscillatory motion. Both the frequency and the stroke of the piston are modified to achieve different test conditions. In the numerical study, use of a FVM (finite volume method) based CFD (computational fluid dynamics) approach for different configurations of small volume matrices leads to a derivation of a twocoefficient based friction factor correlation equation, which could be later implemented in an equivalent porous media with a confidence for future regenerator flow and heat transfer analysis.

Research paper thumbnail of The Computational Modeling of Transitional Flow through a Transonic Linear Turbine: Comparative Performance of Various Turbulence Models

The Computational Modeling of Transitional Flow through a Transonic Linear Turbine: Comparative Performance of Various Turbulence Models

Numerical Heat Transfer, Part A: Applications, 2010

Aero-thermal characteristics of transitional flow through a highly loaded transonic linear turbin... more Aero-thermal characteristics of transitional flow through a highly loaded transonic linear turbine are studied at the design incidence using computational methods. The three-dimensional compressible turbulent flow through a turbine inlet guide vane is simulated using finite-volume method-based fluid flow solutions using both Reynolds-averaged Navier Stokes (RANS) equations-based turbulence models, and a dynamic large eddy simulation (LES) approach which is based

Research paper thumbnail of A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

A numerical study of solidification and viscous dissipation effects on polymer melt flow in plane channels

Journal of Polymer Engineering, 2013

The combined effects of solidification and viscous dissipation on the hydrodynamic and thermal be... more The combined effects of solidification and viscous dissipation on the hydrodynamic and thermal behavior of polymer melt flow during the injection process in a straight plane channel of constant cross section are numerically studied by considering the shear-rate and temperature-dependent viscosity and transient-phase change behavior. A numerical finite volume method, in conjunction with a modified form of the Cross constitutive equation to account for shear rate, temperature-dependent viscosity changes and a slightly modified form of the method proposed by Voller and Prakash to account for solidification of the liquid phase, is used and a validation with an analytical solution is presented for viscous heating effects. The hydrodynamic and solidified layers growth under the influence of a transient phase-change process and viscous dissipation, are analyzed for a commercial polymer melt flow, polypropylene (PP) for different parametric conditions namely, inflow velocity, polymer inject...

Research paper thumbnail of Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

Energy Conversion and Management, 2014

ABSTRACT

Research paper thumbnail of Numerical study of the pressure drop phenomena in wound woven wire matrix of a Stirling regenerator

Energy Conversion and Management, 2013

Friction pressure drop correlation equations are derived from a numerical study by characterizing... more Friction pressure drop correlation equations are derived from a numerical study by characterizing the pressure drop phenomena through porous medium of both types namely stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. First, a finite volume method (FVM) based numerical approach is used and validated against well known experimentally obtained empirical correlations for a misaligned stacked woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The friction pressure drop correlation equation derived from the numerical results corresponds well with the experimentally obtained correlations with less than 5% deviation. Once the numerical approach is validated, the study is further extended to characterize the pressure drop phenomena in a wound woven wire matrix model of a Stirling engine regenerator for a diameter range from 0.080 to 0.110 mm and a porosity range from 0.472 to 0.638 within the same Reynolds number range. Thus, the new correlation equations are derived from this numerical study for different flow configurations of the Stirling engine regenerator. The results indicate flow nature and complex geometry dependent friction pressure drop characteristics within the present Stirling engine regenerator system. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and woven Stirling engine efficiency in the above specified ranges.

Research paper thumbnail of Computational Modeling of the Effects of Viscous Dissipation on Polymer Melt Flow Behavior During Injection Molding Process in Plane Channels

Journal of Manufacturing Science and Engineering, 2013

The present finite volume method based fluid flow solutions investigate the boundary-layer flow a... more The present finite volume method based fluid flow solutions investigate the boundary-layer flow and heat transfer characteristics of polymer melt flow in a rectangular plane channel in the presence of the effect of viscous dissipation and heat transfer by considering the viscosity and density variations in the flow. For different inflow velocity boundary conditions and the injection polymer melt temperatures, the viscous dissipation effects on the velocity and temperature distributions are studied extensively to analyze the degree of interactions of thermal flow field dominated by the viscous heating and momentum diffusion mechanism with varying boundary conditions. The modified forms of Cross constitutive equation and Tait equation of state are adopted for the representation of viscosity variations and density change, respectively, in the polymer melt flow. These models together with the viscous dissipation terms are successfully incorporated into the finite volume method based flu...