The Experts below are selected from a list of 96138 Experts worldwide ranked by ideXlab platform
Teemu Turunensaaresti - One of the best experts on this subject based on the ideXlab platform.
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influence of Turbulence Modelling to condensing steam flow in the 3d low pressure steam turbine stage
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2016Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:With the tremendous role played by steam turbines in power generation cycle, it is essential to understand the flow field of condensing steam flow in a steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The Turbulence has a leading role in condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of Turbulence Modelling on non-equilibrium condensing steam flows in a LP steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation Turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of Turbulence Modelling on the wet-steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.© 2016 ASME
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influence of Turbulence Modelling on non equilibrium condensing flows in nozzle and turbine cascade
International Journal of Heat and Mass Transfer, 2015Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:Abstract The accurate analysis of a condensing flow plays an important role in the development of high-efficiency steam turbines. This paper presents an investigation of Turbulence Modelling influence on non-equilibrium condensing steam flows in a Laval nozzle and in a stationary cascade of turbine blades using a commercial computational fluid dynamics (CFD) code. The calculations were conducted by employing 2D compressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with a two equation Turbulence model. The condensation phenomena were modelled on the basis of the classical nucleation theory. The standard k – e Turbulence model was modified, and the modifications were implemented in the CFD code. The influence of inlet flow Turbulence on condensing process was discussed. The impact of Turbulence Modelling on wet-steam flow was examined based on the experimental data available in the literature. The cascade loss coefficients were calculated numerically as well. The presented study of losses that occur due to the irreversible heat and mass transfer during the condensation process emphasised the importance of Turbulence Modelling for wet-steam flows in turbines. The paper demonstrates that the accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.
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numerical investigation of Turbulence Modelling on condensing steam flows in turbine cascade
Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu Turunensaaresti, Aki GronmaAbstract:Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the Turbulence Modelling on the non-equilibrium homogeneous condensing steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various Turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-e, the RNG k-e, the Realizable k-e, and the SST k-ω) in condensing steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of Turbulence modeling in wet-steam flows.Copyright © 2014 by ASME
Yogini Patel - One of the best experts on this subject based on the ideXlab platform.
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influence of Turbulence Modelling to condensing steam flow in the 3d low pressure steam turbine stage
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2016Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:With the tremendous role played by steam turbines in power generation cycle, it is essential to understand the flow field of condensing steam flow in a steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The Turbulence has a leading role in condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of Turbulence Modelling on non-equilibrium condensing steam flows in a LP steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation Turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of Turbulence Modelling on the wet-steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.© 2016 ASME
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influence of Turbulence Modelling on non equilibrium condensing flows in nozzle and turbine cascade
International Journal of Heat and Mass Transfer, 2015Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:Abstract The accurate analysis of a condensing flow plays an important role in the development of high-efficiency steam turbines. This paper presents an investigation of Turbulence Modelling influence on non-equilibrium condensing steam flows in a Laval nozzle and in a stationary cascade of turbine blades using a commercial computational fluid dynamics (CFD) code. The calculations were conducted by employing 2D compressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with a two equation Turbulence model. The condensation phenomena were modelled on the basis of the classical nucleation theory. The standard k – e Turbulence model was modified, and the modifications were implemented in the CFD code. The influence of inlet flow Turbulence on condensing process was discussed. The impact of Turbulence Modelling on wet-steam flow was examined based on the experimental data available in the literature. The cascade loss coefficients were calculated numerically as well. The presented study of losses that occur due to the irreversible heat and mass transfer during the condensation process emphasised the importance of Turbulence Modelling for wet-steam flows in turbines. The paper demonstrates that the accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.
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numerical investigation of Turbulence Modelling on condensing steam flows in turbine cascade
Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu Turunensaaresti, Aki GronmaAbstract:Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the Turbulence Modelling on the non-equilibrium homogeneous condensing steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various Turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-e, the RNG k-e, the Realizable k-e, and the SST k-ω) in condensing steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of Turbulence modeling in wet-steam flows.Copyright © 2014 by ASME
Jan Carmeliet - One of the best experts on this subject based on the ideXlab platform.
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computational fluid dynamics analysis of cyclist aerodynamics performance of different Turbulence Modelling and boundary layer Modelling approaches
Journal of Biomechanics, 2010Co-Authors: Twj Thijs Defraeye, Bje Bert Blocken, Erwin Koninckx, Peter Hespel, Jan CarmelietAbstract:Abstract This study aims at assessing the accuracy of computational fluid dynamics (CFD) for applications in sports aerodynamics, for example for drag predictions of swimmers, cyclists or skiers, by evaluating the applied numerical Modelling techniques by means of detailed validation experiments. In this study, a wind-tunnel experiment on a scale model of a cyclist (scale 1:2) is presented. Apart from three-component forces and moments, also high-resolution surface pressure measurements on the scale model’s surface, i.e. at 115 locations, are performed to provide detailed information on the flow field. These data are used to compare the performance of different Turbulence-Modelling techniques, such as steady Reynolds-averaged Navier–Stokes (RANS), with several k–e and k–ω Turbulence models, and unsteady large-eddy simulation (LES), and also boundary-layer Modelling techniques, namely wall functions and low-Reynolds number Modelling (LRNM). The commercial CFD code Fluent 6.3 is used for the simulations. The RANS shear-stress transport (SST) k–ω model shows the best overall performance, followed by the more computationally expensive LES. Furthermore, LRNM is clearly preferred over wall functions to model the boundary layer. This study showed that there are more accurate alternatives for evaluating flow around bluff bodies with CFD than the standard k–e model combined with wall functions, which is often used in CFD studies in sports.
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computational fluid dynamics analysis of cyclist aerodynamics performance of different Turbulence Modelling and boundary layer Modelling approaches
Journal of Biomechanics, 2010Co-Authors: Twj Thijs Defraeye, Bje Bert Blocken, Erwin Koninckx, Peter Hespel, Jan CarmelietAbstract:Abstract This study aims at assessing the accuracy of computational fluid dynamics (CFD) for applications in sports aerodynamics, for example for drag predictions of swimmers, cyclists or skiers, by evaluating the applied numerical Modelling techniques by means of detailed validation experiments. In this study, a wind-tunnel experiment on a scale model of a cyclist (scale 1:2) is presented. Apart from three-component forces and moments, also high-resolution surface pressure measurements on the scale model’s surface, i.e. at 115 locations, are performed to provide detailed information on the flow field. These data are used to compare the performance of different Turbulence-Modelling techniques, such as steady Reynolds-averaged Navier–Stokes (RANS), with several k–e and k–ω Turbulence models, and unsteady large-eddy simulation (LES), and also boundary-layer Modelling techniques, namely wall functions and low-Reynolds number Modelling (LRNM). The commercial CFD code Fluent 6.3 is used for the simulations. The RANS shear-stress transport (SST) k–ω model shows the best overall performance, followed by the more computationally expensive LES. Furthermore, LRNM is clearly preferred over wall functions to model the boundary layer. This study showed that there are more accurate alternatives for evaluating flow around bluff bodies with CFD than the standard k–e model combined with wall functions, which is often used in CFD studies in sports.
Giteshkuma Patel - One of the best experts on this subject based on the ideXlab platform.
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influence of Turbulence Modelling to condensing steam flow in the 3d low pressure steam turbine stage
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2016Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:With the tremendous role played by steam turbines in power generation cycle, it is essential to understand the flow field of condensing steam flow in a steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The Turbulence has a leading role in condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of Turbulence Modelling on non-equilibrium condensing steam flows in a LP steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation Turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of Turbulence Modelling on the wet-steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.© 2016 ASME
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influence of Turbulence Modelling on non equilibrium condensing flows in nozzle and turbine cascade
International Journal of Heat and Mass Transfer, 2015Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:Abstract The accurate analysis of a condensing flow plays an important role in the development of high-efficiency steam turbines. This paper presents an investigation of Turbulence Modelling influence on non-equilibrium condensing steam flows in a Laval nozzle and in a stationary cascade of turbine blades using a commercial computational fluid dynamics (CFD) code. The calculations were conducted by employing 2D compressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with a two equation Turbulence model. The condensation phenomena were modelled on the basis of the classical nucleation theory. The standard k – e Turbulence model was modified, and the modifications were implemented in the CFD code. The influence of inlet flow Turbulence on condensing process was discussed. The impact of Turbulence Modelling on wet-steam flow was examined based on the experimental data available in the literature. The cascade loss coefficients were calculated numerically as well. The presented study of losses that occur due to the irreversible heat and mass transfer during the condensation process emphasised the importance of Turbulence Modelling for wet-steam flows in turbines. The paper demonstrates that the accurate computational prediction of condensing steam flow requires the Turbulence to be modelled accurately.
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numerical investigation of Turbulence Modelling on condensing steam flows in turbine cascade
Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu Turunensaaresti, Aki GronmaAbstract:Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the Turbulence Modelling on the non-equilibrium homogeneous condensing steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various Turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-e, the RNG k-e, the Realizable k-e, and the SST k-ω) in condensing steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of Turbulence modeling in wet-steam flows.Copyright © 2014 by ASME
M Braza - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of the turbulent transonic interaction and transition location effect involving optimisation around a supercritical airfoil
European Journal of Mechanics - B Fluids, 2016Co-Authors: Damien Szubert, Yannick Hoarau, Ioannis Asproulias, Fernando Grossi, Régis Duvigneau, M BrazaAbstract:The present article analyses the turbulent flow around a supercritical airfoil at high Reynolds number and in the transonic regime, involving shock-wave/boundary-layer interaction (SWBLI) and buffet, by means of numerical simulation and Turbulence Modelling. Emphasis is put on the transition position influence on the SWBLI and optimisation of this position in order to provide a maximum lift/drag ratio. A non-classical optimisation approach based on Kriging method, coupled with the URANS Modelling, has been applied on steady and unsteady flow regimes. Therefore, the present study contributes to the so-called 'laminar-wing design' with the aim of reducing the drag coefficient by providing an optimum laminar region upstream of the SWBLI.
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Prediction of Transonic Buffet around a Wing with Flap
Progress in Hybrid RANS-LES Modelling, 2010Co-Authors: G. Barbut, George N. Barakos, M Braza, Yannick Hoarau, A. Sevrain, Jan B. VosAbstract:The present study presents numerical simulations and Turbulence Modelling of the flow around a NACA0012 airfoil including a deflected aileron. The results are compared with experiments that have been performed in the N-3 wind tunnel of the Institute of Aviation (IoA), Warsaw. The experiment focused on unsteady flow characteristics and buffet phenomena arising as the result of the transonic shock wave / boundary layer interaction (SWBLI). The transonic buffet is a natural and self-sustaining oscillation of the shock wave and separated flow region, caused by pressure fluctuation. The first objective is to capture the transonic buffet unsteadiness by means of URANS and DES Turbulence Modelling approaches. Secondly, the periodic flap oscillation has been used to modify the oscillation amplitudes towards an outlook of attenuation of the transonic buffet.
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Turbulence Modelling of the flow past a pitching naca0012 airfoil at 105 and 106 reynolds numbers
Journal of Fluids and Structures, 2008Co-Authors: G. Martinat, M Braza, Yannick Hoarau, G. HarranAbstract:Abstract This paper provides a study of the NACA0012 dynamic stall at Reynolds numbers 10 5 and 10 6 by means of two- and three-dimensional numerical simulations. The Turbulence effect on the dynamic stall is studied by statistical Modelling. The results are compared with experiments concerning each test case. Standard URANS Turbulence Modelling have shown a quite dissipative character that attenuates the instabilities and the vortex structures related to the dynamic stall. The URANS approach Organised Eddy Simulation (OES) has shown an improved behaviour at the high Reynolds number range. Emphasis is given to the physical analysis of the three-dimensional dynamic stall structure, for which there exist few numerical results in the literature, as far as the Reynolds number range is concerned. This study has shown that the downstroke phases of the pitching motion are subjected to strong three-dimensional Turbulence effects along the span, whereas the flow is practically two-dimensional during the upstroke motion.
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Turbulence Modelling of the flow past a pitching NACA0012airfoil at 10^5 and 10^6 Reynolds numbers
Journal of Fluids and Structures, 2008Co-Authors: G. Martinat, M Braza, Yannick Hoarau, G. HarranAbstract:This paper provides a study of the NACA0012 dynamic stall at Reynolds numbers 10 5 and 10 6 by means of two and three dimensional numerical simulation. The Turbulence effect on the dynamic stall is studied by statistical Turbulence Modelling. The results are compared with experiments concerning each test case. Standard URANS Turbulence Modelling have shown a quite dissipative character that attenuates the instabilities and the vortex structures related to the dynamic stall. The URANS approach OES, Organised Eddy Simulation, has shown an improved behaviour at the high Reynolds number range. Emphasis is given to the physical analysis of the three dimensional dynamic stall structure, for which there exist few numerical results in the literature, as far as the Reynolds number range is concerned. This study has shown that the downstroke phases of the pitching motion are subjected to strong three-dimensional Turbulence effects along the span, whereas the flow is practically two-dimensional during the upstroke motion.
