Dépouillements

Effect of J-groove on the suppression of swirl flow in a conical diffuser / Junichi Kurokawa in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Titre : Effect of J-groove on the suppression of swirl flow in a conical diffuser Type de document : texte imprimé Auteurs : Junichi Kurokawa, Auteur ; Hiroshi Imamura, Auteur ; Young-Do Choi, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  diffusers Résumé : The purpose of this study is to examine the validity of J-grooves in controlling and suppressing the swirl flow in a conical diffuser, for draft surge suppression in a Francis turbine, which is caused by the swirl flow from the runner outlet into the draft tube. “J-groove” composed of shallow grooves and mounted parallel to the pressure gradient on the diffuser wall is a very simple passive device to suppress several abnormal phenomena in turbomachinery. The experimental study has been performed using the conical diffuser with a divergent angle of 20 deg. The measured results of the velocity distribution in the diffuser show that a considerable reduction in the swirl intensity is attained by using J-grooves. Besides, the amplitude of pressure fluctuation caused by the rotation of the vortex core around the dead water region near the diffuser inlet is reduced by J-grooves. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Effect of J-groove on the suppression of swirl flow in a conical diffuser [texte imprimé] / Junichi Kurokawa, Auteur ; Hiroshi Imamura, Auteur ; Young-Do Choi, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Mots-clés : pressure;  flow  (dynamics);  diffusers Résumé : The purpose of this study is to examine the validity of J-grooves in controlling and suppressing the swirl flow in a conical diffuser, for draft surge suppression in a Francis turbine, which is caused by the swirl flow from the runner outlet into the draft tube. “J-groove” composed of shallow grooves and mounted parallel to the pressure gradient on the diffuser wall is a very simple passive device to suppress several abnormal phenomena in turbomachinery. The experimental study has been performed using the conical diffuser with a divergent angle of 20 deg. The measured results of the velocity distribution in the diffuser show that a considerable reduction in the swirl intensity is attained by using J-grooves. Besides, the amplitude of pressure fluctuation caused by the rotation of the vortex core around the dead water region near the diffuser inlet is reduced by J-grooves. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Rotordynamic moment on the backshroud of a francis turbine runner under whirling motion / Bingwei Song in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 09 p. Titre : Rotordynamic moment on the backshroud of a francis turbine runner under whirling motion Type de document : texte imprimé Auteurs : Bingwei Song, Auteur ; Hironori Horiguchi, Auteur ; Zhenyue Ma, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  pressure;  flow  (dynamics);  fluids;  motion;  clearances  (engineering);  rotors;  vibration;  disks;  whirls;  leakage  flows;  francis  turbines Résumé : This paper addresses the rotordynamic instability of an overhung rotor caused by a hydrodynamic moment due to whirling motion through the structural coupling between whirl and precession modes. First, the possibility of instability is discussed based on a vibration model in which the hydrodynamic forces and moments are assumed to be smaller than structural forces with the structural coupling being represented by a structural influence factor. Then, the fundamental characteristics of rotordynamic moment on the backshroud of a Francis turbine runner under whirling motion were studied using model tests and numerical calculations. The runner is modeled by a disk positioned close to a casing with a small radial clearance at the outer periphery. The moment is caused by an inward leakage flow that is produced by an external pump in the model test. The experiments were designed to measure the rotordynamic fluid force moments under various leakage flow rates with various preswirl velocities and various axial clearances between the backshroud and casing. The computation was carried out based on a bulk flow model. It was found that the fluid force moment is generally destabilizing, except for a small region of positive whirling speed ratios. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Rotordynamic moment on the backshroud of a francis turbine runner under whirling motion [texte imprimé] / Bingwei Song, Auteur ; Hironori Horiguchi, Auteur ; Zhenyue Ma, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 09 p. Mots-clés : force;  pressure;  flow  (dynamics);  fluids;  motion;  clearances  (engineering);  rotors;  vibration;  disks;  whirls;  leakage  flows;  francis  turbines Résumé : This paper addresses the rotordynamic instability of an overhung rotor caused by a hydrodynamic moment due to whirling motion through the structural coupling between whirl and precession modes. First, the possibility of instability is discussed based on a vibration model in which the hydrodynamic forces and moments are assumed to be smaller than structural forces with the structural coupling being represented by a structural influence factor. Then, the fundamental characteristics of rotordynamic moment on the backshroud of a Francis turbine runner under whirling motion were studied using model tests and numerical calculations. The runner is modeled by a disk positioned close to a casing with a small radial clearance at the outer periphery. The moment is caused by an inward leakage flow that is produced by an external pump in the model test. The experiments were designed to measure the rotordynamic fluid force moments under various leakage flow rates with various preswirl velocities and various axial clearances between the backshroud and casing. The computation was carried out based on a bulk flow model. It was found that the fluid force moment is generally destabilizing, except for a small region of positive whirling speed ratios. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

An experimental study of the flow around a formula one racing car tire / Emin Issakhanian in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Titre : An experimental study of the flow around a formula one racing car tire Type de document : texte imprimé Auteurs : Emin Issakhanian, Auteur ; Chris J. Elkins, Auteur ; Kin Pong Lo, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  wakes;  vortices;  tires;  wind  tunnels Résumé : The wake of the front tires affects the airflow over the remainder of a fenderless race car. The tires can also be responsible for up to 40% of the vehicle’s drag. Prior experiments have used compromised models with solid, symmetric hubs and nondeformable tires. The present experiment acquires particle image velocimetry measurements around a 60% scale model of a deformable pneumatic tire fitted to a spoked Formula 1 wheel with complete brake geometry and supplementary brake cooling ducts. The results show reversed flow regions in the tire wake, asymmetric longitudinal vortex structures behind the tire, and a tire wake profile that is unlike previous experimental results and postulations. The flow through the hub of the wheel causes a shift of the wake inboard (toward the car) so that the outboard side of the wake does not extend past the outline of the tire. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] An experimental study of the flow around a formula one racing car tire [texte imprimé] / Emin Issakhanian, Auteur ; Chris J. Elkins, Auteur ; Kin Pong Lo, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Mots-clés : flow  (dynamics);  wakes;  vortices;  tires;  wind  tunnels Résumé : The wake of the front tires affects the airflow over the remainder of a fenderless race car. The tires can also be responsible for up to 40% of the vehicle’s drag. Prior experiments have used compromised models with solid, symmetric hubs and nondeformable tires. The present experiment acquires particle image velocimetry measurements around a 60% scale model of a deformable pneumatic tire fitted to a spoked Formula 1 wheel with complete brake geometry and supplementary brake cooling ducts. The results show reversed flow regions in the tire wake, asymmetric longitudinal vortex structures behind the tire, and a tire wake profile that is unlike previous experimental results and postulations. The flow through the hub of the wheel causes a shift of the wake inboard (toward the car) so that the outboard side of the wake does not extend past the outline of the tire. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

PIV study of laminar wall jets of non-newtonian fluids / K. F. K. Adane in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Titre : PIV study of laminar wall jets of non-newtonian fluids Type de document : texte imprimé Auteurs : K. F. K. Adane, Auteur ; Tachie, M. F., Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  fluids;  Reynolds  number;  shear  (mechanics);  jets;  non-newtonian  fluids Résumé : Three-dimensional laminar wall jet flows of shear-thinning non-Newtonian fluids have been studied using a particle image velocimetry technique. The non-Newtonian fluids were prepared from xanthan gum solutions of various concentrations. The velocity measurements were performed in various streamwise-transverse and streamwise-spanwise planes at various inlet Reynolds numbers. From these measurements, the maximum velocity decay, jet half-widths, and velocity profiles were obtained to study the effects of Reynolds number and fluid type on the characteristics of the wall jet flows. It was observed that the maximum velocity decay and jet half-widths depend on inlet Reynolds number and fluid but the similarity velocities profiles are independent of both Reynolds number and specific fluid type. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] PIV study of laminar wall jets of non-newtonian fluids [texte imprimé] / K. F. K. Adane, Auteur ; Tachie, M. F., Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Mots-clés : flow  (dynamics);  fluids;  Reynolds  number;  shear  (mechanics);  jets;  non-newtonian  fluids Résumé : Three-dimensional laminar wall jet flows of shear-thinning non-Newtonian fluids have been studied using a particle image velocimetry technique. The non-Newtonian fluids were prepared from xanthan gum solutions of various concentrations. The velocity measurements were performed in various streamwise-transverse and streamwise-spanwise planes at various inlet Reynolds numbers. From these measurements, the maximum velocity decay, jet half-widths, and velocity profiles were obtained to study the effects of Reynolds number and fluid type on the characteristics of the wall jet flows. It was observed that the maximum velocity decay and jet half-widths depend on inlet Reynolds number and fluid but the similarity velocities profiles are independent of both Reynolds number and specific fluid type. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Low Reynolds number flow in spiral microchannels / Denis Lepchev in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Titre : Low Reynolds number flow in spiral microchannels Type de document : texte imprimé Auteurs : Denis Lepchev, Auteur ; Daniel Weihs, Auteur Année de publication : 2010 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  channels  (hydraulic  engineering);  equations;  microchannels Résumé : We study the creeping flow of an incompressible fluid in spiral microchannels such as that used in DNA identifying “lab-on-a-chip” installations. The equations of motion for incompressible, time-independent flow are developed in a three-dimensional orthogonal curvilinear spiral coordinate system where two of the dimensions are orthogonal spirals. The small size of the channels results in a low Reynolds number flow in the system, which reduces the Navier–Stokes set of equations to the Stokes equations for creeping flow. We obtain analytical solutions of the Stokes equations that calculate velocity profiles and pressure drop in several practical configurations of channels. Both pressure and velocity have exponential dependence on the expansion/contraction parameter and on the streamwise position along the channel. In both expanding and converging channels, the pressure drop is increased when the expansion/contraction parameter k and/or the curvature is increased. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Low Reynolds number flow in spiral microchannels [texte imprimé] / Denis Lepchev, Auteur ; Daniel Weihs, Auteur . - 2010 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Mots-clés : pressure;  flow  (dynamics);  channels  (hydraulic  engineering);  equations;  microchannels Résumé : We study the creeping flow of an incompressible fluid in spiral microchannels such as that used in DNA identifying “lab-on-a-chip” installations. The equations of motion for incompressible, time-independent flow are developed in a three-dimensional orthogonal curvilinear spiral coordinate system where two of the dimensions are orthogonal spirals. The small size of the channels results in a low Reynolds number flow in the system, which reduces the Navier–Stokes set of equations to the Stokes equations for creeping flow. We obtain analytical solutions of the Stokes equations that calculate velocity profiles and pressure drop in several practical configurations of channels. Both pressure and velocity have exponential dependence on the expansion/contraction parameter and on the streamwise position along the channel. In both expanding and converging channels, the pressure drop is increased when the expansion/contraction parameter k and/or the curvature is increased. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Numerical and experimental analysis of turbulent flow in corrugated pipes / Henrique Stel in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Titre : Numerical and experimental analysis of turbulent flow in corrugated pipes Type de document : texte imprimé Auteurs : Henrique Stel, Auteur ; Rigoberto E. M. Morales, Auteur ; Admilson T. Franco, Auteur Année de publication : 2010 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : momentum;  flow  (dynamics);  friction;  measurement;  turbulence;  Reynolds  number;  stress;  shear  (mechanics);  pipes;  cavities Résumé : This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Numerical and experimental analysis of turbulent flow in corrugated pipes [texte imprimé] / Henrique Stel, Auteur ; Rigoberto E. M. Morales, Auteur ; Admilson T. Franco, Auteur . - 2010 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Mots-clés : momentum;  flow  (dynamics);  friction;  measurement;  turbulence;  Reynolds  number;  stress;  shear  (mechanics);  pipes;  cavities Résumé : This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Influence of gas-liquid two-phase intermittent flow on hydraulic sand dune migration in horizontal pipelines / Afshin Goharzadeh in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 07 p. Titre : Influence of gas-liquid two-phase intermittent flow on hydraulic sand dune migration in horizontal pipelines Type de document : texte imprimé Auteurs : Afshin Goharzadeh, Auteur ; Peter Rodgers, Auteur ; Chokri Touati, Auteur Année de publication : 2010 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  sands;  particulate  matter;  pipelines;  pipes;  mixtures;  slug;  water Résumé : This paper presents an experimental study of three-phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of a gas-liquid two-phase intermittent flow. Sand dune pitch, length, height, and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for intermittent flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with intermittent flows. The sand dune local velocity (within the slug body) was measured to be three times higher than the averaged dune velocities, due to turbulent enhancement within the slug body. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Influence of gas-liquid two-phase intermittent flow on hydraulic sand dune migration in horizontal pipelines [texte imprimé] / Afshin Goharzadeh, Auteur ; Peter Rodgers, Auteur ; Chokri Touati, Auteur . - 2010 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 07 p. Mots-clés : flow  (dynamics);  sands;  particulate  matter;  pipelines;  pipes;  mixtures;  slug;  water Résumé : This paper presents an experimental study of three-phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of a gas-liquid two-phase intermittent flow. Sand dune pitch, length, height, and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for intermittent flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with intermittent flows. The sand dune local velocity (within the slug body) was measured to be three times higher than the averaged dune velocities, due to turbulent enhancement within the slug body. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Modeling the unsteady cavitating flow in a cross-flow water turbine / E. Sansone in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Titre : Modeling the unsteady cavitating flow in a cross-flow water turbine Type de document : texte imprimé Auteurs : E. Sansone, Auteur ; C. Pellone, Auteur ; T. Maitre, Auteur Année de publication : 2010 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  pressure;  flow  (dynamics);  vapors;  cavitation;  turbines;  blades;  equations;  hydraulic  turbines;  hydrofoil;  cross-flow Résumé : The noncavitating and cavitating flows over a cross-flow water turbine are simulated by using an unsteady Navier–Stokes formulation. For the cavitating flow case, a homogeneous mixture with a varying density is considered and one additional transport equation is explicitly solved in time for the liquid volume fraction. The instantaneous rate of vapor production and absorption appearing as a source term is governed by a hydrodynamic model based on a simplified bubble dynamic equation. The spatial discretization is achieved by a 2D multiblock technique consisting of fixed and rotating blocks, which were especially adapted for Darrieus geometry. Several test cases corresponding to experiments performed on fixed and rotating blades are selected to compare the numerical results with experimental data. Finally, a calculation of a monobladed cavitating cross-flow turbine is presented. The effect of cavitation on the dynamic stall phenomenon and on the turbine performance is analyzed. In particular, it is shown that cavitation earlier reveals the stall phenomenon on the blades and magnifies the size of the shedding vortex structures in the turbine. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Modeling the unsteady cavitating flow in a cross-flow water turbine [texte imprimé] / E. Sansone, Auteur ; C. Pellone, Auteur ; T. Maitre, Auteur . - 2010 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 13 p. Mots-clés : force;  pressure;  flow  (dynamics);  vapors;  cavitation;  turbines;  blades;  equations;  hydraulic  turbines;  hydrofoil;  cross-flow Résumé : The noncavitating and cavitating flows over a cross-flow water turbine are simulated by using an unsteady Navier–Stokes formulation. For the cavitating flow case, a homogeneous mixture with a varying density is considered and one additional transport equation is explicitly solved in time for the liquid volume fraction. The instantaneous rate of vapor production and absorption appearing as a source term is governed by a hydrodynamic model based on a simplified bubble dynamic equation. The spatial discretization is achieved by a 2D multiblock technique consisting of fixed and rotating blocks, which were especially adapted for Darrieus geometry. Several test cases corresponding to experiments performed on fixed and rotating blades are selected to compare the numerical results with experimental data. Finally, a calculation of a monobladed cavitating cross-flow turbine is presented. The effect of cavitation on the dynamic stall phenomenon and on the turbine performance is analyzed. In particular, it is shown that cavitation earlier reveals the stall phenomenon on the blades and magnifies the size of the shedding vortex structures in the turbine. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

CFD evaluation of solid particles erosion in curved ducts / Samy M. El-Behery in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 10 p. Titre : CFD evaluation of solid particles erosion in curved ducts Type de document : texte imprimé Auteurs : Samy M. El-Behery, Auteur ; Mofreh H. Hamed, Auteur ; K. A. Ibrahim, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  particulate  matter;  exterior  walls;  computational  fluid  dynamics;  erosion;  modeling;  ducts;  equations Résumé : This paper investigates numerically the erosion phenomenon that occurs in 90 deg and 180 deg curved ducts. The erosion prediction model comprises from three stages: flow modeling, particle tracking, and erosion calculations. The proposed three stages of the present model are tested and validated. Comparisons between predicted penetration rate and published experimental data show a good agreement. The effects of bend orientation, inlet gas velocity, bend dimensions, loading ratio, and particle size on the penetration rate are also simulated. In addition, based on many predictions of erosion rate results, new CFD based correlations are developed for the maximum penetration rate and its location. These correlations can be used to predict the bend lifetime for particular operating conditions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] CFD evaluation of solid particles erosion in curved ducts [texte imprimé] / Samy M. El-Behery, Auteur ; Mofreh H. Hamed, Auteur ; K. A. Ibrahim, Auteur . - 2010 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 10 p. Mots-clés : flow  (dynamics);  particulate  matter;  exterior  walls;  computational  fluid  dynamics;  erosion;  modeling;  ducts;  equations Résumé : This paper investigates numerically the erosion phenomenon that occurs in 90 deg and 180 deg curved ducts. The erosion prediction model comprises from three stages: flow modeling, particle tracking, and erosion calculations. The proposed three stages of the present model are tested and validated. Comparisons between predicted penetration rate and published experimental data show a good agreement. The effects of bend orientation, inlet gas velocity, bend dimensions, loading ratio, and particle size on the penetration rate are also simulated. In addition, based on many predictions of erosion rate results, new CFD based correlations are developed for the maximum penetration rate and its location. These correlations can be used to predict the bend lifetime for particular operating conditions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Pressure loss in a horizontal two-phase slug flow / A. R. Kabiri-Samani in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Titre : Pressure loss in a horizontal two-phase slug flow Type de document : texte imprimé Auteurs : A. R. Kabiri-Samani, Auteur ; S. M. Borghei, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  pipes;  two-phase  flow;  slug;  water Résumé : The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure loss in a pipeline or tunnel involving resonance and shock waves introduced by a two-phase air-water slug flow. For this purpose, differential pressure transducers were used to measure pressure loss variations in time along the pipeline at different sections and for different air/water flow rates. The experimental results of pressure loss for different hydraulic and geometric properties indicate that Weber number (We), Froude number (Fr), and air concentration (C) are the most important parameters affecting pressure loss. Finally, relations for forecasting pressure loss in these situations are presented as a function of flow characteristics. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Pressure loss in a horizontal two-phase slug flow [texte imprimé] / A. R. Kabiri-Samani, Auteur ; S. M. Borghei, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 08 p. Mots-clés : pressure;  flow  (dynamics);  pipes;  two-phase  flow;  slug;  water Résumé : The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure loss in a pipeline or tunnel involving resonance and shock waves introduced by a two-phase air-water slug flow. For this purpose, differential pressure transducers were used to measure pressure loss variations in time along the pipeline at different sections and for different air/water flow rates. The experimental results of pressure loss for different hydraulic and geometric properties indicate that Weber number (We), Froude number (Fr), and air concentration (C) are the most important parameters affecting pressure loss. Finally, relations for forecasting pressure loss in these situations are presented as a function of flow characteristics. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Study of unguided flow in a chamber / A. Abdel-Fattah in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 07 p. Titre : Study of unguided flow in a chamber Type de document : texte imprimé Auteurs : A. Abdel-Fattah, Auteur Année de publication : 2010 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  heat  transfer;  Reynolds  number Résumé : In the present, a steady laminar of two dimensional and incompressible fluid flow induces from wall injection in a circular chamber has been studied experimentally and numerically. The water is injected from injection system into the chamber through the wall jets. The centerline static pressure variation with the distance along the chamber length is measured and calculated at different Reynolds numbers and inlet flow angles. The average heat transfer with Reynolds number at different values of the inlet flow angle is obtained. The velocity vectors are presented and Reynolds number is varied between 433 and 910 with inlet flow angle of 0 deg, 15 deg, 30 deg, 45 deg, and 60 deg. The results indicate that the pressure recovery coefficient decreases as both Reynolds number and flow angle increase. The average heat transfer coefficient increases with increasing both Reynolds number and flow angle. The results showed that two recirculation zones occur in the sides of centerline of the chamber behind the step. The size of these recirculation zones decreases by increasing the inlet flow angle. At high value of the inlet flow angle, other recirculation zone occurs on the wall chamber. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Study of unguided flow in a chamber [texte imprimé] / A. Abdel-Fattah, Auteur . - 2010 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 07 p. Mots-clés : pressure;  flow  (dynamics);  heat  transfer;  Reynolds  number Résumé : In the present, a steady laminar of two dimensional and incompressible fluid flow induces from wall injection in a circular chamber has been studied experimentally and numerically. The water is injected from injection system into the chamber through the wall jets. The centerline static pressure variation with the distance along the chamber length is measured and calculated at different Reynolds numbers and inlet flow angles. The average heat transfer with Reynolds number at different values of the inlet flow angle is obtained. The velocity vectors are presented and Reynolds number is varied between 433 and 910 with inlet flow angle of 0 deg, 15 deg, 30 deg, 45 deg, and 60 deg. The results indicate that the pressure recovery coefficient decreases as both Reynolds number and flow angle increase. The average heat transfer coefficient increases with increasing both Reynolds number and flow angle. The results showed that two recirculation zones occur in the sides of centerline of the chamber behind the step. The size of these recirculation zones decreases by increasing the inlet flow angle. At high value of the inlet flow angle, other recirculation zone occurs on the wall chamber. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

The analysis of cavitation problems in the axial piston pump / Wang, Shu in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 06 p. Titre : The analysis of cavitation problems in the axial piston pump Type de document : texte imprimé Auteurs : Wang, Shu, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  cavitation;  pumps;  valves;  pistons Résumé : This paper discusses and analyzes the control volume of a piston bore constrained by the valve plate in axial piston pumps. The vacuum within the piston bore caused by the rise volume needs to be compensated by the flow; otherwise, the low pressure may cause the cavitations and aerations. In the research, the valve plate geometry can be optimized by some analytical limitations to prevent the piston pressure below the vapor pressure. The limitations provide the design guide of the timings and overlap areas between valve plate ports and barrel kidneys to consider the cavitations and aerations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] The analysis of cavitation problems in the axial piston pump [texte imprimé] / Wang, Shu, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 06 p. Mots-clés : pressure;  flow  (dynamics);  cavitation;  pumps;  valves;  pistons Résumé : This paper discusses and analyzes the control volume of a piston bore constrained by the valve plate in axial piston pumps. The vacuum within the piston bore caused by the rise volume needs to be compensated by the flow; otherwise, the low pressure may cause the cavitations and aerations. In the research, the valve plate geometry can be optimized by some analytical limitations to prevent the piston pressure below the vapor pressure. The limitations provide the design guide of the timings and overlap areas between valve plate ports and barrel kidneys to consider the cavitations and aerations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

Effect of second order velocity-slip/temperature-jump on basic gaseous fluctuating micro flows / M. A. Hamdan in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 06 p. Titre : Effect of second order velocity-slip/temperature-jump on basic gaseous fluctuating micro flows Type de document : texte imprimé Auteurs : M. A. Hamdan, Auteur ; M. A. Al-Nimr, Auteur ; Vladimir A. Hammoudeh, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  flow  (dynamics);  temperature;  natural  convection;  boundary-value  problems;  frequency;  pressure  gradient Résumé : In this work, the effect of the second-order term to the velocity-slip/temperature-jump boundary conditions on the solution of four cases in which the driving force is fluctuating harmonically was studied. The study aims to establish criteria that secure the use of the first order velocity-slip/temperature-jump model boundary conditions instead of the second-order ones. The four cases studied were the transient Couette flow, the pulsating Poiseuille flow, Stoke’s second problem, and the transient natural convection flow. It was found that at any given Kn number, increasing the driving force frequency, increases the difference between the first and second-order models. Assuming that a difference between the two models of over 5% is significant enough to justify the use of the more complex second-order model, the critical frequencies for the four different cases were found. For the cases for which the flow is induced by the fluctuating wall as in cases 1 and 3, we found that critical frequency at Kn=0.1 to be ω=8. For the cases of flow driven by a fluctuating pressure gradient as in case 2, this frequency was found to be ω=1, at the same Kn number. In case 4, for the temperature-jump model, the critical frequency was found to be ω=7 and for the velocity-slip model the critical frequency at the same Kn number was found to be ω=1.35. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...] [article] Effect of second order velocity-slip/temperature-jump on basic gaseous fluctuating micro flows [texte imprimé] / M. A. Hamdan, Auteur ; M. A. Al-Nimr, Auteur ; Vladimir A. Hammoudeh, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 7 (Juillet 2010) . - 06 p. Mots-clés : force;  flow  (dynamics);  temperature;  natural  convection;  boundary-value  problems;  frequency;  pressure  gradient Résumé : In this work, the effect of the second-order term to the velocity-slip/temperature-jump boundary conditions on the solution of four cases in which the driving force is fluctuating harmonically was studied. The study aims to establish criteria that secure the use of the first order velocity-slip/temperature-jump model boundary conditions instead of the second-order ones. The four cases studied were the transient Couette flow, the pulsating Poiseuille flow, Stoke’s second problem, and the transient natural convection flow. It was found that at any given Kn number, increasing the driving force frequency, increases the difference between the first and second-order models. Assuming that a difference between the two models of over 5% is significant enough to justify the use of the more complex second-order model, the critical frequencies for the four different cases were found. For the cases for which the flow is induced by the fluctuating wall as in cases 1 and 3, we found that critical frequency at Kn=0.1 to be ω=8. For the cases of flow driven by a fluctuating pressure gradient as in case 2, this frequency was found to be ω=1, at the same Kn number. In case 4, for the temperature-jump model, the critical frequency was found to be ω=7 and for the velocity-slip model the critical frequency at the same Kn number was found to be ω=1.35. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27423 [...]

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