Dépouillements

Discrete particle study of turbulence coupling in a confined jet gas-liquid separator / Wayne Strasser in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 11 p. Titre : Discrete particle study of turbulence coupling in a confined jet gas-liquid separator Type de document : texte imprimé Auteurs : Wayne Strasser, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Particulate  matter;  turbulence;  vessels;  flow  (dynamics);  anisotropy Résumé : A 3D computational fluid dynamics investigation of particle-induced flow effects and liquid entrainment from an industrial-scale separator has been carried out using the Eulerian–Lagrangian two-way coupled multiphase approach. A differential Reynolds stress model was used to predict the gas phase turbulence field. The dispersed (liquid) phase was present at an intermediate mass loading (0.25) but low volume fraction (0.05). A discrete random walk method was used to track the paths of the liquid droplet releases. It was found that gas phase deformation and turbulence fields were significantly impacted by the presence of the liquid phase; these effects have been parametrically quantified. Substantial enhancement of both the turbulence and the anisotropy of the continuous phase by the liquid phase was demonstrated. It was also found that a large number (⩾1000) of independent liquid droplet release events were needed to make conclusions about liquid entrainment. Known plant run conditions and entrainment rates validated the numerical method. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Discrete particle study of turbulence coupling in a confined jet gas-liquid separator [texte imprimé] / Wayne Strasser, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 11 p. Mots-clés : Particulate  matter;  turbulence;  vessels;  flow  (dynamics);  anisotropy Résumé : A 3D computational fluid dynamics investigation of particle-induced flow effects and liquid entrainment from an industrial-scale separator has been carried out using the Eulerian–Lagrangian two-way coupled multiphase approach. A differential Reynolds stress model was used to predict the gas phase turbulence field. The dispersed (liquid) phase was present at an intermediate mass loading (0.25) but low volume fraction (0.05). A discrete random walk method was used to track the paths of the liquid droplet releases. It was found that gas phase deformation and turbulence fields were significantly impacted by the presence of the liquid phase; these effects have been parametrically quantified. Substantial enhancement of both the turbulence and the anisotropy of the continuous phase by the liquid phase was demonstrated. It was also found that a large number (⩾1000) of independent liquid droplet release events were needed to make conclusions about liquid entrainment. Known plant run conditions and entrainment rates validated the numerical method. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Three-dimensional modeling and geometrical influence on the hydraulic performance of a control valve / Guillermo Palau-Salvador in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Titre : Three-dimensional modeling and geometrical influence on the hydraulic performance of a control valve Type de document : texte imprimé Auteurs : Guillermo Palau-Salvador, Auteur ; Pablo González-Altozano, Auteur ; Jaime Arviza-Valverde, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure;  flow  (dynamics);  cavitation;  valves;  geometry;  pistons;  computational  fluid  dynamics Résumé : The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier–Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase Cv and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower Cv with higher velocity magnitude within the valve, whereas after smoothing Cv increased and served to delay cavitation inception. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Three-dimensional modeling and geometrical influence on the hydraulic performance of a control valve [texte imprimé] / Guillermo Palau-Salvador, Auteur ; Pablo González-Altozano, Auteur ; Jaime Arviza-Valverde, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Mots-clés : Pressure;  flow  (dynamics);  cavitation;  valves;  geometry;  pistons;  computational  fluid  dynamics Résumé : The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier–Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase Cv and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower Cv with higher velocity magnitude within the valve, whereas after smoothing Cv increased and served to delay cavitation inception. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Experimental investigation of the submarine crashback maneuver / David H. Bridges in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 11 p. Titre : Experimental investigation of the submarine crashback maneuver Type de document : texte imprimé Auteurs : David H. Bridges, Auteur ; Martin J. Donnelly, Auteur ; Joel T. Park, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Force;  propellers;  tunnels;  underwater  vehicles;  flow  (dynamics);  vortices;  veasurement;  Laser  Doppler  anemometry;  light  trucks;  rotation Résumé : In order to decelerate a forward-moving submarine rapidly, often the propeller of the submarine is placed abruptly into reverse rotation, causing the propeller to generate a thrust force in the direction opposite to the submarine’s motion. This maneuver is known as the “crashback” maneuver. During crashback, the relative flow velocities in the vicinity of the propeller lead to the creation of a ring vortex around the propeller. This vortex has an unsteady asymmetry, which produces off-axis forces and moments on the propeller that are transmitted to the submarine. Tests were conducted in the William B. Morgan Large Cavitation Channel using an existing submarine model and propeller. A range of steady crashback conditions with fixed tunnel and propeller speeds was investigated. The dimensionless force and moment data were found to collapse well when plotted against the parameter η, which is defined as the ratio of the actual propeller speed to the propeller speed required for self-propulsion in forward motion. Unsteady crashback maneuvers were also investigated with two different types of simulations in which propeller and tunnel speeds were allowed to vary. It was noted during these simulations that the peak out-of-plane force and moment coefficient magnitudes in some cases exceeded those observed during the steady crashback measurements. Flow visualization and LDV studies showed that the ring vortex structure varied from an elongated vortex structure centered downstream of the propeller to a more compact structure that was located nearer the propeller as η became more negative, up to η=−0.8. For more negative values of η, the vortex core appeared to move out toward the propeller tip. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Experimental investigation of the submarine crashback maneuver [texte imprimé] / David H. Bridges, Auteur ; Martin J. Donnelly, Auteur ; Joel T. Park, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 11 p. Mots-clés : Force;  propellers;  tunnels;  underwater  vehicles;  flow  (dynamics);  vortices;  veasurement;  Laser  Doppler  anemometry;  light  trucks;  rotation Résumé : In order to decelerate a forward-moving submarine rapidly, often the propeller of the submarine is placed abruptly into reverse rotation, causing the propeller to generate a thrust force in the direction opposite to the submarine’s motion. This maneuver is known as the “crashback” maneuver. During crashback, the relative flow velocities in the vicinity of the propeller lead to the creation of a ring vortex around the propeller. This vortex has an unsteady asymmetry, which produces off-axis forces and moments on the propeller that are transmitted to the submarine. Tests were conducted in the William B. Morgan Large Cavitation Channel using an existing submarine model and propeller. A range of steady crashback conditions with fixed tunnel and propeller speeds was investigated. The dimensionless force and moment data were found to collapse well when plotted against the parameter η, which is defined as the ratio of the actual propeller speed to the propeller speed required for self-propulsion in forward motion. Unsteady crashback maneuvers were also investigated with two different types of simulations in which propeller and tunnel speeds were allowed to vary. It was noted during these simulations that the peak out-of-plane force and moment coefficient magnitudes in some cases exceeded those observed during the steady crashback measurements. Flow visualization and LDV studies showed that the ring vortex structure varied from an elongated vortex structure centered downstream of the propeller to a more compact structure that was located nearer the propeller as η became more negative, up to η=−0.8. For more negative values of η, the vortex core appeared to move out toward the propeller tip. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Analysis of turbulent mixing jets in a large scale tank / Si Y. Lee in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 13 p. Titre : Analysis of turbulent mixing jets in a large scale tank Type de document : texte imprimé Auteurs : Si Y. Lee, Auteur ; Richard A. Dimenna, Auteur ; Robert A. Leishear, Auteur Année de publication : 2009 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  nozzles;  pumps;  turbulence;  fluids;  jets Résumé : Flow evolution models were developed to evaluate the performance of the new advanced design mixer pump for sludge mixing and removal operations with high-velocity liquid jets in one of the large-scale Savannah River Site waste tanks, Tank 18. This paper describes the computational model, the flow measurements used to provide validation data in the region far from the jet nozzle, and the extension of the computational results to real tank conditions through the use of existing sludge suspension data. A computational fluid dynamics approach was used to simulate the sludge removal operations. The models employed a three-dimensional representation of the tank with a two-equation turbulence model. Both the computational approach and the models were validated with onsite test data reported here and literature data. The model was then extended to actual conditions in Tank 18 through a velocity criterion to predict the ability of the new pump design to suspend settled sludge. A qualitative comparison with sludge removal operations in Tank 18 showed a reasonably good comparison with final results subject to significant uncertainties in actual sludge properties. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of turbulent mixing jets in a large scale tank [texte imprimé] / Si Y. Lee, Auteur ; Richard A. Dimenna, Auteur ; Robert A. Leishear, Auteur . - 2009 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 13 p. Mots-clés : Flow  (dynamics);  nozzles;  pumps;  turbulence;  fluids;  jets Résumé : Flow evolution models were developed to evaluate the performance of the new advanced design mixer pump for sludge mixing and removal operations with high-velocity liquid jets in one of the large-scale Savannah River Site waste tanks, Tank 18. This paper describes the computational model, the flow measurements used to provide validation data in the region far from the jet nozzle, and the extension of the computational results to real tank conditions through the use of existing sludge suspension data. A computational fluid dynamics approach was used to simulate the sludge removal operations. The models employed a three-dimensional representation of the tank with a two-equation turbulence model. Both the computational approach and the models were validated with onsite test data reported here and literature data. The model was then extended to actual conditions in Tank 18 through a velocity criterion to predict the ability of the new pump design to suspend settled sludge. A qualitative comparison with sludge removal operations in Tank 18 showed a reasonably good comparison with final results subject to significant uncertainties in actual sludge properties. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

A grid-free Lagrangian approach of vortex method and particle trajectory tracking method applied to internal fluid-solid two-phase flows / Yoshiyuki Iso in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 10 p. Titre : A grid-free Lagrangian approach of vortex method and particle trajectory tracking method applied to internal fluid-solid two-phase flows Type de document : texte imprimé Auteurs : Yoshiyuki Iso, Auteur ; Kyoji Kamemoto, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  particulate  matter;  two-phase  flow;  vortices;  fluids;  trajectories  (physics);  channels  (hydraulic  engineering) Résumé : We have developed a numerical simulation scheme combining a vortex method and a particle trajectory tracking method, which is applicable to internal unsteady two-phase flows. It is a completely grid-free Lagrangian–Lagrangian simulation, which is able to simulate the primary effect of vortical flow on the unsteady particle motion and dispersion. It can handle unsteady high Reynolds number flows. So far, no one has applied this kind of method internal multiphase flows, though many industrial multiphase flows are internal. In this study, internal liquid-solid two-phase flows in a vertical channel and a mixing tee have been calculated by the new method, in which use of the vortex introduction model enables the simulation of the dynamic behavior of separation or reattachment. In the mixing tee, solid particle phenomena such as depositions or particle-wall collisions have been simulated and measured. Numerical results based on simple two-dimensional flow and one-way model show good agreement with the experimental data. The results show that turbulent vortices dominate particle motion. It has been shown that the present method can be useful in the design of industrial multiphase flows with particle mixing, dispersion, deposition, and particle-wall collision because it is possible to simulate the effect of turbulent vortices on the particle motion. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A grid-free Lagrangian approach of vortex method and particle trajectory tracking method applied to internal fluid-solid two-phase flows [texte imprimé] / Yoshiyuki Iso, Auteur ; Kyoji Kamemoto, Auteur . - 2009 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 10 p. Mots-clés : Flow  (dynamics);  particulate  matter;  two-phase  flow;  vortices;  fluids;  trajectories  (physics);  channels  (hydraulic  engineering) Résumé : We have developed a numerical simulation scheme combining a vortex method and a particle trajectory tracking method, which is applicable to internal unsteady two-phase flows. It is a completely grid-free Lagrangian–Lagrangian simulation, which is able to simulate the primary effect of vortical flow on the unsteady particle motion and dispersion. It can handle unsteady high Reynolds number flows. So far, no one has applied this kind of method internal multiphase flows, though many industrial multiphase flows are internal. In this study, internal liquid-solid two-phase flows in a vertical channel and a mixing tee have been calculated by the new method, in which use of the vortex introduction model enables the simulation of the dynamic behavior of separation or reattachment. In the mixing tee, solid particle phenomena such as depositions or particle-wall collisions have been simulated and measured. Numerical results based on simple two-dimensional flow and one-way model show good agreement with the experimental data. The results show that turbulent vortices dominate particle motion. It has been shown that the present method can be useful in the design of industrial multiphase flows with particle mixing, dispersion, deposition, and particle-wall collision because it is possible to simulate the effect of turbulent vortices on the particle motion. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Autogenous suction to prevent laminar boundary-layer separation / Hediye Atik in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 8 p. Titre : Autogenous suction to prevent laminar boundary-layer separation Type de document : texte imprimé Auteurs : Hediye Atik, Auteur ; Leon van Dommelen, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Separation  (technology);  suction;  boundary  layers Résumé : Boundary-layer separation can be prevented or delayed by sucking part of the boundary layer into the surface, but in a straightforward application the required hydraulics entail significant penalties in terms of weight and cost. By means of computational techniques, this paper explores the possibility of autogenous suction, in which the local pressure differences that lead to separation drive the suction used to prevent it. The chosen examples include steady and unsteady laminar flows around leading edges of thin airfoils. No fundamental theoretical limit to autogenous suction was found in the range of angles of attack that could be studied, but rapidly increasing suction volumes suggest that practical application will become increasingly difficult for more severe adverse pressure gradients. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Autogenous suction to prevent laminar boundary-layer separation [texte imprimé] / Hediye Atik, Auteur ; Leon van Dommelen, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 8 p. Mots-clés : Separation  (technology);  suction;  boundary  layers Résumé : Boundary-layer separation can be prevented or delayed by sucking part of the boundary layer into the surface, but in a straightforward application the required hydraulics entail significant penalties in terms of weight and cost. By means of computational techniques, this paper explores the possibility of autogenous suction, in which the local pressure differences that lead to separation drive the suction used to prevent it. The chosen examples include steady and unsteady laminar flows around leading edges of thin airfoils. No fundamental theoretical limit to autogenous suction was found in the range of angles of attack that could be studied, but rapidly increasing suction volumes suggest that practical application will become increasingly difficult for more severe adverse pressure gradients. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition / A.-M. Shinneeb in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Titre : Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition Type de document : texte imprimé Auteurs : A.-M. Shinneeb, Auteur ; Balachandar, R., Auteur ; J. D. Bugg, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Particulate  matter;  turbulence;  vortices;  principal  component  analysis;  flow  (dynamics);  water;  algorithms Résumé : This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9mm) into a stationary body of water. The jet exit velocity was 2.5m∕s and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of coherent structures in the far-field region of an axisymmetric free jet identified using particle image velocimetry and proper orthogonal decomposition [texte imprimé] / A.-M. Shinneeb, Auteur ; Balachandar, R., Auteur ; J. D. Bugg, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Mots-clés : Particulate  matter;  turbulence;  vortices;  principal  component  analysis;  flow  (dynamics);  water;  algorithms Résumé : This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9mm) into a stationary body of water. The jet exit velocity was 2.5m∕s and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Destabilization of laminar wall jet flow and relaminarization of the turbulent confined jet flow in axially rotating circular pipe / Snehamoy Majumder in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 8 p. Titre : Destabilization of laminar wall jet flow and relaminarization of the turbulent confined jet flow in axially rotating circular pipe Type de document : texte imprimé Auteurs : Snehamoy Majumder, Auteur ; Dipankar Sanyal, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Rotation;  flow  (dynamics);  turbulence;  jets;  pipes;  ducts Résumé : Destabilization and relaminarization phenomena have been investigated in an axially rotating circular duct. Standard k-ε model with modification for streamline curvature has been used in the numerical study. The laminar and turbulent velocity distributions at inlet have been observed to become turbulent and laminar, respectively, toward the exit of the pipe. A local velocity profile with parabolic or nearly uniform variation has been considered as the characteristic of laminarlike or turbulent flow, respectively, and changeover of flow from former to the later variation or vice versa has been taken to characterize destabilization and relaminarization, respectively. The predicted azimuthal velocity component was found to be reasonably accurate near the wall and not so encouraging in the core region of the swirling flow. The recirculation bubble generated by a central jet flow at the wall has been observed to reduce in size due to rotation of the pipe confirming the relaminarization phenomenon, whereas with laminar wall jet waspredicted recirculation bubble growing with rotation rate manifesting the destabilization effects. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Destabilization of laminar wall jet flow and relaminarization of the turbulent confined jet flow in axially rotating circular pipe [texte imprimé] / Snehamoy Majumder, Auteur ; Dipankar Sanyal, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 8 p. Mots-clés : Rotation;  flow  (dynamics);  turbulence;  jets;  pipes;  ducts Résumé : Destabilization and relaminarization phenomena have been investigated in an axially rotating circular duct. Standard k-ε model with modification for streamline curvature has been used in the numerical study. The laminar and turbulent velocity distributions at inlet have been observed to become turbulent and laminar, respectively, toward the exit of the pipe. A local velocity profile with parabolic or nearly uniform variation has been considered as the characteristic of laminarlike or turbulent flow, respectively, and changeover of flow from former to the later variation or vice versa has been taken to characterize destabilization and relaminarization, respectively. The predicted azimuthal velocity component was found to be reasonably accurate near the wall and not so encouraging in the core region of the swirling flow. The recirculation bubble generated by a central jet flow at the wall has been observed to reduce in size due to rotation of the pipe confirming the relaminarization phenomenon, whereas with laminar wall jet waspredicted recirculation bubble growing with rotation rate manifesting the destabilization effects. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

PIV study of turbulent flow in asymmetric converging and diverging channels / M. K. Shah in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 15 p. Titre : PIV study of turbulent flow in asymmetric converging and diverging channels Type de document : texte imprimé Auteurs : M. K. Shah, Auteur ; Tachie, M. F., Auteur Année de publication : 2009 Article en page(s) : 15 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  channels  (hydraulic  engineering);  urbulence;  stress;  boundary  layers;  pressure  gradient;  shear  (mechanics);  eddies  (fluid  dynamics);  viscosity;  particulate  matter Résumé : An experimental investigation of turbulent flow subjected to variable adverse and favorable pressure gradients in two-dimensional asymmetric channels is reported. The floors of the diverging and converging channels were flat while the roofs of the channels were curved. Adverse pressure gradient flows at Reh=27,050 and 12,450 and favorable pressure gradient flow at Reh=19,280 were studied. A particle image velocimetry was used to conduct detailed measurements at several planes upstream, within the variable section and within the downstream sections. The boundary layer parameters were obtained in the upper and lower boundary layers to study the effects of pressure gradients on the development of the mean flow on the floor and roof of the channels. The profiles of the mean velocities, turbulence intensities, Reynolds shear stress, mixing length, eddy viscosity, and turbulence production were also obtained to document the salient features of pressure gradient turbulent flows in asymmetric converging and diverging channels. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] PIV study of turbulent flow in asymmetric converging and diverging channels [texte imprimé] / M. K. Shah, Auteur ; Tachie, M. F., Auteur . - 2009 . - 15 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 15 p. Mots-clés : Flow  (dynamics);  channels  (hydraulic  engineering);  urbulence;  stress;  boundary  layers;  pressure  gradient;  shear  (mechanics);  eddies  (fluid  dynamics);  viscosity;  particulate  matter Résumé : An experimental investigation of turbulent flow subjected to variable adverse and favorable pressure gradients in two-dimensional asymmetric channels is reported. The floors of the diverging and converging channels were flat while the roofs of the channels were curved. Adverse pressure gradient flows at Reh=27,050 and 12,450 and favorable pressure gradient flow at Reh=19,280 were studied. A particle image velocimetry was used to conduct detailed measurements at several planes upstream, within the variable section and within the downstream sections. The boundary layer parameters were obtained in the upper and lower boundary layers to study the effects of pressure gradients on the development of the mean flow on the floor and roof of the channels. The profiles of the mean velocities, turbulence intensities, Reynolds shear stress, mixing length, eddy viscosity, and turbulence production were also obtained to document the salient features of pressure gradient turbulent flows in asymmetric converging and diverging channels. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Simulation of shallow flows in nonuniform open channels / Liang, Qiuhua in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Titre : Simulation of shallow flows in nonuniform open channels Type de document : texte imprimé Auteurs : Liang, Qiuhua, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  channels  (hydraulic  engineering);  computer  simulation;  hydraulic  jump;  open  channels  (hydraulics);  equations;  shallow  water  equations;  water;  simulation;  drops Résumé : This paper presents a new formulation of the 2D shallow water equations, based on which a numerical model (referred to as NewChan) is developed for simulating complex flows in nonuniform open channels. The new shallow water equations mathematically balance the flux and source terms and can be directly applied to predict flows over irregular bed topography without any necessity for a special numerical treatment of source terms. The balanced governing equations are solved on uniform Cartesian grids using a finite-volume Godunov-type scheme, enabling automatic capture of transcritical flows. A high-order numerical scheme is achieved using a second-order Runge–Kutta integration method. A very simple immersed boundary approach is used to deal with an irregular domain geometry. This method can be easily implemented in a Cartesian model and does not have any influence on computational efficiency. The numerical model is validated against several benchmark tests. The computed results are compared with analytical solutions, previously published predictions, and experimental measurements and excellent agreements are achieved. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Simulation of shallow flows in nonuniform open channels [texte imprimé] / Liang, Qiuhua, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 9 p. Mots-clés : Flow  (dynamics);  channels  (hydraulic  engineering);  computer  simulation;  hydraulic  jump;  open  channels  (hydraulics);  equations;  shallow  water  equations;  water;  simulation;  drops Résumé : This paper presents a new formulation of the 2D shallow water equations, based on which a numerical model (referred to as NewChan) is developed for simulating complex flows in nonuniform open channels. The new shallow water equations mathematically balance the flux and source terms and can be directly applied to predict flows over irregular bed topography without any necessity for a special numerical treatment of source terms. The balanced governing equations are solved on uniform Cartesian grids using a finite-volume Godunov-type scheme, enabling automatic capture of transcritical flows. A high-order numerical scheme is achieved using a second-order Runge–Kutta integration method. A very simple immersed boundary approach is used to deal with an irregular domain geometry. This method can be easily implemented in a Cartesian model and does not have any influence on computational efficiency. The numerical model is validated against several benchmark tests. The computed results are compared with analytical solutions, previously published predictions, and experimental measurements and excellent agreements are achieved. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Incipience of liquid entrainment from a stratified gas-liquid region in multiple discharging branches / R. C. Bowden in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 10 p. Titre : Incipience of liquid entrainment from a stratified gas-liquid region in multiple discharging branches Type de document : texte imprimé Auteurs : R. C. Bowden, Auteur ; I. G. Hassan, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Bifurcation Résumé : The onset of liquid entrainment in discharging branches, from a stratified gas-liquid region, has implications in industrial applications where safety is of concern. The onset criterion was characterized by the critical height, the vertical distance from the discharge inlet to the gas-liquid interface, and was shown to be a function of the Froude number. The critical height signified a transition in the discharging flow quality from a single phase gas to a two-phase gas-liquid mixture. The onset of liquid entrainment with multiple discharging branches, and a stratified gas-liquid region, was experimentally investigated using air and water. A test section with a semicircular cross section and three discharging branches at 0deg, 45deg, and 90deg was used. The critical height was recorded using both increasing and decreasing liquid level methods, thereby demonstrating surface tension and wetness effects. A total of eight cases were investigated for single, dual, and triple discharges, with onset occurring in the branch closest to and above the gas-liquid interface. Wall curvature effects were discussed through comparison with previous flat wall studies. Agreement between previously developed analytical models and the decreasing liquid level results was found. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Incipience of liquid entrainment from a stratified gas-liquid region in multiple discharging branches [texte imprimé] / R. C. Bowden, Auteur ; I. G. Hassan, Auteur . - 2009 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 10 p. Mots-clés : Bifurcation Résumé : The onset of liquid entrainment in discharging branches, from a stratified gas-liquid region, has implications in industrial applications where safety is of concern. The onset criterion was characterized by the critical height, the vertical distance from the discharge inlet to the gas-liquid interface, and was shown to be a function of the Froude number. The critical height signified a transition in the discharging flow quality from a single phase gas to a two-phase gas-liquid mixture. The onset of liquid entrainment with multiple discharging branches, and a stratified gas-liquid region, was experimentally investigated using air and water. A test section with a semicircular cross section and three discharging branches at 0deg, 45deg, and 90deg was used. The critical height was recorded using both increasing and decreasing liquid level methods, thereby demonstrating surface tension and wetness effects. A total of eight cases were investigated for single, dual, and triple discharges, with onset occurring in the branch closest to and above the gas-liquid interface. Wall curvature effects were discussed through comparison with previous flat wall studies. Agreement between previously developed analytical models and the decreasing liquid level results was found. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Numerical simulation of cavitation around a hydrofoil and evaluation of a RNG κ-ε model / Lingjiu Zhou in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 7 p. Titre : Numerical simulation of cavitation around a hydrofoil and evaluation of a RNG κ-ε model Type de document : texte imprimé Auteurs : Lingjiu Zhou, Auteur ; Zhengwei Wang, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure;  flow  (dynamics);  turbulence;  cavitation;  cavities;  equations;  hydrofoil;  suction;  vapors;  computer  simulation Résumé : Cavitating flow around a hydrofoil was simulated using a transport equation-based model with consideration of the influence of noncondensable gases. The cavity length and the pressure distributions on the suction side can be well predicted for stable cavities using the standard renormalization-group (RNG) κ-ε turbulence model with proper noncondensable gas mass fraction. The unstable cavity shedding at lower cavitation numbers was not well predicted by the standard RNG κ-ε turbulence model. A modified RNG κ-ε turbulence model was evaluated by comparing the calculated spatial-temporal pressure distributions on the suction wall with experimental data. The results showed that the predicted cavity growth and shedding cycle and its frequency agree well with the experimental data. However, the pressure increase caused by interaction of the reentrant flow and the cavity interface is overestimated, which caused the time-averaged pressure on the front part of the hydrofoil to be overestimated. The time-averaged pressure on the rear of the hydrofoil was low because the small cavity shedding on the rear part of the cavity was not predicted. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Numerical simulation of cavitation around a hydrofoil and evaluation of a RNG κ-ε model [texte imprimé] / Lingjiu Zhou, Auteur ; Zhengwei Wang, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 1 (Janvier 2008) . - 7 p. Mots-clés : Pressure;  flow  (dynamics);  turbulence;  cavitation;  cavities;  equations;  hydrofoil;  suction;  vapors;  computer  simulation Résumé : Cavitating flow around a hydrofoil was simulated using a transport equation-based model with consideration of the influence of noncondensable gases. The cavity length and the pressure distributions on the suction side can be well predicted for stable cavities using the standard renormalization-group (RNG) κ-ε turbulence model with proper noncondensable gas mass fraction. The unstable cavity shedding at lower cavitation numbers was not well predicted by the standard RNG κ-ε turbulence model. A modified RNG κ-ε turbulence model was evaluated by comparing the calculated spatial-temporal pressure distributions on the suction wall with experimental data. The results showed that the predicted cavity growth and shedding cycle and its frequency agree well with the experimental data. However, the pressure increase caused by interaction of the reentrant flow and the cavity interface is overestimated, which caused the time-averaged pressure on the front part of the hydrofoil to be overestimated. The time-averaged pressure on the rear of the hydrofoil was low because the small cavity shedding on the rear part of the cavity was not predicted. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse