Dépouillements

Flowfield investigation at propeller thrust reverse / Eric W. M. Roosenboom in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 08 p. Titre : Flowfield investigation at propeller thrust reverse Type de document : texte imprimé Auteurs : Eric W. M. Roosenboom, Auteur ; Andreas Schröder, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  particulate  matter;  turbulence;  thrust;  vorticity;  blades;  propellers;  wind  tunnels Résumé : The flow phenomena in the slipstream around an eight-bladed propeller at thrust reverse conditions are analyzed using double stereoscopic particle image velocimetry in the Airbus Low-Speed Wind Tunnel Facility in Bremen, Germany. Several planes are scanned using a traversing system, as well as measurements at several phase angles. In the present paper only properties in the propeller symmetry plane will be compared. The fluid mechanical properties for two different propeller blade pitch angle settings are investigated and compared for their ability to deliver a negative thrust. The first setting has identical blade pitch angles for all propeller blades; the second setting has alternating blade pitch angles. It is concluded that the latter setting provides better aerodynamic flow properties. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Flowfield investigation at propeller thrust reverse [texte imprimé] / Eric W. M. Roosenboom, Auteur ; Andreas Schröder, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 08 p. Mots-clés : flow  (dynamics);  particulate  matter;  turbulence;  thrust;  vorticity;  blades;  propellers;  wind  tunnels Résumé : The flow phenomena in the slipstream around an eight-bladed propeller at thrust reverse conditions are analyzed using double stereoscopic particle image velocimetry in the Airbus Low-Speed Wind Tunnel Facility in Bremen, Germany. Several planes are scanned using a traversing system, as well as measurements at several phase angles. In the present paper only properties in the propeller symmetry plane will be compared. The fluid mechanical properties for two different propeller blade pitch angle settings are investigated and compared for their ability to deliver a negative thrust. The first setting has identical blade pitch angles for all propeller blades; the second setting has alternating blade pitch angles. It is concluded that the latter setting provides better aerodynamic flow properties. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

An analytical modeling of the central core flow in a rotor-stator system with several preswirl conditions / Roger Debuchy in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 11 p. Titre : An analytical modeling of the central core flow in a rotor-stator system with several preswirl conditions Type de document : texte imprimé Auteurs : Roger Debuchy, Auteur ; Fadi Abdel Nour, Auteur ; Gérard Bois, Auteur Année de publication : 2010 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : rotor-stator  system;  boundary  layers;  core-swirl  ratio Résumé : In the most part of an enclosed rotor-stator system with separated boundary layers, the flow structure is characterized by a central core rotating as a solid body with a constant core-swirl ratio. This behavior is not always observed in an isolated rotor-stator cavity, i.e., without any centripetal or centrifugal throughflow, opened to the atmosphere at the periphery: Recent works have brought to evidence an increasing level of the core-swirl ratio from the periphery to the axis, as in the case of a rotor-stator with superposed centripetal flow. The present work is based on an asymptotical approach in order to provide a better understanding of this process. Assuming that the boundary layers behave as on a single rotating disk in a stationary fluid on the rotor side, and on a stationary disk in a rotating fluid on the stator side, new analytical relations are obtained for the core-swirl ratio, the static pressure on the stator, and also the total pressure at midheight of the cavity. An experimental study is performed: Detailed measurements provide data for several values of the significant dimensionless parameters: 1.14≤10−6×Re≤1.96, 0.05≤G≤0.10, and 0.07≤104×Ek≤2.65. The analysis of the results shows a good agreement between the theoretical solution and the experimental results. The analytical model can be used to provide a better understanding of the flow features. In addition, radial distributions of both core-swirl ratio, dimensionless static pressure on the stator, as well as dimensionless total pressure at midheight of the cavity, which are of interest to the designers, can be computed with an acceptable accuracy knowing the levels of the preswirl coefficient Kp and the solid body rotation swirl coefficient KB. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] An analytical modeling of the central core flow in a rotor-stator system with several preswirl conditions [texte imprimé] / Roger Debuchy, Auteur ; Fadi Abdel Nour, Auteur ; Gérard Bois, Auteur . - 2010 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 11 p. Mots-clés : rotor-stator  system;  boundary  layers;  core-swirl  ratio Résumé : In the most part of an enclosed rotor-stator system with separated boundary layers, the flow structure is characterized by a central core rotating as a solid body with a constant core-swirl ratio. This behavior is not always observed in an isolated rotor-stator cavity, i.e., without any centripetal or centrifugal throughflow, opened to the atmosphere at the periphery: Recent works have brought to evidence an increasing level of the core-swirl ratio from the periphery to the axis, as in the case of a rotor-stator with superposed centripetal flow. The present work is based on an asymptotical approach in order to provide a better understanding of this process. Assuming that the boundary layers behave as on a single rotating disk in a stationary fluid on the rotor side, and on a stationary disk in a rotating fluid on the stator side, new analytical relations are obtained for the core-swirl ratio, the static pressure on the stator, and also the total pressure at midheight of the cavity. An experimental study is performed: Detailed measurements provide data for several values of the significant dimensionless parameters: 1.14≤10−6×Re≤1.96, 0.05≤G≤0.10, and 0.07≤104×Ek≤2.65. The analysis of the results shows a good agreement between the theoretical solution and the experimental results. The analytical model can be used to provide a better understanding of the flow features. In addition, radial distributions of both core-swirl ratio, dimensionless static pressure on the stator, as well as dimensionless total pressure at midheight of the cavity, which are of interest to the designers, can be computed with an acceptable accuracy knowing the levels of the preswirl coefficient Kp and the solid body rotation swirl coefficient KB. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

A numerical investigation of the constant-velocity volute design approach as applied to the single blade impeller pump / Brian de Souza in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 07 p. Titre : A numerical investigation of the constant-velocity volute design approach as applied to the single blade impeller pump Type de document : texte imprimé Auteurs : Brian de Souza, Auteur ; Andrew Niven, Auteur ; Richard McEvoy, Auteur Année de publication : 2010 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  impellers;  design;  pumps;  blades Résumé : This contribution addresses volute design as applied to single-blade-impeller pumps. Traditionally, volute design for multiblade impeller pumps has been carried out using either the constant-velocity or constant-swirl methodologies. Here, the constant velocity approach was investigated in order to determine whether or not it was appropriate for single-blade-impeller pumps, and whether the theoretical formulation would agree with numerically calculated data. In a numerical approach, three volutes were designed of the constant velocity type with design velocities of 0.8, 1.0, and 1.20 Cref. The performance of all three volutes was calculated using transient, three-dimensional, viscous numerical simulations, using the commercially available ANSYS CFX -11.0 code, over a range of flowrates 0.55 DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A numerical investigation of the constant-velocity volute design approach as applied to the single blade impeller pump [texte imprimé] / Brian de Souza, Auteur ; Andrew Niven, Auteur ; Richard McEvoy, Auteur . - 2010 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 07 p. Mots-clés : flow  (dynamics);  impellers;  design;  pumps;  blades Résumé : This contribution addresses volute design as applied to single-blade-impeller pumps. Traditionally, volute design for multiblade impeller pumps has been carried out using either the constant-velocity or constant-swirl methodologies. Here, the constant velocity approach was investigated in order to determine whether or not it was appropriate for single-blade-impeller pumps, and whether the theoretical formulation would agree with numerically calculated data. In a numerical approach, three volutes were designed of the constant velocity type with design velocities of 0.8, 1.0, and 1.20 Cref. The performance of all three volutes was calculated using transient, three-dimensional, viscous numerical simulations, using the commercially available ANSYS CFX -11.0 code, over a range of flowrates 0.55 DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

PIV measurements and CFD computations of secondary flow in a centrifugal pump impeller / R. W. Westra in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 08 p. Titre : PIV measurements and CFD computations of secondary flow in a centrifugal pump impeller Type de document : texte imprimé Auteurs : R. W. Westra, Auteur ; L. Broersma, Auteur ; K. van Andel, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  measurement;  suction;  impellers;  computational  fluid  dynamics;  blades;  centrifugal  pumps;  computation Résumé : Two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics (CFD) analyses have been performed on the steady velocity field inside the shrouded impeller of a low specific-speed centrifugal pump operating with a vaneless diffuser. Flow rates ranging from 80% to 120% of the design flow rate are considered in detail. It is observed from the velocity measurements that secondary flows occur. These flows result in the formation of regions of low velocity near the intersection of blade suction side and shroud. The extent of this jet-wake structure decreases with increasing flow rate. Velocity fields have also been computed from Reynolds-averaged Navier–Stokes equations with the Spalart–Allmaras turbulence model using a commercial CFD code. For the considered flow rates, the qualitative agreement between measured and computed velocity profiles is very good. Overall, the average relative difference between these velocity profiles is around 5%. Additional CFD computations have been performed to assess the influence of Reynolds number and the shape of the inlet velocity profile on the computed velocity fields. It is found that the influence of Reynolds number is mild. The shape of the inlet profile has only a weak effect at the shroud. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] PIV measurements and CFD computations of secondary flow in a centrifugal pump impeller [texte imprimé] / R. W. Westra, Auteur ; L. Broersma, Auteur ; K. van Andel, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 08 p. Mots-clés : flow  (dynamics);  measurement;  suction;  impellers;  computational  fluid  dynamics;  blades;  centrifugal  pumps;  computation Résumé : Two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics (CFD) analyses have been performed on the steady velocity field inside the shrouded impeller of a low specific-speed centrifugal pump operating with a vaneless diffuser. Flow rates ranging from 80% to 120% of the design flow rate are considered in detail. It is observed from the velocity measurements that secondary flows occur. These flows result in the formation of regions of low velocity near the intersection of blade suction side and shroud. The extent of this jet-wake structure decreases with increasing flow rate. Velocity fields have also been computed from Reynolds-averaged Navier–Stokes equations with the Spalart–Allmaras turbulence model using a commercial CFD code. For the considered flow rates, the qualitative agreement between measured and computed velocity profiles is very good. Overall, the average relative difference between these velocity profiles is around 5%. Additional CFD computations have been performed to assess the influence of Reynolds number and the shape of the inlet velocity profile on the computed velocity fields. It is found that the influence of Reynolds number is mild. The shape of the inlet profile has only a weak effect at the shroud. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Rotordynamic forces acting on three-bladed inducer under supersynchronous/synchronous rotating cavitation / Yoshida, Yoshiki in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 09 p. Titre : Rotordynamic forces acting on three-bladed inducer under supersynchronous/synchronous rotating cavitation Type de document : texte imprimé Auteurs : Yoshida, Yoshiki, Auteur ; Masato Eguchi, Auteur ; Taiichi Motomura, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  fluids;  cavitation;  rotordynamics;  vibration;  cavities;  whirls Résumé : Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers, and whirl/shaft speed ratios included supersynchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Rotordynamic forces acting on three-bladed inducer under supersynchronous/synchronous rotating cavitation [texte imprimé] / Yoshida, Yoshiki, Auteur ; Masato Eguchi, Auteur ; Taiichi Motomura, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 09 p. Mots-clés : force;  fluids;  cavitation;  rotordynamics;  vibration;  cavities;  whirls Résumé : Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers, and whirl/shaft speed ratios included supersynchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Effects of channel scale on slip length of flow in micro/nanochannels / Xiaofan Yang in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Titre : Effects of channel scale on slip length of flow in micro/nanochannels Type de document : texte imprimé Auteurs : Xiaofan Yang, Auteur ; Zhongquan C. Zheng, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  fluids;  channels  (hydraulic  engineering);  shear  (mechanics);  boundary-value  problems;  molecular  dynamics  simulation Résumé : The concept of slip length, related to surface velocity and shear rate, is often used to analyze the slip surface property for flow in micro- or nanochannels. In this study, a hybrid scheme that couples molecular dynamics simulation (used near the solid boundary to include the surface effect) and a continuum solution (to study the fluid mechanics) is validated and used for the study of slip length behavior in the Couette flow problem. By varying the height of the channel across multiple length scales, we investigate the effect of channel scale on surface slip length. In addition, by changing the velocity of the moving-solid wall, the influence of shear rate on the slip length is studied. The results show that within a certain range of the channel heights, the slip length is size dependent. This upper bound of the channel height can vary with the shear rate. Under different magnitudes of moving velocities and channel heights, a relative slip length can be introduced, which changes with channel height following a logarithmic function, with the coefficients of the function being the properties of the fluid and wall materials. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Effects of channel scale on slip length of flow in micro/nanochannels [texte imprimé] / Xiaofan Yang, Auteur ; Zhongquan C. Zheng, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Mots-clés : flow  (dynamics);  fluids;  channels  (hydraulic  engineering);  shear  (mechanics);  boundary-value  problems;  molecular  dynamics  simulation Résumé : The concept of slip length, related to surface velocity and shear rate, is often used to analyze the slip surface property for flow in micro- or nanochannels. In this study, a hybrid scheme that couples molecular dynamics simulation (used near the solid boundary to include the surface effect) and a continuum solution (to study the fluid mechanics) is validated and used for the study of slip length behavior in the Couette flow problem. By varying the height of the channel across multiple length scales, we investigate the effect of channel scale on surface slip length. In addition, by changing the velocity of the moving-solid wall, the influence of shear rate on the slip length is studied. The results show that within a certain range of the channel heights, the slip length is size dependent. This upper bound of the channel height can vary with the shear rate. Under different magnitudes of moving velocities and channel heights, a relative slip length can be introduced, which changes with channel height following a logarithmic function, with the coefficients of the function being the properties of the fluid and wall materials. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Application of the k-ε turbulence model to buoyant adiabatic wall plumes / Michael A. Delichatsios in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 05 p. Titre : Application of the k-ε turbulence model to buoyant adiabatic wall plumes Type de document : texte imprimé Auteurs : Michael A. Delichatsios, Auteur ; C. P. Brescianini, Auteur ; D. Paterson, Auteur Année de publication : 2010 Article en page(s) : 05 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  turbulence;  fluctuations  (physics);  plumes  (fluid  dynamics);  mixtures Résumé : Computational fluid dynamics based on Reynolds averaged Navier–Stokes equations is used to model a turbulent planar buoyant adiabatic wall plume. The plume is generated by directing a helium/air source upwards at the base of the wall. Far from the source, the resulting plume becomes self-similar to a good approximation. Several turbulence models based predominantly on the k-ε modeling technique, including algebraic stress modeling, are examined and evaluated against experimental data for the mean mixture fraction, the mixture fraction fluctuations, the mean velocity, and the Reynolds shear stress. Several versions of the k-ε model are identified that can predict important flow quantities with reasonable accuracy. Some new results are presented for the variation in a mixing function for the mixture normal to the wall. Finally, the predicted (velocity) lateral spread is as expected smaller for wall flows in comparison to the free flows, but quite importantly, it depends on the wall boundary conditions in agreement with experiments, i.e., it is larger for adiabatic than for hot wall plumes. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Application of the k-ε turbulence model to buoyant adiabatic wall plumes [texte imprimé] / Michael A. Delichatsios, Auteur ; C. P. Brescianini, Auteur ; D. Paterson, Auteur . - 2010 . - 05 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 05 p. Mots-clés : flow  (dynamics);  turbulence;  fluctuations  (physics);  plumes  (fluid  dynamics);  mixtures Résumé : Computational fluid dynamics based on Reynolds averaged Navier–Stokes equations is used to model a turbulent planar buoyant adiabatic wall plume. The plume is generated by directing a helium/air source upwards at the base of the wall. Far from the source, the resulting plume becomes self-similar to a good approximation. Several turbulence models based predominantly on the k-ε modeling technique, including algebraic stress modeling, are examined and evaluated against experimental data for the mean mixture fraction, the mixture fraction fluctuations, the mean velocity, and the Reynolds shear stress. Several versions of the k-ε model are identified that can predict important flow quantities with reasonable accuracy. Some new results are presented for the variation in a mixing function for the mixture normal to the wall. Finally, the predicted (velocity) lateral spread is as expected smaller for wall flows in comparison to the free flows, but quite importantly, it depends on the wall boundary conditions in agreement with experiments, i.e., it is larger for adiabatic than for hot wall plumes. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Unsteady cavitation at the tongue of the volute of a centrifugal pump / Rudolf Bachert in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Titre : Unsteady cavitation at the tongue of the volute of a centrifugal pump Type de document : texte imprimé Auteurs : Rudolf Bachert, Auteur ; Bernd Stoffel, Auteur ; Matevž Dular, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  impellers;  cavitation;  pumps;  blades;  centrifugal  pumps Résumé : The paper deals with unsteady effects of cavitation at the tongue of the volute of a centrifugal pump. For the investigations parts of the volute casing, including the tongue and the hub of the impeller, were made of acrylic glass. Experiments were carried out at a flow rate above optimal value (slight overload) and at 3% head drop conditions. In this operating point there was no cavitation present in the impeller of the pump, hence, the whole 3% head drop resulted from cavitation on the tongue of the volute. By use of particle image velocimetry combined with special fluorescent particles it was possible to obtain information about the velocity field outside and inside the cavitating zone. An additional camera provided information about the location and extent of cavitation. The results imply that cloud cavitation similar to the one seen on single hydrofoils appears on the tongue. Periodical evolution of cavitation structures, from incipient to developed, with cavitation cloud shedding, is seen during each passing of a blade. The Results imply that greater consideration should be given to the possibility of cavitation appearance on the tongue of the volute as it is possible that this cavitation location alone causes the 3% head drop. Moreover, the appearance of unsteady cavitation in a higher-pressure region, such as the volute of the pump, can cause severe erosion to the solid surfaces. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Unsteady cavitation at the tongue of the volute of a centrifugal pump [texte imprimé] / Rudolf Bachert, Auteur ; Bernd Stoffel, Auteur ; Matevž Dular, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Mots-clés : flow  (dynamics);  impellers;  cavitation;  pumps;  blades;  centrifugal  pumps Résumé : The paper deals with unsteady effects of cavitation at the tongue of the volute of a centrifugal pump. For the investigations parts of the volute casing, including the tongue and the hub of the impeller, were made of acrylic glass. Experiments were carried out at a flow rate above optimal value (slight overload) and at 3% head drop conditions. In this operating point there was no cavitation present in the impeller of the pump, hence, the whole 3% head drop resulted from cavitation on the tongue of the volute. By use of particle image velocimetry combined with special fluorescent particles it was possible to obtain information about the velocity field outside and inside the cavitating zone. An additional camera provided information about the location and extent of cavitation. The results imply that cloud cavitation similar to the one seen on single hydrofoils appears on the tongue. Periodical evolution of cavitation structures, from incipient to developed, with cavitation cloud shedding, is seen during each passing of a blade. The Results imply that greater consideration should be given to the possibility of cavitation appearance on the tongue of the volute as it is possible that this cavitation location alone causes the 3% head drop. Moreover, the appearance of unsteady cavitation in a higher-pressure region, such as the volute of the pump, can cause severe erosion to the solid surfaces. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Maximum spread of droplet on solid surface / Ri Li in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 05 p. Titre : Maximum spread of droplet on solid surface : low Reynolds and weber numbers Type de document : texte imprimé Auteurs : Ri Li, Auteur ; Nasser Ashgriz, Auteur ; Sanjeev Chandra, Auteur Année de publication : 2010 Article en page(s) : 05 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : physics;  surface  tension;  kinetic  energy;  potential  energy;  Reynolds  number;  drops;  energy  dissipation;  equilibrium  (physics);  energy  conservation;  equations;  shapes Résumé : This theoretical study proposes an analytical model to predict the maximum spread of single droplets on solid surfaces with zero or low Weber and Reynolds numbers. The spreading droplet is assumed as a spherical cap considering low impact velocities. Three spreading states are considered, which include equilibrium spread, maximum spontaneous spread, and maximum spread. Energy conservation is applied to the droplet as a control volume. The model equation contains two viscous dissipation terms, each of which has a defined coefficient. One term is for viscous dissipation in spontaneous spreading and the other one is for viscous dissipation of the initial kinetic energy of the droplet. The new model satisfies the fundamental physics of drop-surface interaction and can be used for droplets impacting on solid surfaces with or without initial kinetic energy. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Maximum spread of droplet on solid surface : low Reynolds and weber numbers [texte imprimé] / Ri Li, Auteur ; Nasser Ashgriz, Auteur ; Sanjeev Chandra, Auteur . - 2010 . - 05 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 05 p. Mots-clés : physics;  surface  tension;  kinetic  energy;  potential  energy;  Reynolds  number;  drops;  energy  dissipation;  equilibrium  (physics);  energy  conservation;  equations;  shapes Résumé : This theoretical study proposes an analytical model to predict the maximum spread of single droplets on solid surfaces with zero or low Weber and Reynolds numbers. The spreading droplet is assumed as a spherical cap considering low impact velocities. Three spreading states are considered, which include equilibrium spread, maximum spontaneous spread, and maximum spread. Energy conservation is applied to the droplet as a control volume. The model equation contains two viscous dissipation terms, each of which has a defined coefficient. One term is for viscous dissipation in spontaneous spreading and the other one is for viscous dissipation of the initial kinetic energy of the droplet. The new model satisfies the fundamental physics of drop-surface interaction and can be used for droplets impacting on solid surfaces with or without initial kinetic energy. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Passenger train slipstream characterization using a rotating rail rig / N. Gil in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 11 p. Titre : Passenger train slipstream characterization using a rotating rail rig Type de document : texte imprimé Auteurs : N. Gil, Auteur ; C. J. Baker, Auteur ; C. Roberts, Auteur Année de publication : 2010 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  measurement;  turbulence;  probes;  rails;  trains;  slipstream Résumé : This paper presents the results of a new experimental technique to determine the structure of train slipstreams. The highly turbulent, nonstationary nature of the slipstreams make their measurement difficult and time consuming as in order to identify the trends of behavior several passings of the train have to be made. This new technique has been developed in order to minimize considerably the measuring time. It consists of a rotating rail rig to which a 1/50 scale model of a four car high speed train is attached. Flow velocities were measured using two multihole Cobra probes, positioned close to the model sides and top. Tests were carried out at different model speeds, although if the results were suitably normalized, the effect of model speed was not significant. Velocity time histories for each configuration were obtained from ensemble averages of the results of a large number of runs (of the order of 80). From these it was possible to define velocity and turbulence intensity contours along the train, as well as the displacement thickness of the boundary layer, allowing a more detailed analysis of the flow. Also, wavelet analysis was carried out on different runs to reveal details of the unsteady flow structure around the vehicle. It is concluded that, although this methodology introduces some problems, the results obtained with this technique are in good agreement with previous model and full scale measurements. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Passenger train slipstream characterization using a rotating rail rig [texte imprimé] / N. Gil, Auteur ; C. J. Baker, Auteur ; C. Roberts, Auteur . - 2010 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 11 p. Mots-clés : flow  (dynamics);  measurement;  turbulence;  probes;  rails;  trains;  slipstream Résumé : This paper presents the results of a new experimental technique to determine the structure of train slipstreams. The highly turbulent, nonstationary nature of the slipstreams make their measurement difficult and time consuming as in order to identify the trends of behavior several passings of the train have to be made. This new technique has been developed in order to minimize considerably the measuring time. It consists of a rotating rail rig to which a 1/50 scale model of a four car high speed train is attached. Flow velocities were measured using two multihole Cobra probes, positioned close to the model sides and top. Tests were carried out at different model speeds, although if the results were suitably normalized, the effect of model speed was not significant. Velocity time histories for each configuration were obtained from ensemble averages of the results of a large number of runs (of the order of 80). From these it was possible to define velocity and turbulence intensity contours along the train, as well as the displacement thickness of the boundary layer, allowing a more detailed analysis of the flow. Also, wavelet analysis was carried out on different runs to reveal details of the unsteady flow structure around the vehicle. It is concluded that, although this methodology introduces some problems, the results obtained with this technique are in good agreement with previous model and full scale measurements. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

A comparison of phase doppler analyzer (dual-PDA) and optical patternator data for twin-fluid and pressure-swirl atomizer sprays / Ariel R. Muliadi in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 10 p. Titre : A comparison of phase doppler analyzer (dual-PDA) and optical patternator data for twin-fluid and pressure-swirl atomizer sprays Type de document : texte imprimé Auteurs : Ariel R. Muliadi, Auteur ; Paul E. Sojka, Auteur ; Yudaya R. Sivathanu, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  measurement;  drops;  sprays Résumé : The goal of this study was to determine when patternation information derived from Phase Doppler Analyzer (Dantec Dynamics, Skovlunde, Denmark, dual-PDA) measurements of volume flux, drop velocity, and mean size agreed with corresponding values measured using an optical patternator (Enurga, Inc., West Lafayette, IN, SetScan OP-600). To achieve this, data from each instrument were transformed into spatially resolved absorptances (equivalent to drop surface area per unit spray volume) and compared. Key conclusion is absorptance agreement to within 20% in many cases. However, discrepancies between phase Doppler analyzer (PDA)-calculated and optical patternator-measured absorptances become larger as the drop arrival rate increases, as the mean drop size decreases, and when a significant drop size-velocity correlation is present. These discrepancies are attributed to an underestimation of the volume flux (which becomes more important with increasing droplet arrival rate), an over-reporting of the mean drop diameter (which is the result of the restrictive data acquisition scheme applied when ensuring mass closure for the PDA measurements), the limited PDA dynamic range (which can preclude simultaneously accounting for both the largest and smallest drops in the spray), and by the optical patternator’s number-density based measurement scheme (which will not yield the same results as the flux-based PDA when a drop size-velocity correlation is present). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A comparison of phase doppler analyzer (dual-PDA) and optical patternator data for twin-fluid and pressure-swirl atomizer sprays [texte imprimé] / Ariel R. Muliadi, Auteur ; Paul E. Sojka, Auteur ; Yudaya R. Sivathanu, Auteur . - 2010 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 10 p. Mots-clés : pressure;  measurement;  drops;  sprays Résumé : The goal of this study was to determine when patternation information derived from Phase Doppler Analyzer (Dantec Dynamics, Skovlunde, Denmark, dual-PDA) measurements of volume flux, drop velocity, and mean size agreed with corresponding values measured using an optical patternator (Enurga, Inc., West Lafayette, IN, SetScan OP-600). To achieve this, data from each instrument were transformed into spatially resolved absorptances (equivalent to drop surface area per unit spray volume) and compared. Key conclusion is absorptance agreement to within 20% in many cases. However, discrepancies between phase Doppler analyzer (PDA)-calculated and optical patternator-measured absorptances become larger as the drop arrival rate increases, as the mean drop size decreases, and when a significant drop size-velocity correlation is present. These discrepancies are attributed to an underestimation of the volume flux (which becomes more important with increasing droplet arrival rate), an over-reporting of the mean drop diameter (which is the result of the restrictive data acquisition scheme applied when ensuring mass closure for the PDA measurements), the limited PDA dynamic range (which can preclude simultaneously accounting for both the largest and smallest drops in the spray), and by the optical patternator’s number-density based measurement scheme (which will not yield the same results as the flux-based PDA when a drop size-velocity correlation is present). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Factors of safety for richardson extrapolation / Tao Xing in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 13 p. Titre : Factors of safety for richardson extrapolation Type de document : texte imprimé Auteurs : Tao Xing, Auteur ; Frederick Stern, Auteur Année de publication : 2010 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : hydrodynamics;  safety;  reliability;  safety  engineering;  errors;  ships;  statistical  analysis;  uncertainty Résumé : A factor of safety method for quantitative estimates of grid-spacing and time-step uncertainties for solution verification is developed. It removes the two deficiencies of the grid convergence index and correction factor methods, namely, unreasonably small uncertainty when the estimated order of accuracy using the Richardson extrapolation method is greater than the theoretical order of accuracy and lack of statistical evidence that the interval of uncertainty at the 95% confidence level bounds the comparison error. Different error estimates are evaluated using the effectivity index. The uncertainty estimate builds on the correction factor method, but with significant improvements. The ratio of the estimated order of accuracy and theoretical order of accuracy P instead of the correction factor is used as the distance metric to the asymptotic range. The best error estimate is used to construct the uncertainty estimate. The assumption that the factor of safety is symmetric with respect to the asymptotic range was removed through the use of three instead of two factor of safety coefficients. The factor of safety method is validated using statistical analysis of 25 samples with different sizes based on 17 studies covering fluids, thermal, and structure disciplines. Only the factor of safety method, compared with the grid convergence index and correction factor methods, provides a reliability larger than 95% and a lower confidence limit greater than or equal to 1.2 at the 95% confidence level for the true mean of the parent population of the actual factor of safety. This conclusion is true for different studies, variables, ranges of P values, and single P values where multiple actual factors of safety are available. The number of samples is large and the range of P values is wide such that the factor of safety method is also valid for other applications including results not in the asymptotic range, which is typical in industrial and fluid engineering applications. An example for ship hydrodynamics is provided. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Factors of safety for richardson extrapolation [texte imprimé] / Tao Xing, Auteur ; Frederick Stern, Auteur . - 2010 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 13 p. Mots-clés : hydrodynamics;  safety;  reliability;  safety  engineering;  errors;  ships;  statistical  analysis;  uncertainty Résumé : A factor of safety method for quantitative estimates of grid-spacing and time-step uncertainties for solution verification is developed. It removes the two deficiencies of the grid convergence index and correction factor methods, namely, unreasonably small uncertainty when the estimated order of accuracy using the Richardson extrapolation method is greater than the theoretical order of accuracy and lack of statistical evidence that the interval of uncertainty at the 95% confidence level bounds the comparison error. Different error estimates are evaluated using the effectivity index. The uncertainty estimate builds on the correction factor method, but with significant improvements. The ratio of the estimated order of accuracy and theoretical order of accuracy P instead of the correction factor is used as the distance metric to the asymptotic range. The best error estimate is used to construct the uncertainty estimate. The assumption that the factor of safety is symmetric with respect to the asymptotic range was removed through the use of three instead of two factor of safety coefficients. The factor of safety method is validated using statistical analysis of 25 samples with different sizes based on 17 studies covering fluids, thermal, and structure disciplines. Only the factor of safety method, compared with the grid convergence index and correction factor methods, provides a reliability larger than 95% and a lower confidence limit greater than or equal to 1.2 at the 95% confidence level for the true mean of the parent population of the actual factor of safety. This conclusion is true for different studies, variables, ranges of P values, and single P values where multiple actual factors of safety are available. The number of samples is large and the range of P values is wide such that the factor of safety method is also valid for other applications including results not in the asymptotic range, which is typical in industrial and fluid engineering applications. An example for ship hydrodynamics is provided. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Development-length requirements for fully developed laminar flow in concentric annuli / R. J. Poole in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 04 p. Titre : Development-length requirements for fully developed laminar flow in concentric annuli Type de document : texte imprimé Auteurs : R. J. Poole, Auteur Année de publication : 2010 Article en page(s) : 04 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  laminar  flow;  Reynolds  number;  channel  flow;  annulus;  collapse Résumé : In this technical brief we report the results of a systematic numerical investigation of developing laminar flow in axisymmetric concentric annuli over a wide range of radius ratio (0.01 DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Development-length requirements for fully developed laminar flow in concentric annuli [texte imprimé] / R. J. Poole, Auteur . - 2010 . - 04 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 04 p. Mots-clés : flow  (dynamics);  laminar  flow;  Reynolds  number;  channel  flow;  annulus;  collapse Résumé : In this technical brief we report the results of a systematic numerical investigation of developing laminar flow in axisymmetric concentric annuli over a wide range of radius ratio (0.01 DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Impact of surface roughness on compressor cascade performance / Seung Chul Back in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 6 (Juin 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Titre : Impact of surface roughness on compressor cascade performance Type de document : texte imprimé Auteurs : Seung Chul Back, Auteur ; June Hyuk Sohn, Auteur ; Seung Jin Song, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  compressors;  surface  roughness;  cascades  (fluid  dynamics);  chords  (trusses);  blades Résumé : This paper presents an experimental investigation of roughness effects on aerodynamic performance in a low-speed linear compressor cascade. Equivalent sandgrain roughnesses of 12 μm, 180 μm, 300 μm, 425 μm, and 850 μm have been tested. In nondimensional terms, these roughnesses represent compressor blade roughnesses found in actual gas turbines. Downstream pressure, velocity, and angle have been measured with a five-hole probe at 0.3 chord downstream of the blade trailing edge. For the tested roughnesses of 180 μm, 300 μm, 425 μm, and 850 μm, the axial velocity ratio across the blade row decreases by 0.1%, 2.1%, 2.5%, and 5.4%, respectively. For the same cases, the exit flow angle deviation increases by 24%, 38%, 51%, and 70%, respectively. Finally, the mass-averaged total pressure loss increases by 12%, 44%, 132%, and 217%, respectively. Also, the loss increases more rapidly in the transitionally rough region. Thus, among the three parameters, the loss responds most sensitively to changes in compressor blade roughness. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Impact of surface roughness on compressor cascade performance [texte imprimé] / Seung Chul Back, Auteur ; June Hyuk Sohn, Auteur ; Seung Jin Song, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 6 (Juin 2010) . - 06 p. Mots-clés : pressure;  compressors;  surface  roughness;  cascades  (fluid  dynamics);  chords  (trusses);  blades Résumé : This paper presents an experimental investigation of roughness effects on aerodynamic performance in a low-speed linear compressor cascade. Equivalent sandgrain roughnesses of 12 μm, 180 μm, 300 μm, 425 μm, and 850 μm have been tested. In nondimensional terms, these roughnesses represent compressor blade roughnesses found in actual gas turbines. Downstream pressure, velocity, and angle have been measured with a five-hole probe at 0.3 chord downstream of the blade trailing edge. For the tested roughnesses of 180 μm, 300 μm, 425 μm, and 850 μm, the axial velocity ratio across the blade row decreases by 0.1%, 2.1%, 2.5%, and 5.4%, respectively. For the same cases, the exit flow angle deviation increases by 24%, 38%, 51%, and 70%, respectively. Finally, the mass-averaged total pressure loss increases by 12%, 44%, 132%, and 217%, respectively. Also, the loss increases more rapidly in the transitionally rough region. Thus, among the three parameters, the loss responds most sensitively to changes in compressor blade roughness. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

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