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Ajouter le résultat dans votre panierConsiderations on a mass-based system representation of a pneumatic cylinder / M. Brian Thomas in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 4 (Avril 2009)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 10 p.
Titre : Considerations on a mass-based system representation of a pneumatic cylinder Type de document : texte imprimé Auteurs : M. Brian Thomas, Auteur ; Gary P. Maul, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pneumatic actuators; hydraulic actuators Résumé : Pneumatic actuators can be advantageous over electromagnetic and hydraulic actuators in many servo motion applications. The difficulty in their practical use comes from the highly nonlinear dynamics of the actuator and control valve. Previous works have used the cylinder’s position, velocity, and internal pressure as state variables in system models. This paper replaces pressure in the state model with the mass of gas in each chamber of the cylinder, giving a better representation of the system dynamics. Under certain circumstances, the total mass of gas in the cylinder may be assumed to be constant. This allows development of a reduced-order system model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Considerations on a mass-based system representation of a pneumatic cylinder [texte imprimé] / M. Brian Thomas, Auteur ; Gary P. Maul, Auteur . - 2009 . - 10 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 10 p.
Mots-clés : pneumatic actuators; hydraulic actuators Résumé : Pneumatic actuators can be advantageous over electromagnetic and hydraulic actuators in many servo motion applications. The difficulty in their practical use comes from the highly nonlinear dynamics of the actuator and control valve. Previous works have used the cylinder’s position, velocity, and internal pressure as state variables in system models. This paper replaces pressure in the state model with the mass of gas in each chamber of the cylinder, giving a better representation of the system dynamics. Under certain circumstances, the total mass of gas in the cylinder may be assumed to be constant. This allows development of a reduced-order system model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Titre : Dynamic model and numerical simulation for synchronal rotary compressor Type de document : texte imprimé Auteurs : Hui Zhou, Auteur ; Qu, Zongchang, Auteur ; Hua Yang, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : synchronal rotary compressor; key components—cylinder; numerical simulation Résumé : The synchronal rotary compressor (SRC) has been developed to resolve high friction and severe wear that usually occur in conventional rotary compressors due to the high relative velocity between the key tribo-pairs. In this study, the working principle and structural characteristics of the SRC are presented first. Then, the kinematic and force models are established for the key components—cylinder, sliding vane, and rotor. The velocity, acceleration, and force equations with shaft rotation angle are derived for each component. Based on the established models, numerical simulations are performed for a SRC prototype. Moreover, experiments are conducted to verify the established models. The simulated results show that the average relative velocity between the rotor and the cylinder of the present compressor decreases by 80–82% compared with that of the conventional rotary compressors with the same size and operating parameters. Moreover, the average relative velocity between the sliding contact tribo-pairs of the SRC decreases by 93–94.3% compared with that of the conventional rotary compressors. In addition, the simulated results show that the stresses on the sliding vane are greater than those on the other components. The experimental results indicate that the wear of the side surface of the sliding vane is more severe than that of the other components. Therefore, special treatments are needed for the sliding vane in order to improve its reliability. These findings confirm that the new SRC has lower frictional losses and higher mechanical efficiency for its advanced structure and working principle. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Dynamic model and numerical simulation for synchronal rotary compressor [texte imprimé] / Hui Zhou, Auteur ; Qu, Zongchang, Auteur ; Hua Yang, Auteur . - 2009 . - 09 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Mots-clés : synchronal rotary compressor; key components—cylinder; numerical simulation Résumé : The synchronal rotary compressor (SRC) has been developed to resolve high friction and severe wear that usually occur in conventional rotary compressors due to the high relative velocity between the key tribo-pairs. In this study, the working principle and structural characteristics of the SRC are presented first. Then, the kinematic and force models are established for the key components—cylinder, sliding vane, and rotor. The velocity, acceleration, and force equations with shaft rotation angle are derived for each component. Based on the established models, numerical simulations are performed for a SRC prototype. Moreover, experiments are conducted to verify the established models. The simulated results show that the average relative velocity between the rotor and the cylinder of the present compressor decreases by 80–82% compared with that of the conventional rotary compressors with the same size and operating parameters. Moreover, the average relative velocity between the sliding contact tribo-pairs of the SRC decreases by 93–94.3% compared with that of the conventional rotary compressors. In addition, the simulated results show that the stresses on the sliding vane are greater than those on the other components. The experimental results indicate that the wear of the side surface of the sliding vane is more severe than that of the other components. Therefore, special treatments are needed for the sliding vane in order to improve its reliability. These findings confirm that the new SRC has lower frictional losses and higher mechanical efficiency for its advanced structure and working principle. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Titre : Evaluation of the dynamic transfer matrix of cavitating inducers by means of a simplified “lumped-parameter” model Type de document : texte imprimé Auteurs : Angelo Cervone, Auteur ; Yoshinobu Tsujimoto, Auteur ; Yutaka Kawata, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure; flow rate oscillations; analytical model; axial inducer test facility Résumé : The paper will present an analytical model for the evaluation of the pressure and flow rate oscillations in a given axial inducer test facility. The proposed reduced order model is based on several simplifying assumptions and takes into account the facility design and the dynamic properties of the tested inducer. The model has been used for evaluating the dynamic performance of a prototype of the LE-7 engine liquid oxygen (LOX) inducer, in tests carried out under given external flow rate excitations. The main results of these calculations will be shown, including the expected oscillations under a wide range of operational conditions and the influence of facility design. Calculations showed that the only way to obtain the two linearly independent test conditions, necessary for evaluating the inducer transfer matrix, is by changing the facility suction line: Any other changes in the facility design would result ineffective. Some other important design indications provided by the analytical model will be presented in the paper. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Evaluation of the dynamic transfer matrix of cavitating inducers by means of a simplified “lumped-parameter” model [texte imprimé] / Angelo Cervone, Auteur ; Yoshinobu Tsujimoto, Auteur ; Yutaka Kawata, Auteur . - 2009 . - 09 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Mots-clés : pressure; flow rate oscillations; analytical model; axial inducer test facility Résumé : The paper will present an analytical model for the evaluation of the pressure and flow rate oscillations in a given axial inducer test facility. The proposed reduced order model is based on several simplifying assumptions and takes into account the facility design and the dynamic properties of the tested inducer. The model has been used for evaluating the dynamic performance of a prototype of the LE-7 engine liquid oxygen (LOX) inducer, in tests carried out under given external flow rate excitations. The main results of these calculations will be shown, including the expected oscillations under a wide range of operational conditions and the influence of facility design. Calculations showed that the only way to obtain the two linearly independent test conditions, necessary for evaluating the inducer transfer matrix, is by changing the facility suction line: Any other changes in the facility design would result ineffective. Some other important design indications provided by the analytical model will be presented in the paper. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 17 p.
Titre : RANS analyses of turbofan nozzles with internal wedge deflectors for noise reduction Type de document : texte imprimé Auteurs : James R. DeBonis, Auteur Année de publication : 2009 Article en page(s) : 17 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : computational fluid dynamics; offset stream technology; Reynolds averaged Navier–Stokes code; flow field Résumé : Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] RANS analyses of turbofan nozzles with internal wedge deflectors for noise reduction [texte imprimé] / James R. DeBonis, Auteur . - 2009 . - 17 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 17 p.
Mots-clés : computational fluid dynamics; offset stream technology; Reynolds averaged Navier–Stokes code; flow field Résumé : Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 07 p.
Titre : Choking phenomena in a vortex flow passing a laval tube : an analytical treatment Type de document : texte imprimé Auteurs : Theo Van Holten, Auteur ; Monique Heiligers, Auteur ; Annemie Jaeken, Auteur Année de publication : 2009 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : vortex flow; Laval nozzle Résumé : The behavior of a vortex flow through a Laval nozzle was studied in connection with the purification of natural gas. By creating a vortex and passing it through a Laval nozzle, the gas will be cooled, and water droplets will form and will be centrifuged out of the gas. This system is named the Condi-Cyclone. An analytical theory is developed to reveal the most important phenomena of the flow, to first order accuracy. Experiments have been performed with a prototype of the Condi-Cyclone. A Euler numerical simulation was performed, using the geometry of the test channel. This paper presents an analytical theory for a vortex flow through a Laval nozzle. It will demonstrate that when a vortex is present the total velocity reaches sonic conditions upstream of the nozzle throat, that the axial component of the velocity in the nozzle throat is equal to the local speed of sound and that the mass flow through the Laval nozzle decreases with increasing vortex strength. The predictions of the analytical theory have been compared with the results of the experiments and the Euler numerical simulation, and it can be concluded that the analytical theory describes the main characteristics of the flow very well. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Choking phenomena in a vortex flow passing a laval tube : an analytical treatment [texte imprimé] / Theo Van Holten, Auteur ; Monique Heiligers, Auteur ; Annemie Jaeken, Auteur . - 2009 . - 07 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 07 p.
Mots-clés : vortex flow; Laval nozzle Résumé : The behavior of a vortex flow through a Laval nozzle was studied in connection with the purification of natural gas. By creating a vortex and passing it through a Laval nozzle, the gas will be cooled, and water droplets will form and will be centrifuged out of the gas. This system is named the Condi-Cyclone. An analytical theory is developed to reveal the most important phenomena of the flow, to first order accuracy. Experiments have been performed with a prototype of the Condi-Cyclone. A Euler numerical simulation was performed, using the geometry of the test channel. This paper presents an analytical theory for a vortex flow through a Laval nozzle. It will demonstrate that when a vortex is present the total velocity reaches sonic conditions upstream of the nozzle throat, that the axial component of the velocity in the nozzle throat is equal to the local speed of sound and that the mass flow through the Laval nozzle decreases with increasing vortex strength. The predictions of the analytical theory have been compared with the results of the experiments and the Euler numerical simulation, and it can be concluded that the analytical theory describes the main characteristics of the flow very well. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 08 p.
Titre : Pressure drop in rectangular microchannels as compared with theory based on arbitrary cross section Type de document : texte imprimé Auteurs : Mohsen Akbari, Auteur ; David Sinton, Auteur ; Majid Bahrami, Auteur Année de publication : 2009 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure drop; rectangular cross-section microchannels; friction factor; Reynolds number Résumé : Pressure driven liquid flow through rectangular cross-section microchannels is investigated experimentally. Polydimethylsiloxane microchannels are fabricated using soft lithography. Pressure drop data are used to characterize the friction factor over a range of aspect ratios from 0.13 to 0.76 and Reynolds number from 1 to 35 with distilled water as working fluid. Results are compared with the general model developed to predict the fully developed pressure drop in arbitrary cross-section microchannels. Using available theories, effects of different losses, such as developing region, minor flow contraction and expansion, and streaming potential on the measured pressure drop, are investigated. Experimental results compare well with the theory based on the presure drop in channels of arbitrary cross section. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Pressure drop in rectangular microchannels as compared with theory based on arbitrary cross section [texte imprimé] / Mohsen Akbari, Auteur ; David Sinton, Auteur ; Majid Bahrami, Auteur . - 2009 . - 08 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 08 p.
Mots-clés : pressure drop; rectangular cross-section microchannels; friction factor; Reynolds number Résumé : Pressure driven liquid flow through rectangular cross-section microchannels is investigated experimentally. Polydimethylsiloxane microchannels are fabricated using soft lithography. Pressure drop data are used to characterize the friction factor over a range of aspect ratios from 0.13 to 0.76 and Reynolds number from 1 to 35 with distilled water as working fluid. Results are compared with the general model developed to predict the fully developed pressure drop in arbitrary cross-section microchannels. Using available theories, effects of different losses, such as developing region, minor flow contraction and expansion, and streaming potential on the measured pressure drop, are investigated. Experimental results compare well with the theory based on the presure drop in channels of arbitrary cross section. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Titre : Numerical modeling of laminar pulsating flow in porous media Type de document : texte imprimé Auteurs : S.-M. Kim, Auteur ; S. M. Ghiaasiaan, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : laminar pulsating; generic porous structures; computational fluid mechanics tool Résumé : The laminar pulsating flow through porous media was numerically studied. Two-dimensional flows in systems composed of a number of unit cells of generic porous structures were simulated using a computational fluid mechanics tool, with sinusoidal variations in flow with time as the boundary condition. The porous media were periodic arrays of square cylinders. Detailed numerical data for the porosity ranging from 0.64 to 0.84, with flow pulsation frequencies of 20–64 Hz were obtained. Based on these numerical data, the instantaneous as well as the cycle-average permeability and Forchheimer coefficients, to be used in the standard unsteady volume-averaged momentum conservation equation for flow in porous media, were derived. It was found that the cycle-average permeability coefficients were nearly the same as those for steady flow, but the cycle-average Forchheimer coefficients were significantly larger than those for steady flow and were sensitive to the flow oscillation frequency. Significant phase lags were observed between the volume-averaged velocity and the pressure waves. The phase difference between pressure and velocity waves, which is important for pulse tube cryocooling, depended strongly on porosity and the mean-flow Reynolds number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Numerical modeling of laminar pulsating flow in porous media [texte imprimé] / S.-M. Kim, Auteur ; S. M. Ghiaasiaan, Auteur . - 2009 . - 09 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 09 p.
Mots-clés : laminar pulsating; generic porous structures; computational fluid mechanics tool Résumé : The laminar pulsating flow through porous media was numerically studied. Two-dimensional flows in systems composed of a number of unit cells of generic porous structures were simulated using a computational fluid mechanics tool, with sinusoidal variations in flow with time as the boundary condition. The porous media were periodic arrays of square cylinders. Detailed numerical data for the porosity ranging from 0.64 to 0.84, with flow pulsation frequencies of 20–64 Hz were obtained. Based on these numerical data, the instantaneous as well as the cycle-average permeability and Forchheimer coefficients, to be used in the standard unsteady volume-averaged momentum conservation equation for flow in porous media, were derived. It was found that the cycle-average permeability coefficients were nearly the same as those for steady flow, but the cycle-average Forchheimer coefficients were significantly larger than those for steady flow and were sensitive to the flow oscillation frequency. Significant phase lags were observed between the volume-averaged velocity and the pressure waves. The phase difference between pressure and velocity waves, which is important for pulse tube cryocooling, depended strongly on porosity and the mean-flow Reynolds number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 17 p.
Titre : Aerodynamic analysis of a vehicle tanker Type de document : texte imprimé Auteurs : Ramon Miralbes Buil, Auteur ; Luis Castejon Herrer, Auteur Année de publication : 2009 Article en page(s) : 17 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : turbulence; vehicles; tankers Résumé : The aim of this article is the presentation of a series of aerodynamic improvements for semitrailer tankers, which reduce the aerodynamic resistance of these vehicles, and, consequently, result in a positive impact on fuel consumption, which is substantially reduced (up to 11%). To make the analysis the computational fluid dynamics (CFD) methodology, using FLUENT , has been used since it allows simulating some geometries and modifications of the geometry without making physical prototypes that considerably increase the time and the economical resources needed. Three improvements are studied: the aerodynamic front, the undercarriage skirt, and the final box adaptor. First they are studied in isolation, so that the independent contribution of each improvement can be appreciated, while helping in the selection of the most convenient one. With the aerodynamic front the drag coefficient has a reduction of 6.13%, with the underskirt 9.6%, and with the boat tail 7.72%. Finally, all the improvements are jointly examined, resulting in a decrease of up to 23% in aerodynamic drag coefficient. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Aerodynamic analysis of a vehicle tanker [texte imprimé] / Ramon Miralbes Buil, Auteur ; Luis Castejon Herrer, Auteur . - 2009 . - 17 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 17 p.
Mots-clés : turbulence; vehicles; tankers Résumé : The aim of this article is the presentation of a series of aerodynamic improvements for semitrailer tankers, which reduce the aerodynamic resistance of these vehicles, and, consequently, result in a positive impact on fuel consumption, which is substantially reduced (up to 11%). To make the analysis the computational fluid dynamics (CFD) methodology, using FLUENT , has been used since it allows simulating some geometries and modifications of the geometry without making physical prototypes that considerably increase the time and the economical resources needed. Three improvements are studied: the aerodynamic front, the undercarriage skirt, and the final box adaptor. First they are studied in isolation, so that the independent contribution of each improvement can be appreciated, while helping in the selection of the most convenient one. With the aerodynamic front the drag coefficient has a reduction of 6.13%, with the underskirt 9.6%, and with the boat tail 7.72%. Finally, all the improvements are jointly examined, resulting in a decrease of up to 23% in aerodynamic drag coefficient. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 05 p.
Titre : Free surface model derived from the analytical solution of stokes flow in a wedge Type de document : texte imprimé Auteurs : R. W. Hewson, Auteur Année de publication : 2009 Article en page(s) : 05 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow (dynamics); lubrication; coating processes; coatings; finite element methods; differential equations; finite element analysis; boundary-value problems; creeping flow; equations; film thickness; finite element model; wedges; lubrication theory Résumé : The formation of a thin liquid film onto a moving substrate is a commonly encountered industrial process, and one that is encountered in lubrication, oil extraction processes, and coating flows. The formation of such a film is analyzed via the analytical Stokes flow solution for the flow in a wedge bounded on one side by a free surface and on the other by a moving surface. The full solution is obtained by numerically integrating a set of ordinary differential equations from far downstream, in the region of the final film thickness. The results show excellent agreement with the results obtained by the Bretherton equation, the Ruschak equation, the Coyne and Elrod model, and a two-dimensional free surface finite element simulation of the problem. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Free surface model derived from the analytical solution of stokes flow in a wedge [texte imprimé] / R. W. Hewson, Auteur . - 2009 . - 05 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 05 p.
Mots-clés : flow (dynamics); lubrication; coating processes; coatings; finite element methods; differential equations; finite element analysis; boundary-value problems; creeping flow; equations; film thickness; finite element model; wedges; lubrication theory Résumé : The formation of a thin liquid film onto a moving substrate is a commonly encountered industrial process, and one that is encountered in lubrication, oil extraction processes, and coating flows. The formation of such a film is analyzed via the analytical Stokes flow solution for the flow in a wedge bounded on one side by a free surface and on the other by a moving surface. The full solution is obtained by numerically integrating a set of ordinary differential equations from far downstream, in the region of the final film thickness. The results show excellent agreement with the results obtained by the Bretherton equation, the Ruschak equation, the Coyne and Elrod model, and a two-dimensional free surface finite element simulation of the problem. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 11 p.
Titre : Numerical and experimental investigations of steam condensation in LP part of a large power turbine Type de document : texte imprimé Auteurs : WIodzimierz Wroblewski, Auteur ; SIawomir Dykas, Auteur ; Andrzej Gardzilewicz, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : steam flow; low-pressure; condensation Résumé : This paper presents the experimental investigations of steam flow with condensation in the blading system of the low-pressure (LP) part of a 360 MW turbine. To this end, special probes were used, which provided flow visualization opportunities including localization of the front of condensation, determining distributions of pressure, temperature, velocity, and flow angle in the inter-row gaps, measurements of water droplet concentration and sizes. The measurements have proved that the condensation process in the LP turbine might be of heterogeneous nature, depending on the concentration of chemical impurities in steam. The measurement results constituted the basis for computational fluid dynamics (CFD) flow calculations, which were performed using the time-dependent 3D Reynolds averaged Navier–Stokes equations coupled with two-equation turbulence model (k-ω SST) and additional conservation equations for the liquid phase. The set of governing equations has been closed by a “local” real gas equation of state. The condensation phenomena were modeled on the basis of the classical nucleation theory. The heterogeneous condensation model on the insoluble and soluble impurities was implemented into presented CFD code. The system of governing equations was solved by means of a finite volume method on a multiblock structured grid. The obtained numerical results and experimental data were compared and discussed. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Numerical and experimental investigations of steam condensation in LP part of a large power turbine [texte imprimé] / WIodzimierz Wroblewski, Auteur ; SIawomir Dykas, Auteur ; Andrzej Gardzilewicz, Auteur . - 2009 . - 11 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 11 p.
Mots-clés : steam flow; low-pressure; condensation Résumé : This paper presents the experimental investigations of steam flow with condensation in the blading system of the low-pressure (LP) part of a 360 MW turbine. To this end, special probes were used, which provided flow visualization opportunities including localization of the front of condensation, determining distributions of pressure, temperature, velocity, and flow angle in the inter-row gaps, measurements of water droplet concentration and sizes. The measurements have proved that the condensation process in the LP turbine might be of heterogeneous nature, depending on the concentration of chemical impurities in steam. The measurement results constituted the basis for computational fluid dynamics (CFD) flow calculations, which were performed using the time-dependent 3D Reynolds averaged Navier–Stokes equations coupled with two-equation turbulence model (k-ω SST) and additional conservation equations for the liquid phase. The set of governing equations has been closed by a “local” real gas equation of state. The condensation phenomena were modeled on the basis of the classical nucleation theory. The heterogeneous condensation model on the insoluble and soluble impurities was implemented into presented CFD code. The system of governing equations was solved by means of a finite volume method on a multiblock structured grid. The obtained numerical results and experimental data were compared and discussed. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 07 p.
Titre : The effects of inlet geometry and gas-liquid mixing on two-phase flow in microchannels Type de document : texte imprimé Auteurs : M. Kawaji, Auteur ; K. Mori, Auteur ; D. Bolintineanu, Auteur Année de publication : 2009 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : gas-liquid inlet geometry; adiabatic gas-liquid two-phase flow; T-junction inlet; microchannel Résumé : The effects of gas-liquid inlet geometry and mixing method on adiabatic gas-liquid two-phase flow in a microchannel of 100 μm diameter have been investigated using a T-junction inlet with the same internal diameter as the microchannel. Two-phase flow patterns, void fraction, and friction pressure drop data obtained with the T-junction inlet were found to be significantly different from those obtained previously with a reducer inlet. For the T-junction inlet, the two-phase flow patterns in the microchannel were predominantly intermittent flows with short gas and liquid plugs/slugs flowing with nearly equal velocities. The void fraction data then conformed nearly to that of a homogeneous flow model, and the two-phase friction multiplier data could be described by the Lockhart–Martinelli correlation applicable to larger channels. However, when a reducer inlet was used previously and the diameter of the inlet section was much larger than that of the microchannel, an intermittent flow of long gas slugs separated by long liquid slugs became prevalent and the void fraction decreased to values far below the homogeneous void fraction. The differences in the two-phase flow characteristics between a T-junction inlet and reducer inlet were attributed to the differences in the gas bubble/slug generation mechanisms. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] The effects of inlet geometry and gas-liquid mixing on two-phase flow in microchannels [texte imprimé] / M. Kawaji, Auteur ; K. Mori, Auteur ; D. Bolintineanu, Auteur . - 2009 . - 07 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 07 p.
Mots-clés : gas-liquid inlet geometry; adiabatic gas-liquid two-phase flow; T-junction inlet; microchannel Résumé : The effects of gas-liquid inlet geometry and mixing method on adiabatic gas-liquid two-phase flow in a microchannel of 100 μm diameter have been investigated using a T-junction inlet with the same internal diameter as the microchannel. Two-phase flow patterns, void fraction, and friction pressure drop data obtained with the T-junction inlet were found to be significantly different from those obtained previously with a reducer inlet. For the T-junction inlet, the two-phase flow patterns in the microchannel were predominantly intermittent flows with short gas and liquid plugs/slugs flowing with nearly equal velocities. The void fraction data then conformed nearly to that of a homogeneous flow model, and the two-phase friction multiplier data could be described by the Lockhart–Martinelli correlation applicable to larger channels. However, when a reducer inlet was used previously and the diameter of the inlet section was much larger than that of the microchannel, an intermittent flow of long gas slugs separated by long liquid slugs became prevalent and the void fraction decreased to values far below the homogeneous void fraction. The differences in the two-phase flow characteristics between a T-junction inlet and reducer inlet were attributed to the differences in the gas bubble/slug generation mechanisms. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 06 p.
Titre : A principle to generate flow for thermal convective base sensors Type de document : texte imprimé Auteurs : Dinh, Thien X., Auteur ; Ogami, Yoshifumi, Auteur Année de publication : 2009 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow (dynamics); channels (hydraulic engineering); sensors; jets; nozzles; membranes Résumé : This paper presents a thin millimeter-scaled device that can generate a closed flow within itself with a velocity of the order of a few m/s. The device comprises a piezoelectric pump with a PZT membrane, housing chamber, and a closed network channel connected to the housing chamber through a specific throat. We investigate the device by computational fluid dynamics. This device is used to produce several free jet flows depending on the structure of the network channel. In this study, four jet flows comprising two perpendicular pairs of flows are demonstrated. If the PZT membrane vibrates within a suitable range, the self-similarity of the axial velocity (along the jet direction) to the cross distances scaled by the half-widths of the jet is observed for a certain range of axial distance. Each jet flow can bend almost freely in three dimensions. The two remaining flow components are small as compared to the axial component. The device potentially has wide applications in flow-based sensors. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A principle to generate flow for thermal convective base sensors [texte imprimé] / Dinh, Thien X., Auteur ; Ogami, Yoshifumi, Auteur . - 2009 . - 06 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 06 p.
Mots-clés : flow (dynamics); channels (hydraulic engineering); sensors; jets; nozzles; membranes Résumé : This paper presents a thin millimeter-scaled device that can generate a closed flow within itself with a velocity of the order of a few m/s. The device comprises a piezoelectric pump with a PZT membrane, housing chamber, and a closed network channel connected to the housing chamber through a specific throat. We investigate the device by computational fluid dynamics. This device is used to produce several free jet flows depending on the structure of the network channel. In this study, four jet flows comprising two perpendicular pairs of flows are demonstrated. If the PZT membrane vibrates within a suitable range, the self-similarity of the axial velocity (along the jet direction) to the cross distances scaled by the half-widths of the jet is observed for a certain range of axial distance. Each jet flow can bend almost freely in three dimensions. The two remaining flow components are small as compared to the axial component. The device potentially has wide applications in flow-based sensors. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 03 p.
Titre : Pressurized flow in a mesostructured silica modified by silane groups Type de document : texte imprimé Auteurs : Venkata K. Punyamurtula, Auteur ; Aijie Han, Auteur ; Qiao, Yu, Auteur Année de publication : 2009 Article en page(s) : 03 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : quasihydrostatic pressure; electrolyte solution; MSU-H mesoporous silica Résumé : By applying a quasihydrostatic pressure, water or electrolyte solution can be compressed into a surface treated MSU-H mesoporous silica. Based on the pressure-volume curves, thermodynamic and kinetic characteristics of the pressurized flow are analyzed. For pure water based system, continuum theory explains the testing data quite well but fails to capture the rate effect. For electrolyte solution based system, the classic interface theory breaks down, probably due to the unique ion behaviors in the nanoenvironment. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Pressurized flow in a mesostructured silica modified by silane groups [texte imprimé] / Venkata K. Punyamurtula, Auteur ; Aijie Han, Auteur ; Qiao, Yu, Auteur . - 2009 . - 03 p.
fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 4 (Avril 2009) . - 03 p.
Mots-clés : quasihydrostatic pressure; electrolyte solution; MSU-H mesoporous silica Résumé : By applying a quasihydrostatic pressure, water or electrolyte solution can be compressed into a surface treated MSU-H mesoporous silica. Based on the pressure-volume curves, thermodynamic and kinetic characteristics of the pressurized flow are analyzed. For pure water based system, continuum theory explains the testing data quite well but fails to capture the rate effect. For electrolyte solution based system, the classic interface theory breaks down, probably due to the unique ion behaviors in the nanoenvironment. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
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