Dépouillements

A method to generate propulsor side forces / Huyer, Stephen A. in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Titre : A method to generate propulsor side forces Type de document : texte imprimé Auteurs : Huyer, Stephen A., Auteur ; Dropkin, Amanda, Auteur ; James Dick, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : generate  vehicle;  preswirl  propulsor;  upstream  stator;  downstream  rotor Résumé : A computational study was performed to investigate a method to generate vehicle maneuvering forces from a propulsor alone. A ducted, preswirl propulsor was configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and preswirl the flow into the propulsor while generating a roll moment to counter the moment produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the axial velocity and swirl that is ingested into the propulsor. The rotor then generates a side force in response to the inflow. Both potential flow and fully viscous 3D Reynolds averaged Navier–Stokes (RANS) computations were used to predict the stator forces, velocity field, and rotor response. Potential flow methods were used for initial examination of a wide variety of stator configurations. The most promising were then modeled using RANS. The RANS inflow was then computed and used as velocity boundary conditions during rotor blade design using potential flow methods. Blade parameters including blade number, rake, skew, and a combination of the two were varied to characterize their effects. RANS was used to then validate the final propulsor design. Computations demonstrated that total side force coefficients on the order of 0.1 and moment coefficients about the stator leading edge of 0.066 could be generated by the propulsor alone. This translates to an additional 50% control authority at 3 kn for current Navy 21″ unmanned undersea vehicles. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A method to generate propulsor side forces [texte imprimé] / Huyer, Stephen A., Auteur ; Dropkin, Amanda, Auteur ; James Dick, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Mots-clés : generate  vehicle;  preswirl  propulsor;  upstream  stator;  downstream  rotor Résumé : A computational study was performed to investigate a method to generate vehicle maneuvering forces from a propulsor alone. A ducted, preswirl propulsor was configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and preswirl the flow into the propulsor while generating a roll moment to counter the moment produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the axial velocity and swirl that is ingested into the propulsor. The rotor then generates a side force in response to the inflow. Both potential flow and fully viscous 3D Reynolds averaged Navier–Stokes (RANS) computations were used to predict the stator forces, velocity field, and rotor response. Potential flow methods were used for initial examination of a wide variety of stator configurations. The most promising were then modeled using RANS. The RANS inflow was then computed and used as velocity boundary conditions during rotor blade design using potential flow methods. Blade parameters including blade number, rake, skew, and a combination of the two were varied to characterize their effects. RANS was used to then validate the final propulsor design. Computations demonstrated that total side force coefficients on the order of 0.1 and moment coefficients about the stator leading edge of 0.066 could be generated by the propulsor alone. This translates to an additional 50% control authority at 3 kn for current Navy 21″ unmanned undersea vehicles. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Computational investigation of a race car wing with vortex generators in ground effect in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) Titre : Computational investigation of a race car wing with vortex generators in ground effect Type de document : texte imprimé Année de publication : 2010 Langues : Anglais (eng) Mots-clés : race  car;  vortex  generator DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Computational investigation of a race car wing with vortex generators in ground effect [texte imprimé] . - 2010. Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) Mots-clés : race  car;  vortex  generator DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Comparison of experiments and simulation of joule heating in ac electrokinetic chips / Stuart J. Williams in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 07 p. Titre : Comparison of experiments and simulation of joule heating in ac electrokinetic chips Type de document : texte imprimé Auteurs : Stuart J. Williams, Auteur ; Pramod Chamarthy, Auteur ; Steven T. Wereley, Auteur Année de publication : 2010 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Résumé : ac electrokinetic manipulations of particles and fluids are important techniques in the development of lab-on-a-chip technologies. Most of these systems involve planar micro-electrode geometries, generating high strength electric fields. When these fields are applied to a dielectric medium, Joule heating occurs. Understanding electrothermal heating and monitoring the temperature in these environments are critical for temperature-sensitive investigations including biological applications. Additionally, significant changes in fluid temperature when subjected to an electric field will induce electrohydrodynamic flows, potentially disrupting the intended microfluidic profile. This work investigates heat generated from the interaction of ac electric fields and water at various electrical conductivities (from 0.92 mS/m to 390 mS/m). The electrode geometry is an indium tin oxide (ITO) electrode strip 20 μm wide and a grounded, planar ITO substrate separated by a 50 μm spacer with microfluidic features. Laser-induced fluorescence is used to measure the experimental changes in temperature. A normalization procedure that requires a single temperature-sensitive dye, Rhodamine B (RhB), is used to reduce uncertainty. The experimental electrothermal results are compared with theory and computer simulations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Comparison of experiments and simulation of joule heating in ac electrokinetic chips [texte imprimé] / Stuart J. Williams, Auteur ; Pramod Chamarthy, Auteur ; Steven T. Wereley, Auteur . - 2010 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 07 p. Résumé : ac electrokinetic manipulations of particles and fluids are important techniques in the development of lab-on-a-chip technologies. Most of these systems involve planar micro-electrode geometries, generating high strength electric fields. When these fields are applied to a dielectric medium, Joule heating occurs. Understanding electrothermal heating and monitoring the temperature in these environments are critical for temperature-sensitive investigations including biological applications. Additionally, significant changes in fluid temperature when subjected to an electric field will induce electrohydrodynamic flows, potentially disrupting the intended microfluidic profile. This work investigates heat generated from the interaction of ac electric fields and water at various electrical conductivities (from 0.92 mS/m to 390 mS/m). The electrode geometry is an indium tin oxide (ITO) electrode strip 20 μm wide and a grounded, planar ITO substrate separated by a 50 μm spacer with microfluidic features. Laser-induced fluorescence is used to measure the experimental changes in temperature. A normalization procedure that requires a single temperature-sensitive dye, Rhodamine B (RhB), is used to reduce uncertainty. The experimental electrothermal results are compared with theory and computer simulations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Wave propagation in thin-walled aortic analogues / Giannopapa, C. G. in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 06 p. Titre : Wave propagation in thin-walled aortic analogues Type de document : texte imprimé Auteurs : Giannopapa, C. G., Auteur ; J. M. B. Kroot, Auteur ; A. S. Tijsseling, Auteur Année de publication : 2010 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  wave  propagation;  measurement;  waves;  vessels Résumé : Research on wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flows. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one-dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models, well defined in vitro experiments are of great importance. The objective of this paper is to present a frequency domain analytical model based on the one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogs. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, volumetric flow rate, and wall distention obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Wave propagation in thin-walled aortic analogues [texte imprimé] / Giannopapa, C. G., Auteur ; J. M. B. Kroot, Auteur ; A. S. Tijsseling, Auteur . - 2010 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 06 p. Mots-clés : pressure;  flow  (dynamics);  wave  propagation;  measurement;  waves;  vessels Résumé : Research on wave propagation in liquid filled vessels is often motivated by the need to understand arterial blood flows. Theoretical and experimental investigation of the propagation of waves in flexible tubes has been studied by many researchers. The analytical one-dimensional frequency domain wave theory has a great advantage of providing accurate results without the additional computational cost related to the modern time domain simulation models. For assessing the validity of analytical and numerical models, well defined in vitro experiments are of great importance. The objective of this paper is to present a frequency domain analytical model based on the one-dimensional wave propagation theory and validate it against experimental data obtained for aortic analogs. The elastic and viscoelastic properties of the wall are included in the analytical model. The pressure, volumetric flow rate, and wall distention obtained from the analytical model are compared with experimental data in two straight tubes with aortic relevance. The analytical results and the experimental measurements were found to be in good agreement when the viscoelastic properties of the wall are taken into account. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Large Eddy simulation of turbulent axial flow along an array of rods / F. Abbasian in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 11 p. Titre : Large Eddy simulation of turbulent axial flow along an array of rods Type de document : texte imprimé Auteurs : F. Abbasian, Auteur ; S. D. Yu, Auteur ; J. Cao, Auteur Année de publication : 2010 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  turbulence;  axial  flow;  rods;  large  eddy  simulation Résumé : Large eddy simulation (LES) is employed in this paper to model the axial flow along a circular array of rods with a focus on anisotropic large-scale turbulence. The circular array consists of four whole rods and eight half rods, with a pitch-to-diameter ratio of 1.08. A dynamic Smagorinsky model with SIMPLE coupling method and a bounded central difference scheme are used to reduce numerical errors. The high demands for computations of the three-dimensional turbulent flows are afforded through parallel processing and utilization of 20 processors. The numerical results obtained using LES are compared with independent experimental data available in the literature; good agreement is achieved. The LES model was developed to accurately predict (i) the dependence of turbulence intensity and dominant frequency on the gap size and (ii) the turbulence structure in different directions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] Large Eddy simulation of turbulent axial flow along an array of rods [texte imprimé] / F. Abbasian, Auteur ; S. D. Yu, Auteur ; J. Cao, Auteur . - 2010 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 11 p. Mots-clés : flow  (dynamics);  turbulence;  axial  flow;  rods;  large  eddy  simulation Résumé : Large eddy simulation (LES) is employed in this paper to model the axial flow along a circular array of rods with a focus on anisotropic large-scale turbulence. The circular array consists of four whole rods and eight half rods, with a pitch-to-diameter ratio of 1.08. A dynamic Smagorinsky model with SIMPLE coupling method and a bounded central difference scheme are used to reduce numerical errors. The high demands for computations of the three-dimensional turbulent flows are afforded through parallel processing and utilization of 20 processors. The numerical results obtained using LES are compared with independent experimental data available in the literature; good agreement is achieved. The LES model was developed to accurately predict (i) the dependence of turbulence intensity and dominant frequency on the gap size and (ii) the turbulence structure in different directions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

A single-stage centripetal pump / Mihael Sekavcnik in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 10 p. Titre : A single-stage centripetal pump : design features and an investigation of the operating characteristics Type de document : texte imprimé Auteurs : Mihael Sekavcnik, Auteur ; Tine Gantar, Auteur ; Mitja Mori, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  impellers;  computational  fluid  dynamics;  design;  pumps;  stators;  inflow Résumé : In this paper, we present an experimental and numerical investigation of a single-stage centripetal pump (SSCP). This SSCP is designed to operate in the pump regime, while forcing the working media through impeller-stator flow channels in the radial inward direction. The measured performance curves are characterized by a hysteresis, since the throttle-closing performance curves do not correspond to the throttle-opening performance curves throughout the whole operating range. A computational fluid dynamics (CFD) model was developed to establish these throttle-closing and throttle-opening performance curves. The flow conditions obtained with the CFD simulations confirm that the hydraulic behavior of the SSCP is influenced by the partial circumferential stall that occurs in the impeller-stator flow channels. It was shown that the inflow conditions to the impeller-stator assembly considerably influence the flow rate of the stall cessation, the size of the hysteresis, and the head generated during part-load operations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] A single-stage centripetal pump : design features and an investigation of the operating characteristics [texte imprimé] / Mihael Sekavcnik, Auteur ; Tine Gantar, Auteur ; Mitja Mori, Auteur . - 2010 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 10 p. Mots-clés : flow  (dynamics);  impellers;  computational  fluid  dynamics;  design;  pumps;  stators;  inflow Résumé : In this paper, we present an experimental and numerical investigation of a single-stage centripetal pump (SSCP). This SSCP is designed to operate in the pump regime, while forcing the working media through impeller-stator flow channels in the radial inward direction. The measured performance curves are characterized by a hysteresis, since the throttle-closing performance curves do not correspond to the throttle-opening performance curves throughout the whole operating range. A computational fluid dynamics (CFD) model was developed to establish these throttle-closing and throttle-opening performance curves. The flow conditions obtained with the CFD simulations confirm that the hydraulic behavior of the SSCP is influenced by the partial circumferential stall that occurs in the impeller-stator flow channels. It was shown that the inflow conditions to the impeller-stator assembly considerably influence the flow rate of the stall cessation, the size of the hysteresis, and the head generated during part-load operations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

On the relationships among strouhal number, pressure drag, and separation pressure for blocked bluff-body flow / W. W. H. Yeung in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 10 p. Titre : On the relationships among strouhal number, pressure drag, and separation pressure for blocked bluff-body flow Type de document : texte imprimé Auteurs : W. W. H. Yeung, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Résumé : Strouhal number, pressure drag, and separation pressure are some of the intrinsic parameters for investigating the flow around a bluff-body. An attempt is made to formulate a relationship involving these quantities for flow around a two-dimensional bluff section of various shapes in a confined environment such as a wind tunnel. It includes (a) establishing a relation between the Strouhal number and a modified Strouhal number by a theoretical wake width and (b) incorporating this wake width into a momentum equation to determine the pressure drag. Comparisons have been made with the experimental data, a theoretical prediction (for unconfined flow), and an empirical proposal in literature to indicate that the present methodology is appropriate. Together with its extension to axisymmetric bodies, the current method is able to provide proper limits to the experimental data for a rectangular flat-plate of various width-to-span ratios. In addition, if the separation pressure is given, then the Strouhal number is inversely proportional to the drag coefficient, being comparable to a proposal based on statistical results. Finally, through an example, it is also demonstrated how one of these three parameters may be reasonably estimated from the measured values of the other two. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] On the relationships among strouhal number, pressure drag, and separation pressure for blocked bluff-body flow [texte imprimé] / W. W. H. Yeung, Auteur . - 2010 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 10 p. Résumé : Strouhal number, pressure drag, and separation pressure are some of the intrinsic parameters for investigating the flow around a bluff-body. An attempt is made to formulate a relationship involving these quantities for flow around a two-dimensional bluff section of various shapes in a confined environment such as a wind tunnel. It includes (a) establishing a relation between the Strouhal number and a modified Strouhal number by a theoretical wake width and (b) incorporating this wake width into a momentum equation to determine the pressure drag. Comparisons have been made with the experimental data, a theoretical prediction (for unconfined flow), and an empirical proposal in literature to indicate that the present methodology is appropriate. Together with its extension to axisymmetric bodies, the current method is able to provide proper limits to the experimental data for a rectangular flat-plate of various width-to-span ratios. In addition, if the separation pressure is given, then the Strouhal number is inversely proportional to the drag coefficient, being comparable to a proposal based on statistical results. Finally, through an example, it is also demonstrated how one of these three parameters may be reasonably estimated from the measured values of the other two. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

On the streamwise development of density jumps / A. Regev in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Titre : On the streamwise development of density jumps Type de document : texte imprimé Auteurs : A. Regev, Auteur ; S. Hassid, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : density  jump;  entrainment;  stratified  flow Résumé : The analysis of density jumps in two-layer channel flows of miscible fluids controlled by a downstream obstruction, in which one of the layers is infinitely deep and at rest, is extended to consider the dependence of its features on its streamwise dimension. The momentum conservation equation in the entrainment and roller regions, and the energy conservation equation after the jump are corrected to account for friction. The streamwise coordinate is related to the increase in the density layer height through a linear expression derived from CFD calculations. Three regimes are distinguished: (1) for short distances from the origin to the obstruction, only an entrainment region exists; (2) for medium distances, two regions can be distinguished, i.e., the entrainment region, and the roller region, in which no entrainment is assumed; and (3) for long distances, three regions can be distinguished—the entrainment, the roller, and the postjump regions, characterized by approximate energy conservation. It is shown that initially the dimensionless total entrainment ratio increases as the distance to the obstruction increases, until a roller region appears. A further increase in distance to the obstruction does not have a significant effect on the total entrainment, until the appearance of a postjump region, resulting in a gradual decrease in the total entrainment. These results are supported by numerical calculations using the FLUENT CFD software package, which are in good agreement with experimental results. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] On the streamwise development of density jumps [texte imprimé] / A. Regev, Auteur ; S. Hassid, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Mots-clés : density  jump;  entrainment;  stratified  flow Résumé : The analysis of density jumps in two-layer channel flows of miscible fluids controlled by a downstream obstruction, in which one of the layers is infinitely deep and at rest, is extended to consider the dependence of its features on its streamwise dimension. The momentum conservation equation in the entrainment and roller regions, and the energy conservation equation after the jump are corrected to account for friction. The streamwise coordinate is related to the increase in the density layer height through a linear expression derived from CFD calculations. Three regimes are distinguished: (1) for short distances from the origin to the obstruction, only an entrainment region exists; (2) for medium distances, two regions can be distinguished, i.e., the entrainment region, and the roller region, in which no entrainment is assumed; and (3) for long distances, three regions can be distinguished—the entrainment, the roller, and the postjump regions, characterized by approximate energy conservation. It is shown that initially the dimensionless total entrainment ratio increases as the distance to the obstruction increases, until a roller region appears. A further increase in distance to the obstruction does not have a significant effect on the total entrainment, until the appearance of a postjump region, resulting in a gradual decrease in the total entrainment. These results are supported by numerical calculations using the FLUENT CFD software package, which are in good agreement with experimental results. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

Experimental study of a cavitating centrifugal pump during fast startups / S. Duplaa in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 12 p. Titre : Experimental study of a cavitating centrifugal pump during fast startups Type de document : texte imprimé Auteurs : S. Duplaa, Auteur ; O. Coutier-Delgosha, Auteur ; A. Dazin, Auteur Année de publication : 2010 Article en page(s) : 12 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : cavitating  centrifugal  pump Résumé : The startup of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations, which may result in partial flow vaporization, i.e., cavitation. An existing experimental test rig has been updated in the LML Laboratory (Lille, France) for the startups of a centrifugal pump. The study focuses on the cavitation induced during the pump startup. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast startup behaviors have been identified. According to the final operating point, the startup is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed in both the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] Experimental study of a cavitating centrifugal pump during fast startups [texte imprimé] / S. Duplaa, Auteur ; O. Coutier-Delgosha, Auteur ; A. Dazin, Auteur . - 2010 . - 12 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 12 p. Mots-clés : cavitating  centrifugal  pump Résumé : The startup of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations, which may result in partial flow vaporization, i.e., cavitation. An existing experimental test rig has been updated in the LML Laboratory (Lille, France) for the startups of a centrifugal pump. The study focuses on the cavitation induced during the pump startup. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast startup behaviors have been identified. According to the final operating point, the startup is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed in both the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

Computational and experimental studies on cavity filling process by cold gas dynamic spray / Hidemasa Takana in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Titre : Computational and experimental studies on cavity filling process by cold gas dynamic spray Type de document : texte imprimé Auteurs : Hidemasa Takana, Auteur ; HongYang Li, Auteur ; Kazuhiro Ogawa, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Résumé : Time-dependent computational simulations on cavity filling process by cold gas dynamic spray and powder jet deposition process ranging from microscale to macroscale were carried out in order to give an insight for their advanced applications to joining, crack repair, and dental treatment. Shock wave appears in front of the substrate due to underexpansion of jet and in-flight particles interact with the shock wave before their impact. The relation between shock wave, cavity configuration, and particle in-flight behavior in supersonic jet has been discussed in detail. Based on numerical and experimental studies, it was found that when the shock wave covers up the cylindrical cavity, the cavity cannot be filled at all by deposited powders. Moreover, under the condition of shock wave appearing inside the cylindrical cavity, conical deposition was formed due to the secondary back flow jet along the cavity side wall. By adopting conical cavity, cavity can be filled completely resulting from the suppression of the secondary back flow jet along the cavity side wall. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] Computational and experimental studies on cavity filling process by cold gas dynamic spray [texte imprimé] / Hidemasa Takana, Auteur ; HongYang Li, Auteur ; Kazuhiro Ogawa, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Résumé : Time-dependent computational simulations on cavity filling process by cold gas dynamic spray and powder jet deposition process ranging from microscale to macroscale were carried out in order to give an insight for their advanced applications to joining, crack repair, and dental treatment. Shock wave appears in front of the substrate due to underexpansion of jet and in-flight particles interact with the shock wave before their impact. The relation between shock wave, cavity configuration, and particle in-flight behavior in supersonic jet has been discussed in detail. Based on numerical and experimental studies, it was found that when the shock wave covers up the cylindrical cavity, the cavity cannot be filled at all by deposited powders. Moreover, under the condition of shock wave appearing inside the cylindrical cavity, conical deposition was formed due to the secondary back flow jet along the cavity side wall. By adopting conical cavity, cavity can be filled completely resulting from the suppression of the secondary back flow jet along the cavity side wall. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

Thermodynamic effect on a cavitating inducer—Part I: geometrical similarity of leading edge cavities and cavitation instabilities / Jean-Pierre Franc in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 08 p. Titre : Thermodynamic effect on a cavitating inducer—Part I: geometrical similarity of leading edge cavities and cavitation instabilities Type de document : texte imprimé Auteurs : Jean-Pierre Franc, Auteur ; Guillaume Boitel, Auteur ; Michel Riondet, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Résumé : The thermodynamic effect on a cavitating inducer is investigated from joint experiments in cold water and Refrigerant 114. The analysis is focused on leading edge cavitation and cavitation instabilities, especially on alternate blade cavitation and supersynchronous rotating cavitation. The cavity length along cylindrical cuts at different radii between the hub and casing is analyzed with respect to the local cavitation number and angle of attack. The similarity in shape of the cavity closure line between water and R114 is examined and deviation caused by thermodynamic effect is clarified. The influence of rotation speed on cavity length is investigated in both fluids and analyzed on the basis of a comparison of characteristic times, namely, the transit time and a thermal time. Thermodynamic delay in the development of leading edge cavities is determined and temperature depressions within the cavities are estimated. Thresholds for the onset of cavitation instabilities are determined for both fluids. The occurrence of cavitation instabilities is discussed with respect to the extent of leading edge cavitation. The thermodynamic delay affecting the occurrence of cavitation instabilities is estimated and compared with the delay on cavity development. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] Thermodynamic effect on a cavitating inducer—Part I: geometrical similarity of leading edge cavities and cavitation instabilities [texte imprimé] / Jean-Pierre Franc, Auteur ; Guillaume Boitel, Auteur ; Michel Riondet, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 08 p. Résumé : The thermodynamic effect on a cavitating inducer is investigated from joint experiments in cold water and Refrigerant 114. The analysis is focused on leading edge cavitation and cavitation instabilities, especially on alternate blade cavitation and supersynchronous rotating cavitation. The cavity length along cylindrical cuts at different radii between the hub and casing is analyzed with respect to the local cavitation number and angle of attack. The similarity in shape of the cavity closure line between water and R114 is examined and deviation caused by thermodynamic effect is clarified. The influence of rotation speed on cavity length is investigated in both fluids and analyzed on the basis of a comparison of characteristic times, namely, the transit time and a thermal time. Thermodynamic delay in the development of leading edge cavities is determined and temperature depressions within the cavities are estimated. Thresholds for the onset of cavitation instabilities are determined for both fluids. The occurrence of cavitation instabilities is discussed with respect to the extent of leading edge cavitation. The thermodynamic delay affecting the occurrence of cavitation instabilities is estimated and compared with the delay on cavity development. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

Thermodynamic effect on a cavitating inducer—Part II: on-board measurements of temperature depression within leading edge cavities / Jean-Pierre Franc in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Titre : Thermodynamic effect on a cavitating inducer—Part II: on-board measurements of temperature depression within leading edge cavities Type de document : texte imprimé Auteurs : Jean-Pierre Franc, Auteur ; Guillaume Boitel, Auteur ; Michel Riondet, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Temperature,  Cavitation,  Blades,  Cavities Résumé : Temperature depression within the leading edge cavities on a space inducer is measured in Refrigerant 114 using miniature thermocouples mounted on the rotating blades. Time-averaged values of cavity temperature depression are determined all along the descent in cavitation number and correlated with the extent of cavities. In addition to mean values, temperature fluctuations are analyzed with respect to the onset of cavitation instabilities, namely, alternate blade cavitation and supersynchronous rotating cavitation. Temperature spectra relative to a rotating frame of reference are compared with pressure spectra obtained in a fixed frame of reference. Temperature oscillations issued from different blades are compared, and phase shifts between consecutive and opposite blades are evaluated in the case of the supersynchronous instability regime. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] Thermodynamic effect on a cavitating inducer—Part II: on-board measurements of temperature depression within leading edge cavities [texte imprimé] / Jean-Pierre Franc, Auteur ; Guillaume Boitel, Auteur ; Michel Riondet, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 09 p. Mots-clés : Temperature,  Cavitation,  Blades,  Cavities Résumé : Temperature depression within the leading edge cavities on a space inducer is measured in Refrigerant 114 using miniature thermocouples mounted on the rotating blades. Time-averaged values of cavity temperature depression are determined all along the descent in cavitation number and correlated with the extent of cavities. In addition to mean values, temperature fluctuations are analyzed with respect to the onset of cavitation instabilities, namely, alternate blade cavitation and supersynchronous rotating cavitation. Temperature spectra relative to a rotating frame of reference are compared with pressure spectra obtained in a fixed frame of reference. Temperature oscillations issued from different blades are compared, and phase shifts between consecutive and opposite blades are evaluated in the case of the supersynchronous instability regime. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

An experimental investigation for bubble rising in non-Newtonian fluids and empirical correlation of drag coefficient / Fan Wenyuan in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 07 p. Titre : An experimental investigation for bubble rising in non-Newtonian fluids and empirical correlation of drag coefficient Type de document : texte imprimé Auteurs : Fan Wenyuan, Auteur ; Youguang Ma, Auteur ; Shaokun Jiang, Auteur Année de publication : 2010 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : drag  (fluid  dynamics);  bubbles;  non-Newtonian  fluids Résumé : The velocity, shape, and trajectory of the rising bubble in polyacrylamide (PAM) and carboxymethylcellulose (CMC) aqueous solutions were experimentally investigated using a set of homemade velocimeters and a video camera. The effects of gas the flowrate and solution concentration on the bubble terminal velocity were examined respectively. Results show that the terminal velocity of the bubble increases with the increase in the gas flowrate and the decrease in the solution concentration. The shape of the bubble is gradually flattened horizontally to an ellipsoid with the increase in the Reynolds number (Re), Eötvös number (Eo), and Morton number (Mo). With the increase in the Re and Eo, the rising bubble in PAM aqueous solutions begin to oscillate, but there is no oscillation phenomena for CMC aqueous solutions. By dimensional analysis, the drag coefficient of a single bubble in non-Newtonian fluids in a moderate Reynolds number was correlated as a function of Re, Eo, and Archimedes number (Ar) based on the equivalent bubble diameter. The predicted results by the present correlation agree well with the experimental data. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...] [article] An experimental investigation for bubble rising in non-Newtonian fluids and empirical correlation of drag coefficient [texte imprimé] / Fan Wenyuan, Auteur ; Youguang Ma, Auteur ; Shaokun Jiang, Auteur . - 2010 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 2 (Fevrier 2010) . - 07 p. Mots-clés : drag  (fluid  dynamics);  bubbles;  non-Newtonian  fluids Résumé : The velocity, shape, and trajectory of the rising bubble in polyacrylamide (PAM) and carboxymethylcellulose (CMC) aqueous solutions were experimentally investigated using a set of homemade velocimeters and a video camera. The effects of gas the flowrate and solution concentration on the bubble terminal velocity were examined respectively. Results show that the terminal velocity of the bubble increases with the increase in the gas flowrate and the decrease in the solution concentration. The shape of the bubble is gradually flattened horizontally to an ellipsoid with the increase in the Reynolds number (Re), Eötvös number (Eo), and Morton number (Mo). With the increase in the Re and Eo, the rising bubble in PAM aqueous solutions begin to oscillate, but there is no oscillation phenomena for CMC aqueous solutions. By dimensional analysis, the drag coefficient of a single bubble in non-Newtonian fluids in a moderate Reynolds number was correlated as a function of Re, Eo, and Archimedes number (Ar) based on the equivalent bubble diameter. The predicted results by the present correlation agree well with the experimental data. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27408 [...]

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