Dépouillements

Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes / Jesús Manuel Fernández Oro in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 12 p. Titre : Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes Type de document : texte imprimé Auteurs : Jesús Manuel Fernández Oro, Auteur ; Katia María Argüelles Díaz, Auteur ; Carlos Santolaria Morros, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Periodic  stator-rotor  interaction;  low-speed  axial  fan;  inlet  guide  vanes;  fluctuation Résumé : This paper is conceived as an extension in the analysis of the periodic stator-rotor interaction in a low-speed axial fan with inlet guide vanes. Here, the present work focuses on the deterministic fluctuations that occur in the axial gap between the blade rows. In particular, we present experimental data on the phase averaged velocity in the stator frame of reference. Detailed measurements of the flow field were obtained using hot-wire anemometry in a traverse sector that covered the whole span of the stage for a complete stator pitch. The blade-to-blade velocity gradient in the rotor passage is observed as an unsteady flow in the stator frame of reference due to the relative motion of the blades. As a consequence, this periodic fluctuation is superimposed on the steady vane-to-vane velocity distribution, resulting in a nonuniform unsteadiness with additional phase-dependent wake-blockage interaction. This phase-dependent interaction is determined by the difference between the overall deterministic fluctuation and the rotating spatial blade-to-blade distribution, when the latter is accurately transformed to the stator reference frame. The results revealed that high unsteadiness in the tip region is mainly derived from the radial increase of the blade-to-blade nonuniformities in the rotor, whereas the wake-blockage interaction exhibits a spanwise uniform distribution. Hence, the hub-to-tip torsion of the blades is responsible for setting off a major spatial distortion between the rows. Complementarily, we observed that a reduction in the rows’ spacing or an increase in the blade loadings leads to a higher wake-blockage interaction, modifying the impingement of the incoming stator wakes. In addition, the deterministic stresses were calculated by time averaging the phase-dependent velocity correlations and compared to the turbulent stresses. The deterministic stresses were also segregated in temporal, spatial, and spatial-temporal correlations in order to analyze the dominant mechanisms involved in their generation. At this point, the deterministic kinetic energy levels were found to be generally lower than turbulent kinetic energy levels, with both temporal and spatial correlations being the most significant terms of the tensor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes [texte imprimé] / Jesús Manuel Fernández Oro, Auteur ; Katia María Argüelles Díaz, Auteur ; Carlos Santolaria Morros, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 12 p. Mots-clés : Periodic  stator-rotor  interaction;  low-speed  axial  fan;  inlet  guide  vanes;  fluctuation Résumé : This paper is conceived as an extension in the analysis of the periodic stator-rotor interaction in a low-speed axial fan with inlet guide vanes. Here, the present work focuses on the deterministic fluctuations that occur in the axial gap between the blade rows. In particular, we present experimental data on the phase averaged velocity in the stator frame of reference. Detailed measurements of the flow field were obtained using hot-wire anemometry in a traverse sector that covered the whole span of the stage for a complete stator pitch. The blade-to-blade velocity gradient in the rotor passage is observed as an unsteady flow in the stator frame of reference due to the relative motion of the blades. As a consequence, this periodic fluctuation is superimposed on the steady vane-to-vane velocity distribution, resulting in a nonuniform unsteadiness with additional phase-dependent wake-blockage interaction. This phase-dependent interaction is determined by the difference between the overall deterministic fluctuation and the rotating spatial blade-to-blade distribution, when the latter is accurately transformed to the stator reference frame. The results revealed that high unsteadiness in the tip region is mainly derived from the radial increase of the blade-to-blade nonuniformities in the rotor, whereas the wake-blockage interaction exhibits a spanwise uniform distribution. Hence, the hub-to-tip torsion of the blades is responsible for setting off a major spatial distortion between the rows. Complementarily, we observed that a reduction in the rows’ spacing or an increase in the blade loadings leads to a higher wake-blockage interaction, modifying the impingement of the incoming stator wakes. In addition, the deterministic stresses were calculated by time averaging the phase-dependent velocity correlations and compared to the turbulent stresses. The deterministic stresses were also segregated in temporal, spatial, and spatial-temporal correlations in order to analyze the dominant mechanisms involved in their generation. At this point, the deterministic kinetic energy levels were found to be generally lower than turbulent kinetic energy levels, with both temporal and spatial correlations being the most significant terms of the tensor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Effects of corrugated roughness on developed laminar flow in microtubes / Zhipeng Duan in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Titre : Effects of corrugated roughness on developed laminar flow in microtubes Type de document : texte imprimé Auteurs : Zhipeng Duan, Auteur ; Y. S. Muzychka, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Corrugated  surface  roughness;  laminar  flow;  momentum  equation Résumé : The effects of corrugated surface roughness on developed laminar flow in microtubes are investigated. The momentum equation is solved using a perturbation method with slip at the boundary. Novel analytical models are developed to predict friction factor and pressure drop in corrugated rough microtubes for continuum flow and slip flow. The developed model proposes an explanation on the observed phenomenon that some experimental pressure drop results for microchannel flow have shown a significant increase (15–50%) due to roughness. The developed model for slip flow illustrates the coupled effects between velocity slip and small corrugated roughness. Compressibility effect has also been examined and simple models are proposed to predict the pressure distribution and mass flow rate for slip flow in corrugated rough microtubes. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Effects of corrugated roughness on developed laminar flow in microtubes [texte imprimé] / Zhipeng Duan, Auteur ; Y. S. Muzychka, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Mots-clés : Corrugated  surface  roughness;  laminar  flow;  momentum  equation Résumé : The effects of corrugated surface roughness on developed laminar flow in microtubes are investigated. The momentum equation is solved using a perturbation method with slip at the boundary. Novel analytical models are developed to predict friction factor and pressure drop in corrugated rough microtubes for continuum flow and slip flow. The developed model proposes an explanation on the observed phenomenon that some experimental pressure drop results for microchannel flow have shown a significant increase (15–50%) due to roughness. The developed model for slip flow illustrates the coupled effects between velocity slip and small corrugated roughness. Compressibility effect has also been examined and simple models are proposed to predict the pressure distribution and mass flow rate for slip flow in corrugated rough microtubes. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Influence of staggering angle of a rotating rod on flow past a circular cylinder / T. Ayyappan in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 11 p. Titre : Influence of staggering angle of a rotating rod on flow past a circular cylinder Type de document : texte imprimé Auteurs : T. Ayyappan, Auteur ; S. Vengadesan, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Circular  cylinder;  rotating  rod;  Reynolds  number Résumé : The influence of the staggering position of a rotating rod on flow past a main circular cylinder is investigated numerically. The rod is rotated at a constant speed ratio of 3. The effect of the diameter ratio of the rotating rod is studied by considering two different diameter ratios. The investigation is carried out at a fixed pitch length of 1. The study is carried out for two Reynolds number, viz., 100 and 500. The momentum injection from the rod is found to alter the flow characteristics behind the main cylinder. For a certain arrangement of stagger angle and diameter ratio, the vortex shedding behind the main cylinder gets suppressed. The corresponding configuration for which minimum drag coefficient is achieved is suggested from this study. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Influence of staggering angle of a rotating rod on flow past a circular cylinder [texte imprimé] / T. Ayyappan, Auteur ; S. Vengadesan, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 11 p. Mots-clés : Circular  cylinder;  rotating  rod;  Reynolds  number Résumé : The influence of the staggering position of a rotating rod on flow past a main circular cylinder is investigated numerically. The rod is rotated at a constant speed ratio of 3. The effect of the diameter ratio of the rotating rod is studied by considering two different diameter ratios. The investigation is carried out at a fixed pitch length of 1. The study is carried out for two Reynolds number, viz., 100 and 500. The momentum injection from the rod is found to alter the flow characteristics behind the main cylinder. For a certain arrangement of stagger angle and diameter ratio, the vortex shedding behind the main cylinder gets suppressed. The corresponding configuration for which minimum drag coefficient is achieved is suggested from this study. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Numerical and experimental studies of oscillatory airflows induced by rotation of a grass-cutting blade / F. Abbasian in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Titre : Numerical and experimental studies of oscillatory airflows induced by rotation of a grass-cutting blade Type de document : texte imprimé Auteurs : F. Abbasian, Auteur ; J. Cao, Auteur ; S. D. Yu, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Three-dimensional  oscillatory  airflows;  cylindrical  chamber;  Navier–Stokes  equations Résumé : Three-dimensional oscillatory airflows induced by a rotating grass-cutting blade in a cylindrical chamber are studied experimentally and numerically in this paper. Experimental pressure results are obtained using a sound pressure transducer and a data acquisition system. The measured pressure data contain background noise and high-frequency sound signals due to the blade vibrations. The background noise is separately measured; its effect on the signal is determined from a spectral subtraction algorithm. A time-accurate finite volume numerical solution to the three-dimensional incompressible unsteady Navier–Stokes equations is also sought using the sliding frame technique and the unstructured tetrahedral mesh. Convergence studies are conducted using various combinations of mesh sizes and time increments to ensure the stability of the numerical scheme. The experimental and numerical pressure results are in good agreement. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Numerical and experimental studies of oscillatory airflows induced by rotation of a grass-cutting blade [texte imprimé] / F. Abbasian, Auteur ; J. Cao, Auteur ; S. D. Yu, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Mots-clés : Three-dimensional  oscillatory  airflows;  cylindrical  chamber;  Navier–Stokes  equations Résumé : Three-dimensional oscillatory airflows induced by a rotating grass-cutting blade in a cylindrical chamber are studied experimentally and numerically in this paper. Experimental pressure results are obtained using a sound pressure transducer and a data acquisition system. The measured pressure data contain background noise and high-frequency sound signals due to the blade vibrations. The background noise is separately measured; its effect on the signal is determined from a spectral subtraction algorithm. A time-accurate finite volume numerical solution to the three-dimensional incompressible unsteady Navier–Stokes equations is also sought using the sliding frame technique and the unstructured tetrahedral mesh. Convergence studies are conducted using various combinations of mesh sizes and time increments to ensure the stability of the numerical scheme. The experimental and numerical pressure results are in good agreement. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Unsteady vortex flows produced by trailing edge articulation / Huyer, Stephen A. in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Titre : Unsteady vortex flows produced by trailing edge articulation Type de document : texte imprimé Auteurs : Huyer, Stephen A., Auteur ; David Beal, Auteur ; Daniel Macumber, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  wakes;  vortices;  light  trucks;  measurement;  vortex  flow;  laser  doppler  anemometry;  stators;  particulate  matter;  blades;  noise  (sound);  drag  (fluid  dynamics) Résumé : The unsteady vortex flows produced by biologically inspired tail articulation are investigated. The application is to provide active means of reducing tonal noise due to upstream wake interaction with downstream propellers on underwater vehicles. By reducing the wake velocity defect, the periodic unsteady propeller blade pressure fluctuations that are the source of the noise should be reduced. Accordingly, experiments to measure the flows produced by an upstream stator fitted with a movable trailing edge were carried out in a water tunnel for Reynolds numbers in the range 75,000 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Unsteady vortex flows produced by trailing edge articulation [texte imprimé] / Huyer, Stephen A., Auteur ; David Beal, Auteur ; Daniel Macumber, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Mots-clés : Flow  (dynamics);  wakes;  vortices;  light  trucks;  measurement;  vortex  flow;  laser  doppler  anemometry;  stators;  particulate  matter;  blades;  noise  (sound);  drag  (fluid  dynamics) Résumé : The unsteady vortex flows produced by biologically inspired tail articulation are investigated. The application is to provide active means of reducing tonal noise due to upstream wake interaction with downstream propellers on underwater vehicles. By reducing the wake velocity defect, the periodic unsteady propeller blade pressure fluctuations that are the source of the noise should be reduced. Accordingly, experiments to measure the flows produced by an upstream stator fitted with a movable trailing edge were carried out in a water tunnel for Reynolds numbers in the range 75,000 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

A numerical and experimental study on the effect of the cone angle of the spindle in murata vortex spinning machine / Huifen Guo in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 5 p. Titre : A numerical and experimental study on the effect of the cone angle of the spindle in murata vortex spinning machine Type de document : texte imprimé Auteurs : Huifen Guo, Auteur ; Xianglong An, Auteur ; Zhaosheng Yu, Auteur Année de publication : 2009 Article en page(s) : 5 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Spindles  (textile  machinery);  yarns;  nozzles;  vortices;  swirling  flow;  fluid  dynamics;  fibers;  turbulence;  exterior  walls;  air  flow;  computer  simulation;  spinning  machinery;  polyester  fabrics;  flow  (dynamics) Résumé : To study the effect of the cone angle of the hollow spindle in the nozzle of Murata vortex spinning (MVS) on yarn properties, the k‐ε turbulence model is employed to simulate the airflow patterns inside the different nozzles with different spindle cone angles. A set of corresponding spinning experiments is designed to verify numerical predictions. The simulation results show that some factors, such as the counter-rotating vortex pair (CVP) over the spindle, high supersonic zone in the inlet of the swirling chamber, and the distribution of wall shear stress (WSS) along the outer wall of the spindle caused by variation of the cone angle of the spindle, are significantly related to fluid flow, and consequently to MVS yarn properties. A rational cone angle (Case 2) can form an axisymmetric CVP and high WSS, which can ensure sufficient twisting of the yarn and produce high quality yarn. The experimental results, which yarn properties spun using 100% cotton, 100% polyester, and polyester 70∕cotton 30 blends with different nozzles, are well consistent with the numerical study. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] A numerical and experimental study on the effect of the cone angle of the spindle in murata vortex spinning machine [texte imprimé] / Huifen Guo, Auteur ; Xianglong An, Auteur ; Zhaosheng Yu, Auteur . - 2009 . - 5 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 5 p. Mots-clés : Spindles  (textile  machinery);  yarns;  nozzles;  vortices;  swirling  flow;  fluid  dynamics;  fibers;  turbulence;  exterior  walls;  air  flow;  computer  simulation;  spinning  machinery;  polyester  fabrics;  flow  (dynamics) Résumé : To study the effect of the cone angle of the hollow spindle in the nozzle of Murata vortex spinning (MVS) on yarn properties, the k‐ε turbulence model is employed to simulate the airflow patterns inside the different nozzles with different spindle cone angles. A set of corresponding spinning experiments is designed to verify numerical predictions. The simulation results show that some factors, such as the counter-rotating vortex pair (CVP) over the spindle, high supersonic zone in the inlet of the swirling chamber, and the distribution of wall shear stress (WSS) along the outer wall of the spindle caused by variation of the cone angle of the spindle, are significantly related to fluid flow, and consequently to MVS yarn properties. A rational cone angle (Case 2) can form an axisymmetric CVP and high WSS, which can ensure sufficient twisting of the yarn and produce high quality yarn. The experimental results, which yarn properties spun using 100% cotton, 100% polyester, and polyester 70∕cotton 30 blends with different nozzles, are well consistent with the numerical study. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Improvement of hydrofoil performance by partial ventilated cavitation in steady flow and periodic gusts / Jim Kopriva in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Titre : Improvement of hydrofoil performance by partial ventilated cavitation in steady flow and periodic gusts Type de document : texte imprimé Auteurs : Jim Kopriva, Auteur ; Roger E. Arndt, Auteur ; Eduard L. Amromin, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Ventilated  cavitation;  flow;  periodic  gusts Résumé : This paper describes a study of the response of a recently developed low-drag partially cavitating hydrofoil (denoted as OK-2003) to periodical perturbations of incoming flow. A two-flap assembly specially designed to simulate sea wave impact on the cavitating hydrofoil generates the perturbations. The design range of cavitation number was maintained by ventilation. Unsteady flow can be simulated over a range of ratios of gust flow wavelength to cavity length. The measurement of time-average lift and drag coefficients and their fluctuating values over a range of inflow characteristics allows a determination of hydrofoil performance over a range of conditions that could be expected for a prototype hydrofoil. Both regular interaction with practically linear perturbations and resonancelike singular interaction with substantial nonlinear effects were noted. The observations are accompanied by a numerical analysis that identifies resonance phenomena as a function of excitation frequency. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Improvement of hydrofoil performance by partial ventilated cavitation in steady flow and periodic gusts [texte imprimé] / Jim Kopriva, Auteur ; Roger E. Arndt, Auteur ; Eduard L. Amromin, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Mots-clés : Ventilated  cavitation;  flow;  periodic  gusts Résumé : This paper describes a study of the response of a recently developed low-drag partially cavitating hydrofoil (denoted as OK-2003) to periodical perturbations of incoming flow. A two-flap assembly specially designed to simulate sea wave impact on the cavitating hydrofoil generates the perturbations. The design range of cavitation number was maintained by ventilation. Unsteady flow can be simulated over a range of ratios of gust flow wavelength to cavity length. The measurement of time-average lift and drag coefficients and their fluctuating values over a range of inflow characteristics allows a determination of hydrofoil performance over a range of conditions that could be expected for a prototype hydrofoil. Both regular interaction with practically linear perturbations and resonancelike singular interaction with substantial nonlinear effects were noted. The observations are accompanied by a numerical analysis that identifies resonance phenomena as a function of excitation frequency. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Cavitation resonance / Li, S. C. in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Titre : Cavitation resonance Type de document : texte imprimé Auteurs : Li, S. C., Auteur ; Z. G. Zuo, Auteur ; S. H. Liu, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cavitation  resonanc Résumé : This article deals with a phenomenon named as cavitation resonance. Cavitation-associated pressure fluctuations in hydraulic systems affect their design, operation, and safety. Under certain conditions, the amplitude of a particular component of these fluctuations will be significantly magnified, causing a resonance. Here, the observed phenomenon from three different flow systems is briefly introduced. Based on the coupling of two subsystems, a hypothesis of (macroscopic) mechanism reduced from these experimental observations is presented. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Cavitation resonance [texte imprimé] / Li, S. C., Auteur ; Z. G. Zuo, Auteur ; S. H. Liu, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 7 p. Mots-clés : Cavitation  resonanc Résumé : This article deals with a phenomenon named as cavitation resonance. Cavitation-associated pressure fluctuations in hydraulic systems affect their design, operation, and safety. Under certain conditions, the amplitude of a particular component of these fluctuations will be significantly magnified, causing a resonance. Here, the observed phenomenon from three different flow systems is briefly introduced. Based on the coupling of two subsystems, a hypothesis of (macroscopic) mechanism reduced from these experimental observations is presented. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

An assessment of the influence of environmental factors on cavitation instabilities / Damien T. Kawakami in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Titre : An assessment of the influence of environmental factors on cavitation instabilities Type de document : texte imprimé Auteurs : Damien T. Kawakami, Auteur ; A. Fuji, Auteur ; Y. Tsujimoto, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cavitation Résumé : Cavitation induced flow instabilities are of interest in numerous applications. Experimental and numerical investigations of this phenomenon are taking place at several institutions around the world. Although there is qualitative agreement among the numerous recent papers on the subject, there is a lack of agreement with regard to important details, such as the spectral content of unsteady lift oscillations. This paper summarizes observations of a cavitating NACA0015 foil in three different tunnels that revealed remarkably different cavity shedding appearances and behaviors. Some of the differences were attributed to system instabilities. However, in addition to a different cavitation behavior attributed to system instabilities, it was found that differences in gas content could significantly alter the lift spectrum of a cavitating foil. For a certain range of the composite parameter σ∕2α near 4, the dominant frequency appears to double when the gas content is reduced by a half. It is also argued that surface effects can have a significant influence on fully wetted time during cavity shedding. Normally, surface effects are assumed to play an important role in the initial inception of a fully wetted hydrofoil with gas content being the primary factor governing developed cavitation behavior. However, the repetitive nature of the process implies that each shedding cycle is an individual inception process. Hence, the unexpected role of surface effects in partially cavitating hydrofoils. The conclusions reached have important ramifications concerning numerical code verification that is a topic of major concern. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] An assessment of the influence of environmental factors on cavitation instabilities [texte imprimé] / Damien T. Kawakami, Auteur ; A. Fuji, Auteur ; Y. Tsujimoto, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Mots-clés : Cavitation Résumé : Cavitation induced flow instabilities are of interest in numerous applications. Experimental and numerical investigations of this phenomenon are taking place at several institutions around the world. Although there is qualitative agreement among the numerous recent papers on the subject, there is a lack of agreement with regard to important details, such as the spectral content of unsteady lift oscillations. This paper summarizes observations of a cavitating NACA0015 foil in three different tunnels that revealed remarkably different cavity shedding appearances and behaviors. Some of the differences were attributed to system instabilities. However, in addition to a different cavitation behavior attributed to system instabilities, it was found that differences in gas content could significantly alter the lift spectrum of a cavitating foil. For a certain range of the composite parameter σ∕2α near 4, the dominant frequency appears to double when the gas content is reduced by a half. It is also argued that surface effects can have a significant influence on fully wetted time during cavity shedding. Normally, surface effects are assumed to play an important role in the initial inception of a fully wetted hydrofoil with gas content being the primary factor governing developed cavitation behavior. However, the repetitive nature of the process implies that each shedding cycle is an individual inception process. Hence, the unexpected role of surface effects in partially cavitating hydrofoils. The conclusions reached have important ramifications concerning numerical code verification that is a topic of major concern. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Cavitation analogy to gasdynamic shocks / Alessandro Ferrari in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 14 p. Titre : Cavitation analogy to gasdynamic shocks : model conservativeness effects on the simulation of transient flows in high-pressure pipelines Type de document : texte imprimé Auteurs : Alessandro Ferrari, Auteur ; Michele Manno, Auteur ; Antonio Mittica, Auteur Année de publication : 2009 Article en page(s) : 14 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Transient  flows;  pipeline Résumé : A comparison between conservative and nonconservative models has been carried out for evaluating the influence of conservativeness on the prediction of transient flows in high-pressure pipelines. For the numerical tests, a pump-line-nozzle Diesel injection system was considered because the pipe flow presented interesting cases of cavitation. The validity of a conservative model in the simulation of cavitating transient flows was substantiated by the comparison between computed pressure time histories and experimental results at two pipeline locations in the injection system. Although nonconservative models can assure satisfactory accuracy in the evaluation of the wave propagation phenomena, they introduce fictitious source terms in the discretized equations. Such terms are usually negligible, but can play a significant role in the presence of acoustic cavitation, i.e., pressure-wave-induced cavitation, producing errors in the pressure-wave speed prediction. A theoretical analysis based on unsteady characteristic lines was carried out, showing that the cavitation desinence is a shock gas-dynamic-like event, whereas cavitation inception is a supersonic expansion. The Rankine–Hugoniot jump conditions were applied to evaluate the shock wave speed in the presence of cavitation. Analytical relations to calculate the flow property variations across the cavitation-induced discontinuities were also derived. A previously published analytical expression of the sound speed in a homogeneous two-phase flow model was also derived from the eigenvalues of the Euler flow equations for the two distinct phases and a comparison was made with Wallis’ formula, which is commonly applied to cavitating flow simulation in transmission lines. Finally, a novel algorithm for calculating the shock speed, as is predicted by nonconservative models, was presented and applied to Burgers’ equation, pointing out the contribution of internal fictitious fluxes in the shock-speed wrong estimation. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Cavitation analogy to gasdynamic shocks : model conservativeness effects on the simulation of transient flows in high-pressure pipelines [texte imprimé] / Alessandro Ferrari, Auteur ; Michele Manno, Auteur ; Antonio Mittica, Auteur . - 2009 . - 14 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 14 p. Mots-clés : Transient  flows;  pipeline Résumé : A comparison between conservative and nonconservative models has been carried out for evaluating the influence of conservativeness on the prediction of transient flows in high-pressure pipelines. For the numerical tests, a pump-line-nozzle Diesel injection system was considered because the pipe flow presented interesting cases of cavitation. The validity of a conservative model in the simulation of cavitating transient flows was substantiated by the comparison between computed pressure time histories and experimental results at two pipeline locations in the injection system. Although nonconservative models can assure satisfactory accuracy in the evaluation of the wave propagation phenomena, they introduce fictitious source terms in the discretized equations. Such terms are usually negligible, but can play a significant role in the presence of acoustic cavitation, i.e., pressure-wave-induced cavitation, producing errors in the pressure-wave speed prediction. A theoretical analysis based on unsteady characteristic lines was carried out, showing that the cavitation desinence is a shock gas-dynamic-like event, whereas cavitation inception is a supersonic expansion. The Rankine–Hugoniot jump conditions were applied to evaluate the shock wave speed in the presence of cavitation. Analytical relations to calculate the flow property variations across the cavitation-induced discontinuities were also derived. A previously published analytical expression of the sound speed in a homogeneous two-phase flow model was also derived from the eigenvalues of the Euler flow equations for the two distinct phases and a comparison was made with Wallis’ formula, which is commonly applied to cavitating flow simulation in transmission lines. Finally, a novel algorithm for calculating the shock speed, as is predicted by nonconservative models, was presented and applied to Burgers’ equation, pointing out the contribution of internal fictitious fluxes in the shock-speed wrong estimation. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Hydrodynamics and sound generation of low speed planar jet / Victoria Suponitsky in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Titre : Hydrodynamics and sound generation of low speed planar jet Type de document : texte imprimé Auteurs : Victoria Suponitsky, Auteur ; Eldad Avital, Auteur ; Mike Gaster, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Low  speed  planar  jet;  hydrodynamics Résumé : Hydrodynamics and sound radiation of a low speed planar jet with Re=3000 have been studied by large eddy simulation combined with Lighthill’s acoustic analogy. Jets evolving from both well-developed (parabolic) and undeveloped (top-hat) mean velocity profiles have been simulated. The results showed the following: (i) initial domination of a symmetrical mode for jets evolving from top-hat profiles and prevailing of an antisymmetrical mode resulting in a sinuous distortion of the potential core for jets evolving from parabolic profiles, and (ii) shape of a mean velocity profile has some effect on mean flow characteristics; however, the major differences were observed in the development of the fluctuations. Velocity fluctuations were significantly higher for jets evolving from a parabolic profile in the region beyond the end of the potential core before the flow reached a self-preserving state. To calculate the basic sound radiation, the sources in Lighthill’s equation were treated either as compact in all directions or as noncompact in the spanwise direction. The spanwise length of the computational domain was found to have a little effect on the results obtained with compact in all directions solution provided that spanwise length exceeds the correlation length. Results showed that the majority of sound was generated by the region beyond the end of the potential core. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Hydrodynamics and sound generation of low speed planar jet [texte imprimé] / Victoria Suponitsky, Auteur ; Eldad Avital, Auteur ; Mike Gaster, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 8 p. Mots-clés : Low  speed  planar  jet;  hydrodynamics Résumé : Hydrodynamics and sound radiation of a low speed planar jet with Re=3000 have been studied by large eddy simulation combined with Lighthill’s acoustic analogy. Jets evolving from both well-developed (parabolic) and undeveloped (top-hat) mean velocity profiles have been simulated. The results showed the following: (i) initial domination of a symmetrical mode for jets evolving from top-hat profiles and prevailing of an antisymmetrical mode resulting in a sinuous distortion of the potential core for jets evolving from parabolic profiles, and (ii) shape of a mean velocity profile has some effect on mean flow characteristics; however, the major differences were observed in the development of the fluctuations. Velocity fluctuations were significantly higher for jets evolving from a parabolic profile in the region beyond the end of the potential core before the flow reached a self-preserving state. To calculate the basic sound radiation, the sources in Lighthill’s equation were treated either as compact in all directions or as noncompact in the spanwise direction. The spanwise length of the computational domain was found to have a little effect on the results obtained with compact in all directions solution provided that spanwise length exceeds the correlation length. Results showed that the majority of sound was generated by the region beyond the end of the potential core. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Inhomogeneous multifluid model for prediction of nonequilibrium phase transition and droplet dynamics / A. G. Gerber in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 11 p. Titre : Inhomogeneous multifluid model for prediction of nonequilibrium phase transition and droplet dynamics Type de document : texte imprimé Auteurs : A. G. Gerber, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure;  momentum;  flow  (dynamics);  phase  transitions;  nucleation  (physics);  equations;  cascades  (fluid  dynamics);  dynamics  (mechanics) Résumé : A pressure based Eulerian multifluid model for application to phase transition with droplet dynamics in transonic high-speed flows is described. It is implemented using an element-based finite-volume method, which is implicit in time and solves mass and momentum conservation across all phases via a coupled algebraic multigrid approach. The model emphasizes treatment of the condensed phases, with their respective velocity and thermal fields, in inertial nonequilibrium and metastable gas flow conditions. The droplet energy state is treated either in algebraic form or through transport equations depending on appropriate physical assumptions. Due to the complexity of the two-phase phenomena, the model is presented and validated by exploring phase transition and droplet dynamics in a turbine cascade geometry. The influence of droplet inertia on localized homogeneous nucleation is examined. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Inhomogeneous multifluid model for prediction of nonequilibrium phase transition and droplet dynamics [texte imprimé] / A. G. Gerber, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 11 p. Mots-clés : Pressure;  momentum;  flow  (dynamics);  phase  transitions;  nucleation  (physics);  equations;  cascades  (fluid  dynamics);  dynamics  (mechanics) Résumé : A pressure based Eulerian multifluid model for application to phase transition with droplet dynamics in transonic high-speed flows is described. It is implemented using an element-based finite-volume method, which is implicit in time and solves mass and momentum conservation across all phases via a coupled algebraic multigrid approach. The model emphasizes treatment of the condensed phases, with their respective velocity and thermal fields, in inertial nonequilibrium and metastable gas flow conditions. The droplet energy state is treated either in algebraic form or through transport equations depending on appropriate physical assumptions. Due to the complexity of the two-phase phenomena, the model is presented and validated by exploring phase transition and droplet dynamics in a turbine cascade geometry. The influence of droplet inertia on localized homogeneous nucleation is examined. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

Design of the dense gas flexible asymmetric shock tube / P. Colonna in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 6 p. Titre : Design of the dense gas flexible asymmetric shock tube Type de document : texte imprimé Auteurs : P. Colonna, Auteur ; A. Guardone, Auteur ; N. R. Nannan, Auteur Année de publication : 2009 Article en page(s) : 6 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flexible  asymmetric  shock  tube Résumé : This paper presents the conceptual design of the flexible asymmetric shock tube (FAST) setup for the experimental verification of the existence of nonclassical rarefaction shock waves in molecularly complex dense vapors. The FAST setup is a Ludwieg tube facility composed of a charge tube that is separated from the discharge vessel by a fast-opening valve. A nozzle is interposed between the valve and the charge tube to prevent disturbances from the discharge vessel to propagate into the tube. The speed of the rarefaction wave generated in the tube as the valve opens is measured by means of high-resolution pressure transducers. The provisional working fluid is siloxane D6 (dodecamethylcyclohexasiloxane, C12H36O6Si6). Numerical simulations of the FAST experiment are presented using nonideal thermodynamic models to support the preliminary design. The uncertainties related to the thermodynamic model of the fluid are assessed using a state-of-the-art thermodynamic model of fluid D6. The preliminary design is confirmed to be feasible and construction requirements are found to be well within technological limits. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...] [article] Design of the dense gas flexible asymmetric shock tube [texte imprimé] / P. Colonna, Auteur ; A. Guardone, Auteur ; N. R. Nannan, Auteur . - 2009 . - 6 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 6 p. Mots-clés : Flexible  asymmetric  shock  tube Résumé : This paper presents the conceptual design of the flexible asymmetric shock tube (FAST) setup for the experimental verification of the existence of nonclassical rarefaction shock waves in molecularly complex dense vapors. The FAST setup is a Ludwieg tube facility composed of a charge tube that is separated from the discharge vessel by a fast-opening valve. A nozzle is interposed between the valve and the charge tube to prevent disturbances from the discharge vessel to propagate into the tube. The speed of the rarefaction wave generated in the tube as the valve opens is measured by means of high-resolution pressure transducers. The provisional working fluid is siloxane D6 (dodecamethylcyclohexasiloxane, C12H36O6Si6). Numerical simulations of the FAST experiment are presented using nonideal thermodynamic models to support the preliminary design. The uncertainties related to the thermodynamic model of the fluid are assessed using a state-of-the-art thermodynamic model of fluid D6. The preliminary design is confirmed to be feasible and construction requirements are found to be well within technological limits. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27301 [...]

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