Dépouillements

Investigation of the flow field on a transonic turbine nozzle guide vane with rim seal cavity flow ejection / M. Pau in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Titre : Investigation of the flow field on a transonic turbine nozzle guide vane with rim seal cavity flow ejection Type de document : texte imprimé Auteurs : M. Pau, Auteur ; G. Paniagua, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  shock  (mechanics);  cavity  flows;  nozzles;  turbines;  cavities Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Ensuring an adequate life of high pressure turbines requires efficient cooling methods such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present paper addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process, a numerical study was carried out, combining computational fluid dynamic (CFD) simulations and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed, modeling the purge cavity flow ejected downstream of the stator blade row at three flow regimes: subsonic M2=0.73, transonic M2=1.12, and supersonic M2=1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as a function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase in the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses, and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structure modification downstream of the stator. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Investigation of the flow field on a transonic turbine nozzle guide vane with rim seal cavity flow ejection [texte imprimé] / M. Pau, Auteur ; G. Paniagua, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Mots-clés : pressure;  flow  (dynamics);  shock  (mechanics);  cavity  flows;  nozzles;  turbines;  cavities Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Ensuring an adequate life of high pressure turbines requires efficient cooling methods such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present paper addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process, a numerical study was carried out, combining computational fluid dynamic (CFD) simulations and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed, modeling the purge cavity flow ejected downstream of the stator blade row at three flow regimes: subsonic M2=0.73, transonic M2=1.12, and supersonic M2=1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as a function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase in the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses, and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structure modification downstream of the stator. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Pressure fluctuation characteristics of complex turbulent flow in a single elbow with small curvature radius for a sodium-cooled fast reactor / Shinji Ebara in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : Pressure fluctuation characteristics of complex turbulent flow in a single elbow with small curvature radius for a sodium-cooled fast reactor Type de document : texte imprimé Auteurs : Shinji Ebara, Auteur ; Yuta Aoya, Auteur ; Tsukasa Sato, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  pressure  measurement;  turbulence;  pipes;  flow  separation;  sodium  fast  reactors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Pressure fluctuation characteristics of complex turbulent flow in a single elbow with small curvature radius for a sodium-cooled fast reactor [texte imprimé] / Shinji Ebara, Auteur ; Yuta Aoya, Auteur ; Tsukasa Sato, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : pressure;  flow  (dynamics);  pressure  measurement;  turbulence;  pipes;  flow  separation;  sodium  fast  reactors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Laminar flow in microchannels with noncircular cross section / Ali Tamayol in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Titre : Laminar flow in microchannels with noncircular cross section Type de document : texte imprimé Auteurs : Ali Tamayol, Auteur ; Majid Bahrami, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  channels  (hydraulic  engineering);  laminar  flow;  cross  section  (physics);  corners  (structural  elements);  ducts;  geometry;  poiseuille  flow;  pressure  drop;  shapes;  microchannels Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Analytical solutions are presented for laminar fully developed flow in micro-/minichannels of hyperelliptical and regular polygonal cross sections in the form of compact relationships. The considered geometries cover a wide range of common simply connected shapes including circle, ellipse, rectangle, rectangle-with-round-corners, rhombus, star-shape, equilateral triangle, square, pentagon, and hexagon. A point matching technique is used to calculate closed form solutions for the velocity distributions in the above-mentioned channel cross sections. The developed relationships for the velocity distribution and pressure drop are successfully compared with existing analytical solutions and experimental data collected from various sources for a variety of geometries, including polygonal, rectangular, circular, elliptical, and rhombic cross sections. The present compact solutions provide a convenient and power tool for performing hydrodynamic analyses in a variety of fundamental and engineering applications such as in microfluidics, transport phenomena, and porous media. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Laminar flow in microchannels with noncircular cross section [texte imprimé] / Ali Tamayol, Auteur ; Majid Bahrami, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Mots-clés : flow  (dynamics);  channels  (hydraulic  engineering);  laminar  flow;  cross  section  (physics);  corners  (structural  elements);  ducts;  geometry;  poiseuille  flow;  pressure  drop;  shapes;  microchannels Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Analytical solutions are presented for laminar fully developed flow in micro-/minichannels of hyperelliptical and regular polygonal cross sections in the form of compact relationships. The considered geometries cover a wide range of common simply connected shapes including circle, ellipse, rectangle, rectangle-with-round-corners, rhombus, star-shape, equilateral triangle, square, pentagon, and hexagon. A point matching technique is used to calculate closed form solutions for the velocity distributions in the above-mentioned channel cross sections. The developed relationships for the velocity distribution and pressure drop are successfully compared with existing analytical solutions and experimental data collected from various sources for a variety of geometries, including polygonal, rectangular, circular, elliptical, and rhombic cross sections. The present compact solutions provide a convenient and power tool for performing hydrodynamic analyses in a variety of fundamental and engineering applications such as in microfluidics, transport phenomena, and porous media. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

On a new passive scalar equation with variable mass diffusivity / Fabio Gori in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 11 p. Titre : On a new passive scalar equation with variable mass diffusivity : flow between parallel plates Type de document : texte imprimé Auteurs : Fabio Gori, Auteur ; Andrea Boghi, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : scalars;  flow  (dynamics);  diffusion  (physics);  turbulence;  energy  dissipation;  modeling;  plates  (structures);  equations;  gradients Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance. The equations are solved numerically for flow between parallel plates in order to evaluate the influence of the new terms. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] On a new passive scalar equation with variable mass diffusivity : flow between parallel plates [texte imprimé] / Fabio Gori, Auteur ; Andrea Boghi, Auteur . - 2011 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 11 p. Mots-clés : scalars;  flow  (dynamics);  diffusion  (physics);  turbulence;  energy  dissipation;  modeling;  plates  (structures);  equations;  gradients Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance. The equations are solved numerically for flow between parallel plates in order to evaluate the influence of the new terms. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Effect of initial constant acceleration on the transition to turbulence in transient circular pipe flow / Manabu Iguchi in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Titre : Effect of initial constant acceleration on the transition to turbulence in transient circular pipe flow Type de document : texte imprimé Auteurs : Manabu Iguchi, Auteur ; Kazuyoshi Nishihara, Auteur ; Yusuke Nakahata, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  turbulence;  Reynolds  number;  pipe  flow;  pipes Résumé : Experimental investigation is carried out on the transition to turbulence in a transient circular pipe flow. The flow is accelerated from rest at a constant acceleration until its cross-sectional mean velocity reaches a constant value. Accordingly, the history of the flow thus generated consists of the initial stage of constant acceleration and the following stage of constant cross-sectional mean velocity. The final Reynolds number based on the constant cross-sectional mean velocity and the pipe diameter is chosen to be much greater than the transition Reynolds number of a steady pipe flow of about 3000. The transition to turbulence is judged from the output signal of the axial velocity component and its root-mean-square value measured with a hot-wire anemometer. A turbulent slug appears after the cross-sectional mean velocity of the flow reaches the predetermined constant value under every experimental condition. Turbulence production therefore is suppressed, while the flow is accelerated. The time lag for the appearance of the turbulent slug after the cross-sectional mean velocity of the flow reaches the constant value decreases with an increase in the constant acceleration value. An empirical equation is proposed for estimating the time lag. The propagation velocity of the leading edge of the turbulent slug is independent of the constant acceleration value under the present experimental conditions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Effect of initial constant acceleration on the transition to turbulence in transient circular pipe flow [texte imprimé] / Manabu Iguchi, Auteur ; Kazuyoshi Nishihara, Auteur ; Yusuke Nakahata, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Mots-clés : flow  (dynamics);  turbulence;  Reynolds  number;  pipe  flow;  pipes Résumé : Experimental investigation is carried out on the transition to turbulence in a transient circular pipe flow. The flow is accelerated from rest at a constant acceleration until its cross-sectional mean velocity reaches a constant value. Accordingly, the history of the flow thus generated consists of the initial stage of constant acceleration and the following stage of constant cross-sectional mean velocity. The final Reynolds number based on the constant cross-sectional mean velocity and the pipe diameter is chosen to be much greater than the transition Reynolds number of a steady pipe flow of about 3000. The transition to turbulence is judged from the output signal of the axial velocity component and its root-mean-square value measured with a hot-wire anemometer. A turbulent slug appears after the cross-sectional mean velocity of the flow reaches the predetermined constant value under every experimental condition. Turbulence production therefore is suppressed, while the flow is accelerated. The time lag for the appearance of the turbulent slug after the cross-sectional mean velocity of the flow reaches the constant value decreases with an increase in the constant acceleration value. An empirical equation is proposed for estimating the time lag. The propagation velocity of the leading edge of the turbulent slug is independent of the constant acceleration value under the present experimental conditions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Swirling flow in a fixed container / A. Nahas in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Titre : Swirling flow in a fixed container : generation and attenuation of a vortex column Type de document : texte imprimé Auteurs : A. Nahas, Auteur ; A. Calvo, Auteur ; M. Piva, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  fluids;  containers;  suction;  boundary  layers;  vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The development of a columnar vortex and its attenuation using radial rods at the bottom boundary of a stationary container are experimentally studied. The fluid motion is achieved combining two independent flows: a global circulation around the cylinder axis and a meridian flow generated by recirculating fluid through a central nozzle located at the vessel bottom. The resulting velocity field is analyzed under two conditions: with and without the meridian or suction flow. It is shown that in the second condition a columnar vortex merges and that its intensity increases when the suction flow rate is increased. The key role played by the bottom boundary layer in the vortex formation is demonstrated. In the last part of the work, the attenuation of the vortex intensity produced by a set of rods located at the vessel bottom is investigated. It is found that obstacles with heights of the order of the boundary layer thickness are enough to produce the total annihilation of the vortex column. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Swirling flow in a fixed container : generation and attenuation of a vortex column [texte imprimé] / A. Nahas, Auteur ; A. Calvo, Auteur ; M. Piva, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 09 p. Mots-clés : flow  (dynamics);  fluids;  containers;  suction;  boundary  layers;  vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The development of a columnar vortex and its attenuation using radial rods at the bottom boundary of a stationary container are experimentally studied. The fluid motion is achieved combining two independent flows: a global circulation around the cylinder axis and a meridian flow generated by recirculating fluid through a central nozzle located at the vessel bottom. The resulting velocity field is analyzed under two conditions: with and without the meridian or suction flow. It is shown that in the second condition a columnar vortex merges and that its intensity increases when the suction flow rate is increased. The key role played by the bottom boundary layer in the vortex formation is demonstrated. In the last part of the work, the attenuation of the vortex intensity produced by a set of rods located at the vessel bottom is investigated. It is found that obstacles with heights of the order of the boundary layer thickness are enough to produce the total annihilation of the vortex column. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Prediction of small-scale cavitation in a high speed flow over an open cavity using large-eddy simulation / Ehsan Shams in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 14 p. Titre : Prediction of small-scale cavitation in a high speed flow over an open cavity using large-eddy simulation Type de document : texte imprimé Auteurs : Ehsan Shams, Auteur ; Sourabh V. Apte, Auteur Année de publication : 2011 Article en page(s) : 14 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : scalars;  pressure;  flow  (dynamics);  vapors;  eddies  (fluid  dynamics);  cavitation;  shear  (mechanics);  bubbles;  cavities Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Large-eddy simulation of flow over an open cavity corresponding to the experimental setup of and (2008, “Cavitation Phenomena Occurring Due to Interaction of Shear Layer Vortices With the Trailing Corner of a Two-Dimensional Open Cavity,” Phys. Fluids, 20(4), p. 041702) is performed. The filtered, incompressible Navier–Stokes equations are solved using a co-located grid finite-volume solver with the dynamic Smagorinsky model for a subgrid-scale closure. The computational grid consists of around 7×106 grid points with 3×106 points clustered around the shear layer, and the boundary layer over the leading edge is resolved. The only input from the experimental data is the mean velocity profile at the inlet condition. The mean flow is superimposed with turbulent velocity fluctuations generated by solving a forced periodic duct flow at a freestream Reynolds number. The flow statistics, including mean and rms velocity fields and pressure coefficients, are compared with the experimental data to show reasonable agreement. The dynamic interactions between traveling vortices in the shear layer and the trailing edge affect the value and location of the pressure minima. Cavitation inception is investigated using two approaches: (i) a discrete bubble model wherein the bubble dynamics is computed by solving the Rayleigh–Plesset and the bubble motion equations using an adaptive time-stepping procedure and (ii) a scalar transport model for the liquid volume fraction with source and sink terms for phase change. Large-eddy simulation, together with the cavitation models, predicts that inception occurs near the trailing edge similar to that observed in the experiments. The bubble transport model captures the subgrid dynamics of the vapor better, whereas the scalar model captures the large-scale features more accurately. A hybrid approach combining the bubble model with the scalar transport is needed to capture the broad range of scales observed in cavitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Prediction of small-scale cavitation in a high speed flow over an open cavity using large-eddy simulation [texte imprimé] / Ehsan Shams, Auteur ; Sourabh V. Apte, Auteur . - 2011 . - 14 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 14 p. Mots-clés : scalars;  pressure;  flow  (dynamics);  vapors;  eddies  (fluid  dynamics);  cavitation;  shear  (mechanics);  bubbles;  cavities Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Large-eddy simulation of flow over an open cavity corresponding to the experimental setup of and (2008, “Cavitation Phenomena Occurring Due to Interaction of Shear Layer Vortices With the Trailing Corner of a Two-Dimensional Open Cavity,” Phys. Fluids, 20(4), p. 041702) is performed. The filtered, incompressible Navier–Stokes equations are solved using a co-located grid finite-volume solver with the dynamic Smagorinsky model for a subgrid-scale closure. The computational grid consists of around 7×106 grid points with 3×106 points clustered around the shear layer, and the boundary layer over the leading edge is resolved. The only input from the experimental data is the mean velocity profile at the inlet condition. The mean flow is superimposed with turbulent velocity fluctuations generated by solving a forced periodic duct flow at a freestream Reynolds number. The flow statistics, including mean and rms velocity fields and pressure coefficients, are compared with the experimental data to show reasonable agreement. The dynamic interactions between traveling vortices in the shear layer and the trailing edge affect the value and location of the pressure minima. Cavitation inception is investigated using two approaches: (i) a discrete bubble model wherein the bubble dynamics is computed by solving the Rayleigh–Plesset and the bubble motion equations using an adaptive time-stepping procedure and (ii) a scalar transport model for the liquid volume fraction with source and sink terms for phase change. Large-eddy simulation, together with the cavitation models, predicts that inception occurs near the trailing edge similar to that observed in the experiments. The bubble transport model captures the subgrid dynamics of the vapor better, whereas the scalar model captures the large-scale features more accurately. A hybrid approach combining the bubble model with the scalar transport is needed to capture the broad range of scales observed in cavitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Comparison of local interfacial structures around 90 and 45-degree elbows in horizontal bubbly flows / Mohan Yadav in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 12 p. Titre : Comparison of local interfacial structures around 90 and 45-degree elbows in horizontal bubbly flows Type de document : texte imprimé Auteurs : Mohan Yadav, Auteur ; Justin D. Talley, Auteur ; Kim, Seungjin, Auteur Année de publication : 2011 Article en page(s) : 12 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  gas  flow;  bubbles;  bubbly  flow;  two-phase  flow;  interface  structure;  porosity;  probes Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study presents a comparison of the geometric effects of 90 deg and 45 deg elbows in horizontal two-phase air-water bubbly flow. Two separate experiments were performed in the horizontal test section made out of 50.3 mm inner diameter glass tubes. The first set of data was collected with a 90 deg elbow installed, and then a 45 deg elbow was added to the existing facility to acquire the second set of data. A total of 15 different flow conditions, all within the bubbly flow regime, were identified for the 90 deg experiment, and very similar flow conditions were extended to the 45 deg experiment. A double-sensor conductivity probe was employed to acquire the local data at seven different axial positions along the test section, out of which four measurement locations are associated with the 90 deg experiment and three with the 45 deg experiment. The data show that the elbows have a significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of the two elbows. While the effect of the 45 deg elbow is evident immediately after the elbow, the 90 deg elbow effect tends to propagate further downstream of the elbow rather than immediately after the elbow. Moreover, it is shown that both elbows induce spatial oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillations differ. The effects of the elbows are also compared for the axial transport of the two-phase flow parameters. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Comparison of local interfacial structures around 90 and 45-degree elbows in horizontal bubbly flows [texte imprimé] / Mohan Yadav, Auteur ; Justin D. Talley, Auteur ; Kim, Seungjin, Auteur . - 2011 . - 12 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 12 p. Mots-clés : flow  (dynamics);  gas  flow;  bubbles;  bubbly  flow;  two-phase  flow;  interface  structure;  porosity;  probes Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study presents a comparison of the geometric effects of 90 deg and 45 deg elbows in horizontal two-phase air-water bubbly flow. Two separate experiments were performed in the horizontal test section made out of 50.3 mm inner diameter glass tubes. The first set of data was collected with a 90 deg elbow installed, and then a 45 deg elbow was added to the existing facility to acquire the second set of data. A total of 15 different flow conditions, all within the bubbly flow regime, were identified for the 90 deg experiment, and very similar flow conditions were extended to the 45 deg experiment. A double-sensor conductivity probe was employed to acquire the local data at seven different axial positions along the test section, out of which four measurement locations are associated with the 90 deg experiment and three with the 45 deg experiment. The data show that the elbows have a significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of the two elbows. While the effect of the 45 deg elbow is evident immediately after the elbow, the 90 deg elbow effect tends to propagate further downstream of the elbow rather than immediately after the elbow. Moreover, it is shown that both elbows induce spatial oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillations differ. The effects of the elbows are also compared for the axial transport of the two-phase flow parameters. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

A contribution to study on the lift of ventilated supercavitating vehicle with low froude number / Yu Kaiping in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : A contribution to study on the lift of ventilated supercavitating vehicle with low froude number Type de document : texte imprimé Auteurs : Yu Kaiping, Auteur ; Zhou Jingjun, Auteur ; Min Jingxin, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  fluids;  turbulence;  computer  simulation;  drag  (fluid  dynamics);  simulation;  cavitation;  water  tunnels;  numerical  analysis;  vehicles;  vortices;  cavities;  equations;  formulas;  leakage Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A ventilated cavity was investigated using three-dimensional numerical simulation and cavitation water tunnel experiments under the condition of low Froude number. A two-fluid multiphase flow model was adopted in numerical predictions. The drag between the different phases and gravitational effect, as well as the compressibility of gas, was considered in the numerical simulations. By comparing the ventilated coefficient computational results of three different turbulence models with the Epshtein formula, the shear-stress-transport turbulence model was finally employed. The phenomenon of double-vortex tube gas-leakage was observed in both numerical simulations and experiments. Based on the validity of the numerical method, the change law of the lift coefficient on the afterbody was given by numerical predictions and accorded well with experimental results. The cause for the appearance of an abrupt increase in lift was difficult to get from experiments for the hard measurement, whereas the numerical simulations provided some supplements to analyze the reasons. The distribution of lift coefficient on the afterbody had important significance to the design of underwater vehicles. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] A contribution to study on the lift of ventilated supercavitating vehicle with low froude number [texte imprimé] / Yu Kaiping, Auteur ; Zhou Jingjun, Auteur ; Min Jingxin, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : pressure;  flow  (dynamics);  fluids;  turbulence;  computer  simulation;  drag  (fluid  dynamics);  simulation;  cavitation;  water  tunnels;  numerical  analysis;  vehicles;  vortices;  cavities;  equations;  formulas;  leakage Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A ventilated cavity was investigated using three-dimensional numerical simulation and cavitation water tunnel experiments under the condition of low Froude number. A two-fluid multiphase flow model was adopted in numerical predictions. The drag between the different phases and gravitational effect, as well as the compressibility of gas, was considered in the numerical simulations. By comparing the ventilated coefficient computational results of three different turbulence models with the Epshtein formula, the shear-stress-transport turbulence model was finally employed. The phenomenon of double-vortex tube gas-leakage was observed in both numerical simulations and experiments. Based on the validity of the numerical method, the change law of the lift coefficient on the afterbody was given by numerical predictions and accorded well with experimental results. The cause for the appearance of an abrupt increase in lift was difficult to get from experiments for the hard measurement, whereas the numerical simulations provided some supplements to analyze the reasons. The distribution of lift coefficient on the afterbody had important significance to the design of underwater vehicles. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Study on aeration for disengaged wet clutches using a two-phase flow model / Shihua Yuan in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 06 p. Titre : Study on aeration for disengaged wet clutches using a two-phase flow model Type de document : texte imprimé Auteurs : Shihua Yuan, Auteur ; Kai Guo, Auteur ; Jibin Hu, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : torque;  flow  (dynamics);  drag  (fluid  dynamics);  clearances  (engineering);  computational  fluid  dynamics;  modeling;  two-phase  flow;  equations;  simulation  results;  steady  state Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The existing computational models for disengaged wet clutches are deduced based on the single-phase flow theory. However, the complex gas-liquid two-phase flow is formed due to aeration at high rotational speeds. The objective of this study is to use a two-phase flow model to demonstrate the aeration process at different rotational speeds not only of the friction plate but also of the separator plate. A nongrooved, steady-state, two-phase flow computational fluid dynamics model is built using FLUENT , and it is validated by experimental data. The results reveal that air enters the clearance at a critical rotational speed, which causes the drag torque to sharply decrease. The aeration mode and flow pattern are obtained via simulations. The rotational speed of the separator plate has a significant effect on the aeration, including the speed magnitude and direction. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Study on aeration for disengaged wet clutches using a two-phase flow model [texte imprimé] / Shihua Yuan, Auteur ; Kai Guo, Auteur ; Jibin Hu, Auteur . - 2011 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 06 p. Mots-clés : torque;  flow  (dynamics);  drag  (fluid  dynamics);  clearances  (engineering);  computational  fluid  dynamics;  modeling;  two-phase  flow;  equations;  simulation  results;  steady  state Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The existing computational models for disengaged wet clutches are deduced based on the single-phase flow theory. However, the complex gas-liquid two-phase flow is formed due to aeration at high rotational speeds. The objective of this study is to use a two-phase flow model to demonstrate the aeration process at different rotational speeds not only of the friction plate but also of the separator plate. A nongrooved, steady-state, two-phase flow computational fluid dynamics model is built using FLUENT , and it is validated by experimental data. The results reveal that air enters the clearance at a critical rotational speed, which causes the drag torque to sharply decrease. The aeration mode and flow pattern are obtained via simulations. The rotational speed of the separator plate has a significant effect on the aeration, including the speed magnitude and direction. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Thermodynamic effect on a cavitating inducer in liquid hydrogen / Eric Goncalvès in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : Thermodynamic effect on a cavitating inducer in liquid hydrogen Type de document : texte imprimé Auteurs : Eric Goncalvès, Auteur ; Regiane Fortes Patella, Auteur ; Julien Rolland, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  temperature;  cooling;  fluids;  vapors;  suction;  cavitation;  drops;  blades;  boundary-value  problems;  cavities;  computation;  equations;  geometry;  hydrogen;  temperature  distribution;  wall  temperature;  water;  heating Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study was led in collaboration with the French Space Agency (CNES) and the Rocket Engine Division of Snecma. The main aims were the simulations and the analyses of cavitating flows in the rocket engine turbopump inducers, where the operating fluids are LH2 and LOx under cryogenic conditions. A ρ(P,T) state law modeling the cavitation phenomenon was integrated by the laboratory LEGI in the commercial computational fluid dynamics (CFD) code FINE/TURBO ™ , developed by Numeca International. Various 3D numerical results are given for an inducer geometry and comparisons are made with experimental data (head drop curves) obtained by NASA. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Thermodynamic effect on a cavitating inducer in liquid hydrogen [texte imprimé] / Eric Goncalvès, Auteur ; Regiane Fortes Patella, Auteur ; Julien Rolland, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : pressure;  flow  (dynamics);  temperature;  cooling;  fluids;  vapors;  suction;  cavitation;  drops;  blades;  boundary-value  problems;  cavities;  computation;  equations;  geometry;  hydrogen;  temperature  distribution;  wall  temperature;  water;  heating Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This study was led in collaboration with the French Space Agency (CNES) and the Rocket Engine Division of Snecma. The main aims were the simulations and the analyses of cavitating flows in the rocket engine turbopump inducers, where the operating fluids are LH2 and LOx under cryogenic conditions. A ρ(P,T) state law modeling the cavitation phenomenon was integrated by the laboratory LEGI in the commercial computational fluid dynamics (CFD) code FINE/TURBO ™ , developed by Numeca International. Various 3D numerical results are given for an inducer geometry and comparisons are made with experimental data (head drop curves) obtained by NASA. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Mass transfer coefficients for a non-Newtonian fluid and water with and without antifoam agents / Robert A. Leishear in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : Mass transfer coefficients for a non-Newtonian fluid and water with and without antifoam agents Type de document : texte imprimé Auteurs : Robert A. Leishear, Auteur ; Hector N. Guerrero, Auteur ; Michael L. Restivo, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Mass  transfer;  fluids;  oxygen;  water Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Mass transfer rates were measured in a large scale system, which is consisted of an 8.4 m tall by 0.76 m diameter column, containing one of the three fluids: water with an antifoam agent, water without an antifoam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated and due to flammability concerns, oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from the solution as air bubbled up or sparged through the solution from the bottom of the column. Air sparging was supplied by a single tube, which was co-axial to the column; the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2 mm/s, 5mm/s, and 10 mm/s were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Mass transfer coefficients for a non-Newtonian fluid and water with and without antifoam agents [texte imprimé] / Robert A. Leishear, Auteur ; Hector N. Guerrero, Auteur ; Michael L. Restivo, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : Mass  transfer;  fluids;  oxygen;  water Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Mass transfer rates were measured in a large scale system, which is consisted of an 8.4 m tall by 0.76 m diameter column, containing one of the three fluids: water with an antifoam agent, water without an antifoam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated and due to flammability concerns, oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from the solution as air bubbled up or sparged through the solution from the bottom of the column. Air sparging was supplied by a single tube, which was co-axial to the column; the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2 mm/s, 5mm/s, and 10 mm/s were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Parallel flow through ordered fibers / A. Tamayol in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 11 (Novembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Titre : Parallel flow through ordered fibers : an analytical approach Type de document : texte imprimé Auteurs : A. Tamayol, Auteur ; M. Bahrami, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  permeability;  fibers;  computer  simulation;  cylinders;  poisson  equation;  porosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...] [article] Parallel flow through ordered fibers : an analytical approach [texte imprimé] / A. Tamayol, Auteur ; M. Bahrami, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 11 (Novembre 2010) . - 07 p. Mots-clés : flow  (dynamics);  permeability;  fibers;  computer  simulation;  cylinders;  poisson  equation;  porosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27439 [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse