Dépouillements

LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions / Hassan Hemida in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Titre : LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions Type de document : texte imprimé Auteurs : Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cross-wind  flows;  trains  nose  shape;  large-eddy  simulation;  Smagorinsky  model;  Reynolds  number Résumé : Cross-wind flows around two simplified high-speed trains with different nose shapes are studied using large-eddy simulation (LES) with the standard Smagorinsky model. The Reynolds number is 3×105 based on the height of the train and the freestream velocity. The cross section and the length of the two train models are identical while one model has a nose length twice that of the other. The three-dimensional effects of the nose on the flow structures in the wake and on the aerodynamic quantities such as lift and side force coefficients, flow patterns, local pressure coefficient, and wake frequencies are investigated. The short-nose train simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear-layer instabilities. Prediction of vortex shedding, flow patterns in the train surface, and time-averaged pressure distribution obtained from the long-nose train simulation are in good agreement with the available experimental data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] LES study of the influence of a train-nose shape on the flow structures under cross-wind conditions [texte imprimé] / Hassan Hemida, Auteur ; Siniša Krajnovic, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Mots-clés : Cross-wind  flows;  trains  nose  shape;  large-eddy  simulation;  Smagorinsky  model;  Reynolds  number Résumé : Cross-wind flows around two simplified high-speed trains with different nose shapes are studied using large-eddy simulation (LES) with the standard Smagorinsky model. The Reynolds number is 3×105 based on the height of the train and the freestream velocity. The cross section and the length of the two train models are identical while one model has a nose length twice that of the other. The three-dimensional effects of the nose on the flow structures in the wake and on the aerodynamic quantities such as lift and side force coefficients, flow patterns, local pressure coefficient, and wake frequencies are investigated. The short-nose train simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear-layer instabilities. Prediction of vortex shedding, flow patterns in the train surface, and time-averaged pressure distribution obtained from the long-nose train simulation are in good agreement with the available experimental data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Noise prediction of a centrifugal fan / Rafael Ballesteros-Tajadura in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Titre : Noise prediction of a centrifugal fan : numerical results and experimental validation Type de document : texte imprimé Auteurs : Rafael Ballesteros-Tajadura, Auteur ; Sandra Velarde-Suárez, Auteur ; Juan Pablo Hurtado-Cruz, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Centrifugal  fan;  noise  prediction Résumé : Centrifugal fans are widely used in several applications, and in some cases, the noise generated by these machines has become a serious problem. The centrifugal fan noise is frequently dominated by tones at the blade passing frequency as a consequence of the strong interaction between the flow discharged from the impeller and the volute tongue. In this study, a previously published aeroacoustic prediction methodology (Cho, Y., and Moon, Y.J., 2003, “Discrete Noise Prediction of Variable Pitch Cross-Flow Fans by Unsteady Navier-Stokes Computations ,” ASME J. Fluids Eng., 125, pp. 543–550) has been extended to three-dimensional turbulent flow in order to predict the noise generated by a centrifugal fan. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT ® . The unsteady forces applied by the fan blades to the fluid are obtained from the data provided by the simulation. The Ffowcs Williams and Hawkings model extension of Lighthill’s analogy has been used to predict the aerodynamic noise generated by the centrifugal fan from these unsteady forces. Also, the noise generated by the fan has been measured experimentally, and the experimental results have been compared to the numerical results in order to validate the aerodynamic noise prediction methodology. Reasonable agreement has been found between the numerical and the experimental results. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Noise prediction of a centrifugal fan : numerical results and experimental validation [texte imprimé] / Rafael Ballesteros-Tajadura, Auteur ; Sandra Velarde-Suárez, Auteur ; Juan Pablo Hurtado-Cruz, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Mots-clés : Centrifugal  fan;  noise  prediction Résumé : Centrifugal fans are widely used in several applications, and in some cases, the noise generated by these machines has become a serious problem. The centrifugal fan noise is frequently dominated by tones at the blade passing frequency as a consequence of the strong interaction between the flow discharged from the impeller and the volute tongue. In this study, a previously published aeroacoustic prediction methodology (Cho, Y., and Moon, Y.J., 2003, “Discrete Noise Prediction of Variable Pitch Cross-Flow Fans by Unsteady Navier-Stokes Computations ,” ASME J. Fluids Eng., 125, pp. 543–550) has been extended to three-dimensional turbulent flow in order to predict the noise generated by a centrifugal fan. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT ® . The unsteady forces applied by the fan blades to the fluid are obtained from the data provided by the simulation. The Ffowcs Williams and Hawkings model extension of Lighthill’s analogy has been used to predict the aerodynamic noise generated by the centrifugal fan from these unsteady forces. Also, the noise generated by the fan has been measured experimentally, and the experimental results have been compared to the numerical results in order to validate the aerodynamic noise prediction methodology. Reasonable agreement has been found between the numerical and the experimental results. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Influence of curvature and pressure gradient on turbulent wake development in curved channels / M. T. Schobeiri in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 14 p. Titre : Influence of curvature and pressure gradient on turbulent wake development in curved channels Type de document : texte imprimé Auteurs : M. T. Schobeiri, Auteur Année de publication : 2009 Article en page(s) : 14 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : curved  channels;  turbulent  wake Résumé : The development of steady wake flow downstream of a cylindrical rod within a curved channel under the influence of positive, negative, and zero streamwise pressure gradients is theoretically and experimentally investigated. The measured asymmetric wake quantities, such as the mean velocity, turbulent fluctuations in longitudinal and lateral directions, and the turbulent shear stress, are transformed from the probe coordinate system into the curvilinear wake coordinate system. For the transformed nondimensionalized velocity defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on the experimental observations and using the transformed equations of motion and continuity, a theoretical framework that generally describes a two-dimensional curvilinear steady wake flow is developed. The theory treats the straight wake flow as a special case for which the curvature radius approaches infinity. A comparison of the developed theory with our own experimental results and with the re-evaluated experimental data from the literature establishes the general validity of the theory. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Influence of curvature and pressure gradient on turbulent wake development in curved channels [texte imprimé] / M. T. Schobeiri, Auteur . - 2009 . - 14 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 14 p. Mots-clés : curved  channels;  turbulent  wake Résumé : The development of steady wake flow downstream of a cylindrical rod within a curved channel under the influence of positive, negative, and zero streamwise pressure gradients is theoretically and experimentally investigated. The measured asymmetric wake quantities, such as the mean velocity, turbulent fluctuations in longitudinal and lateral directions, and the turbulent shear stress, are transformed from the probe coordinate system into the curvilinear wake coordinate system. For the transformed nondimensionalized velocity defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on the experimental observations and using the transformed equations of motion and continuity, a theoretical framework that generally describes a two-dimensional curvilinear steady wake flow is developed. The theory treats the straight wake flow as a special case for which the curvature radius approaches infinity. A comparison of the developed theory with our own experimental results and with the re-evaluated experimental data from the literature establishes the general validity of the theory. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Laminarization of internal flows under the combined effect of strong curvature and rotation / K. M. Guleren in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 11 p. Titre : Laminarization of internal flows under the combined effect of strong curvature and rotation Type de document : texte imprimé Auteurs : K. M. Guleren, Auteur ; I. Afgan, Auteur ; A. Turan, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Internal  flow;  curvature;  rotation;  laminarization Résumé : The laminarization phenomenon for the flow under the combined effect of strong curvature and rotation is discussed based on numerical predictions of large-eddy simulation (LES). Initially, the laminarization process is presented for the fully developed flow inside a spanwise rotating straight square duct. LES predictions over a wide range of rotation numbers (Ro=0–5) show that the turbulent kinetic energy decreases monotonically apart from 0.2 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Laminarization of internal flows under the combined effect of strong curvature and rotation [texte imprimé] / K. M. Guleren, Auteur ; I. Afgan, Auteur ; A. Turan, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 11 p. Mots-clés : Internal  flow;  curvature;  rotation;  laminarization Résumé : The laminarization phenomenon for the flow under the combined effect of strong curvature and rotation is discussed based on numerical predictions of large-eddy simulation (LES). Initially, the laminarization process is presented for the fully developed flow inside a spanwise rotating straight square duct. LES predictions over a wide range of rotation numbers (Ro=0–5) show that the turbulent kinetic energy decreases monotonically apart from 0.2 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Buoyancy dominated He–O2 separated jet mixing in a tubular reactor / Ankur Deep Bordoloi in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 13 p. Titre : Buoyancy dominated He–O2 separated jet mixing in a tubular reactor Type de document : texte imprimé Auteurs : Ankur Deep Bordoloi, Auteur ; P. K. Panigrahi, Auteur Année de publication : 2009 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Two  variable-density  jets;  digital  particle  image  velocimetry  technique;  separated  jet Résumé : Mixing of two variable-density jets, one of which is essentially a negatively buoyant jet (He) and the other a nonbuoyant jet (O2) is studied experimentally using digital particle image velocimetry technique for separated nozzle geometry. Two jets are separated from each other, i.e., He jet exit plane is located upstream of the O2 jet exit plane. Experiments were carried out keeping the nonbuoyant O2 jet at constant Reynolds number (Re2=245) and varying the Richardson number (Ri1=1.8,4.7,16.4) of the buoyant He jet. The interaction between two jets as a function of buoyancy strength of helium jet is investigated. The flow visualization images clearly demonstrate the growth and shape of buoyant jet as a function of Richardson number. Mean velocity and vorticity field results provide quantitative picture about the mixing and interaction between the two jets. The stream trace results show the flow structures, i.e., recirculation zone and foci of vortex structures as a function of Richardson number. The mixing between two jets takes place at far downstream region for low Richardson number (Ri1=1.8). At high Richardson number (Ri1=16.4), the buoyant He jet is located near its exit plane without any direct interaction with the O2 jet. At the intermediate Richardson number (Ri1=4.7), the buoyant jet encroaches the nonbuoyant O2 jet at a favorable penetration distance and a good amount of mixing between the two jets take place. The jet growth results based on the y0.5-location development in the streamwise direction clearly demonstrate the interaction between the He and O2 jets in the interjet region. The entrainment coefficient, vorticity magnitude, and turbulent kinetic energy magnitude are maximum at the intermediate Richardson number (Ri1=4.7) demonstrating direct relationship among each other. The mixing between buoyant He jet and nonbuoyant O2 jet is a function of both shear between the two jets and the strength of buoyant plume. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Buoyancy dominated He–O2 separated jet mixing in a tubular reactor [texte imprimé] / Ankur Deep Bordoloi, Auteur ; P. K. Panigrahi, Auteur . - 2009 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 13 p. Mots-clés : Two  variable-density  jets;  digital  particle  image  velocimetry  technique;  separated  jet Résumé : Mixing of two variable-density jets, one of which is essentially a negatively buoyant jet (He) and the other a nonbuoyant jet (O2) is studied experimentally using digital particle image velocimetry technique for separated nozzle geometry. Two jets are separated from each other, i.e., He jet exit plane is located upstream of the O2 jet exit plane. Experiments were carried out keeping the nonbuoyant O2 jet at constant Reynolds number (Re2=245) and varying the Richardson number (Ri1=1.8,4.7,16.4) of the buoyant He jet. The interaction between two jets as a function of buoyancy strength of helium jet is investigated. The flow visualization images clearly demonstrate the growth and shape of buoyant jet as a function of Richardson number. Mean velocity and vorticity field results provide quantitative picture about the mixing and interaction between the two jets. The stream trace results show the flow structures, i.e., recirculation zone and foci of vortex structures as a function of Richardson number. The mixing between two jets takes place at far downstream region for low Richardson number (Ri1=1.8). At high Richardson number (Ri1=16.4), the buoyant He jet is located near its exit plane without any direct interaction with the O2 jet. At the intermediate Richardson number (Ri1=4.7), the buoyant jet encroaches the nonbuoyant O2 jet at a favorable penetration distance and a good amount of mixing between the two jets take place. The jet growth results based on the y0.5-location development in the streamwise direction clearly demonstrate the interaction between the He and O2 jets in the interjet region. The entrainment coefficient, vorticity magnitude, and turbulent kinetic energy magnitude are maximum at the intermediate Richardson number (Ri1=4.7) demonstrating direct relationship among each other. The mixing between buoyant He jet and nonbuoyant O2 jet is a function of both shear between the two jets and the strength of buoyant plume. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Analytical prediction of flow field in magnetohydrodynamic-based microfluidic devices / Hussameddine S. Kabbani in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 6 p. Titre : Analytical prediction of flow field in magnetohydrodynamic-based microfluidic devices Type de document : texte imprimé Auteurs : Hussameddine S. Kabbani, Auteur ; Martin J. Mack, Auteur ; Sang W. Joo, Auteur Année de publication : 2009 Article en page(s) : 6 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Magnetohydrodynamic  (MHD)  flows;  rectangular  microchannel  driven;  velocity;  mass  flow  rate Résumé : A new approximate solution for the velocity profile of steady incompressible magnetohydrodynamic (MHD) flows in a rectangular microchannel driven by the Lorentz force is proposed. Mean velocity and mass flow rate in a channel, subsequently derived, can be used efficiently for many MHD-based microfluidic applications, including the design of a MHD-based microfluidic network without resorting to costly full-scale computational fluid dynamics. The closed-form solutions, provided for both direct-current (dc) and alternating-current (ac) electric and magnetic fields, are in simple forms, without any series or functions to evaluate, and so can be readily used for inverse or control problems associated with MHD-based lab-on-a-chip (LOC) devices. Extensive comparisons with previous analytical, computational, and experimental results are performed, and summarized in the present study. The proposed solutions are shown to agree better with existing experimental and computational reports than previous approximations and are to be used in a broad range of MHD-based LOC applications with both dc and ac fields with required accuracy. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Analytical prediction of flow field in magnetohydrodynamic-based microfluidic devices [texte imprimé] / Hussameddine S. Kabbani, Auteur ; Martin J. Mack, Auteur ; Sang W. Joo, Auteur . - 2009 . - 6 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 6 p. Mots-clés : Magnetohydrodynamic  (MHD)  flows;  rectangular  microchannel  driven;  velocity;  mass  flow  rate Résumé : A new approximate solution for the velocity profile of steady incompressible magnetohydrodynamic (MHD) flows in a rectangular microchannel driven by the Lorentz force is proposed. Mean velocity and mass flow rate in a channel, subsequently derived, can be used efficiently for many MHD-based microfluidic applications, including the design of a MHD-based microfluidic network without resorting to costly full-scale computational fluid dynamics. The closed-form solutions, provided for both direct-current (dc) and alternating-current (ac) electric and magnetic fields, are in simple forms, without any series or functions to evaluate, and so can be readily used for inverse or control problems associated with MHD-based lab-on-a-chip (LOC) devices. Extensive comparisons with previous analytical, computational, and experimental results are performed, and summarized in the present study. The proposed solutions are shown to agree better with existing experimental and computational reports than previous approximations and are to be used in a broad range of MHD-based LOC applications with both dc and ac fields with required accuracy. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Two-dimensional simulation of the collapse of vapor bubbles near a wall / Luo Jing in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 4 p. Titre : Two-dimensional simulation of the collapse of vapor bubbles near a wall Type de document : texte imprimé Auteurs : Luo Jing, Auteur ; Jian Li, Auteur ; Dong Guangneng, Auteur Année de publication : 2009 Article en page(s) : 4 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Vapor  bubbles;  two  dimensional  simulation Résumé : In order to investigate the erosion extent and mode of cavitation in different states by the commercial code FLUENT and evaluate the reliability of the software, the collapse processes of a vapor bubble, which was near or on the wall under the conditions in the stationary water or the high speed water, were simulated by the numerical calculation by using a 2D model. The results are in accordance with results presented by other researchers, so the simulation may testify to the validation of the code. We suppose that a bevel jet, which is generated contrary to the flow direction when the bubble collapses in high speed flow, may cause the ripple and fish-scale pit damage found on the transition parts of many hydraulic systems. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Two-dimensional simulation of the collapse of vapor bubbles near a wall [texte imprimé] / Luo Jing, Auteur ; Jian Li, Auteur ; Dong Guangneng, Auteur . - 2009 . - 4 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 4 p. Mots-clés : Vapor  bubbles;  two  dimensional  simulation Résumé : In order to investigate the erosion extent and mode of cavitation in different states by the commercial code FLUENT and evaluate the reliability of the software, the collapse processes of a vapor bubble, which was near or on the wall under the conditions in the stationary water or the high speed water, were simulated by the numerical calculation by using a 2D model. The results are in accordance with results presented by other researchers, so the simulation may testify to the validation of the code. We suppose that a bevel jet, which is generated contrary to the flow direction when the bubble collapses in high speed flow, may cause the ripple and fish-scale pit damage found on the transition parts of many hydraulic systems. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Distributions of pressure, velocity, and void fraction for one-dimensional gas-liquid bubbly flow in horizontal pipes / Phu D. Tran in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 9 p. Titre : Distributions of pressure, velocity, and void fraction for one-dimensional gas-liquid bubbly flow in horizontal pipes Type de document : texte imprimé Auteurs : Phu D. Tran, Auteur Année de publication : 2009 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : one-dimensional  gas-liquid  bubbly  flow;  horizontal  pipes Résumé : A homogeneous model for prediction of the longitudinal distributions of pressure, velocity, and void fraction for two-phase bubbly flow in horizontal pipes is presented. The mixture flow is described by a system of two nondimensional ordinary differential equations that can be integrated numerically to yield the distributions of the flow variables along the pipe. The viscosity of the two-phase mixture is assumed to vary with the void fraction according to a polynomial form. Experimental data were obtained for a range of air-water bubbly flow in a horizontal pipe. Prediction of pressure distributions along the pipe compares favorably with experimental data, while prediction of void fraction distributions can be achieved with moderate accuracy. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Distributions of pressure, velocity, and void fraction for one-dimensional gas-liquid bubbly flow in horizontal pipes [texte imprimé] / Phu D. Tran, Auteur . - 2009 . - 9 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 9 p. Mots-clés : one-dimensional  gas-liquid  bubbly  flow;  horizontal  pipes Résumé : A homogeneous model for prediction of the longitudinal distributions of pressure, velocity, and void fraction for two-phase bubbly flow in horizontal pipes is presented. The mixture flow is described by a system of two nondimensional ordinary differential equations that can be integrated numerically to yield the distributions of the flow variables along the pipe. The viscosity of the two-phase mixture is assumed to vary with the void fraction according to a polynomial form. Experimental data were obtained for a range of air-water bubbly flow in a horizontal pipe. Prediction of pressure distributions along the pipe compares favorably with experimental data, while prediction of void fraction distributions can be achieved with moderate accuracy. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Hydrofoil cavitation under strong thermodynamic effect / Jonas P. Gustavsson in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 5 p. Titre : Hydrofoil cavitation under strong thermodynamic effect Type de document : texte imprimé Auteurs : Jonas P. Gustavsson, Auteur ; Kyle C. Denning, Auteur ; Corin Segal, Auteur Année de publication : 2009 Article en page(s) : 5 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cavitation;  thermodynamic  effect Résumé : Cavitation was studied for a NACA0015 hydrofoil using a material that simulates cryogenic behavior. Several angles of attack and flow speeds up to 8.6m∕s were tested. The material used, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, hereafter referred to as fluoroketone, exhibits a strong thermodynamic effect even under ambient conditions. Static pressures were measured at seven chordwise locations along the centerline of the hydrofoil suction side and on the test section wall immediately upstream of the hydrofoil. Frequency analysis of the test section static pressure showed that the amplitude of the oscillations increased as the tunnel speed increased. A gradual transition corresponding to the Type II-I sheet cavitation transition observed in water was found to occur near σ∕2α=5 with Strouhal numbers based on chord dropping from 0.5 to 0.1 as the cavitation number was reduced. Flash-exposure high-speed imaging showed the cavity covering a larger portion of the chord for a given cavitation number than in cold water. The bubbles appeared significantly smaller in the current study and the pressure data showed increasing rather than constant static pressure in the downstream direction in the cavitating region, in line with observations made in literature for other geometries with fluids exhibiting strong thermodynamic effect. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Hydrofoil cavitation under strong thermodynamic effect [texte imprimé] / Jonas P. Gustavsson, Auteur ; Kyle C. Denning, Auteur ; Corin Segal, Auteur . - 2009 . - 5 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 5 p. Mots-clés : Cavitation;  thermodynamic  effect Résumé : Cavitation was studied for a NACA0015 hydrofoil using a material that simulates cryogenic behavior. Several angles of attack and flow speeds up to 8.6m∕s were tested. The material used, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, hereafter referred to as fluoroketone, exhibits a strong thermodynamic effect even under ambient conditions. Static pressures were measured at seven chordwise locations along the centerline of the hydrofoil suction side and on the test section wall immediately upstream of the hydrofoil. Frequency analysis of the test section static pressure showed that the amplitude of the oscillations increased as the tunnel speed increased. A gradual transition corresponding to the Type II-I sheet cavitation transition observed in water was found to occur near σ∕2α=5 with Strouhal numbers based on chord dropping from 0.5 to 0.1 as the cavitation number was reduced. Flash-exposure high-speed imaging showed the cavity covering a larger portion of the chord for a given cavitation number than in cold water. The bubbles appeared significantly smaller in the current study and the pressure data showed increasing rather than constant static pressure in the downstream direction in the cavitating region, in line with observations made in literature for other geometries with fluids exhibiting strong thermodynamic effect. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

Assessing rotation/curvature corrections to eddy-viscosity models in the calculations of centrifugal-compressor flows / Dufour, G. in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 10 p. Titre : Assessing rotation/curvature corrections to eddy-viscosity models in the calculations of centrifugal-compressor flows Type de document : texte imprimé Auteurs : Dufour, G., Auteur ; J.-B. Cazalbou, Auteur ; X. Carbonneau, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure;  rotation;  flow  (dynamics);  turbulence;  viscosity;  compressors;  impellers;  errors;  ncertainty;  modeling Résumé : Rotation and curvature (RC) effects on turbulence are expected to impact losses and flow structure in turbomachines. This paper examines two recent eddy-viscosity-model corrections devised to account for these effects: the Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature ,” Aerosp. Sci. Technol., 1(5), pp. 297–302) correction to the model of Spalart and Allmaras (1994, “A One-Equation Turbulence Model for Aerodynamic Flows ,” Rech. Aerosp., 1, pp. 5–21) and the correction of Cazalbou (2005, “Two-Equation Modeling of Turbulent Rotating Flows ,” Phys. Fluids., 17, p. 055110) to the (k,ϵ) model. The method of verification and validation is applied to assess the impact of these corrections on the computation of a centrifugal-compressor test case. First, a review of RC effects on turbulence as they apply to centrifugal compressors is made. The two corrected models are then presented. Second, the Radiver open test case (Ziegler K. U., Gallus, H. E., and Niehuis R., 2003, “A Study on Impeller Diffuser Interaction Part 1: Influence on the Performance ,” ASME J. Turbomach, 125, pp. 173–182) is used as a basis for the assessment of the two corrections. After a physical-consistency analysis, the Richardson extrapolation is applied to quantify the numerical errors involved in all the calculations. Finally, experimental data are used to perform validation for both global and local predictions. The consistency analysis shows that both corrections lead to significant changes in the turbulent field, in perfect agreement with the underlying theoretical considerations. The uncertainty analysis shows that the predictions of the global performances are more sensitive to grid refinement than they are to RC turbulence modeling. However, the opposite conclusion is drawn with regard to the prediction of some local flow properties: Improvements are obtained with the RC corrections, the best results being observed for the RC-corrected (k,ϵ) model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...] [article] Assessing rotation/curvature corrections to eddy-viscosity models in the calculations of centrifugal-compressor flows [texte imprimé] / Dufour, G., Auteur ; J.-B. Cazalbou, Auteur ; X. Carbonneau, Auteur . - 2009 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 10 p. Mots-clés : Pressure;  rotation;  flow  (dynamics);  turbulence;  viscosity;  compressors;  impellers;  errors;  ncertainty;  modeling Résumé : Rotation and curvature (RC) effects on turbulence are expected to impact losses and flow structure in turbomachines. This paper examines two recent eddy-viscosity-model corrections devised to account for these effects: the Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature ,” Aerosp. Sci. Technol., 1(5), pp. 297–302) correction to the model of Spalart and Allmaras (1994, “A One-Equation Turbulence Model for Aerodynamic Flows ,” Rech. Aerosp., 1, pp. 5–21) and the correction of Cazalbou (2005, “Two-Equation Modeling of Turbulent Rotating Flows ,” Phys. Fluids., 17, p. 055110) to the (k,ϵ) model. The method of verification and validation is applied to assess the impact of these corrections on the computation of a centrifugal-compressor test case. First, a review of RC effects on turbulence as they apply to centrifugal compressors is made. The two corrected models are then presented. Second, the Radiver open test case (Ziegler K. U., Gallus, H. E., and Niehuis R., 2003, “A Study on Impeller Diffuser Interaction Part 1: Influence on the Performance ,” ASME J. Turbomach, 125, pp. 173–182) is used as a basis for the assessment of the two corrections. After a physical-consistency analysis, the Richardson extrapolation is applied to quantify the numerical errors involved in all the calculations. Finally, experimental data are used to perform validation for both global and local predictions. The consistency analysis shows that both corrections lead to significant changes in the turbulent field, in perfect agreement with the underlying theoretical considerations. The uncertainty analysis shows that the predictions of the global performances are more sensitive to grid refinement than they are to RC turbulence modeling. However, the opposite conclusion is drawn with regard to the prediction of some local flow properties: Improvements are obtained with the RC corrections, the best results being observed for the RC-corrected (k,ϵ) model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...]

Measurement of fluid distributions in a rotating fluid coupling using high resolution gamma ray tomography / U. Hampel in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 8 p. Titre : Measurement of fluid distributions in a rotating fluid coupling using high resolution gamma ray tomography Type de document : texte imprimé Auteurs : U. Hampel, Auteur ; D. Hoppe, Auteur ; A. Bieberle, Auteur Année de publication : 2009 Article en page(s) : 8 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  gamma  rays;  fluids;  ydraulic  couplings;  resolution  (optics);  pumps;  turbines;  torque;  fluid  measurement;  ensors Résumé : Gamma ray tomography has been used to visualize fluid distributions in a rotating fluid coupling in different operation points at a pump speed of 780rpm and lower turbine speeds. The gamma ray computed tomography system comprises a Cs-137 isotopic source and a high resolution gamma ray detector. An angle synchronized tomographic data acquisition technique was applied to produce sharp slice images from different positions along the coupling axis. The data have been used to assess the hydraulic behavior of the fluid coupling and to help improve our understanding of the flow structure development and its implications on torque transfer in such a device. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...] [article] Measurement of fluid distributions in a rotating fluid coupling using high resolution gamma ray tomography [texte imprimé] / U. Hampel, Auteur ; D. Hoppe, Auteur ; A. Bieberle, Auteur . - 2009 . - 8 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 8 p. Mots-clés : Flow  (dynamics);  gamma  rays;  fluids;  ydraulic  couplings;  resolution  (optics);  pumps;  turbines;  torque;  fluid  measurement;  ensors Résumé : Gamma ray tomography has been used to visualize fluid distributions in a rotating fluid coupling in different operation points at a pump speed of 780rpm and lower turbine speeds. The gamma ray computed tomography system comprises a Cs-137 isotopic source and a high resolution gamma ray detector. An angle synchronized tomographic data acquisition technique was applied to produce sharp slice images from different positions along the coupling axis. The data have been used to assess the hydraulic behavior of the fluid coupling and to help improve our understanding of the flow structure development and its implications on torque transfer in such a device. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...]

An experimental procedure for determining both the density and flow rate from pressure drop measurements in a cylindrical pipe / Ghislain Michaux in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 3 p. Titre : An experimental procedure for determining both the density and flow rate from pressure drop measurements in a cylindrical pipe Type de document : texte imprimé Auteurs : Ghislain Michaux, Auteur ; Olivier Vauquelin, Auteur ; Elsa Gauger, Auteur Année de publication : 2009 Article en page(s) : 3 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure  drop  measurements;  flow  rate;  cylindrical  pipe Résumé : An experimental procedure was developed for determining both the density and flow rate of a gas from measurements of pressure drops caused by an abrupt flow area contraction in a cylindrical pipe. Experiments were carried out by varying the density and flow rate of a light gas mixture of air and helium, spanning a Reynolds number range from 0.2×104 to 3.4×104. From experimental results, a procedure was then proposed for evaluating the density from pressure change measurements in the scope of light gas extraction experiments. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...] [article] An experimental procedure for determining both the density and flow rate from pressure drop measurements in a cylindrical pipe [texte imprimé] / Ghislain Michaux, Auteur ; Olivier Vauquelin, Auteur ; Elsa Gauger, Auteur . - 2009 . - 3 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 3 p. Mots-clés : Pressure  drop  measurements;  flow  rate;  cylindrical  pipe Résumé : An experimental procedure was developed for determining both the density and flow rate of a gas from measurements of pressure drops caused by an abrupt flow area contraction in a cylindrical pipe. Experiments were carried out by varying the density and flow rate of a light gas mixture of air and helium, spanning a Reynolds number range from 0.2×104 to 3.4×104. From experimental results, a procedure was then proposed for evaluating the density from pressure change measurements in the scope of light gas extraction experiments. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?articleID=1 [...]

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