Dépouillements

Mathematical analysis for off-design performance of cryogenic turboexpander / Ghosh, Subrata K. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 06 p. Titre : Mathematical analysis for off-design performance of cryogenic turboexpander Type de document : texte imprimé Auteurs : Ghosh, Subrata K., Auteur ; Sahoo, R. K., Auteur ; Sarangi, Sunil K., Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Radial  turbine  wheel  Nozzle  Vaneless  space  Diffuser Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Mathematical analysis for off-design performance of cryogenic turboexpander [texte imprimé] / Ghosh, Subrata K., Auteur ; Sahoo, R. K., Auteur ; Sarangi, Sunil K., Auteur . - 2011 . - 06 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 06 p. Mots-clés : Radial  turbine  wheel  Nozzle  Vaneless  space  Diffuser Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Detached eddy simulation of atmospheric flow about a surface mounted cube at high reynolds number / Haupt, Sue Ellen in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Titre : Detached eddy simulation of atmospheric flow about a surface mounted cube at high reynolds number Type de document : texte imprimé Auteurs : Haupt, Sue Ellen, Auteur ; Zajaczkowski, Frank J., Auteur ; Peltier, L. Joel, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Atmospheric  turbulence  Computational  fluid  dynamics  External  flows  Flow  simulation  Shapes  (structures)  Wind Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modeling high Reynolds number (Re) flow is important for understanding wind loading on structures, transport and dispersion of airborne contaminants, and turbulence patterns in urban areas. This study reports a high fidelity computational fluid dynamics simulation of flow about a surface mounted cube for a Reynolds number sufficiently high to represent atmospheric flow conditions. Results from detached eddy simulations (DES) and zonal DES that compare well with field experiment data are presented. A study of reducing grid resolution indicates that further grid refinement would not make a significant difference in the flow field, adding confidence in the accuracy of the results. We additionally consider what features are captured by coarser grids. The conclusion is that these methods can produce high fidelity simulations of high Reynolds number atmospheric flow conditions with a modest grid resolution. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Detached eddy simulation of atmospheric flow about a surface mounted cube at high reynolds number [texte imprimé] / Haupt, Sue Ellen, Auteur ; Zajaczkowski, Frank J., Auteur ; Peltier, L. Joel, Auteur . - 2011 . - 08 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Mots-clés : Atmospheric  turbulence  Computational  fluid  dynamics  External  flows  Flow  simulation  Shapes  (structures)  Wind Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Modeling high Reynolds number (Re) flow is important for understanding wind loading on structures, transport and dispersion of airborne contaminants, and turbulence patterns in urban areas. This study reports a high fidelity computational fluid dynamics simulation of flow about a surface mounted cube for a Reynolds number sufficiently high to represent atmospheric flow conditions. Results from detached eddy simulations (DES) and zonal DES that compare well with field experiment data are presented. A study of reducing grid resolution indicates that further grid refinement would not make a significant difference in the flow field, adding confidence in the accuracy of the results. We additionally consider what features are captured by coarser grids. The conclusion is that these methods can produce high fidelity simulations of high Reynolds number atmospheric flow conditions with a modest grid resolution. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Application of nonlinear turbulence models for marine propulsors / Kaewkhiaw, Prachakon in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Titre : Application of nonlinear turbulence models for marine propulsors Type de document : texte imprimé Auteurs : Kaewkhiaw, Prachakon, Auteur ; Tiaple, Yodchai, Auteur ; Dechaumphai, Pramote, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Marine  proppeller  Computational  fluid  dynamics  Nonlinear  turbulence  model  Turbulent  flow  Cavitation  Multiphase  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The realistic simulation of cavitation on a marine propeller is important for the efficient design of the propeller. However, the flow characteristic that occurred on the marine propeller is complicated and difficult to predict due to the combined effects of turbulence, cavitation, and multiphase phenomena. There is still currently no turbulence model that can predict these combined effects satisfactory. The nonlinear turbulence model is therefore modified and applied to predict the cavitation on a marine propeller for the first time in this work. It is found that the nonlinear turbulence model can predict the cavitation and hence the thrust and torque coefficients much more accurately than the existing Reynolds-averaged Navier–Stokes turbulence models including the Reynolds-stress model. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Application of nonlinear turbulence models for marine propulsors [texte imprimé] / Kaewkhiaw, Prachakon, Auteur ; Tiaple, Yodchai, Auteur ; Dechaumphai, Pramote, Auteur . - 2011 . - 07 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Mots-clés : Marine  proppeller  Computational  fluid  dynamics  Nonlinear  turbulence  model  Turbulent  flow  Cavitation  Multiphase  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The realistic simulation of cavitation on a marine propeller is important for the efficient design of the propeller. However, the flow characteristic that occurred on the marine propeller is complicated and difficult to predict due to the combined effects of turbulence, cavitation, and multiphase phenomena. There is still currently no turbulence model that can predict these combined effects satisfactory. The nonlinear turbulence model is therefore modified and applied to predict the cavitation on a marine propeller for the first time in this work. It is found that the nonlinear turbulence model can predict the cavitation and hence the thrust and torque coefficients much more accurately than the existing Reynolds-averaged Navier–Stokes turbulence models including the Reynolds-stress model. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Fluid flow in trapezoidal silicon microchannels with 3D random rough bottoms / Renqiang, Xiong in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Titre : Fluid flow in trapezoidal silicon microchannels with 3D random rough bottoms Type de document : texte imprimé Auteurs : Renqiang, Xiong, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Trapezoidal  microchannel  Random  roughless  Friction  factor Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this paper, a bottom-up approach is used to construct random rough bottom walls for trapezoidal silicon microchannels with hydraulic diameters Dh from 47 µm to 241 µm. The top and side walls are set to be smooth. A computational fluid dynamics solver is used to solve the 3D Navier–Stokes equations for the water flow through the rough trapezoidal microchannels. No-slip and periodic boundary conditions are applied to achieve the fully developed flow characteristics. The effects of Reynolds number Re (75–600), relative roughness height H/Dh (1.66–5.39%), aspect ratio beta (0.13–1), and base angle theta (30–90 deg) on the Poiseuille number Po are investigated. It is found that the roughness strongly affects the flow near the bottom wall but does not have significant effect on the center flow. The Po number in the developing flow region increases with the Re number and in the fully developed region tends to be independent of the Re number. The entrance length Le is found to be smaller than that in smooth channels because the roughness reduces hydraulic diameter Dh of the microchannel. It is also observed that with a certain H/Dh, the Po number has a larger deviation from the theoretical value with a smaller beta, and with the same H/Dh and beta, theta DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Fluid flow in trapezoidal silicon microchannels with 3D random rough bottoms [texte imprimé] / Renqiang, Xiong, Auteur . - 2011 . - 07 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Mots-clés : Trapezoidal  microchannel  Random  roughless  Friction  factor Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this paper, a bottom-up approach is used to construct random rough bottom walls for trapezoidal silicon microchannels with hydraulic diameters Dh from 47 µm to 241 µm. The top and side walls are set to be smooth. A computational fluid dynamics solver is used to solve the 3D Navier–Stokes equations for the water flow through the rough trapezoidal microchannels. No-slip and periodic boundary conditions are applied to achieve the fully developed flow characteristics. The effects of Reynolds number Re (75–600), relative roughness height H/Dh (1.66–5.39%), aspect ratio beta (0.13–1), and base angle theta (30–90 deg) on the Poiseuille number Po are investigated. It is found that the roughness strongly affects the flow near the bottom wall but does not have significant effect on the center flow. The Po number in the developing flow region increases with the Re number and in the fully developed region tends to be independent of the Re number. The entrance length Le is found to be smaller than that in smooth channels because the roughness reduces hydraulic diameter Dh of the microchannel. It is also observed that with a certain H/Dh, the Po number has a larger deviation from the theoretical value with a smaller beta, and with the same H/Dh and beta, theta DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

CFD analysis of gear windage losses / Hill, Matthew J. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 10 p. Titre : CFD analysis of gear windage losses : validation and parametric aerodynamic studies Type de document : texte imprimé Auteurs : Hill, Matthew J., Auteur ; Kunz, Robert F., Auteur ; Medvitz, Richard B., Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Aerodynamics  Computational  fluid  dynamics  Gears Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A computational fluid dynamics (CFD) method has been applied to gear configurations with and without shrouding. The goals of this work have been to validate the numerical and modeling approaches used for these applications and to develop physical understanding of the aerodynamics of gear windage loss. Several spur gear geometries are considered, for which experimental data are available. Various canonical shrouding configurations and free spinning (no shroud) cases are studied. Comparisons are made with experimental data from open literature, and data recently obtained in the NASA Glenn Research Center Gear Windage Test Facility, Cleveland, OH. The results show good agreement with the experiment. The parametric shroud configuration studies carried out in the Glenn experiments and the CFD analyses elucidate the physical mechanisms of windage losses as well as mitigation strategies due to shrouding and newly proposed tooth contour modifications. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] CFD analysis of gear windage losses : validation and parametric aerodynamic studies [texte imprimé] / Hill, Matthew J., Auteur ; Kunz, Robert F., Auteur ; Medvitz, Richard B., Auteur . - 2011 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 10 p. Mots-clés : Aerodynamics  Computational  fluid  dynamics  Gears Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A computational fluid dynamics (CFD) method has been applied to gear configurations with and without shrouding. The goals of this work have been to validate the numerical and modeling approaches used for these applications and to develop physical understanding of the aerodynamics of gear windage loss. Several spur gear geometries are considered, for which experimental data are available. Various canonical shrouding configurations and free spinning (no shroud) cases are studied. Comparisons are made with experimental data from open literature, and data recently obtained in the NASA Glenn Research Center Gear Windage Test Facility, Cleveland, OH. The results show good agreement with the experiment. The parametric shroud configuration studies carried out in the Glenn experiments and the CFD analyses elucidate the physical mechanisms of windage losses as well as mitigation strategies due to shrouding and newly proposed tooth contour modifications. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Direct numerical simulation of single and multiple square jets in cross-flow / Yao, Y. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 10 p. Titre : Direct numerical simulation of single and multiple square jets in cross-flow Type de document : texte imprimé Auteurs : Yao, Y., Auteur ; Maidi, M., Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  simulation  Jets  Laminar  flow  Numerical  analysis  Vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Direct numerical simulations (DNSs) have been carried out for single and multiple square jets issuing normally into a cross-flow, with the primary aim of studying the flow structures and interaction mechanisms associated with the jet in cross-flow (JICF) problems. The single JICF configuration follows a similar study previously done by Sau et al. (2004, Phys. Rev. E, 69, p. 066302) and the multiple JICF configurations are arranged side-by-side in the spanwise direction with a jet-to-jet adjacent edge distance (H) for the twin-jet case and an additional third jet downstream along the centerline with a jet-to-jet adjacent edge distance (L) for the triple-jet case. Simulations are performed for two twin-jet cases with H=1D,2D, respectively, and for one triple-jet case with H=1D, L=2D, where D is the jet exit width. Flow conditions similar to Sau et al. are considered, i.e., the jet to the cross-flow velocity ratio R=2.5 and the Reynolds number 225, based on the freestream velocity and the jet exit width. For the single jet in cross-flow, the vortical structures from our DNS are in good qualitative agreement with the findings of Sau et al. For the side-by-side twin-jet configuration, results have shown that the merging process of the two initially separated counter-rotating vortex pairs (CRVPs) from each jet hole exit is strongly dependent on the jet-to-jet adjacent edge distance H with earlier merging observed for the case H=1D. Downstream, the flow is dominated by a larger CRVP structure, accompanied by a smaller inner vortex pair. The inner vortex pair is found not to survive in the far-field as it rapidly dissipates before exiting the computational domain. These observations are in good agreement with the experimental findings in the literature. Simulations of the triple-jet in cross-flow case have shown some complicated jet-jet and jet-cross-flow interactions with three vortex pairs observed downstream, significantly different from that seen in the twin-jet cases. The evidence of these flow structures and interaction characteristics could provide a valuable reference database for future in-depth flow physics studies of laboratory experimental and numerical investigations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Direct numerical simulation of single and multiple square jets in cross-flow [texte imprimé] / Yao, Y., Auteur ; Maidi, M., Auteur . - 2011 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 10 p. Mots-clés : Flow  simulation  Jets  Laminar  flow  Numerical  analysis  Vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Direct numerical simulations (DNSs) have been carried out for single and multiple square jets issuing normally into a cross-flow, with the primary aim of studying the flow structures and interaction mechanisms associated with the jet in cross-flow (JICF) problems. The single JICF configuration follows a similar study previously done by Sau et al. (2004, Phys. Rev. E, 69, p. 066302) and the multiple JICF configurations are arranged side-by-side in the spanwise direction with a jet-to-jet adjacent edge distance (H) for the twin-jet case and an additional third jet downstream along the centerline with a jet-to-jet adjacent edge distance (L) for the triple-jet case. Simulations are performed for two twin-jet cases with H=1D,2D, respectively, and for one triple-jet case with H=1D, L=2D, where D is the jet exit width. Flow conditions similar to Sau et al. are considered, i.e., the jet to the cross-flow velocity ratio R=2.5 and the Reynolds number 225, based on the freestream velocity and the jet exit width. For the single jet in cross-flow, the vortical structures from our DNS are in good qualitative agreement with the findings of Sau et al. For the side-by-side twin-jet configuration, results have shown that the merging process of the two initially separated counter-rotating vortex pairs (CRVPs) from each jet hole exit is strongly dependent on the jet-to-jet adjacent edge distance H with earlier merging observed for the case H=1D. Downstream, the flow is dominated by a larger CRVP structure, accompanied by a smaller inner vortex pair. The inner vortex pair is found not to survive in the far-field as it rapidly dissipates before exiting the computational domain. These observations are in good agreement with the experimental findings in the literature. Simulations of the triple-jet in cross-flow case have shown some complicated jet-jet and jet-cross-flow interactions with three vortex pairs observed downstream, significantly different from that seen in the twin-jet cases. The evidence of these flow structures and interaction characteristics could provide a valuable reference database for future in-depth flow physics studies of laboratory experimental and numerical investigations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Compound triple jets film cooling improvements via velocity and density ratios / Farhadi-Azar, R. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 13 p. Titre : Compound triple jets film cooling improvements via velocity and density ratios : large eddy simulation Type de document : texte imprimé Auteurs : Farhadi-Azar, R., Auteur ; Ramezanizadeh, M., Auteur ; Taeibi-Rahni, M., Auteur Année de publication : 2011 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Combined  triple  jet  (CTJ)  structure  Film  cooling  Density  ratio  effect  Velocity  ratio  Large  eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Compound triple jets film cooling improvements via velocity and density ratios : large eddy simulation [texte imprimé] / Farhadi-Azar, R., Auteur ; Ramezanizadeh, M., Auteur ; Taeibi-Rahni, M., Auteur . - 2011 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 13 p. Mots-clés : Combined  triple  jet  (CTJ)  structure  Film  cooling  Density  ratio  effect  Velocity  ratio  Large  eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Lubrication of highly viscous core-annular flows in microfluidic chambers / Darvishi, Samira in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Titre : Lubrication of highly viscous core-annular flows in microfluidic chambers Type de document : texte imprimé Auteurs : Darvishi, Samira, Auteur ; Cubaud, Thomas, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Buckling  Lubrication  Microchannel  flow  Viscosity  Wetting Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : We investigate the lubrication transition of high-viscosity fluid threads flowing in sheaths of less viscous fluids, i.e., viscous core-annular flows, in microchannels. Focus is given on the flow behavior of threads as they traverse a quasi-two-dimensional diverging-converging slit microfluidic chamber. The role of the viscosity contrast is examined for both miscible and immiscible fluids, and, for the later case, both partially wetting and nonwetting threads are considered. The conditions for lubrication are established in relation to flow rates of injection, interfacial properties, viscosities, and phenomena such as viscous buckling, wetting, breakup, and coalescence. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Lubrication of highly viscous core-annular flows in microfluidic chambers [texte imprimé] / Darvishi, Samira, Auteur ; Cubaud, Thomas, Auteur . - 2011 . - 07 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 07 p. Mots-clés : Buckling  Lubrication  Microchannel  flow  Viscosity  Wetting Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : We investigate the lubrication transition of high-viscosity fluid threads flowing in sheaths of less viscous fluids, i.e., viscous core-annular flows, in microchannels. Focus is given on the flow behavior of threads as they traverse a quasi-two-dimensional diverging-converging slit microfluidic chamber. The role of the viscosity contrast is examined for both miscible and immiscible fluids, and, for the later case, both partially wetting and nonwetting threads are considered. The conditions for lubrication are established in relation to flow rates of injection, interfacial properties, viscosities, and phenomena such as viscous buckling, wetting, breakup, and coalescence. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Computational investigation of liquid spray dispersion modification by conical nozzle attachments / Pougatch, Konstantin in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 09 p. Titre : Computational investigation of liquid spray dispersion modification by conical nozzle attachments Type de document : texte imprimé Auteurs : Pougatch, Konstantin, Auteur ; Salcudean, Martha, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Sprays  Numerical  modeling  Nozzle  Atomization  Particle  number  density Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Liquid spray characteristics such as the droplet size and dispersion angle are determined by the atomizer design and the physical properties of the liquid and surrounding gas. One of the options to change these characteristics is to attach an especially designed piece to the nozzle exit. While these attachments can have a variety of shapes, we chose a conical geometry to exploit its axial symmetry and, at the same time, obtain the results that can be generalized to other configurations. Thus, we investigate an addition of the conically shaped attachment to the premixed gas-assisted high-pressure atomizer with the previously developed numerical model. This is a two-fluid Eulerian-Eulerian model with a catastrophic phase inversion that was developed for compressible gas-liquid mixtures and can be applied to both the flow through the nozzle-atomizer and to the dispersion of the spray. The model also accounts for the break-up and coalescence effects of bubbles and droplets. Our investigation reveals that the conical nozzle attachments act as spray limiters by reducing the natural expansion angle of a spray. Also, the droplets produced by the nozzle with a conical addition tend to be larger than the ones obtained with a stand alone nozzle. The largest droplets are generated by the smallest attachment angle considered, 10 deg. With the increase of the angle, the spraying characteristics become closer to those of the stand alone nozzle. It can be concluded that the conical shape of the attachments with a relatively small angle may be used when higher jet penetration and lower dispersion are desirable. The attachments with larger angles do not offer a substantial difference from the stand alone nozzle. Another important conclusion is that the dispersion of the jet is determined by the radial momentum transferred to the liquid before or immediately after the phase inversion takes place. Thus, for improved dispersion, the area where the atomization is taking place should not be restricted. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Computational investigation of liquid spray dispersion modification by conical nozzle attachments [texte imprimé] / Pougatch, Konstantin, Auteur ; Salcudean, Martha, Auteur . - 2011 . - 09 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 09 p. Mots-clés : Sprays  Numerical  modeling  Nozzle  Atomization  Particle  number  density Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Liquid spray characteristics such as the droplet size and dispersion angle are determined by the atomizer design and the physical properties of the liquid and surrounding gas. One of the options to change these characteristics is to attach an especially designed piece to the nozzle exit. While these attachments can have a variety of shapes, we chose a conical geometry to exploit its axial symmetry and, at the same time, obtain the results that can be generalized to other configurations. Thus, we investigate an addition of the conically shaped attachment to the premixed gas-assisted high-pressure atomizer with the previously developed numerical model. This is a two-fluid Eulerian-Eulerian model with a catastrophic phase inversion that was developed for compressible gas-liquid mixtures and can be applied to both the flow through the nozzle-atomizer and to the dispersion of the spray. The model also accounts for the break-up and coalescence effects of bubbles and droplets. Our investigation reveals that the conical nozzle attachments act as spray limiters by reducing the natural expansion angle of a spray. Also, the droplets produced by the nozzle with a conical addition tend to be larger than the ones obtained with a stand alone nozzle. The largest droplets are generated by the smallest attachment angle considered, 10 deg. With the increase of the angle, the spraying characteristics become closer to those of the stand alone nozzle. It can be concluded that the conical shape of the attachments with a relatively small angle may be used when higher jet penetration and lower dispersion are desirable. The attachments with larger angles do not offer a substantial difference from the stand alone nozzle. Another important conclusion is that the dispersion of the jet is determined by the radial momentum transferred to the liquid before or immediately after the phase inversion takes place. Thus, for improved dispersion, the area where the atomization is taking place should not be restricted. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Numerical prediction of flow patterns in bubble pumps / Benhmidene, Ali in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Titre : Numerical prediction of flow patterns in bubble pumps Type de document : texte imprimé Auteurs : Benhmidene, Ali, Auteur ; Chaouachi, Bechir, Auteur ; Bourouis, Mahmoud, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Bubble  pump  Flow  pattern  Void  fraction  Simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m−2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m−2, the bubble pump operates under the churn and annular regimes, and the bubble pump performance is improved when the tube diameter increases. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Numerical prediction of flow patterns in bubble pumps [texte imprimé] / Benhmidene, Ali, Auteur ; Chaouachi, Bechir, Auteur ; Bourouis, Mahmoud, Auteur . - 2011 . - 08 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 08 p. Mots-clés : Bubble  pump  Flow  pattern  Void  fraction  Simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m−2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m−2, the bubble pump operates under the churn and annular regimes, and the bubble pump performance is improved when the tube diameter increases. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Numerical simulation of two-dimensional drops suspended in simple shear flow at nonzero reynolds numbers / Mortazavi, S. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 09 p. Titre : Numerical simulation of two-dimensional drops suspended in simple shear flow at nonzero reynolds numbers Type de document : texte imprimé Auteurs : Mortazavi, S., Auteur ; Afshar, Y., Auteur ; Abbaspour, H., Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Channel  flow  Drops  Flow  simulation  Laminar  flow  Shear  flow  Two-phase  flow  Viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Numerical simulation of two-dimensional drops suspended in simple shear flow at nonzero reynolds numbers [texte imprimé] / Mortazavi, S., Auteur ; Afshar, Y., Auteur ; Abbaspour, H., Auteur . - 2011 . - 09 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 09 p. Mots-clés : Channel  flow  Drops  Flow  simulation  Laminar  flow  Shear  flow  Two-phase  flow  Viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Tip and junction vortices generated by the sail of a yawed submarine model at low reynolds numbers / Jiménez, Juan M. in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) Titre : Tip and junction vortices generated by the sail of a yawed submarine model at low reynolds numbers Type de document : texte imprimé Auteurs : Jiménez, Juan M., Auteur ; Smits, Alexander J., Auteur Année de publication : 2011 Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Boundary  layer  turbulence  Flow  separation  Flow  visualisation  Underwater  vehicles  Vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Results are presented on the behavior of the tip and junction vortices generated by the sail of a SUBOFF submarine model at yaw angles from 6 deg to 17 deg for a Reynolds number of 94×103 based on model length. The measurements were conducted in a water channel on a spanwise plane 1.3 chord lengths downstream from the trailing edge of the sail. In the vicinity of the sail hull junction, the presence of streamwise vortices in the form of horseshoe or necklace vortices locally dominates the flow. As the yaw angle is increased from 6 deg to 9 deg, the circulation of the sail tip vortex increases, and is in good accordance with predictions from finite wing theory. However, as the yaw angle is further increased, the sail boundary layer separates with an overall drop in circulation. In contrast, the circulation value for the junction vortex increases with yaw angle, and only drops slightly at the highest yaw angle. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Tip and junction vortices generated by the sail of a yawed submarine model at low reynolds numbers [texte imprimé] / Jiménez, Juan M., Auteur ; Smits, Alexander J., Auteur . - 2011. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) Mots-clés : Boundary  layer  turbulence  Flow  separation  Flow  visualisation  Underwater  vehicles  Vortices Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Results are presented on the behavior of the tip and junction vortices generated by the sail of a SUBOFF submarine model at yaw angles from 6 deg to 17 deg for a Reynolds number of 94×103 based on model length. The measurements were conducted in a water channel on a spanwise plane 1.3 chord lengths downstream from the trailing edge of the sail. In the vicinity of the sail hull junction, the presence of streamwise vortices in the form of horseshoe or necklace vortices locally dominates the flow. As the yaw angle is increased from 6 deg to 9 deg, the circulation of the sail tip vortex increases, and is in good accordance with predictions from finite wing theory. However, as the yaw angle is further increased, the sail boundary layer separates with an overall drop in circulation. In contrast, the circulation value for the junction vortex increases with yaw angle, and only drops slightly at the highest yaw angle. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

Medial axis transform method for shape design of hub and shroud contours of impellers / Pengfei, Wang in Transactions of the ASME . Journal of fluids engineering, Vol. 133 N° 3 (Mars 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 04 p. Titre : Medial axis transform method for shape design of hub and shroud contours of impellers Type de document : texte imprimé Auteurs : Pengfei, Wang, Auteur ; Ruan, Xiaodong, Auteur ; Zou, Jun, Auteur Année de publication : 2011 Article en page(s) : 04 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Hub  and  shroud  contours  Inverse  design  Impeller  Medial  axis  transform  theory Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A novel method of designing hub and shroud contours is presented. The method, based on the medial axis transform theory in differential geometry, gives a uniform description of hub and shroud contours and the formula of cross section area. Through solving the formula of cross section area with an additional constraint, the hub and shroud contours can be determined numerically. The constraint is exposed through a curvature equation, which allows the medial axis or hub (shroud) contour to be a certain form. Using this method, various optimization criteria relating to the cross section area can be conveniently introduced into the design. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...] [article] Medial axis transform method for shape design of hub and shroud contours of impellers [texte imprimé] / Pengfei, Wang, Auteur ; Ruan, Xiaodong, Auteur ; Zou, Jun, Auteur . - 2011 . - 04 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 133 N° 3 (Mars 2011) . - 04 p. Mots-clés : Hub  and  shroud  contours  Inverse  design  Impeller  Medial  axis  transform  theory Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A novel method of designing hub and shroud contours is presented. The method, based on the medial axis transform theory in differential geometry, gives a uniform description of hub and shroud contours and the formula of cross section area. Through solving the formula of cross section area with an additional constraint, the hub and shroud contours can be determined numerically. The constraint is exposed through a curvature equation, which allows the medial axis or hub (shroud) contour to be a certain form. Using this method, various optimization criteria relating to the cross section area can be conveniently introduced into the design. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA400013 [...]

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