Dépouillements

Forces and surface pressure on a blade moving in front of the admission region / Soo-Yong Cho in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 08 p. Titre : Forces and surface pressure on a blade moving in front of the admission region Type de document : texte imprimé Auteurs : Soo-Yong Cho, Auteur ; Chong-Hyun Cho, Auteur ; Kook-Young Ahn, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : blades;  confined  flow;  flow  measurement;  nozzles;  pumps;  rotational  flow;  turbines  Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The partial admission technique is widely used to control the output power of turbines. In some cases, it has more merits than full admission. However, additional losses, such as expansion, mixing, or pumping, are generated in partial admission as compared with full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was rectangular and its size is 200×200 mm2. The tested blade was axial-type and its chord was 200 mm. Nineteen identical blades were applied to the linear cascade for the partial admission experiment. The blades moved along the rotational direction in front of the admission region, and then operating forces and surface pressures on the blades were measured at the steady state. The experiment was conducted at a Reynolds number of 3×105 based on the chord. The nozzle flow angle was set to 65 deg with a solidity of 1.38 for performance test at the design point. In addition, another two different solidities of 1.25 and 1.67 were applied. From the experimental results, when the solidity was decreased, the maximum rotational force increased but the maximum axial force decreased. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Forces and surface pressure on a blade moving in front of the admission region [texte imprimé] / Soo-Yong Cho, Auteur ; Chong-Hyun Cho, Auteur ; Kook-Young Ahn, Auteur . - 2011 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 08 p. Mots-clés : blades;  confined  flow;  flow  measurement;  nozzles;  pumps;  rotational  flow;  turbines  Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The partial admission technique is widely used to control the output power of turbines. In some cases, it has more merits than full admission. However, additional losses, such as expansion, mixing, or pumping, are generated in partial admission as compared with full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was rectangular and its size is 200×200 mm2. The tested blade was axial-type and its chord was 200 mm. Nineteen identical blades were applied to the linear cascade for the partial admission experiment. The blades moved along the rotational direction in front of the admission region, and then operating forces and surface pressures on the blades were measured at the steady state. The experiment was conducted at a Reynolds number of 3×105 based on the chord. The nozzle flow angle was set to 65 deg with a solidity of 1.38 for performance test at the design point. In addition, another two different solidities of 1.25 and 1.67 were applied. From the experimental results, when the solidity was decreased, the maximum rotational force increased but the maximum axial force decreased. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Stall inception mechanism in an axial flow fan under clean and distorted inflows / Pramod B. Salunkhe in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 14 p. Titre : Stall inception mechanism in an axial flow fan under clean and distorted inflows Type de document : texte imprimé Auteurs : Pramod B. Salunkhe, Auteur ; A. M. Pradeep, Auteur Année de publication : 2011 Article en page(s) : 14 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : aerodynamics;  blades;  compressors;  fans;  flow  measurement;  rotational  flow;  turbomachinery;  wavelet  transforms Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present paper describes the use of Morlet wavelet transform in understanding the stall inception mechanism in a single stage axial flow fan. Unsteady pressure data from wall mounted sensors were used in the wavelet transforms. This paper was carried out under undistorted and distorted inflow conditions as well as for slow throttle closure and throttle ramping. It was observed from the wavelet transforms that the stall inception under clean inflow (undistorted) and counter-rotating inflow distortions (in the direction opposing the rotor rotation) incur through short length-scale disturbances and through long length-scale disturbances under static and co-rotating inflow distortions (in the same direction of rotor rotation). Modal activity was observed to be insignificant under clean inflow while under static inflow distortion, long length-scale disturbances evolved due to interaction between rotor blades and the distorted sector, especially near the trailing edge of the distortion screen. The presence of a strong mode was observed under both co- and counter-rotating inflow distortions. With throttle ramping, stall inception occurs through long and short length-scale disturbances under co- and counter-rotating inflow distortions, respectively. Some preliminary flow characteristics were studied using a seven hole probe. A significant increase in flow angle and decrease in axial flow coefficient close to the rotor tip were observed under co-rotating inflow distortion as compared with counter-rotating inflow distortion. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Stall inception mechanism in an axial flow fan under clean and distorted inflows [texte imprimé] / Pramod B. Salunkhe, Auteur ; A. M. Pradeep, Auteur . - 2011 . - 14 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 14 p. Mots-clés : aerodynamics;  blades;  compressors;  fans;  flow  measurement;  rotational  flow;  turbomachinery;  wavelet  transforms Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The present paper describes the use of Morlet wavelet transform in understanding the stall inception mechanism in a single stage axial flow fan. Unsteady pressure data from wall mounted sensors were used in the wavelet transforms. This paper was carried out under undistorted and distorted inflow conditions as well as for slow throttle closure and throttle ramping. It was observed from the wavelet transforms that the stall inception under clean inflow (undistorted) and counter-rotating inflow distortions (in the direction opposing the rotor rotation) incur through short length-scale disturbances and through long length-scale disturbances under static and co-rotating inflow distortions (in the same direction of rotor rotation). Modal activity was observed to be insignificant under clean inflow while under static inflow distortion, long length-scale disturbances evolved due to interaction between rotor blades and the distorted sector, especially near the trailing edge of the distortion screen. The presence of a strong mode was observed under both co- and counter-rotating inflow distortions. With throttle ramping, stall inception occurs through long and short length-scale disturbances under co- and counter-rotating inflow distortions, respectively. Some preliminary flow characteristics were studied using a seven hole probe. A significant increase in flow angle and decrease in axial flow coefficient close to the rotor tip were observed under co-rotating inflow distortion as compared with counter-rotating inflow distortion. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Parametric investigation of circumferential grooves on compressor rotor performance / Yanhui Wu in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 10 p. Titre : Parametric investigation of circumferential grooves on compressor rotor performance Type de document : texte imprimé Auteurs : Yanhui Wu, Auteur ; Wuli Chu, Auteur ; Haoguang Zhang, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : omputational  fluid  dynamics;  flow  simulation;  numerical  analysis;  rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents numerical and experimental investigations about grooved casing treatment with the help of a high-speed small-scale compressor rotor. First, the numerical investigation seeks to offer a contribution of understanding the working mechanism by which circumferential grooves improve stall margin. It is found that stall margin gain due to the presence of circumferential grooves arises from the suction-injection effect and the near-tip unloading effect. Based on that, the philosophy of design of experiment is then set up. Finally, parametric studies are carried out through systematical experiments. It is found that the orthogonal experiment and the factorial analyses are successful in identifying the “best casing configuration” in terms of stall margin improvement. However, the ineffectiveness of the deduction from simulations suggests that the secondary flow circulations on stall margin gain should not be neglected, and the overall contribution of each groove to stall margin gain depends on its unloading effect and the compound effect of suction-injection. Further numerical investigation will focus on how to set up quantitative criteria to evaluate the compound effect of suction-injection and the unloading effect on stall margin gain respectively in each groove. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Parametric investigation of circumferential grooves on compressor rotor performance [texte imprimé] / Yanhui Wu, Auteur ; Wuli Chu, Auteur ; Haoguang Zhang, Auteur . - 2011 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 10 p. Mots-clés : omputational  fluid  dynamics;  flow  simulation;  numerical  analysis;  rotors Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents numerical and experimental investigations about grooved casing treatment with the help of a high-speed small-scale compressor rotor. First, the numerical investigation seeks to offer a contribution of understanding the working mechanism by which circumferential grooves improve stall margin. It is found that stall margin gain due to the presence of circumferential grooves arises from the suction-injection effect and the near-tip unloading effect. Based on that, the philosophy of design of experiment is then set up. Finally, parametric studies are carried out through systematical experiments. It is found that the orthogonal experiment and the factorial analyses are successful in identifying the “best casing configuration” in terms of stall margin improvement. However, the ineffectiveness of the deduction from simulations suggests that the secondary flow circulations on stall margin gain should not be neglected, and the overall contribution of each groove to stall margin gain depends on its unloading effect and the compound effect of suction-injection. Further numerical investigation will focus on how to set up quantitative criteria to evaluate the compound effect of suction-injection and the unloading effect on stall margin gain respectively in each groove. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Computational investigations into draining in an axisymmetric vessel / Adam Robinson in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 07 p. Titre : Computational investigations into draining in an axisymmetric vessel Type de document : texte imprimé Auteurs : Adam Robinson, Auteur ; Hervé Morvan, Auteur ; Carol Eastwick, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : aerospace  engines;  computational  fluid  dynamics;  machine  bearings;  oils;  pipe  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Within an aero-engine, bearing chamber oil is provided for components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure that it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper, a simplified physical situation related to bearing chamber scavenge is computationally modeled. The volume of fluid (VOF) model of Hirt and Nichols (1981, “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries,” J. Comput. Phys., 39, pp. 201–225), implemented within the commercial computational fluid dynamics (CFD) code FLUENT (Fluent, 2006, Fluent 6.3 User's Guide, 10 Cavendish Court, Lebanon, NH 03766), has been applied to investigate the case of transient draining in an axisymmetric vessel. The model is setup to match the experimental work of Lubin and Springer (1967, “The Formation of a Dip on the Surface of a Liquid Draining From a Tank,” J. Fluid Mech., 29(2), pp. 385–390). First, a comparison of the computational predictions with the experimental results for free draining is presented. Second, a comparison between the free surface positions obtained the developed VOF methodology and the results obtained by Zhou and Graebel (1990, “Axisymmetric Draining of a Cylindrical Tank With a Free Surface,” J. Fluid Mech., 221, pp. 511–532) using a boundary integral method is reported. When comparing the results with the observations of Lubin and Springer some differences are noted. These differences, which relate to the effect of initial height and outflow history, may have arisen due to the experimental procedure used by Lubin and Springer. This paper shows that CFD is a promising approach to analyzing these simple draining situations in terms of predicting bulk quantities, transitions, and free-surface shape and position. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Computational investigations into draining in an axisymmetric vessel [texte imprimé] / Adam Robinson, Auteur ; Hervé Morvan, Auteur ; Carol Eastwick, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 07 p. Mots-clés : aerospace  engines;  computational  fluid  dynamics;  machine  bearings;  oils;  pipe  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Within an aero-engine, bearing chamber oil is provided for components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure that it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper, a simplified physical situation related to bearing chamber scavenge is computationally modeled. The volume of fluid (VOF) model of Hirt and Nichols (1981, “Volume of Fluid (VOF) Method for the Dynamics of Free Boundaries,” J. Comput. Phys., 39, pp. 201–225), implemented within the commercial computational fluid dynamics (CFD) code FLUENT (Fluent, 2006, Fluent 6.3 User's Guide, 10 Cavendish Court, Lebanon, NH 03766), has been applied to investigate the case of transient draining in an axisymmetric vessel. The model is setup to match the experimental work of Lubin and Springer (1967, “The Formation of a Dip on the Surface of a Liquid Draining From a Tank,” J. Fluid Mech., 29(2), pp. 385–390). First, a comparison of the computational predictions with the experimental results for free draining is presented. Second, a comparison between the free surface positions obtained the developed VOF methodology and the results obtained by Zhou and Graebel (1990, “Axisymmetric Draining of a Cylindrical Tank With a Free Surface,” J. Fluid Mech., 221, pp. 511–532) using a boundary integral method is reported. When comparing the results with the observations of Lubin and Springer some differences are noted. These differences, which relate to the effect of initial height and outflow history, may have arisen due to the experimental procedure used by Lubin and Springer. This paper shows that CFD is a promising approach to analyzing these simple draining situations in terms of predicting bulk quantities, transitions, and free-surface shape and position. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Experimental observation of inertia-dominated squeeze film damping in liquid / Antoine Fornari in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 10 p. Titre : Experimental observation of inertia-dominated squeeze film damping in liquid Type de document : texte imprimé Auteurs : Antoine Fornari, Auteur ; Matthew Sullivan, Auteur ; Hua Chen, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : damping;  drag;  liquid  films;  lubrication;  microfluidics;  microsensors;  plates  (structures);  vibrations;  viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Experimental observation of inertia-dominated squeeze film damping in liquid [texte imprimé] / Antoine Fornari, Auteur ; Matthew Sullivan, Auteur ; Hua Chen, Auteur . - 2011 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 10 p. Mots-clés : damping;  drag;  liquid  films;  lubrication;  microfluidics;  microsensors;  plates  (structures);  vibrations;  viscosity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Partially averaged Navier–Stokes (PANS) method for turbulence simulations / Sunil Lakshmipathy in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Titre : Partially averaged Navier–Stokes (PANS) method for turbulence simulations : flow past a circular cylinder Type de document : texte imprimé Auteurs : Sunil Lakshmipathy, Auteur ; Sharath S. Girimaji, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : drag;  flow  simulation;  Navier-Stokes  equations;  turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The objective of this study is to evaluate the capability of the partially averaged Navier–Stokes (PANS) method in a moderately high Reynolds number (ReD 1.4×105) turbulent flow past a circular cylinder. PANS is a bridging closure model purported for use at any level of resolution ranging from Reynolds-averaged Navier–Stokes to direct numerical simulations. The closure model is sensitive to the length-scale cut-off via the ratios of unresolved-to-total kinetic energy (fk) and unresolved-to-total dissipation (fepsilon). Several simulations are performed to study the effect of the cut-off length-scale on computed closure model results. The results from various resolutions are compared against experimental data, large eddy simulation, and detached eddy simulation solutions. The quantities examined include coefficient of drag (Cd), Strouhal number (St), and coefficient of pressure distribution (Cp) along with the mean flow statistics and flow structures. Based on the computed results for flow past circular cylinder presented in this paper and analytical attributes of the closure model, it is reasonable to conclude that the PANS bridging method is a theoretically sound and computationally viable variable resolution approach for practical flow computations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Partially averaged Navier–Stokes (PANS) method for turbulence simulations : flow past a circular cylinder [texte imprimé] / Sunil Lakshmipathy, Auteur ; Sharath S. Girimaji, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Mots-clés : drag;  flow  simulation;  Navier-Stokes  equations;  turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The objective of this study is to evaluate the capability of the partially averaged Navier–Stokes (PANS) method in a moderately high Reynolds number (ReD 1.4×105) turbulent flow past a circular cylinder. PANS is a bridging closure model purported for use at any level of resolution ranging from Reynolds-averaged Navier–Stokes to direct numerical simulations. The closure model is sensitive to the length-scale cut-off via the ratios of unresolved-to-total kinetic energy (fk) and unresolved-to-total dissipation (fepsilon). Several simulations are performed to study the effect of the cut-off length-scale on computed closure model results. The results from various resolutions are compared against experimental data, large eddy simulation, and detached eddy simulation solutions. The quantities examined include coefficient of drag (Cd), Strouhal number (St), and coefficient of pressure distribution (Cp) along with the mean flow statistics and flow structures. Based on the computed results for flow past circular cylinder presented in this paper and analytical attributes of the closure model, it is reasonable to conclude that the PANS bridging method is a theoretically sound and computationally viable variable resolution approach for practical flow computations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Partially averaged Navier–Stokes (PANS) method for turbulence simulations / Eunhwan Jeong in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Titre : Partially averaged Navier–Stokes (PANS) method for turbulence simulations : flow past a square cylinder Type de document : texte imprimé Auteurs : Eunhwan Jeong, Auteur ; Sharath S. Girimaji, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : drag;  external  flows;  flow  simulation;  Navier-Stokes  equations;  turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The partially averaged Navier–Stokes (PANS) approach is a bridging closure model intended for any level of resolution between the Reynolds averaged Navier–Stokes (RANS) method and direct numerical simulations. In this paper, the proposed closure model is validated in the flow past a square cylinder. The desired ratio of the modeled-to-resolved scales in the PANS closure is achieved by appropriately specifying two bridging parameters: the ratios of unresolved-to-total kinetic energy (fk) dissipation (fepsilon). PANS calculations of different bridging parameter values are performed and the results are compared with experimental data and large-eddy simulations. The Strouhal number (St), mean/root-mean-square (RMS) drag coefficient (CD), RMS lift coefficient (CL), mean velocity profiles, and various turbulent stresses are investigated. The results gradually improve from the RANS level of accuracy to a close agreement with the experimental results with decreasing value of the bridging parameter fk. Overall, the results indicate that the PANS method clearly satisfies the basic tenets of a bridging model: (i) provides a meaningful turbulence closure at any modeled-to-resolved scale ratio and (ii) yields improved accuracy with increasing resolution (decreasing modeled-to-resolved ratio). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...] [article] Partially averaged Navier–Stokes (PANS) method for turbulence simulations : flow past a square cylinder [texte imprimé] / Eunhwan Jeong, Auteur ; Sharath S. Girimaji, Auteur . - 2011 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Mots-clés : drag;  external  flows;  flow  simulation;  Navier-Stokes  equations;  turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The partially averaged Navier–Stokes (PANS) approach is a bridging closure model intended for any level of resolution between the Reynolds averaged Navier–Stokes (RANS) method and direct numerical simulations. In this paper, the proposed closure model is validated in the flow past a square cylinder. The desired ratio of the modeled-to-resolved scales in the PANS closure is achieved by appropriately specifying two bridging parameters: the ratios of unresolved-to-total kinetic energy (fk) dissipation (fepsilon). PANS calculations of different bridging parameter values are performed and the results are compared with experimental data and large-eddy simulations. The Strouhal number (St), mean/root-mean-square (RMS) drag coefficient (CD), RMS lift coefficient (CL), mean velocity profiles, and various turbulent stresses are investigated. The results gradually improve from the RANS level of accuracy to a close agreement with the experimental results with decreasing value of the bridging parameter fk. Overall, the results indicate that the PANS method clearly satisfies the basic tenets of a bridging model: (i) provides a meaningful turbulence closure at any modeled-to-resolved scale ratio and (ii) yields improved accuracy with increasing resolution (decreasing modeled-to-resolved ratio). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000132000012 [...]

Experimental determination of the virtual mass coefficient for two spheres accelerating in a power law fluid / Abbas H. Sulaymon in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Titre : Experimental determination of the virtual mass coefficient for two spheres accelerating in a power law fluid Type de document : texte imprimé Auteurs : Abbas H. Sulaymon, Auteur ; Catherine A. M. E. Wilson, Auteur ; Abeer I. Alwared, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  separation  (technology);  fluids;  motion;  drag  (fluid  dynamics);  Reynolds  number;  shear  (mechanics);  uncertainty Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The virtual mass coefficient is determined experimentally for the motion of two spheres side by side and in line in a power law fluid. The velocities of the two accelerating spheres and their separation distance was measured as they accelerated under the action of driving weights through a cylindrical column filled with different concentrations of polyacryamaide solution (0.01%, 0.03%, 0.05%, and 0.07% by weight). For comparison purposes, the experiments were repeated with water. Various densities of spheres and separation distances were examined. Within the range of power law indices (0.61–0.834) and Reynolds numbers (1.1–75) examined, the virtual mass coefficient was found to decrease with an increasing Reynolds number for the two spheres moving side by side, and found to be greater than 0.5 when the spheres were touching each other. As the distance between the spheres increased, the virtual mass coefficient was found to decrease and approached the single sphere value of 0.5 when the distance between the spheres was more than ten radii. When the spheres were in line and touching each other, the virtual mass coefficient was found to be less than 0.5, however, when the distance between the spheres increased, the virtual mass coefficient increased and approached the value of 0.5. The virtual mass coefficient was found to be consistent with the shear thinning behavior; for a given Reynolds number, it increased with an increasing power law index. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...] [article] Experimental determination of the virtual mass coefficient for two spheres accelerating in a power law fluid [texte imprimé] / Abbas H. Sulaymon, Auteur ; Catherine A. M. E. Wilson, Auteur ; Abeer I. Alwared, Auteur . - 2011 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Mots-clés : force;  separation  (technology);  fluids;  motion;  drag  (fluid  dynamics);  Reynolds  number;  shear  (mechanics);  uncertainty Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The virtual mass coefficient is determined experimentally for the motion of two spheres side by side and in line in a power law fluid. The velocities of the two accelerating spheres and their separation distance was measured as they accelerated under the action of driving weights through a cylindrical column filled with different concentrations of polyacryamaide solution (0.01%, 0.03%, 0.05%, and 0.07% by weight). For comparison purposes, the experiments were repeated with water. Various densities of spheres and separation distances were examined. Within the range of power law indices (0.61–0.834) and Reynolds numbers (1.1–75) examined, the virtual mass coefficient was found to decrease with an increasing Reynolds number for the two spheres moving side by side, and found to be greater than 0.5 when the spheres were touching each other. As the distance between the spheres increased, the virtual mass coefficient was found to decrease and approached the single sphere value of 0.5 when the distance between the spheres was more than ten radii. When the spheres were in line and touching each other, the virtual mass coefficient was found to be less than 0.5, however, when the distance between the spheres increased, the virtual mass coefficient increased and approached the value of 0.5. The virtual mass coefficient was found to be consistent with the shear thinning behavior; for a given Reynolds number, it increased with an increasing power law index. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...]

Large Eddy simulation of turbulent-cavitation interactions in a venturi nozzle / Nagendra Dittakavi in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Titre : Large Eddy simulation of turbulent-cavitation interactions in a venturi nozzle Type de document : texte imprimé Auteurs : Nagendra Dittakavi, Auteur ; Aditya Chunekar, Auteur ; Steven Frankel, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (Dynamics);  vapors;  turbulence;  cavitation;  vorticity;  nozzles;  vortices;  cavities;  collapse;  equations;  venturi  tubes;  large  Eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Large eddy simulation of turbulent cavitating flow in a venturi nozzle is conducted. The fully compressible Favre-filtered Navier–Stokes equations are coupled with a homogeneous equilibrium cavitation model. The dynamic Smagorinsky subgrid-scale turbulence model is employed to close the filtered nonlinear convection terms. The equations are numerically integrated in the context of a generalized curvilinear coordinate system to facilitate geometric complexities. A sixth-order compact finite difference scheme is employed for the Navier–Stokes equations with the AUSM+-up scheme to handle convective terms in the presence of large density gradients. The stiffness of the system due to the incompressibility of the liquid phase is addressed through an artificial increase in the Mach number. The simulation predicts the formation of a vapor cavity at the venturi throat with an irregular shedding of the small scale vapor structures near the turbulent cavity closure region. The vapor formation at the throat is observed to suppress the velocity fluctuations due to turbulence. The collapse of the vapor structures in the downstream region is a major source of vorticity production, resulting into formation of hair-pin vortices. A detailed analysis of the vorticity transport equation shows a decrease in the vortex-stretching term due to cavitation. A substantial increase in the baroclinic torque is observed in the regions where the vapor structures collapse. A spectra of the pressure fluctuations in the far-field downstream region show an increase in the acoustic noise at high frequencies due to cavitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...] [article] Large Eddy simulation of turbulent-cavitation interactions in a venturi nozzle [texte imprimé] / Nagendra Dittakavi, Auteur ; Aditya Chunekar, Auteur ; Steven Frankel, Auteur . - 2011 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 11 p. Mots-clés : pressure;  flow  (Dynamics);  vapors;  turbulence;  cavitation;  vorticity;  nozzles;  vortices;  cavities;  collapse;  equations;  venturi  tubes;  large  Eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Large eddy simulation of turbulent cavitating flow in a venturi nozzle is conducted. The fully compressible Favre-filtered Navier–Stokes equations are coupled with a homogeneous equilibrium cavitation model. The dynamic Smagorinsky subgrid-scale turbulence model is employed to close the filtered nonlinear convection terms. The equations are numerically integrated in the context of a generalized curvilinear coordinate system to facilitate geometric complexities. A sixth-order compact finite difference scheme is employed for the Navier–Stokes equations with the AUSM+-up scheme to handle convective terms in the presence of large density gradients. The stiffness of the system due to the incompressibility of the liquid phase is addressed through an artificial increase in the Mach number. The simulation predicts the formation of a vapor cavity at the venturi throat with an irregular shedding of the small scale vapor structures near the turbulent cavity closure region. The vapor formation at the throat is observed to suppress the velocity fluctuations due to turbulence. The collapse of the vapor structures in the downstream region is a major source of vorticity production, resulting into formation of hair-pin vortices. A detailed analysis of the vorticity transport equation shows a decrease in the vortex-stretching term due to cavitation. A substantial increase in the baroclinic torque is observed in the regions where the vapor structures collapse. A spectra of the pressure fluctuations in the far-field downstream region show an increase in the acoustic noise at high frequencies due to cavitation. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...]

Research on two phase waterjet nozzles / S. Gowing in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Titre : Research on two phase waterjet nozzles Type de document : texte imprimé Auteurs : S. Gowing, Auteur ; T. Mori, Auteur ; S. Neely, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  thrust;  bubbles;  nozzles;  water Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Air-augmented waterjets derive their propulsion from compressed gas mixed directly into the main flow. The gas bubbles expand as the mixture passes through the pressure gradient of the convergent nozzle, and energy is imparted to the water from the air in a complex fashion. This experiment measures the exchange of air and water energy for three nozzles over a range of flowrates and void fractions using compressed air injected and mixed upstream of the nozzle entrance. Pressures and nozzle thrust are measured to examine flow changes. The results are compared with predictions from a one-dimensional bubbly flow model. The measured efficiencies are lower than or comparable to predicted values. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...] [article] Research on two phase waterjet nozzles [texte imprimé] / S. Gowing, Auteur ; T. Mori, Auteur ; S. Neely, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Mots-clés : pressure;  flow  (dynamics);  thrust;  bubbles;  nozzles;  water Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Air-augmented waterjets derive their propulsion from compressed gas mixed directly into the main flow. The gas bubbles expand as the mixture passes through the pressure gradient of the convergent nozzle, and energy is imparted to the water from the air in a complex fashion. This experiment measures the exchange of air and water energy for three nozzles over a range of flowrates and void fractions using compressed air injected and mixed upstream of the nozzle entrance. Pressures and nozzle thrust are measured to examine flow changes. The results are compared with predictions from a one-dimensional bubbly flow model. The measured efficiencies are lower than or comparable to predicted values. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...]

A fast method for determining the flow conductance of gas microfluidic devices / Matteo Martinelli in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 06 p. Titre : A fast method for determining the flow conductance of gas microfluidic devices Type de document : texte imprimé Auteurs : Matteo Martinelli, Auteur ; Vladimir Viktorov, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  microfluidics;  electrical  conductance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a fast method for determining the conductance of gas microfluidic devices with low flow rates and very small pressure drops starting from 30 Pa, corresponding to Re=0.3. This method is based on discharging a gas-pressurized chamber through the microfluidic device under test. The microfluidic device’s conductance can be estimated as a function of inlet pressure and the Reynolds number of the flow by recording the upstream pressure during the discharging process and calculating the time derivative of the gas pressure. The pressurized chamber is considered as an isothermal chamber. Experimental results show that a sufficiently accurate isothermal discharging process up to an upstream-to-downstream pressure ratio of 0.8 can be achieved by immersing the chamber in a thermal bath. The method presented here is very fast, requiring only a few seconds for the acquisition procedure and computerized data processing. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...] [article] A fast method for determining the flow conductance of gas microfluidic devices [texte imprimé] / Matteo Martinelli, Auteur ; Vladimir Viktorov, Auteur . - 2011 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 06 p. Mots-clés : pressure;  flow  (dynamics);  microfluidics;  electrical  conductance Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a fast method for determining the conductance of gas microfluidic devices with low flow rates and very small pressure drops starting from 30 Pa, corresponding to Re=0.3. This method is based on discharging a gas-pressurized chamber through the microfluidic device under test. The microfluidic device’s conductance can be estimated as a function of inlet pressure and the Reynolds number of the flow by recording the upstream pressure during the discharging process and calculating the time derivative of the gas pressure. The pressurized chamber is considered as an isothermal chamber. Experimental results show that a sufficiently accurate isothermal discharging process up to an upstream-to-downstream pressure ratio of 0.8 can be achieved by immersing the chamber in a thermal bath. The method presented here is very fast, requiring only a few seconds for the acquisition procedure and computerized data processing. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...]

Numerical simulation of droplet size distribution in vertical upward annular flow / Y. Liu in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Titre : Numerical simulation of droplet size distribution in vertical upward annular flow Type de document : texte imprimé Auteurs : Y. Liu, Auteur ; W. Z. Li, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  fluids;  turbulence;  computer  simulation;  bubbles;  computational  fluid  dynamics;  equations;  mechanisms Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The liquid droplet size distribution in gas-liquid vertical upward annular flow is investigated through a CFD (computational fluid dynamics)-PBM (population balance model) coupled model in this paper. Two-fluid Eulerian scheme is employed as the framework of this model and a population balance equation is used to obtain the dispersed liquid droplet diameter distribution, where three different coalescence and breakup kernels are investigated. The Sauter mean diameter d32 is used as a bridge between a two-fluid model and a PBM. The simulation results suggest that the original Luo–Luo kernel and the mixed kernel A (Luo’s coalescence kernel incorporated with Prince and Blanch’s breakup kernel) can only give reasonable predictions for large diameter droplets. Mixed kernel B (Saffman and Turner’s coalescence kernel incorporated with Lehr’s breakup kernel) can accurately capture the particle size distribution (PSD) of liquid droplets covering all droplet sizes, and is appropriate for the description of liquid droplet size distribution in gas-liquid annular flow. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...] [article] Numerical simulation of droplet size distribution in vertical upward annular flow [texte imprimé] / Y. Liu, Auteur ; W. Z. Li, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 12 (Décembre 2010) . - 09 p. Mots-clés : flow  (dynamics);  fluids;  turbulence;  computer  simulation;  bubbles;  computational  fluid  dynamics;  equations;  mechanisms Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The liquid droplet size distribution in gas-liquid vertical upward annular flow is investigated through a CFD (computational fluid dynamics)-PBM (population balance model) coupled model in this paper. Two-fluid Eulerian scheme is employed as the framework of this model and a population balance equation is used to obtain the dispersed liquid droplet diameter distribution, where three different coalescence and breakup kernels are investigated. The Sauter mean diameter d32 is used as a bridge between a two-fluid model and a PBM. The simulation results suggest that the original Luo–Luo kernel and the mixed kernel A (Luo’s coalescence kernel incorporated with Prince and Blanch’s breakup kernel) can only give reasonable predictions for large diameter droplets. Mixed kernel B (Saffman and Turner’s coalescence kernel incorporated with Lehr’s breakup kernel) can accurately capture the particle size distribution (PSD) of liquid droplets covering all droplet sizes, and is appropriate for the description of liquid droplet size distribution in gas-liquid annular flow. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27443 [...]

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