Dépouillements

Low field in the vaned diffuser of a centrifugal pump at different vane setting angles / P. Gaetani in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Titre : Low field in the vaned diffuser of a centrifugal pump at different vane setting angles Type de document : texte imprimé Auteurs : P. Gaetani, Auteur ; A. Boccazzi, Auteur ; R. Sala, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : 2D-PIV  Time  and  phase-averaged  flow  field  Centrifugal  pump  Vane  setting  angles Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Particle image velocimetry (2D-PIV) has been used for the investigation of the time and phase-averaged flow field inside the vaned diffuser of a centrifugal pump operating at the best efficiency point (BEP). Pump performances and the diffuser flow field were analyzed for three different vane setting angles. It was evidenced that flow coefficient at the best efficiency point decreases with the diffuser setting angle reduction. From 2D-PIV measurements in five different blade to blade planes, spanwise averaged flow angles and velocity distribution were computed. It was evidenced an influence of the diffuser setting angle on the spanwise distribution of the flow rate and of the absolute mass averaged flow angle at impeller discharge. An overturning at the diffuser discharge was also evidenced for the two highest setting angles. 2D-PIV flow fields are presented in three different pseudosecondary planes in order to enlighten the cross flows affecting the diffuser flow field. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Low field in the vaned diffuser of a centrifugal pump at different vane setting angles [texte imprimé] / P. Gaetani, Auteur ; A. Boccazzi, Auteur ; R. Sala, Auteur . - 2012 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Mots-clés : 2D-PIV  Time  and  phase-averaged  flow  field  Centrifugal  pump  Vane  setting  angles Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Particle image velocimetry (2D-PIV) has been used for the investigation of the time and phase-averaged flow field inside the vaned diffuser of a centrifugal pump operating at the best efficiency point (BEP). Pump performances and the diffuser flow field were analyzed for three different vane setting angles. It was evidenced that flow coefficient at the best efficiency point decreases with the diffuser setting angle reduction. From 2D-PIV measurements in five different blade to blade planes, spanwise averaged flow angles and velocity distribution were computed. It was evidenced an influence of the diffuser setting angle on the spanwise distribution of the flow rate and of the absolute mass averaged flow angle at impeller discharge. An overturning at the diffuser discharge was also evidenced for the two highest setting angles. 2D-PIV flow fields are presented in three different pseudosecondary planes in order to enlighten the cross flows affecting the diffuser flow field. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Preliminary design and performance estimation of radial inflow turbines / Carlos A.M. Ventura in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 13 p. Titre : Preliminary design and performance estimation of radial inflow turbines : an automated approach Type de document : texte imprimé Auteurs : Carlos A.M. Ventura, Auteur ; Peter A. Jacobs, Auteur ; Andrew S. Rowlands, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Radial  (inflow)  turbine  Premilinary  design  Performance  estimation  Loss  models Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A comprehensive one-dimensional meanline design approach for radial inflow turbines is described in the present work. An original code was developed in Python that takes a novel approach to the automatic selection of feasible machines based on pre-defined performance or geometry characteristics for a given application. It comprises a brute-force search algorithm that traverses the entire search space based on key non-dimensional parameters and rotational speed. In this study, an in-depth analysis and subsequent implementation of relevant loss models as well as selection criteria for radial inflow turbines is addressed. Comparison with previously published designs, as well as other available codes, showed good agreement. Sample (real and theoretical) test cases were trialed and results showed good agreement when compared to other available codes. The presented approach was found to be valid and the model was found to be a useful tool with regards to the preliminary design and performance estimation of radial inflow turbines, enabling its integration with other thermodynamic cycle analysis and three-dimensional blade design codes. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Preliminary design and performance estimation of radial inflow turbines : an automated approach [texte imprimé] / Carlos A.M. Ventura, Auteur ; Peter A. Jacobs, Auteur ; Andrew S. Rowlands, Auteur . - 2012 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 13 p. Mots-clés : Radial  (inflow)  turbine  Premilinary  design  Performance  estimation  Loss  models Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A comprehensive one-dimensional meanline design approach for radial inflow turbines is described in the present work. An original code was developed in Python that takes a novel approach to the automatic selection of feasible machines based on pre-defined performance or geometry characteristics for a given application. It comprises a brute-force search algorithm that traverses the entire search space based on key non-dimensional parameters and rotational speed. In this study, an in-depth analysis and subsequent implementation of relevant loss models as well as selection criteria for radial inflow turbines is addressed. Comparison with previously published designs, as well as other available codes, showed good agreement. Sample (real and theoretical) test cases were trialed and results showed good agreement when compared to other available codes. The presented approach was found to be valid and the model was found to be a useful tool with regards to the preliminary design and performance estimation of radial inflow turbines, enabling its integration with other thermodynamic cycle analysis and three-dimensional blade design codes. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Optimal tandem configuration for oscillating-foils hydrokinetic turbine / Thomas Kinsey in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 11 p. Titre : Optimal tandem configuration for oscillating-foils hydrokinetic turbine Type de document : texte imprimé Auteurs : Thomas Kinsey, Auteur ; Guy Dumas, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Oscillating  foils  Optimal  spatial  configuration  Hydrokinetic  turbine  Power  extraction  efficiency Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A numerical investigation based on 2D URANS simulations is performed in order to seek an optimal spatial configuration for two oscillating foils within a hydrokinetic turbine. The objective of the study is to maximize the power extraction efficiency of the turbine. Tandem spatial configurations are considered because in such arrangement both hydrofoils are sharing the same flow window, which allows the turbine to reach higher efficiencies. The relative positioning of the downstream foil oscillating in the wake shed by the upstream hydrofoil is seen to be critical. Indeed, favorable interactions between the downstream foil and the wake vortices may lead to unexpectedly high power-extraction efficiencies (up to 64%), while unfavorable interactions may cause the downstream foil to contribute negatively to the total power extracted. A global phase shift parameter is introduced to characterize the tandem configuration. This parameter combines the inter-foil spacing and motion phase-shift into a single term. It is found useful to predict additional favorable configurations based on known results for cases with similar upstream-foil wake behavior. A comparison with experimental data is provided. Numerical predictions are seen to overpredict the power extraction performance in some cases. This is likely due to the broken 2D coherence of vortices in the 3D reality which affects the vortex-induced velocities and the subsequent foil-wake interactions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Optimal tandem configuration for oscillating-foils hydrokinetic turbine [texte imprimé] / Thomas Kinsey, Auteur ; Guy Dumas, Auteur . - 2012 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 11 p. Mots-clés : Oscillating  foils  Optimal  spatial  configuration  Hydrokinetic  turbine  Power  extraction  efficiency Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A numerical investigation based on 2D URANS simulations is performed in order to seek an optimal spatial configuration for two oscillating foils within a hydrokinetic turbine. The objective of the study is to maximize the power extraction efficiency of the turbine. Tandem spatial configurations are considered because in such arrangement both hydrofoils are sharing the same flow window, which allows the turbine to reach higher efficiencies. The relative positioning of the downstream foil oscillating in the wake shed by the upstream hydrofoil is seen to be critical. Indeed, favorable interactions between the downstream foil and the wake vortices may lead to unexpectedly high power-extraction efficiencies (up to 64%), while unfavorable interactions may cause the downstream foil to contribute negatively to the total power extracted. A global phase shift parameter is introduced to characterize the tandem configuration. This parameter combines the inter-foil spacing and motion phase-shift into a single term. It is found useful to predict additional favorable configurations based on known results for cases with similar upstream-foil wake behavior. A comparison with experimental data is provided. Numerical predictions are seen to overpredict the power extraction performance in some cases. This is likely due to the broken 2D coherence of vortices in the 3D reality which affects the vortex-induced velocities and the subsequent foil-wake interactions. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Vortical structures and instability analysis for athena wetted transom flow with full-scale validation / Shanti Bhushan in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 18 p. Titre : Vortical structures and instability analysis for athena wetted transom flow with full-scale validation Type de document : texte imprimé Auteurs : Shanti Bhushan, Auteur ; Tao Xing, Auteur ; Frederick Stern, Auteur Année de publication : 2012 Article en page(s) : 18 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Transform  flow  Full-scale  validation  Vortex  instability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Vortical structures and associated instabilities of appended Athena wetted transom flow in full-scale conditions are studied using DES to explain the source of dominant transom flow frequency, including verification and validation using full-scale experimental data. The results are also compared with model-scale bare and appended hull predictions and experiments. The grid used for the validation is sufficiently fine as it resolves 70% and 91% of the experimental inertial subrange and turbulent kinetic energy values, respectively. The model-scale bare and appended hull resistance predictions compare within 2.5%D and 5.4%D of the experimental data D, respectively. The full-scale appended hull resistance predictions compare within 4.2%D of the extrapolated data using the ITTC line. The averaged comparison error of the full-scale transom wave elevation mean, RMS and dominant frequency predictions and the experimental data is 8.1%D, and the predictions are validated at an averaged 11.2%D interval. The transom wave elevation unsteadiness is attributed to the Karman-like transom vortex shedding as both show the same dominant frequency. The Karman-like instability shows St = 0.148 for the bare hull and St = 0.103 ± 4.4% for model- and full-scale appended hull. The appended hull simulations also predict: horseshoe vortices at the juncture of rudder-hull with St = 0.146 ± 3.9% and strut-hull with St = 0.053 ± 2%; shear layer instability at the strut-hull intersection with St = 0.0067 ± 3%; and unsteady sinkage and trim induced by transom vortex shedding with St = 2.19. The instabilities do not show significant variation on scale, propeller or motions. The bare hull simulation also predicts flapping-like instability in the wake with St = 0.144. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Vortical structures and instability analysis for athena wetted transom flow with full-scale validation [texte imprimé] / Shanti Bhushan, Auteur ; Tao Xing, Auteur ; Frederick Stern, Auteur . - 2012 . - 18 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 18 p. Mots-clés : Transform  flow  Full-scale  validation  Vortex  instability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Vortical structures and associated instabilities of appended Athena wetted transom flow in full-scale conditions are studied using DES to explain the source of dominant transom flow frequency, including verification and validation using full-scale experimental data. The results are also compared with model-scale bare and appended hull predictions and experiments. The grid used for the validation is sufficiently fine as it resolves 70% and 91% of the experimental inertial subrange and turbulent kinetic energy values, respectively. The model-scale bare and appended hull resistance predictions compare within 2.5%D and 5.4%D of the experimental data D, respectively. The full-scale appended hull resistance predictions compare within 4.2%D of the extrapolated data using the ITTC line. The averaged comparison error of the full-scale transom wave elevation mean, RMS and dominant frequency predictions and the experimental data is 8.1%D, and the predictions are validated at an averaged 11.2%D interval. The transom wave elevation unsteadiness is attributed to the Karman-like transom vortex shedding as both show the same dominant frequency. The Karman-like instability shows St = 0.148 for the bare hull and St = 0.103 ± 4.4% for model- and full-scale appended hull. The appended hull simulations also predict: horseshoe vortices at the juncture of rudder-hull with St = 0.146 ± 3.9% and strut-hull with St = 0.053 ± 2%; shear layer instability at the strut-hull intersection with St = 0.0067 ± 3%; and unsteady sinkage and trim induced by transom vortex shedding with St = 2.19. The instabilities do not show significant variation on scale, propeller or motions. The bare hull simulation also predicts flapping-like instability in the wake with St = 0.144. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

The effect of spanwise width on rectangular jets with sidewalls / Deepak Rangarajan in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 08 p. Titre : The effect of spanwise width on rectangular jets with sidewalls Type de document : texte imprimé Auteurs : Deepak Rangarajan, Auteur ; Jennifer S. Curtis, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Spanwise  width;  rectangular  jet;  sidewalls Résumé : A CFD study on the effect of spanwise width on a rectangular jet with sidewalls is conducted using a standard k-epsilon model with wall functions. An order of magnitude analysis reveals the role played by spanwise turbulent shear terms, arising from the wall bounded flow, as the aspect ratio is decreased at high streamwise distances. A comparative study involving experimental data and other turbulence models is also presented to validate the k-epsilon model for this confined jet flow. It is found that the effect of bounding walls is negligible up to a streamwise distance of at least 105 jet diameters for an aspect ratio of 40, however this distance, within which the flow can be approximated as two-dimensional, decreases with decrease in aspect ratio. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] The effect of spanwise width on rectangular jets with sidewalls [texte imprimé] / Deepak Rangarajan, Auteur ; Jennifer S. Curtis, Auteur . - 2012 . - 08 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 08 p. Mots-clés : Spanwise  width;  rectangular  jet;  sidewalls Résumé : A CFD study on the effect of spanwise width on a rectangular jet with sidewalls is conducted using a standard k-epsilon model with wall functions. An order of magnitude analysis reveals the role played by spanwise turbulent shear terms, arising from the wall bounded flow, as the aspect ratio is decreased at high streamwise distances. A comparative study involving experimental data and other turbulence models is also presented to validate the k-epsilon model for this confined jet flow. It is found that the effect of bounding walls is negligible up to a streamwise distance of at least 105 jet diameters for an aspect ratio of 40, however this distance, within which the flow can be approximated as two-dimensional, decreases with decrease in aspect ratio. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

A review of external hydrodynamics with experimental data assessment for low-speed ocean flows / Max Blanco in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Titre : A review of external hydrodynamics with experimental data assessment for low-speed ocean flows Type de document : texte imprimé Auteurs : Max Blanco, Auteur ; Philip A. Wilson, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Economic geology Langues : Anglais (eng) Mots-clés : External  flows;  survey-class  autonomous  underwater  vehicles  (AUVs) Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This article describes a literature review focused on published empirical measurements of external flows over bodies of revolution that can be employed for verification and validation of calculations of survey-class autonomous underwater vehicles (AUVs) or other like bodies. The flow regime for a survey-class AUV is defined, and a mathematically optimal velocity results for these energy-limited vehicles. A range-maximal hotel load is one of the inferences. Cavitation is shown not to affect this type of AUV. Environmental and computational problems of turbulence are discussed. A table of vital statistics of contemporary survey-class AUVs is provided. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] A review of external hydrodynamics with experimental data assessment for low-speed ocean flows [texte imprimé] / Max Blanco, Auteur ; Philip A. Wilson, Auteur . - 2012 . - 12 p. Economic geology Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Mots-clés : External  flows;  survey-class  autonomous  underwater  vehicles  (AUVs) Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This article describes a literature review focused on published empirical measurements of external flows over bodies of revolution that can be employed for verification and validation of calculations of survey-class autonomous underwater vehicles (AUVs) or other like bodies. The flow regime for a survey-class AUV is defined, and a mathematically optimal velocity results for these energy-limited vehicles. A range-maximal hotel load is one of the inferences. Cavitation is shown not to affect this type of AUV. Environmental and computational problems of turbulence are discussed. A table of vital statistics of contemporary survey-class AUVs is provided. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Characteristics of a jet in the vicinity of a free surface / Jiahao Tian in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Titre : Characteristics of a jet in the vicinity of a free surface Type de document : texte imprimé Auteurs : Jiahao Tian, Auteur ; Roussinova Vesselina, Auteur ; Ram Balachandar, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Round  turbulent  jet;  free  surface;  velocity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, the characteristics of a round turbulent jet in the vicinity of a free surface are investigated. The jet issued from a nozzle located at a depth five times the nozzle diameter (d = 10 mm) below and parallel to the free surface. The jet exit velocity was 2.8 m/s and the resulting Reynolds number was 28,000. Instantaneous two-dimensional PIV measurements were obtained in the vertical central plane and in several horizontal planes at various distances (y/d = 0,±1,±2,±3± 4) from the axis of the nozzle. All fields-of-view were positioned at streamwise locations in the range of 28 < x/d < 62, where the jet interacts significantly with the free surface. The results reveal that the behavior of the surface jet is very similar to that of the free jet before it interacts with the free surface which occurs at about x/d = 30. Beyond this, the velocity normal to the free surface is diminished and those parallel to the free surface are enhanced in the region near the free surface. In the horizontal plane near the free surface (y/d = +4), the spreading of the surface jet is significantly greater than that of the free jet. The mean lateral flow in this region tends to be outward everywhere for the surface jet, while the opposite trend occurs in the free jet. Turbulence intensities in all three directions are reduced by the effect of the free surface confinement. Near the free surface, at y/d = +4, unlike the single peak streamwise turbulence intensity profile noticed in the case of the free jet, the off-axis double peaks reappear in the case of the surface jet. The magnitude of shear stress in the vertical central plane of the surface jet is smaller than that noticed in the free jet near the free surface. In identical horizontal planes, the shear stress (-[overline uw]) profiles are similar in both free jets and surface jets in regions where the interaction with the free surface is not significant (x/d [approximate] 30). As the downstream distance increases near the free surface, the magnitudes of the shear stress profiles are larger compared to that of the free jet. An increase in the normal component of vorticity is observed in the horizontal planes near the free surface. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Characteristics of a jet in the vicinity of a free surface [texte imprimé] / Jiahao Tian, Auteur ; Roussinova Vesselina, Auteur ; Ram Balachandar, Auteur . - 2012 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Mots-clés : Round  turbulent  jet;  free  surface;  velocity Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this study, the characteristics of a round turbulent jet in the vicinity of a free surface are investigated. The jet issued from a nozzle located at a depth five times the nozzle diameter (d = 10 mm) below and parallel to the free surface. The jet exit velocity was 2.8 m/s and the resulting Reynolds number was 28,000. Instantaneous two-dimensional PIV measurements were obtained in the vertical central plane and in several horizontal planes at various distances (y/d = 0,±1,±2,±3± 4) from the axis of the nozzle. All fields-of-view were positioned at streamwise locations in the range of 28 < x/d < 62, where the jet interacts significantly with the free surface. The results reveal that the behavior of the surface jet is very similar to that of the free jet before it interacts with the free surface which occurs at about x/d = 30. Beyond this, the velocity normal to the free surface is diminished and those parallel to the free surface are enhanced in the region near the free surface. In the horizontal plane near the free surface (y/d = +4), the spreading of the surface jet is significantly greater than that of the free jet. The mean lateral flow in this region tends to be outward everywhere for the surface jet, while the opposite trend occurs in the free jet. Turbulence intensities in all three directions are reduced by the effect of the free surface confinement. Near the free surface, at y/d = +4, unlike the single peak streamwise turbulence intensity profile noticed in the case of the free jet, the off-axis double peaks reappear in the case of the surface jet. The magnitude of shear stress in the vertical central plane of the surface jet is smaller than that noticed in the free jet near the free surface. In identical horizontal planes, the shear stress (-[overline uw]) profiles are similar in both free jets and surface jets in regions where the interaction with the free surface is not significant (x/d [approximate] 30). As the downstream distance increases near the free surface, the magnitudes of the shear stress profiles are larger compared to that of the free jet. An increase in the normal component of vorticity is observed in the horizontal planes near the free surface. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Numerical simulation of an oscillating cylinder using large eddy simulation and implicit large eddy simulation / A. Feymark in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 10 p. Titre : Numerical simulation of an oscillating cylinder using large eddy simulation and implicit large eddy simulation Type de document : texte imprimé Auteurs : A. Feymark, Auteur ; N. Alin, Auteur ; R. Bensow, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Large  eddy  simulation;  fixed  cylinder;  numerical  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this work, we use large eddy simulation (LES) to study the influence of grid and subgrid model on the lift and drag force predictions of a fixed cylinder undergoing streamwise sinusoidal oscillations in a steady flow, resulting in a varying Reynolds number, Re, within the range 405 <= Re <= 2482. This benchmark case is a first step toward studying engineering applications related to flow-induced vibrations. We examine the influence of both grid resolution and the subgrid model using implicit and explicit LES. The methodology used, LES based on a finite-volume method capable of handling moving meshes, are found to provide force predictions that agree well with experimentally measured data, with respect both to the overall flow development and force magnitude. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Numerical simulation of an oscillating cylinder using large eddy simulation and implicit large eddy simulation [texte imprimé] / A. Feymark, Auteur ; N. Alin, Auteur ; R. Bensow, Auteur . - 2012 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 10 p. Mots-clés : Large  eddy  simulation;  fixed  cylinder;  numerical  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this work, we use large eddy simulation (LES) to study the influence of grid and subgrid model on the lift and drag force predictions of a fixed cylinder undergoing streamwise sinusoidal oscillations in a steady flow, resulting in a varying Reynolds number, Re, within the range 405 <= Re <= 2482. This benchmark case is a first step toward studying engineering applications related to flow-induced vibrations. We examine the influence of both grid resolution and the subgrid model using implicit and explicit LES. The methodology used, LES based on a finite-volume method capable of handling moving meshes, are found to provide force predictions that agree well with experimentally measured data, with respect both to the overall flow development and force magnitude. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

Numerical and experimental study of the interaction of a spark-generated bubble and a vertical wall / Arvind Jayaprakash in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Titre : Numerical and experimental study of the interaction of a spark-generated bubble and a vertical wall Type de document : texte imprimé Auteurs : Arvind Jayaprakash, Auteur ; Chao-Tsung Hsiao, Auteur ; Georges Chahine, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Bubble  collapse;  vertical  wall;  Dynaflow's  three-dimensional  code;  numerical  predictions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An understanding of the fundamental mechanisms involved in the interaction between bubbles and structures is of importance for many applications involving cavitation erosion. Generally, the final stage of bubble collapse is associated with the formation of a high-speed reentrant liquid jet directed toward the solid surface. Local forces associated with the collapse of such bubbles can be very high and can exert significant loads on the materials. This formation and impact of liquid jet is an area of intense research. Under some conditions, the presence of gravity and other nearby boundaries and free surfaces alters the jet direction and need to be understood, especially that in the laboratory, small scale tests in finite containers have these effects inherently present. In this work, experiments and numerical simulations of the interaction between a vertical wall and a bubble are carried out using Dynaflow's three-dimensional code, 3DYNAFS-BEM, which models the unsteady dynamics of a liquid flow including the presence of highly nonlinear time evolving gas-liquid interfaces. The numerical predictions were validated using scaled experiments carried out using spark generated bubbles. These spark bubble tests produced high fidelity test data that properly scale the fluid dynamics as long as the geometric nondimensional parameters, gravity and time are properly scaled. The use of a high speed camera allowing framing rates as high as 50,000 frames per second to photograph the bubbles produced high quality observations of bubble dynamics including clear visualizations of the reentrant jet formation inside the bubble. Such observations were very useful in developing and validating the numerical models. The cases studied showed very good correlation between the numerical simulations and the experimental observations and allowed development of predictive rules for the re-entrant jet characteristics, including jet angle, jet speed, and various geometric characteristics of the jet. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] Numerical and experimental study of the interaction of a spark-generated bubble and a vertical wall [texte imprimé] / Arvind Jayaprakash, Auteur ; Chao-Tsung Hsiao, Auteur ; Georges Chahine, Auteur . - 2012 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 12 p. Mots-clés : Bubble  collapse;  vertical  wall;  Dynaflow's  three-dimensional  code;  numerical  predictions Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An understanding of the fundamental mechanisms involved in the interaction between bubbles and structures is of importance for many applications involving cavitation erosion. Generally, the final stage of bubble collapse is associated with the formation of a high-speed reentrant liquid jet directed toward the solid surface. Local forces associated with the collapse of such bubbles can be very high and can exert significant loads on the materials. This formation and impact of liquid jet is an area of intense research. Under some conditions, the presence of gravity and other nearby boundaries and free surfaces alters the jet direction and need to be understood, especially that in the laboratory, small scale tests in finite containers have these effects inherently present. In this work, experiments and numerical simulations of the interaction between a vertical wall and a bubble are carried out using Dynaflow's three-dimensional code, 3DYNAFS-BEM, which models the unsteady dynamics of a liquid flow including the presence of highly nonlinear time evolving gas-liquid interfaces. The numerical predictions were validated using scaled experiments carried out using spark generated bubbles. These spark bubble tests produced high fidelity test data that properly scale the fluid dynamics as long as the geometric nondimensional parameters, gravity and time are properly scaled. The use of a high speed camera allowing framing rates as high as 50,000 frames per second to photograph the bubbles produced high quality observations of bubble dynamics including clear visualizations of the reentrant jet formation inside the bubble. Such observations were very useful in developing and validating the numerical models. The cases studied showed very good correlation between the numerical simulations and the experimental observations and allowed development of predictive rules for the re-entrant jet characteristics, including jet angle, jet speed, and various geometric characteristics of the jet. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

On the volume fraction effects of inertial colliding particles in homogeneous isotropic turbulence / Martin Ernst in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 16 p. Titre : On the volume fraction effects of inertial colliding particles in homogeneous isotropic turbulence Type de document : texte imprimé Auteurs : Martin Ernst, Auteur ; Martin Sommerfeld, Auteur Année de publication : 2012 Article en page(s) : 16 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Solid  volume  fraction;  Lattice-Bolzmann  method;  turbulence;  point-particles;  collision  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The main objective of the present study is the investigation of volume fraction effects on the collision statistics of nonsettling inertial particles in a granular medium as well as suspended in an unsteady homogeneous isotropic turbulent flow. For this purpose, different studies with mono-disperse Lagrangian point-particles having different Stokes numbers are considered in which the volume fraction of the dispersed phase is varied between 0.001 and 0.01. The fluid behavior is computed using a three-dimensional Lattice-Boltzmann method. The carrier-fluid turbulence is maintained at Taylor microscale Reynolds number 65.26 by applying a spectral forcing scheme. The Lagrangian particle tracking is based on considering the drag force only and a deterministic model is applied for collision detection. The influence of the particle phase on the fluid flow is neglected at this stage. The particle size is maintained at a constant value for all Stokes numbers so that the ratio of particle diameter to Kolmogorov length scale is fixed at 0.58. The variation of the particle Stokes number was realized by modifying the solids density. The observed particle Reynolds and Stokes numbers are in between [1.07, 2.61] and [0.34, 9.79], respectively. In the present simulations, the fluid flow and the particle motion including particle-particle collisions are based on different temporal discretization. Hence, an adaptive time stepping scheme is introduced. The particle motion as well as the occurrence of inter-particle collisions is characterized among others by Lagrangian correlation functions, the velocity angles between colliding particles and the collision frequencies. Initially, a fluid-free particle system is simulated and compared with the principles of the kinetic theory to validate the implemented deterministic collision model. Moreover, a selection of results obtained for homogeneous isotropic turbulence is compared with in literature available DNS and LES results as well. According to the performed simulations, the collision rate of particles with large Stokes numbers strongly depends on the adopted volume fraction, whereas for particles with small Stokes numbers the influence of particle volume fraction is less pronounced. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...] [article] On the volume fraction effects of inertial colliding particles in homogeneous isotropic turbulence [texte imprimé] / Martin Ernst, Auteur ; Martin Sommerfeld, Auteur . - 2012 . - 16 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 3 (Mars 2012) . - 16 p. Mots-clés : Solid  volume  fraction;  Lattice-Bolzmann  method;  turbulence;  point-particles;  collision  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The main objective of the present study is the investigation of volume fraction effects on the collision statistics of nonsettling inertial particles in a granular medium as well as suspended in an unsteady homogeneous isotropic turbulent flow. For this purpose, different studies with mono-disperse Lagrangian point-particles having different Stokes numbers are considered in which the volume fraction of the dispersed phase is varied between 0.001 and 0.01. The fluid behavior is computed using a three-dimensional Lattice-Boltzmann method. The carrier-fluid turbulence is maintained at Taylor microscale Reynolds number 65.26 by applying a spectral forcing scheme. The Lagrangian particle tracking is based on considering the drag force only and a deterministic model is applied for collision detection. The influence of the particle phase on the fluid flow is neglected at this stage. The particle size is maintained at a constant value for all Stokes numbers so that the ratio of particle diameter to Kolmogorov length scale is fixed at 0.58. The variation of the particle Stokes number was realized by modifying the solids density. The observed particle Reynolds and Stokes numbers are in between [1.07, 2.61] and [0.34, 9.79], respectively. In the present simulations, the fluid flow and the particle motion including particle-particle collisions are based on different temporal discretization. Hence, an adaptive time stepping scheme is introduced. The particle motion as well as the occurrence of inter-particle collisions is characterized among others by Lagrangian correlation functions, the velocity angles between colliding particles and the collision frequencies. Initially, a fluid-free particle system is simulated and compared with the principles of the kinetic theory to validate the implemented deterministic collision model. Moreover, a selection of results obtained for homogeneous isotropic turbulence is compared with in literature available DNS and LES results as well. According to the performed simulations, the collision rate of particles with large Stokes numbers strongly depends on the adopted volume fraction, whereas for particles with small Stokes numbers the influence of particle volume fraction is less pronounced. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000003 [...]

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