Les Inscriptions à la Bibliothèque sont ouvertes en
ligne via le site: https://biblio.enp.edu.dz
Les Réinscriptions se font à :
• La Bibliothèque Annexe pour les étudiants en
2ème Année CPST
• La Bibliothèque Centrale pour les étudiants en Spécialités
A partir de cette page vous pouvez :
| Retourner au premier écran avec les recherches... |
Journal of fluids engineering |
Dépouillements
Ajouter le résultat dans votre panierAerodynamics of large-scale vortex generator in ground effect / Joseph Katz in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 7 (Juillet 2008)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 6 p.
Titre : Aerodynamics of large-scale vortex generator in ground effect Type de document : texte imprimé Auteurs : Joseph Katz, Auteur ; Frederic Morey, Auteur Année de publication : 2014 Article en page(s) : 6 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Vortex generator; large scale; aerodynamic performance Résumé : The aerodynamic performance of several vortex generators (VGs) of the type used on the lower surface of race cars was tested in a low-speed wind tunnel. In this particular application, the vortices emanating from the VGs create a suction force between the vehicle and the ground, thereby improving tire adhesion and the vehicle’s cornering∕traction performance. Since the size of these devices is much larger than the local boundary layer thickness, they are termed “large scale” in this study. Results of the wind tunnel tests indicate that the aerodynamic adhesion forces increase with reduced ground clearance while the corresponding drag increase is much smaller. The parameters investigated in this study are the VG length, shape, and the effect of incidence angle. Amongst the various shapes tested, the traditional rectangular VG created the largest forces while the simple triangular design was the most efficient in terms of the incremental lift to drag ratio. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Aerodynamics of large-scale vortex generator in ground effect [texte imprimé] / Joseph Katz, Auteur ; Frederic Morey, Auteur . - 2014 . - 6 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 6 p.
Mots-clés : Vortex generator; large scale; aerodynamic performance Résumé : The aerodynamic performance of several vortex generators (VGs) of the type used on the lower surface of race cars was tested in a low-speed wind tunnel. In this particular application, the vortices emanating from the VGs create a suction force between the vehicle and the ground, thereby improving tire adhesion and the vehicle’s cornering∕traction performance. Since the size of these devices is much larger than the local boundary layer thickness, they are termed “large scale” in this study. Results of the wind tunnel tests indicate that the aerodynamic adhesion forces increase with reduced ground clearance while the corresponding drag increase is much smaller. The parameters investigated in this study are the VG length, shape, and the effect of incidence angle. Amongst the various shapes tested, the traditional rectangular VG created the largest forces while the simple triangular design was the most efficient in terms of the incremental lift to drag ratio. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Titre : Evaluation of the mixing performance of the micromixers with grooved or obstructed channels Type de document : texte imprimé Auteurs : Yeng-Yung Tsui, Auteur ; Ching-Shiang Yang, Auteur ; Chung-Ming Hsieh, Auteur Année de publication : 2014 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Mixing flow; obstructed channels; grooved channels Résumé : The mixing flows in microchannels were examined using numerical methods. To speed up fluid mixing, it is essential to generate lateral transport of mass. In this study, the mixing flow is disrupted by either placing grooves or block obstacles on the walls of the channels. Since the grooves or the blocks appear in a periodic configuration, the velocity is solved only in a section of the channel. With the repeating cycle of flow velocity field, the fluid concentration can be calculated throughout the entire length of the channel. Good agreement with experiments in the mixing performance justifies the present methodology. Two different channel configurations are under consideration: grooved channels and obstructed channels. The results reveal that with straight grooves, a well organized vortex flow is formed in the vertical plane along the groove, which leads to a helical flow in the channel. The mixing performance can be enhanced by having grooves on both the top and the bottom walls arranged in a staggered manner, by which the transversal velocity is largely increased. It is seen that the strength of the secondary flow and, thus, the mixing can be improved by suitably choosing geometric parameters of the groove, such as the depth, the width, and the oblique angle. It is also shown that the efficient mixing for the staggered herringbone type groove is due to the fluid stratification caused by the exchange of position of the resulted counter-rotating vortices. As for the obstructed channels, the flows are in essence two dimensional. Very strong transversal velocity can be produced by narrowing down the flow passage in the channel. However, the efficient mixing is obtained at the cost of large pressure head loss. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Evaluation of the mixing performance of the micromixers with grooved or obstructed channels [texte imprimé] / Yeng-Yung Tsui, Auteur ; Ching-Shiang Yang, Auteur ; Chung-Ming Hsieh, Auteur . - 2014 . - 10 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Mots-clés : Mixing flow; obstructed channels; grooved channels Résumé : The mixing flows in microchannels were examined using numerical methods. To speed up fluid mixing, it is essential to generate lateral transport of mass. In this study, the mixing flow is disrupted by either placing grooves or block obstacles on the walls of the channels. Since the grooves or the blocks appear in a periodic configuration, the velocity is solved only in a section of the channel. With the repeating cycle of flow velocity field, the fluid concentration can be calculated throughout the entire length of the channel. Good agreement with experiments in the mixing performance justifies the present methodology. Two different channel configurations are under consideration: grooved channels and obstructed channels. The results reveal that with straight grooves, a well organized vortex flow is formed in the vertical plane along the groove, which leads to a helical flow in the channel. The mixing performance can be enhanced by having grooves on both the top and the bottom walls arranged in a staggered manner, by which the transversal velocity is largely increased. It is seen that the strength of the secondary flow and, thus, the mixing can be improved by suitably choosing geometric parameters of the groove, such as the depth, the width, and the oblique angle. It is also shown that the efficient mixing for the staggered herringbone type groove is due to the fluid stratification caused by the exchange of position of the resulted counter-rotating vortices. As for the obstructed channels, the flows are in essence two dimensional. Very strong transversal velocity can be produced by narrowing down the flow passage in the channel. However, the efficient mixing is obtained at the cost of large pressure head loss. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Titre : Analytic and experimental investigation of dihedral configurations of three-winglet planforms Type de document : texte imprimé Auteurs : David S. Miklosovic, Auteur Année de publication : 2014 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Dihedral configurations; three-winglet planforms Résumé : An analytic and experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing. The winglets, with an aspect ratio of 4.6, were mounted on a half-span wing having an effective aspect ratio of 6.29. 13 configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. While the analytic method provided fair agreement with the experimental results, the predicted trends in lift, drag, and (to a lesser degree) pitching moment were in good agreement. The analytic distributions of wake velocity, circulation, and downwash angle verified that highly nonplanar configurations tended to reduce and diffuse the regions of highest circulation and to create more moderate downwash angles in the wake. This was manifest as an overall drag reduction. More specifically, the results showed that the winglets could be placed in various optimum orientations to increase the lift coefficient as much as 65% at the same angle of attack, decrease the drag coefficient as much as 54% at the same lift coefficient, or improve the maximum L∕D by up to 57%. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the magnitude and slope of the pitching moment coefficient. These observations suggest that multiple winglet dihedral variations may be feasible for use as actively controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the configuration. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analytic and experimental investigation of dihedral configurations of three-winglet planforms [texte imprimé] / David S. Miklosovic, Auteur . - 2014 . - 10 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Mots-clés : Dihedral configurations; three-winglet planforms Résumé : An analytic and experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing. The winglets, with an aspect ratio of 4.6, were mounted on a half-span wing having an effective aspect ratio of 6.29. 13 configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. While the analytic method provided fair agreement with the experimental results, the predicted trends in lift, drag, and (to a lesser degree) pitching moment were in good agreement. The analytic distributions of wake velocity, circulation, and downwash angle verified that highly nonplanar configurations tended to reduce and diffuse the regions of highest circulation and to create more moderate downwash angles in the wake. This was manifest as an overall drag reduction. More specifically, the results showed that the winglets could be placed in various optimum orientations to increase the lift coefficient as much as 65% at the same angle of attack, decrease the drag coefficient as much as 54% at the same lift coefficient, or improve the maximum L∕D by up to 57%. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the magnitude and slope of the pitching moment coefficient. These observations suggest that multiple winglet dihedral variations may be feasible for use as actively controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the configuration. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Titre : An alternating magnetic field driven flow in a spinning cylindrical container Type de document : texte imprimé Auteurs : Victor Shatrov, Auteur ; Gunter Gerbeth, Auteur ; Regina Hermann, Auteur Année de publication : 2014 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Axisymmetric flow structure; magnetohydrodynamic interaction parameter; Ekman numbers Résumé : This paper presents a numerical analysis of the free surface liquid metal flow driven by an alternating current magnetic field in a spinning cylindrical container. The axisymmetric flow structure is analyzed for various values of the magnetohydrodynamic interaction parameter and Ekman numbers. The governing hydrodynamic equations are solved by a spectral collocation method, and the alternating magnetic field distribution is found by a boundary-integral method. The electromagnetic and hydrodynamic fields are fully coupled via the shape of the liquid free surface. It is found that the container rotation may reduce the meridional flow significantly. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] An alternating magnetic field driven flow in a spinning cylindrical container [texte imprimé] / Victor Shatrov, Auteur ; Gunter Gerbeth, Auteur ; Regina Hermann, Auteur . - 2014 . - 10 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Mots-clés : Axisymmetric flow structure; magnetohydrodynamic interaction parameter; Ekman numbers Résumé : This paper presents a numerical analysis of the free surface liquid metal flow driven by an alternating current magnetic field in a spinning cylindrical container. The axisymmetric flow structure is analyzed for various values of the magnetohydrodynamic interaction parameter and Ekman numbers. The governing hydrodynamic equations are solved by a spectral collocation method, and the alternating magnetic field distribution is found by a boundary-integral method. The electromagnetic and hydrodynamic fields are fully coupled via the shape of the liquid free surface. It is found that the container rotation may reduce the meridional flow significantly. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 11 p.
Titre : Comparison between theoretical CFV flow models and NIST’s primary flow data in the laminar, turbulent, and transition flow regimes Type de document : texte imprimé Auteurs : Aaron Johnson, Auteur ; John Wright, Auteur Année de publication : 2014 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : CFV flow model; NIST's primary flow data; Reynolds number; laminar regime; transition; turbulent flow regimes Résumé : State-of-the art dimensional metrology was used to measure the throat diameter and throat curvature of nine critical flow venturis (CFVs) with nominal throat diameters ranging from 5mmto25mm. The throat curvature was used in calculating the theoretical discharge coefficients, while the throat diameter was used in computing the experimental discharge coefficients. The nine CFVs were calibrated in dry air using two NIST primary flow standards with expanded uncertainties of 0.05% and 0.09%, respectively. The calibration data span a Reynolds number range from 7.2×104 to 2.5×106, including laminar, transition, and turbulent flow regimes. By correcting for both the throat diameter and curvature, the agreement between predicted and measured discharge coefficients was less than 0.17% in the turbulent regime and less than 0.07% in the laminar regime. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Comparison between theoretical CFV flow models and NIST’s primary flow data in the laminar, turbulent, and transition flow regimes [texte imprimé] / Aaron Johnson, Auteur ; John Wright, Auteur . - 2014 . - 11 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 11 p.
Mots-clés : CFV flow model; NIST's primary flow data; Reynolds number; laminar regime; transition; turbulent flow regimes Résumé : State-of-the art dimensional metrology was used to measure the throat diameter and throat curvature of nine critical flow venturis (CFVs) with nominal throat diameters ranging from 5mmto25mm. The throat curvature was used in calculating the theoretical discharge coefficients, while the throat diameter was used in computing the experimental discharge coefficients. The nine CFVs were calibrated in dry air using two NIST primary flow standards with expanded uncertainties of 0.05% and 0.09%, respectively. The calibration data span a Reynolds number range from 7.2×104 to 2.5×106, including laminar, transition, and turbulent flow regimes. By correcting for both the throat diameter and curvature, the agreement between predicted and measured discharge coefficients was less than 0.17% in the turbulent regime and less than 0.07% in the laminar regime. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Titre : Measurement of velocities in two-phase flow by laser velocimetry : interaction between solid particles’ motion and turbulence Type de document : texte imprimé Auteurs : N. Sad Chemloul, Auteur ; O. Benrabah, Auteur Année de publication : 2014 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Two phase flow; velocity; turbulence Résumé : In this work, an experimental method based on laser anemometry with Doppller effects is developed. This allows the measurement of velocities and their fluctuations in a flow of solid-liquid suspension in an ascendant vertical pipe. In order to distinguish between the signals coming from the continuous phase, water, and those of the glass bead particles larger than the Kolmogorov length scale, an electronic logic circuit was incorporated in the measuring equipment. This enabled the study of both the slip velocity of the solid-liquid suspension and the influence of the large particles on turbulence. The results show that a fine particle suspension, which represents a tracer, behaves as a homogeneous fluid. For large particles, we confirmed the existence of a slip velocity and the effect of particle size on the turbulence. The use of two distinct measurement volumes produces good results for the direct measurement of the turbulent length scales. The results show that the presence of solid particles modifies the turbulence characteristics. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Measurement of velocities in two-phase flow by laser velocimetry : interaction between solid particles’ motion and turbulence [texte imprimé] / N. Sad Chemloul, Auteur ; O. Benrabah, Auteur . - 2014 . - 10 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 10 p.
Mots-clés : Two phase flow; velocity; turbulence Résumé : In this work, an experimental method based on laser anemometry with Doppller effects is developed. This allows the measurement of velocities and their fluctuations in a flow of solid-liquid suspension in an ascendant vertical pipe. In order to distinguish between the signals coming from the continuous phase, water, and those of the glass bead particles larger than the Kolmogorov length scale, an electronic logic circuit was incorporated in the measuring equipment. This enabled the study of both the slip velocity of the solid-liquid suspension and the influence of the large particles on turbulence. The results show that a fine particle suspension, which represents a tracer, behaves as a homogeneous fluid. For large particles, we confirmed the existence of a slip velocity and the effect of particle size on the turbulence. The use of two distinct measurement volumes produces good results for the direct measurement of the turbulent length scales. The results show that the presence of solid particles modifies the turbulence characteristics. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 13 p.
Titre : Pressure drop predictions in microfibrous materials using computational fluid dynamics Type de document : texte imprimé Auteurs : Ravi K. Duggirala, Auteur ; Christopher J. Roy, Auteur ; S. M. Saeidi, Auteur Année de publication : 2014 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Fluid dynamics simulations; microfibrous materials; pressure drop prediction Résumé : Three-dimensional computational fluid dynamics simulations are performed for the flow of air through microfibrous materials for void fractions of 0.41 and 0.47 and face velocities ranging between 0.04ms and 1.29m∕s. The microfibrous materials consist of activated carbon powder with diameters of 137×10−6m entrapped in a matrix of cylindrical fibers with diameters of 8×10−6m. These sintered microfibrous materials are a new class of patented materials with properties that are advantageous compared to traditional packed beds or monoliths. Microfibrous materials have demonstrated enhanced heat and mass transfer compared to packed beds of particles of similar dimensions. In this paper, the simulations are used to predict the pressure drop per unit length through the materials and to analyze the details of the flow that are difficult to interrogate experimentally. Various geometric approximations are employed in order to allow the simulations to be performed in an efficient manner. The Knudsen number, defined as the ratio of the mean free path between molecular collisions to the fiber diameter, is 0.011; thus, velocity-slip boundary conditions are employed and shown to have only a minor effect on the pressure drop predictions. Significant effort is made to estimate numerical errors associated with the discretization process, and these errors are shown to be negligible (less than 3%). The computational predictions for pressure drop are compared to available experimental data as well as to two theory-based correlations: Ergun’s equation and the porous media permeability equation. The agreement between the simulations and the experiments is within 30% and is reasonable considering the significant geometric approximations employed. The errors in the simulations and correlations with respect to experimental data exhibit the same trend with face velocity for both void fractions. This consistent trend suggests the presence of experimental bias errors that correlate with the face velocity. The simulations generally underpredict the experimental pressure drop for the low void fraction case and overpredict the experimental pressure drop for the high void fraction case. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Pressure drop predictions in microfibrous materials using computational fluid dynamics [texte imprimé] / Ravi K. Duggirala, Auteur ; Christopher J. Roy, Auteur ; S. M. Saeidi, Auteur . - 2014 . - 13 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 13 p.
Mots-clés : Fluid dynamics simulations; microfibrous materials; pressure drop prediction Résumé : Three-dimensional computational fluid dynamics simulations are performed for the flow of air through microfibrous materials for void fractions of 0.41 and 0.47 and face velocities ranging between 0.04ms and 1.29m∕s. The microfibrous materials consist of activated carbon powder with diameters of 137×10−6m entrapped in a matrix of cylindrical fibers with diameters of 8×10−6m. These sintered microfibrous materials are a new class of patented materials with properties that are advantageous compared to traditional packed beds or monoliths. Microfibrous materials have demonstrated enhanced heat and mass transfer compared to packed beds of particles of similar dimensions. In this paper, the simulations are used to predict the pressure drop per unit length through the materials and to analyze the details of the flow that are difficult to interrogate experimentally. Various geometric approximations are employed in order to allow the simulations to be performed in an efficient manner. The Knudsen number, defined as the ratio of the mean free path between molecular collisions to the fiber diameter, is 0.011; thus, velocity-slip boundary conditions are employed and shown to have only a minor effect on the pressure drop predictions. Significant effort is made to estimate numerical errors associated with the discretization process, and these errors are shown to be negligible (less than 3%). The computational predictions for pressure drop are compared to available experimental data as well as to two theory-based correlations: Ergun’s equation and the porous media permeability equation. The agreement between the simulations and the experiments is within 30% and is reasonable considering the significant geometric approximations employed. The errors in the simulations and correlations with respect to experimental data exhibit the same trend with face velocity for both void fractions. This consistent trend suggests the presence of experimental bias errors that correlate with the face velocity. The simulations generally underpredict the experimental pressure drop for the low void fraction case and overpredict the experimental pressure drop for the high void fraction case. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 9 p.
Titre : On the collapse structure of an attached cavity on a three-dimensional hydrofoil Type de document : texte imprimé Auteurs : Evert-Jan Foeth, Auteur ; Tom van Terwisga, Auteur ; Cas van Doorne, Auteur Année de publication : 2014 Article en page(s) : 9 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Three-dimensional twisted hydrofoil; collapse Résumé : A three-dimensional twisted hydrofoil with an attached cavitaty closely related to propellers was observed with a high-speed camera at the University of Delft Cavitation Tunnel. Reentrant flow coming from the sides of the cavity aimed at the center plane—termed side-entrant flow—collided in the closure region of the cavity, pinching off a part of the sheet resulting in a periodic shedding. The collapse of the remainder of the sheet appears to be a mixing layer at the location of the colliding reentrant flows. Collision of side-entrant jets in the closure region of a cavity is identified as a second shedding mechanism, in addition to reentrant flow impinging the sheet interface at the leading edge. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] On the collapse structure of an attached cavity on a three-dimensional hydrofoil [texte imprimé] / Evert-Jan Foeth, Auteur ; Tom van Terwisga, Auteur ; Cas van Doorne, Auteur . - 2014 . - 9 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 9 p.
Mots-clés : Three-dimensional twisted hydrofoil; collapse Résumé : A three-dimensional twisted hydrofoil with an attached cavitaty closely related to propellers was observed with a high-speed camera at the University of Delft Cavitation Tunnel. Reentrant flow coming from the sides of the cavity aimed at the center plane—termed side-entrant flow—collided in the closure region of the cavity, pinching off a part of the sheet resulting in a periodic shedding. The collapse of the remainder of the sheet appears to be a mixing layer at the location of the colliding reentrant flows. Collision of side-entrant jets in the closure region of a cavity is identified as a second shedding mechanism, in addition to reentrant flow impinging the sheet interface at the leading edge. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 7 p.
Titre : Cavitation structures in a venturi flow with various backward facing steps Type de document : texte imprimé Auteurs : Hailing An, Auteur ; Michael W. Plesniak, Auteur Année de publication : 2014 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cavitation; venturi flow; backward facing steps Résumé : Cavitation inception and development caused by a backward facing step in a Venturi-type test section were studied experimentally for different step heights (0.8–4mm). High-speed cinematography and particle image velocimetry images were used to demonstrate the cloud shedding process and cavitation development stages. It was found that for small step height (0.8mm, h∕δ0=1.7) cavitation started in the reattachment region in the form of a reentrant jet, and caused cloud shedding in its developed stage. For high step height (4mm, h∕δ0=8.5) cavitation started midway downstream of the shear layer and resembled the spanwise vortices in the separated shear layer. This study contributes experimental results for better understanding of cavitation inception and development in the separated shear layer. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Cavitation structures in a venturi flow with various backward facing steps [texte imprimé] / Hailing An, Auteur ; Michael W. Plesniak, Auteur . - 2014 . - 7 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 7 p.
Mots-clés : Cavitation; venturi flow; backward facing steps Résumé : Cavitation inception and development caused by a backward facing step in a Venturi-type test section were studied experimentally for different step heights (0.8–4mm). High-speed cinematography and particle image velocimetry images were used to demonstrate the cloud shedding process and cavitation development stages. It was found that for small step height (0.8mm, h∕δ0=1.7) cavitation started in the reattachment region in the form of a reentrant jet, and caused cloud shedding in its developed stage. For high step height (4mm, h∕δ0=8.5) cavitation started midway downstream of the shear layer and resembled the spanwise vortices in the separated shear layer. This study contributes experimental results for better understanding of cavitation inception and development in the separated shear layer. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 11 p.
Titre : Image treatment of a 2D vapor-liquid compound droplet in a linearized steady viscous flow Type de document : texte imprimé Auteurs : D. Palaniappan, Auteur Année de publication : 2014 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow (dynamics); vapors; geometry; fluids; cylinders; functions; viscosity; drops Résumé : The classical method of images is used to construct closed form exact solutions for the two-dimensional (2D) perturbed flow fields in the presence of a 2D vapor-liquid compound droplet in the limit of low-Reynolds number. The geometry of the multiphase droplet is composed of two overlapping infinitely long cylinders Ca and Cb of radii a and b, respectively, intersecting at a vertex angle π∕2. The composite inclusion has the shape resembling a 2D snowman type of object with a vapor cylinder Ca partly protruded into the cylinder Cb filled with another fluid whose viscosity is different from that of the host fluid. The mathematical problem with this inclusion in the Stokes flow environment is formulated in terms of Stokes stream function with mixed boundary conditions at the boundary of the hybrid droplet. General expressions for the perturbed stream functions in the two phases are obtained in a straightforward fashion using Kelvin’s inversion together with shift and reflection properties of biharmonic functions. Application of our method to other related problems in creeping flow and possible further generalizations are also discussed. The general results are then exploited to derive singularity solutions for the hybrid droplet embedded in (i) a centered shear flow, (ii) a quadratic potential flow, and (iii) an extensional flow past the 2D vapor-liquid compound droplet. The image singularities in each case depend on the two radii of the cylinders, the center-to-center distance, and the viscosity ratio. The exact solutions are utilized to plot the flow streamlines and they show some interesting patterns. While the flow fields exterior to the droplet exhibit symmetrical topological structures, the interior flow fields show existence of free eddies—enclosed in a figure-eight separatrix—and stagnation points (hyperbolic points). The flow characteristics are influenced by the viscosity and radii ratios. Furthermore, the asymptotic analysis leads to a rather surprising conclusion that there is a (subdominant) uniform flow far away from the droplet in all cases. The existence of an origin, the natural center of the drop of the composite geometry, which neutralizes the uniform flow for a particular choice of the physical parameters, is illustrated. This reveals the sensitivity of the geometry in 2D Stokes flow. The present results may be of some interest in models involving a combination of stick and slip boundaries. Moreover, the method discussed here can be useful both as a teaching tool and as a building block for further calculations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Image treatment of a 2D vapor-liquid compound droplet in a linearized steady viscous flow [texte imprimé] / D. Palaniappan, Auteur . - 2014 . - 11 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 11 p.
Mots-clés : Flow (dynamics); vapors; geometry; fluids; cylinders; functions; viscosity; drops Résumé : The classical method of images is used to construct closed form exact solutions for the two-dimensional (2D) perturbed flow fields in the presence of a 2D vapor-liquid compound droplet in the limit of low-Reynolds number. The geometry of the multiphase droplet is composed of two overlapping infinitely long cylinders Ca and Cb of radii a and b, respectively, intersecting at a vertex angle π∕2. The composite inclusion has the shape resembling a 2D snowman type of object with a vapor cylinder Ca partly protruded into the cylinder Cb filled with another fluid whose viscosity is different from that of the host fluid. The mathematical problem with this inclusion in the Stokes flow environment is formulated in terms of Stokes stream function with mixed boundary conditions at the boundary of the hybrid droplet. General expressions for the perturbed stream functions in the two phases are obtained in a straightforward fashion using Kelvin’s inversion together with shift and reflection properties of biharmonic functions. Application of our method to other related problems in creeping flow and possible further generalizations are also discussed. The general results are then exploited to derive singularity solutions for the hybrid droplet embedded in (i) a centered shear flow, (ii) a quadratic potential flow, and (iii) an extensional flow past the 2D vapor-liquid compound droplet. The image singularities in each case depend on the two radii of the cylinders, the center-to-center distance, and the viscosity ratio. The exact solutions are utilized to plot the flow streamlines and they show some interesting patterns. While the flow fields exterior to the droplet exhibit symmetrical topological structures, the interior flow fields show existence of free eddies—enclosed in a figure-eight separatrix—and stagnation points (hyperbolic points). The flow characteristics are influenced by the viscosity and radii ratios. Furthermore, the asymptotic analysis leads to a rather surprising conclusion that there is a (subdominant) uniform flow far away from the droplet in all cases. The existence of an origin, the natural center of the drop of the composite geometry, which neutralizes the uniform flow for a particular choice of the physical parameters, is illustrated. This reveals the sensitivity of the geometry in 2D Stokes flow. The present results may be of some interest in models involving a combination of stick and slip boundaries. Moreover, the method discussed here can be useful both as a teaching tool and as a building block for further calculations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 5 p.
Titre : Particle deposition onto rough surfaces Type de document : texte imprimé Auteurs : Giovanni Lo Iacono, Auteur ; Andy M. Reynolds, Auteur ; Paul G. Tucker, Auteur Année de publication : 2014 Article en page(s) : 5 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Rough surfaces Résumé : Predictions for the number of particles depositing from fully developed turbulence onto a fully roughened k-type surface are obtained from the results of large-eddy simulations for a ribbed-channel flow. Simulation data are found to provide only partial support for the “mass-sink hypothesis,” i.e., the notion that all particles entering a mass sink, a volume of fluid extending vertically from the deposition surface, are captured and eventually deposited. The equality of the number of particles entering the mass sink and the number of particles depositing is attained, and a qualitative agreement with the empirical model of Wood (1981, “A Simple Method for the Calculation of Turbulent Deposition to Smooth and Rough Surfaces ,” J. Aerosol Sci., 12(3), pp. 275–290) for the height of this mass sink is obtained. However, a significant proportion of particles escapes from the mass sink and the equality of numbers is attained only because many particles deposit onto rib surfaces above the mass sink, without first entering the mass sink. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Particle deposition onto rough surfaces [texte imprimé] / Giovanni Lo Iacono, Auteur ; Andy M. Reynolds, Auteur ; Paul G. Tucker, Auteur . - 2014 . - 5 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 5 p.
Mots-clés : Rough surfaces Résumé : Predictions for the number of particles depositing from fully developed turbulence onto a fully roughened k-type surface are obtained from the results of large-eddy simulations for a ribbed-channel flow. Simulation data are found to provide only partial support for the “mass-sink hypothesis,” i.e., the notion that all particles entering a mass sink, a volume of fluid extending vertically from the deposition surface, are captured and eventually deposited. The equality of the number of particles entering the mass sink and the number of particles depositing is attained, and a qualitative agreement with the empirical model of Wood (1981, “A Simple Method for the Calculation of Turbulent Deposition to Smooth and Rough Surfaces ,” J. Aerosol Sci., 12(3), pp. 275–290) for the height of this mass sink is obtained. However, a significant proportion of particles escapes from the mass sink and the equality of numbers is attained only because many particles deposit onto rib surfaces above the mass sink, without first entering the mass sink. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 7 p.
Titre : Understanding the boundary stencil effects on the adjacent field resolution in compact finite differences Type de document : texte imprimé Auteurs : Stephen A. Jordan, Auteur Année de publication : 2014 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Boundary stencil effects; field resolution Résumé : When establishing the spatial resolution character of a composite compact finite differencing template for high-order field solutions, the stencils selected at nonperiodic boundaries are commonly treated independent of the interior scheme. This position quantifies a false influence of the boundary scheme on the resultant interior dispersive and dissipative consequences of the compound template. Of the three ingredients inherent in the composite template, only its numerical accuracy and global stability have been properly treated in a coupled fashion. Herein, we present a companion means for quantifying the resultant spatial resolution properties that lead to improved predictions of the salient problem physics. Compact boundary stencils with free parameters to minimize the field dispersion (or phase error) and dissipation are included in the procedure. Application of the coupled templates for resolving the viscous Burgers wave and two-dimensional acoustic scattering reveal significant differences in the predictive error. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Understanding the boundary stencil effects on the adjacent field resolution in compact finite differences [texte imprimé] / Stephen A. Jordan, Auteur . - 2014 . - 7 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 7 p.
Mots-clés : Boundary stencil effects; field resolution Résumé : When establishing the spatial resolution character of a composite compact finite differencing template for high-order field solutions, the stencils selected at nonperiodic boundaries are commonly treated independent of the interior scheme. This position quantifies a false influence of the boundary scheme on the resultant interior dispersive and dissipative consequences of the compound template. Of the three ingredients inherent in the composite template, only its numerical accuracy and global stability have been properly treated in a coupled fashion. Herein, we present a companion means for quantifying the resultant spatial resolution properties that lead to improved predictions of the salient problem physics. Compact boundary stencils with free parameters to minimize the field dispersion (or phase error) and dissipation are included in the procedure. Application of the coupled templates for resolving the viscous Burgers wave and two-dimensional acoustic scattering reveal significant differences in the predictive error. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Titre : Finite-amplitude long-wave instability of a thin power-law liquid film flowing down a vertical column in a magnetic field Type de document : texte imprimé Auteurs : Po-Jen Cheng, Auteur Année de publication : 2014 Article en page(s) : 4 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Long-wave perturbation method; magnetic field Résumé : The long-wave perturbation method is employed to investigate the nonlinear hydromagnetic stability of a thin electrically conductive power-law liquid film flowing down a vertical cylinder. In contrast to most previous studies presented in literature, the solution scheme employed in this study is based on a numerical approximation approach rather than an analytical method. The modeling results reveal that the stability of the film flow system is weakened as the radius of the cylinder is reduced. However, the flow stability can be enhanced by increasing the intensity of the magnetic field and the flow index. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Finite-amplitude long-wave instability of a thin power-law liquid film flowing down a vertical column in a magnetic field [texte imprimé] / Po-Jen Cheng, Auteur . - 2014 . - 4 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Mots-clés : Long-wave perturbation method; magnetic field Résumé : The long-wave perturbation method is employed to investigate the nonlinear hydromagnetic stability of a thin electrically conductive power-law liquid film flowing down a vertical cylinder. In contrast to most previous studies presented in literature, the solution scheme employed in this study is based on a numerical approximation approach rather than an analytical method. The modeling results reveal that the stability of the film flow system is weakened as the radius of the cylinder is reduced. However, the flow stability can be enhanced by increasing the intensity of the magnetic field and the flow index. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Titre : NPSHr optimization of axial-flow pumps Type de document : texte imprimé Auteurs : Wen-Guang, Li, Auteur Année de publication : 2014 Article en page(s) : 4 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Impellers; optimization; pumps; axial flow; blades; flow (dynamics); cavitation; suction; equations; thickness; geometry; design; vortices; equilibrium (physics); actuators; disks Résumé : The two-step method for optimizing net positive suction head required (NPSHr) of axial-flow pumps is proposed in this paper. First, the NPSHr at the impeller tip is optimized with impeller diameter based on experimental data of 2D cascades in available wind tunnels. Then, it is optimized again with the velocity moment at the impeller outlet, which is expressed in terms of two parameters. The blade geometry is generated and flow details are clarified by using the radial equilibrium equation, actuator disk theory, and 2D vortex element method in the optimizing process. The NPSHr response surface has been established in terms of these two parameters. The results illustrate that the second optimization allows NPSHr to be reduced by 37.5% compared to the first optimization. Therefore, this two-step method is effective and expects to be applied in the axial-flow pump impeller blade design. The simulations of 3D turbulent flow with various cavitation models and related confirming experiments are going to be done in the axial-flow impellers designed with this method. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] NPSHr optimization of axial-flow pumps [texte imprimé] / Wen-Guang, Li, Auteur . - 2014 . - 4 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Mots-clés : Impellers; optimization; pumps; axial flow; blades; flow (dynamics); cavitation; suction; equations; thickness; geometry; design; vortices; equilibrium (physics); actuators; disks Résumé : The two-step method for optimizing net positive suction head required (NPSHr) of axial-flow pumps is proposed in this paper. First, the NPSHr at the impeller tip is optimized with impeller diameter based on experimental data of 2D cascades in available wind tunnels. Then, it is optimized again with the velocity moment at the impeller outlet, which is expressed in terms of two parameters. The blade geometry is generated and flow details are clarified by using the radial equilibrium equation, actuator disk theory, and 2D vortex element method in the optimizing process. The NPSHr response surface has been established in terms of these two parameters. The results illustrate that the second optimization allows NPSHr to be reduced by 37.5% compared to the first optimization. Therefore, this two-step method is effective and expects to be applied in the axial-flow pump impeller blade design. The simulations of 3D turbulent flow with various cavitation models and related confirming experiments are going to be done in the axial-flow impellers designed with this method. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Titre : Procedure for estimation and reporting of uncertainty due to discretization in CFD applications Type de document : texte imprimé Année de publication : 2014 Article en page(s) : 4 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Computational fluid dynamics; errors; uncertainty Résumé : Since 1990, the Fluids Engineering Division of ASME has pursued activities concerning the detection, estimation and control of numerical uncertainty and/or error in computational fluid dynamics (CFD) studies. The first quality-control measures in this area were issued in 1986 (1986, “Editorial Policy Statement on Control of Numerical Accuracy ,” ASME J. Fluids Eng., 108, p. 2) and revised in 1993 (1993, “Journal of Fluids Engineering Editorial Policy Statement on the Control of Numerical Accuracy ,” ASME J. Fluids Eng., 115, pp. 339–340). Given the continued increase in CFD related publications, and the many significant advancements in computational techniques and computer technology, it has become necessary to revisit the issue and formulate a more detailed policy to further improve the quality of publications in this area. This brief note provides specific guidelines for prospective authors for calculation and reporting of discretization error estimates in CFD simulations where experimental data may or may not be available for comparison. The underlying perspective is that CFD-related studies will eventually aim to predict the outcome of a physical event for which experimental data is not available. It should be emphasized that the requirements outlined in this note do not preclude those already published in the previous two policy statements. It is also important to keep in mind that the procedure recommended in this note cannot possibly encompass all possible scenarios or applications. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...] [article] Procedure for estimation and reporting of uncertainty due to discretization in CFD applications [texte imprimé] . - 2014 . - 4 p.
Fluids engineering
Langues : Anglais (eng)
in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 7 (Juillet 2008) . - 4 p.
Mots-clés : Computational fluid dynamics; errors; uncertainty Résumé : Since 1990, the Fluids Engineering Division of ASME has pursued activities concerning the detection, estimation and control of numerical uncertainty and/or error in computational fluid dynamics (CFD) studies. The first quality-control measures in this area were issued in 1986 (1986, “Editorial Policy Statement on Control of Numerical Accuracy ,” ASME J. Fluids Eng., 108, p. 2) and revised in 1993 (1993, “Journal of Fluids Engineering Editorial Policy Statement on the Control of Numerical Accuracy ,” ASME J. Fluids Eng., 115, pp. 339–340). Given the continued increase in CFD related publications, and the many significant advancements in computational techniques and computer technology, it has become necessary to revisit the issue and formulate a more detailed policy to further improve the quality of publications in this area. This brief note provides specific guidelines for prospective authors for calculation and reporting of discretization error estimates in CFD simulations where experimental data may or may not be available for comparison. The underlying perspective is that CFD-related studies will eventually aim to predict the outcome of a physical event for which experimental data is not available. It should be emphasized that the requirements outlined in this note do not preclude those already published in the previous two policy statements. It is also important to keep in mind that the procedure recommended in this note cannot possibly encompass all possible scenarios or applications. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27324 [...]
Exemplaires
| Code-barres | Cote | Support | Localisation | Section | Disponibilité |
|---|---|---|---|---|---|
| aucun exemplaire | |||||
