Dépouillements

Numerical simulation of flow past multiple porous cylinders / M. H. Al-Hajeri in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Titre : Numerical simulation of flow past multiple porous cylinders Type de document : texte imprimé Auteurs : M. H. Al-Hajeri, Auteur ; A. Aroussi, Auteur ; A. Witry, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : two-dimensional  laminar  flow  past;  three  circular  porous  cylinders;  numerical  simulation Résumé : The present study numerically investigates two-dimensional laminar flow past three circular porous cylinders arranged in an in-line array. Six approaches to face velocity (Vi/Vf) ratios are used and particle trajectories are computed for a range of velocities and particle diameters. Furthermore, the flow past a solid cylinder, which had similar geometry characteristics to the porous cylinders used in this study, is compared with the flow around multiple porous cylinders. For the same range of Reynolds number (312–520), the flow behavior around the solid cylinder differs from the flow around the porous cylinders. The flow characteristics around solid cylinders are determined by the Reynolds number, whereas the flow characteristics around the porous cylinders are detrained by the Vi/Vf ratio. Stagnation areas are found behind each porous cylinder, and the size of these areas increases as the Vi/Vf velocity ratio increases. Furthermore, for the particle ranges used in power plants (<50 μm), the particles were uniformly distributed around the surface of the porous cylinders. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Numerical simulation of flow past multiple porous cylinders [texte imprimé] / M. H. Al-Hajeri, Auteur ; A. Aroussi, Auteur ; A. Witry, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Mots-clés : two-dimensional  laminar  flow  past;  three  circular  porous  cylinders;  numerical  simulation Résumé : The present study numerically investigates two-dimensional laminar flow past three circular porous cylinders arranged in an in-line array. Six approaches to face velocity (Vi/Vf) ratios are used and particle trajectories are computed for a range of velocities and particle diameters. Furthermore, the flow past a solid cylinder, which had similar geometry characteristics to the porous cylinders used in this study, is compared with the flow around multiple porous cylinders. For the same range of Reynolds number (312–520), the flow behavior around the solid cylinder differs from the flow around the porous cylinders. The flow characteristics around solid cylinders are determined by the Reynolds number, whereas the flow characteristics around the porous cylinders are detrained by the Vi/Vf ratio. Stagnation areas are found behind each porous cylinder, and the size of these areas increases as the Vi/Vf velocity ratio increases. Furthermore, for the particle ranges used in power plants (<50 μm), the particles were uniformly distributed around the surface of the porous cylinders. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Unsteady flow patterns for a double suction centrifugal pump / José González in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 09 p. Titre : Unsteady flow patterns for a double suction centrifugal pump Type de document : texte imprimé Auteurs : José González, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Katia M. Argüelles Díaz, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : double  suction  centrifugal  pump;  Unsteady  Reynolds  Averaged  Navier–Stokes  Equations  (URANS)  calculation Résumé : The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Unsteady flow patterns for a double suction centrifugal pump [texte imprimé] / José González, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Katia M. Argüelles Díaz, Auteur . - 2009 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 09 p. Mots-clés : double  suction  centrifugal  pump;  Unsteady  Reynolds  Averaged  Navier–Stokes  Equations  (URANS)  calculation Résumé : The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Detailed CFD analysis of the steady flow in a wells turbine under incipient and deep stall conditions / M. Torresi in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 17 p. Titre : Detailed CFD analysis of the steady flow in a wells turbine under incipient and deep stall conditions Type de document : texte imprimé Auteurs : M. Torresi, Auteur ; G. Pascazio, Auteur ; S. M. Camporeale, Auteur Année de publication : 2009 Article en page(s) : 17 p. Note générale : fluids enginering Langues : Anglais (eng) Mots-clés : Wells  turbine;  flow-field;  Reynolds-averaged  Navier–Stokes  equations Résumé : This paper presents the results of the numerical simulations carried out to evaluate the performance of a high solidity Wells turbine designed for an oscillating water column wave energy conversion device. The Wells turbine has several favorable features (e.g., simplicity and high rotational speed) but is characterized by a relatively narrow operating range with high efficiency. The aim of this work is to investigate the flow-field through the turbine blades in order to offer a description of the complex flow mechanism that originates separation and, consequently, low efficiency at high flow-rates. Simulations have been performed by solving the Reynolds-averaged Navier–Stokes equations together with three turbulence models, namely, the Spalart–Allmaras, k-ω, and Reynolds-stress models. The capability of the three models to provide an accurate prediction of the complex flow through the Wells turbine has been assessed in two ways: the comparison of the computed results with the available experimental data and the analysis of the flow by means of the anisotropy invariant maps. Then, a detailed description of the flow at different flow-rates is provided, focusing on the interaction of the tip-leakage flow with the main stream and enlightening its role on the turbine performance. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Detailed CFD analysis of the steady flow in a wells turbine under incipient and deep stall conditions [texte imprimé] / M. Torresi, Auteur ; G. Pascazio, Auteur ; S. M. Camporeale, Auteur . - 2009 . - 17 p. fluids enginering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 17 p. Mots-clés : Wells  turbine;  flow-field;  Reynolds-averaged  Navier–Stokes  equations Résumé : This paper presents the results of the numerical simulations carried out to evaluate the performance of a high solidity Wells turbine designed for an oscillating water column wave energy conversion device. The Wells turbine has several favorable features (e.g., simplicity and high rotational speed) but is characterized by a relatively narrow operating range with high efficiency. The aim of this work is to investigate the flow-field through the turbine blades in order to offer a description of the complex flow mechanism that originates separation and, consequently, low efficiency at high flow-rates. Simulations have been performed by solving the Reynolds-averaged Navier–Stokes equations together with three turbulence models, namely, the Spalart–Allmaras, k-ω, and Reynolds-stress models. The capability of the three models to provide an accurate prediction of the complex flow through the Wells turbine has been assessed in two ways: the comparison of the computed results with the available experimental data and the analysis of the flow by means of the anisotropy invariant maps. Then, a detailed description of the flow at different flow-rates is provided, focusing on the interaction of the tip-leakage flow with the main stream and enlightening its role on the turbine performance. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Assessment of large-eddy simulation of internal separated flow / Marco Hahn in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 15 p. Titre : Assessment of large-eddy simulation of internal separated flow Type de document : texte imprimé Auteurs : Marco Hahn, Auteur ; Drikakis, Dimitris, Auteur Année de publication : 2009 Article en page(s) : 15 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : separated  flows;  implicit  large-eddy  simulations Résumé : This paper presents a systematic numerical investigation of different implicit large-eddy simulations (LESs) for massively separated flows. Three numerical schemes, a third-order accurate monotonic upwind scheme for scalar conservation laws (MUSCL) scheme, a fifth-order accurate MUSCL scheme, and a ninth-order accurate weighted essentially non-oscillatory (WENO) method, are tested in the context of separation from a gently curved surface. The case considered here is a simple wall-bounded flow that consists of a channel with a hill-type curvature on the lower wall. The separation and reattachment locations, velocity, and Reynolds stress profiles are presented and compared against solutions from classical LES simulations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Assessment of large-eddy simulation of internal separated flow [texte imprimé] / Marco Hahn, Auteur ; Drikakis, Dimitris, Auteur . - 2009 . - 15 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 15 p. Mots-clés : separated  flows;  implicit  large-eddy  simulations Résumé : This paper presents a systematic numerical investigation of different implicit large-eddy simulations (LESs) for massively separated flows. Three numerical schemes, a third-order accurate monotonic upwind scheme for scalar conservation laws (MUSCL) scheme, a fifth-order accurate MUSCL scheme, and a ninth-order accurate weighted essentially non-oscillatory (WENO) method, are tested in the context of separation from a gently curved surface. The case considered here is a simple wall-bounded flow that consists of a channel with a hill-type curvature on the lower wall. The separation and reattachment locations, velocity, and Reynolds stress profiles are presented and compared against solutions from classical LES simulations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Investigations of tripping effect on the friction factor in turbulent pipe flows / A. Al-Salaymeh in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Titre : Investigations of tripping effect on the friction factor in turbulent pipe flows Type de document : texte imprimé Auteurs : A. Al-Salaymeh, Auteur ; O. A. Bayoumi, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : turbulent  flow  sooner;  tripping  devices Résumé : Tripping devices are usually installed at the entrance of laboratory-scale pipe test sections to obtain a fully developed turbulent flow sooner. The tripping of laminar flow to induce turbulence can be carried out in different ways, such as using cylindrical wires, sand papers, well-organized tape elements, fences, etc. Claims of tripping effects have been made since the classical experiments of Nikuradse (1932, Gesetzmässigkeit der turbulenten Strömung in glatten Rohren, Forschungsheft 356, Ausgabe B, Vol. 3, VDI-Verlag, Berlin), which covered a significant range of Reynolds numbers. Nikuradse’s data have become the metric by which theories are established and have also been the subject of intense scrutiny. Several subsequent experiments reported friction factors as much as 5% lower than those measured by Nikuradse, and the authors of those reports attributed the difference to tripping effects, e.g., work of (2003, “Investigation of the Mean-Flow Scaling and Tripping Effect on Fully Developed Turbulent Pipe Flow,” J. Hydrodynam., 15(1), pp. 14–22). In the present study, measurements with and without ring tripping devices of different blocking areas of 10%, 20%, 30%, and 40% have been carried out to determine the effect of entrance condition on the developing flow field in pipes. Along with pressure drop measurements to compute the skin friction, both the Pitot tube and hot-wire anemometry measurements have been used to accurately determine the mean velocity profile over the working test section at different Reynolds numbers based on the mean velocity and pipe diameter in the range of 1.0×105–4.5×105. The results we obtained suggest that the tripping technique has an insignificant effect on the wall friction factor, in agreement with Nikuradse’s original data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Investigations of tripping effect on the friction factor in turbulent pipe flows [texte imprimé] / A. Al-Salaymeh, Auteur ; O. A. Bayoumi, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Mots-clés : turbulent  flow  sooner;  tripping  devices Résumé : Tripping devices are usually installed at the entrance of laboratory-scale pipe test sections to obtain a fully developed turbulent flow sooner. The tripping of laminar flow to induce turbulence can be carried out in different ways, such as using cylindrical wires, sand papers, well-organized tape elements, fences, etc. Claims of tripping effects have been made since the classical experiments of Nikuradse (1932, Gesetzmässigkeit der turbulenten Strömung in glatten Rohren, Forschungsheft 356, Ausgabe B, Vol. 3, VDI-Verlag, Berlin), which covered a significant range of Reynolds numbers. Nikuradse’s data have become the metric by which theories are established and have also been the subject of intense scrutiny. Several subsequent experiments reported friction factors as much as 5% lower than those measured by Nikuradse, and the authors of those reports attributed the difference to tripping effects, e.g., work of (2003, “Investigation of the Mean-Flow Scaling and Tripping Effect on Fully Developed Turbulent Pipe Flow,” J. Hydrodynam., 15(1), pp. 14–22). In the present study, measurements with and without ring tripping devices of different blocking areas of 10%, 20%, 30%, and 40% have been carried out to determine the effect of entrance condition on the developing flow field in pipes. Along with pressure drop measurements to compute the skin friction, both the Pitot tube and hot-wire anemometry measurements have been used to accurately determine the mean velocity profile over the working test section at different Reynolds numbers based on the mean velocity and pipe diameter in the range of 1.0×105–4.5×105. The results we obtained suggest that the tripping technique has an insignificant effect on the wall friction factor, in agreement with Nikuradse’s original data. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Annular extrudate swell of newtonian fluids revisited / Evan Mitsoulis in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Titre : Annular extrudate swell of newtonian fluids revisited : extended range of compressible simulations Type de document : texte imprimé Auteurs : Evan Mitsoulis, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Newtonian  fluids;  annular  extrudate  swell;  range Résumé : In a recent article (, 2007, “Annular Extrudate Swell of Newtonian Fluids: Effects of Compressibility and Slip at the Wall,” ASME J. Fluids Eng., 129, pp. 1384–1393), numerical simulations were undertaken for the benchmark problem of annular extrudate swell of Newtonian fluids. The effects of weak compressibility and slip at the wall were studied through simple linear laws. While slip was studied in the full range of parameter values, compressibility was confined within a narrow range of values for weakly compressible fluids, where the results were slightly affected. This range is now markedly extended (threefold), based on a consistent finite element method formulation for the continuity equation. Such results correspond to foam extrusion, where compressibility can be substantial. The new extended numerical results are given for different inner/outer diameter ratios κ under steady-state conditions for Newtonian fluids. They provide the shape of the extrudate, and, in particular, the thickness and diameter swells, as a function of the dimensionless compressibility coefficient B. The pressures from the simulations have been used to compute the excess pressure losses in the flow field (exit correction). As before, weak compressibility slightly affects the thickness swell (about 1% in the range of 0≤B≤0.02) mainly by a swell reduction, after which a substantial and monotonic increase occurs for B>0.02. The exit correction increases with increasing compressibility levels in the lower B-range and is highest for the tube (κ=0) and lowest for the slit (κ=1). Then it passes through a maximum around B≈0.02, after which it decreases slowly. This decrease is attributed to the limited length of the flow channel (here chosen to be eight die gaps). En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Annular extrudate swell of newtonian fluids revisited : extended range of compressible simulations [texte imprimé] / Evan Mitsoulis, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Mots-clés : Newtonian  fluids;  annular  extrudate  swell;  range Résumé : In a recent article (, 2007, “Annular Extrudate Swell of Newtonian Fluids: Effects of Compressibility and Slip at the Wall,” ASME J. Fluids Eng., 129, pp. 1384–1393), numerical simulations were undertaken for the benchmark problem of annular extrudate swell of Newtonian fluids. The effects of weak compressibility and slip at the wall were studied through simple linear laws. While slip was studied in the full range of parameter values, compressibility was confined within a narrow range of values for weakly compressible fluids, where the results were slightly affected. This range is now markedly extended (threefold), based on a consistent finite element method formulation for the continuity equation. Such results correspond to foam extrusion, where compressibility can be substantial. The new extended numerical results are given for different inner/outer diameter ratios κ under steady-state conditions for Newtonian fluids. They provide the shape of the extrudate, and, in particular, the thickness and diameter swells, as a function of the dimensionless compressibility coefficient B. The pressures from the simulations have been used to compute the excess pressure losses in the flow field (exit correction). As before, weak compressibility slightly affects the thickness swell (about 1% in the range of 0≤B≤0.02) mainly by a swell reduction, after which a substantial and monotonic increase occurs for B>0.02. The exit correction increases with increasing compressibility levels in the lower B-range and is highest for the tube (κ=0) and lowest for the slit (κ=1). Then it passes through a maximum around B≈0.02, after which it decreases slowly. This decrease is attributed to the limited length of the flow channel (here chosen to be eight die gaps). En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Tip vortex cavitation inception scaling for high Reynolds number applications / Young T. Shen in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 06 p. Titre : Tip vortex cavitation inception scaling for high Reynolds number applications Type de document : texte imprimé Auteurs : Young T. Shen, Auteur ; Stuart Jessup, Auteur ; Scott Gowing, Auteur Année de publication : 2009 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : vortex  cavitation;  Reynolds  number  variations Résumé : Tip vortices generated by marine lifting surfaces such as propeller blades, ship rudders, hydrofoil wings, and antiroll fins can lead to cavitation. Prediction of the onset of this cavitation depends on model tests at Reynolds numbers much lower than those for the corresponding full-scale flows. The effect of Reynolds number variations on the scaling of tip vortex cavitation inception is investigated using a theoretical flow similarity approach. The ratio of the circulations in the full-scale and model-scale trailing vortices is obtained by assuming that the spanwise distributions of the section lift coefficients are the same between the model-scale and the full-scale. The vortex pressure distributions and core sizes are derived using the Rankine vortex model and McCormick’s assumption about the dependence of the vortex core size on the boundary layer thickness at the tip region. Using a logarithmic law to describe the velocity profile in the boundary layer over a large range of Reynolds number, the boundary layer thickness becomes dependent on the Reynolds number to a varying power. In deriving the scaling of the cavitation inception index as the ratio of Reynolds numbers to an exponent m, the values of m are not constant and are dependent on the values of the model- and full-scale Reynolds numbers themselves. This contrasts traditional scaling for which m is treated as a fixed value that is independent of Reynolds numbers. At very high Reynolds numbers, the present theory predicts the value of m to approach zero, consistent with the trend of these flows to become inviscid. Comparison of the present theory with available experimental data shows promising results, especially with recent results from high Reynolds number tests. Numerical examples of the values of m are given for different model- to full-scale sizes and Reynolds numbers. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Tip vortex cavitation inception scaling for high Reynolds number applications [texte imprimé] / Young T. Shen, Auteur ; Stuart Jessup, Auteur ; Scott Gowing, Auteur . - 2009 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 06 p. Mots-clés : vortex  cavitation;  Reynolds  number  variations Résumé : Tip vortices generated by marine lifting surfaces such as propeller blades, ship rudders, hydrofoil wings, and antiroll fins can lead to cavitation. Prediction of the onset of this cavitation depends on model tests at Reynolds numbers much lower than those for the corresponding full-scale flows. The effect of Reynolds number variations on the scaling of tip vortex cavitation inception is investigated using a theoretical flow similarity approach. The ratio of the circulations in the full-scale and model-scale trailing vortices is obtained by assuming that the spanwise distributions of the section lift coefficients are the same between the model-scale and the full-scale. The vortex pressure distributions and core sizes are derived using the Rankine vortex model and McCormick’s assumption about the dependence of the vortex core size on the boundary layer thickness at the tip region. Using a logarithmic law to describe the velocity profile in the boundary layer over a large range of Reynolds number, the boundary layer thickness becomes dependent on the Reynolds number to a varying power. In deriving the scaling of the cavitation inception index as the ratio of Reynolds numbers to an exponent m, the values of m are not constant and are dependent on the values of the model- and full-scale Reynolds numbers themselves. This contrasts traditional scaling for which m is treated as a fixed value that is independent of Reynolds numbers. At very high Reynolds numbers, the present theory predicts the value of m to approach zero, consistent with the trend of these flows to become inviscid. Comparison of the present theory with available experimental data shows promising results, especially with recent results from high Reynolds number tests. Numerical examples of the values of m are given for different model- to full-scale sizes and Reynolds numbers. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

A new method for numerical prediction of liquid column separation accompanying hydraulic transients in pipelines / Adam Adamkowski in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 11 p. Titre : A new method for numerical prediction of liquid column separation accompanying hydraulic transients in pipelines Type de document : texte imprimé Auteurs : Adam Adamkowski, Auteur ; Mariusz Lewandowski, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : calculating  pressure  fluctuations;  discrete-vapor-cavity  model;  liquid  column  separation Résumé : This paper presents a new method for calculating pressure fluctuations in pipelines during a water hammer with liquid column separation. The method is based on the discrete-vapor-cavity model (DVCM). Such kind of models assumes that vaporous cavities are formed in each computational section of the pipeline whenever the pressure drops to the vapor pressure at a given temperature. The proposed new model (new DVCM) brings a significant improvement in the reliability of predictions compared with existing DVCMs. The calculation method based on it eliminates some disadvantages of basic methods used in practice, as shown by comparisons between calculations made for simple hydraulic system under theoretical frictionless conditions using various DVCMs. Additionally, the authors present preliminary verification of the proposed model based on experimental results. The positive results of this verification, and the advantages of the new DVCM, could lead to incorporating them into commercial codes. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A new method for numerical prediction of liquid column separation accompanying hydraulic transients in pipelines [texte imprimé] / Adam Adamkowski, Auteur ; Mariusz Lewandowski, Auteur . - 2009 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 11 p. Mots-clés : calculating  pressure  fluctuations;  discrete-vapor-cavity  model;  liquid  column  separation Résumé : This paper presents a new method for calculating pressure fluctuations in pipelines during a water hammer with liquid column separation. The method is based on the discrete-vapor-cavity model (DVCM). Such kind of models assumes that vaporous cavities are formed in each computational section of the pipeline whenever the pressure drops to the vapor pressure at a given temperature. The proposed new model (new DVCM) brings a significant improvement in the reliability of predictions compared with existing DVCMs. The calculation method based on it eliminates some disadvantages of basic methods used in practice, as shown by comparisons between calculations made for simple hydraulic system under theoretical frictionless conditions using various DVCMs. Additionally, the authors present preliminary verification of the proposed model based on experimental results. The positive results of this verification, and the advantages of the new DVCM, could lead to incorporating them into commercial codes. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Experimental Study of Liquid Slosh Dynamics in a Partially-Filled Tank / Guorong Yan in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 14 p. Titre : Experimental Study of Liquid Slosh Dynamics in a Partially-Filled Tank Type de document : texte imprimé Auteurs : Guorong Yan, Auteur ; Subhash Rakheja, Auteur ; Kamran Siddiqui, Auteur Année de publication : 2009 Article en page(s) : 14 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : slosh  forces;  filled  tank Résumé : This article reports on an experimental study conducted to investigate slosh forces and moments caused by fluid slosh within a partly-filled tank subjected to lateral and longitudinal excitations applied independently. The experiments were performed on a scale model cleanbore and a baffled tank with laterally placed single- and multiple-orifice baffles. The experiments were conducted for three different fill volumes and different types of excitations: continuous harmonic and single-cycle sinusoidal excitations of different amplitudes and discrete frequencies. The dynamic forces and moments caused by fluid slosh with the baffled and cleanbore tank configurations were measured for different fill volumes and excitations using three-axis dynamometers. It is shown that the resulting forces and moments comprise many spectral components that can be associated with the excitation, resonance, and vibration and beat frequencies. Modulation of excitation frequency with the resonant frequency was also evident for all fill conditions and tank configurations when the two were in close proximity. The results also showed that the peak amplifications of forces and moments occur in the vicinity of the resonant frequency. At higher frequencies, the peak magnitudes of the forces, however, reduced significantly to values lower than the inertial forces developed by an equivalent rigid mass. At a given excitation condition, the slosh force amplitude increased with a decrease in the fill volume. It was also observed that the presence of baffles has negligible effect on the lateral slosh force and the corresponding resonant frequency. However, it caused a significant increase in the longitudinal mode resonant frequency. The baffles greatly reduced the amplifications in longitudinal force and pitch moment under longitudinal acceleration excitations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Experimental Study of Liquid Slosh Dynamics in a Partially-Filled Tank [texte imprimé] / Guorong Yan, Auteur ; Subhash Rakheja, Auteur ; Kamran Siddiqui, Auteur . - 2009 . - 14 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 14 p. Mots-clés : slosh  forces;  filled  tank Résumé : This article reports on an experimental study conducted to investigate slosh forces and moments caused by fluid slosh within a partly-filled tank subjected to lateral and longitudinal excitations applied independently. The experiments were performed on a scale model cleanbore and a baffled tank with laterally placed single- and multiple-orifice baffles. The experiments were conducted for three different fill volumes and different types of excitations: continuous harmonic and single-cycle sinusoidal excitations of different amplitudes and discrete frequencies. The dynamic forces and moments caused by fluid slosh with the baffled and cleanbore tank configurations were measured for different fill volumes and excitations using three-axis dynamometers. It is shown that the resulting forces and moments comprise many spectral components that can be associated with the excitation, resonance, and vibration and beat frequencies. Modulation of excitation frequency with the resonant frequency was also evident for all fill conditions and tank configurations when the two were in close proximity. The results also showed that the peak amplifications of forces and moments occur in the vicinity of the resonant frequency. At higher frequencies, the peak magnitudes of the forces, however, reduced significantly to values lower than the inertial forces developed by an equivalent rigid mass. At a given excitation condition, the slosh force amplitude increased with a decrease in the fill volume. It was also observed that the presence of baffles has negligible effect on the lateral slosh force and the corresponding resonant frequency. However, it caused a significant increase in the longitudinal mode resonant frequency. The baffles greatly reduced the amplifications in longitudinal force and pitch moment under longitudinal acceleration excitations. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow / A.-R. A. Khaled in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Titre : Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow Type de document : texte imprimé Auteurs : A.-R. A. Khaled, Auteur ; Abdulhaiy M. Radhwan, Auteur ; S. A. Al-Muaikel, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Laminar  falling  film  condensations;  assumptions;  accelerating  vapor  flow Résumé : Laminar falling film condensations over a vertical plate with an accelerating vapor flow is analyzed in this work in the presence of condensate suction or slip effects at the plate surface. The following assumptions are made: (i) laminar condensate flow having constant properties, (ii) pure vapor with a uniform saturation temperature in the vapor region, and (iii) the shear stress at the liquid/vapor interface is negligible. The appropriate fundamental governing partial differential equations for the condensate and vapor flows (continuity, momentum, and energy equations) for the above case are identified, nondimensionalized, and transformed using nonsimilarity transformation. The transformed equations were solved using numerical, iterative, and implicit finite-difference methods. It is shown that the freestream striking angle has insignificant influence on the condensation mass and heat transfer rates, except when slip condition is present and at relatively small Grl/Re2 values. Moreover, it is shown that increasing the values of the dimensionless suction parameter (VS) results to an increase in dimensionless mass of condensate (Γ(L)/(μl Re)) and Nusselt number (Nu(L)/Re1/2). Thus, it results in an increase in condensation mass and heat transfer rates. Finally, it is found that the condensation and heat transfer rates increase as Jakob number, slip parameter, and saturation temperature increase. Finally, the results of this work not only enrich the literature of condensation but also provide additional methods for saving thermal energy. Topics: En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow [texte imprimé] / A.-R. A. Khaled, Auteur ; Abdulhaiy M. Radhwan, Auteur ; S. A. Al-Muaikel, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Mots-clés : Laminar  falling  film  condensations;  assumptions;  accelerating  vapor  flow Résumé : Laminar falling film condensations over a vertical plate with an accelerating vapor flow is analyzed in this work in the presence of condensate suction or slip effects at the plate surface. The following assumptions are made: (i) laminar condensate flow having constant properties, (ii) pure vapor with a uniform saturation temperature in the vapor region, and (iii) the shear stress at the liquid/vapor interface is negligible. The appropriate fundamental governing partial differential equations for the condensate and vapor flows (continuity, momentum, and energy equations) for the above case are identified, nondimensionalized, and transformed using nonsimilarity transformation. The transformed equations were solved using numerical, iterative, and implicit finite-difference methods. It is shown that the freestream striking angle has insignificant influence on the condensation mass and heat transfer rates, except when slip condition is present and at relatively small Grl/Re2 values. Moreover, it is shown that increasing the values of the dimensionless suction parameter (VS) results to an increase in dimensionless mass of condensate (Γ(L)/(μl Re)) and Nusselt number (Nu(L)/Re1/2). Thus, it results in an increase in condensation mass and heat transfer rates. Finally, it is found that the condensation and heat transfer rates increase as Jakob number, slip parameter, and saturation temperature increase. Finally, the results of this work not only enrich the literature of condensation but also provide additional methods for saving thermal energy. Topics: En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Equation-free/galerkin-free reduced-order modeling of the shallow water equations based on proper orthogonal decomposition / Vahid Esfahanian in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 13 p. Titre : Equation-free/galerkin-free reduced-order modeling of the shallow water equations based on proper orthogonal decomposition Type de document : texte imprimé Auteurs : Vahid Esfahanian, Auteur ; Khosro Ashrafi, Auteur Année de publication : 2009 Article en page(s) : 13 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  equations;  functions;  hydraulic  jump;  modeling Résumé : In this paper, two categories of reduced-order modeling (ROM) of the shallow water equations (SWEs) based on the proper orthogonal decomposition (POD) are presented. First, the traditional Galerkin-projection POD/ROM is applied to the one-dimensional (1D) SWEs. The result indicates that although the Galerkin-projection POD/ROM is suitable for describing the physical properties of flows (during the POD basis functions’ construction time), it cannot predict that the dynamics of the shallow water flows properly as it was expected, especially with complex initial conditions. Then, the study is extended to applying the equation-free/Galerkin-free POD/ROM to both 1D and 2D SWEs. In the equation-free/Galerkin-free framework, the numerical simulation switches between a fine-scale model, which provides data for construction of the POD basis functions, and a coarse-scale model, which is designed for the coarse-grained computational study of complex, multiscale problems like SWEs. In the present work, the Beam & Warming and semi-implicit time integration schemes are applied to the 1D and 2D SWEs, respectively, as fine-scale models and the coefficients of a few POD basis functions (reduced-order model) are considered as a coarse-scale model. Projective integration is applied to the coarse-scale model in an equation-free framework with a time step grater than the one used for a fine-scale model. It is demonstrated that equation-free/Galerkin-free POD/ROM can resolve the dynamics of the complex shallow water flows. Moreover, the computational cost of the approach is less than the one for a fine-scale model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Equation-free/galerkin-free reduced-order modeling of the shallow water equations based on proper orthogonal decomposition [texte imprimé] / Vahid Esfahanian, Auteur ; Khosro Ashrafi, Auteur . - 2009 . - 13 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 13 p. Mots-clés : flow  (dynamics);  equations;  functions;  hydraulic  jump;  modeling Résumé : In this paper, two categories of reduced-order modeling (ROM) of the shallow water equations (SWEs) based on the proper orthogonal decomposition (POD) are presented. First, the traditional Galerkin-projection POD/ROM is applied to the one-dimensional (1D) SWEs. The result indicates that although the Galerkin-projection POD/ROM is suitable for describing the physical properties of flows (during the POD basis functions’ construction time), it cannot predict that the dynamics of the shallow water flows properly as it was expected, especially with complex initial conditions. Then, the study is extended to applying the equation-free/Galerkin-free POD/ROM to both 1D and 2D SWEs. In the equation-free/Galerkin-free framework, the numerical simulation switches between a fine-scale model, which provides data for construction of the POD basis functions, and a coarse-scale model, which is designed for the coarse-grained computational study of complex, multiscale problems like SWEs. In the present work, the Beam & Warming and semi-implicit time integration schemes are applied to the 1D and 2D SWEs, respectively, as fine-scale models and the coefficients of a few POD basis functions (reduced-order model) are considered as a coarse-scale model. Projective integration is applied to the coarse-scale model in an equation-free framework with a time step grater than the one used for a fine-scale model. It is demonstrated that equation-free/Galerkin-free POD/ROM can resolve the dynamics of the complex shallow water flows. Moreover, the computational cost of the approach is less than the one for a fine-scale model. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Nonaxisymmetric three-dimensional stagnation-point flow and heat transfer on a flat plate / Ali Shokrgozar Abbassi in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 05 p. Titre : Nonaxisymmetric three-dimensional stagnation-point flow and heat transfer on a flat plate Type de document : texte imprimé Auteurs : Ali Shokrgozar Abbassi, Auteur ; Asghar Baradaran Rahimi, Auteur Année de publication : 2009 Article en page(s) : 05 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : stagnation-point  flow;  flat  plate;  Navier–Stokes  equations;  energy  equation Résumé : The existing solutions of Navier–Stokes and energy equations in the literature regarding the three-dimensional problem of stagnation-point flow either on a flat plate or on a cylinder are only for the case of axisymmetric formulation. The only exception is the study of three-dimensional stagnation-point flow on a flat plate by (1951, “The Boundary Layer in Three-Dimensional Flow—Part II: The Flow Near Stagnation Point,” Philos. Mag., 42, pp. 1433–1440), which is based on boundary layer theory approximation and zero pressure assumption in direction of normal to the surface. In our study the nonaxisymmetric three-dimensional steady viscous stagnation-point flow and heat transfer in the vicinity of a flat plate are investigated based on potential flow theory, which is the most general solution. An external fluid, along z-direction, with strain rate a impinges on this flat plate and produces a two-dimensional flow with different components of velocity on the plate. This situation may happen if the flow pattern on the plate is bounded from both sides in one of the directions, for example x-axis, because of any physical limitation. A similarity solution of the Navier–Stokes equations and energy equation is presented in this problem. A reduction in these equations is obtained by the use of appropriate similarity transformations. Velocity profiles and surface stress-tensors and temperature profiles along with pressure profile are presented for different values of velocity ratios, and Prandtl number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Nonaxisymmetric three-dimensional stagnation-point flow and heat transfer on a flat plate [texte imprimé] / Ali Shokrgozar Abbassi, Auteur ; Asghar Baradaran Rahimi, Auteur . - 2009 . - 05 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 05 p. Mots-clés : stagnation-point  flow;  flat  plate;  Navier–Stokes  equations;  energy  equation Résumé : The existing solutions of Navier–Stokes and energy equations in the literature regarding the three-dimensional problem of stagnation-point flow either on a flat plate or on a cylinder are only for the case of axisymmetric formulation. The only exception is the study of three-dimensional stagnation-point flow on a flat plate by (1951, “The Boundary Layer in Three-Dimensional Flow—Part II: The Flow Near Stagnation Point,” Philos. Mag., 42, pp. 1433–1440), which is based on boundary layer theory approximation and zero pressure assumption in direction of normal to the surface. In our study the nonaxisymmetric three-dimensional steady viscous stagnation-point flow and heat transfer in the vicinity of a flat plate are investigated based on potential flow theory, which is the most general solution. An external fluid, along z-direction, with strain rate a impinges on this flat plate and produces a two-dimensional flow with different components of velocity on the plate. This situation may happen if the flow pattern on the plate is bounded from both sides in one of the directions, for example x-axis, because of any physical limitation. A similarity solution of the Navier–Stokes equations and energy equation is presented in this problem. A reduction in these equations is obtained by the use of appropriate similarity transformations. Velocity profiles and surface stress-tensors and temperature profiles along with pressure profile are presented for different values of velocity ratios, and Prandtl number. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

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