Dépouillements

Relaminarization of axisymmetric turbulent flow with combined axial jet and side injection in a pipe / Snehamoy Majumder in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 06 p. Titre : Relaminarization of axisymmetric turbulent flow with combined axial jet and side injection in a pipe Type de document : texte imprimé Auteurs : Snehamoy Majumder, Auteur ; Dipankar Bhanja, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  turbulence;  Reynolds  number;  pipes;  ducts Résumé : The effect of side mass injection on turbulent flow with axial entry to a circular duct in the form of centrally confined jet has been investigated. A standard κ-ε model modified for streamline curvature has been used for detailed analysis following a comparison with a κ-ω model for some test cases. Results show that flow stabilization and relaminarization could occur due to the side injection. The predicted recirculation zone, friction factor, total turbulent energy, turbulent shear stress, Taylor scale Reynolds number, and turbulent energy flux show gradual reduction with increase in the side injection velocity. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Relaminarization of axisymmetric turbulent flow with combined axial jet and side injection in a pipe [texte imprimé] / Snehamoy Majumder, Auteur ; Dipankar Bhanja, Auteur . - 2011 . - 06 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 06 p. Mots-clés : flow  (dynamics);  turbulence;  Reynolds  number;  pipes;  ducts Résumé : The effect of side mass injection on turbulent flow with axial entry to a circular duct in the form of centrally confined jet has been investigated. A standard κ-ε model modified for streamline curvature has been used for detailed analysis following a comparison with a κ-ω model for some test cases. Results show that flow stabilization and relaminarization could occur due to the side injection. The predicted recirculation zone, friction factor, total turbulent energy, turbulent shear stress, Taylor scale Reynolds number, and turbulent energy flux show gradual reduction with increase in the side injection velocity. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Viscous disk air flow displacement device (VDAFDD) / Jonathan M. Hilton in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Titre : Viscous disk air flow displacement device (VDAFDD) : development and performance Type de document : texte imprimé Auteurs : Jonathan M. Hilton, Auteur ; Phillip M. Ligrani, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  disks;  ducts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The development and performance of a unique viscous disk air flow displacement device (or VDAFDD) for inducing airflow in confined spaces is described. The development is motivated by electronic cooling, where limitations on space are especially severe and the need exists to circulate air over or through the key components using a compact and efficient device. To induce air motion, array of disks are employed with their axis of rotation perpendicular to the air stream. Results from the most successful prototype, which was developed and tested, prototype 2, are presented for Reynolds numbers up to 671 to illustrate nominal behavior, as well as behavior as a number of different parameters are altered, including the magnitude of exit flow restriction, the air gap above the disks, and the number of disks employed to induce air motion. Also discussed are the effects of disk rotational speed, comparisons with theoretical predictions, and one earlier prototype whose performance is significantly less than that of prototype 2. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Viscous disk air flow displacement device (VDAFDD) : development and performance [texte imprimé] / Jonathan M. Hilton, Auteur ; Phillip M. Ligrani, Auteur . - 2011 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Mots-clés : pressure;  flow  (dynamics);  disks;  ducts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The development and performance of a unique viscous disk air flow displacement device (or VDAFDD) for inducing airflow in confined spaces is described. The development is motivated by electronic cooling, where limitations on space are especially severe and the need exists to circulate air over or through the key components using a compact and efficient device. To induce air motion, array of disks are employed with their axis of rotation perpendicular to the air stream. Results from the most successful prototype, which was developed and tested, prototype 2, are presented for Reynolds numbers up to 671 to illustrate nominal behavior, as well as behavior as a number of different parameters are altered, including the magnitude of exit flow restriction, the air gap above the disks, and the number of disks employed to induce air motion. Also discussed are the effects of disk rotational speed, comparisons with theoretical predictions, and one earlier prototype whose performance is significantly less than that of prototype 2. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Integral force/moment waterjet model for CFD simulations / Manivannan Kandasamy in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Titre : Integral force/moment waterjet model for CFD simulations Type de document : texte imprimé Auteurs : Manivannan Kandasamy, Auteur ; Seng Keat Ooi, Auteur ; Pablo Carrica, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  flow  (dynamics);  computational  fluid  dynamics;  engineering  simulation;  ships;  hull Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An integral force/moment waterjet model for computational fluid dynamics (CFD) is derived for ship local flow/powering predictions, including sinkage and trim. The waterjet induced reaction forces and moment and waterjet/hull interaction stern force replicate the effects of the waterjet without requiring detailed simulations of the waterjet system. The model extends the International Towing Tank Conference (ITTC) waterjet model for sinkage and trim by using an alternative control volume also appropriate for CFD and by including vertical forces and pitching moment in the waterjet/hull force/moment balance. The same grid is used for both without and with waterjet simulations. The CFD waterjet model requires limited waterjet geometry (inlet and outlet areas and locations, and weight of working fluid) and several waterjet flow (mass flow rate, inlet pressure force, inlet and outlet momentum correction factors and flow angles, and stern force and location) input variables. The CFD waterjet model can be used for local flow predictions by using waterjet flow input variables provided by ITTC waterjet model test data, including additional data for waterjet induced inlet pressure and stern forces. It can also be used for powering predictions once waterjet flow input variable correlations are available based on CFD for the waterjet system and/or experimental data. The CFD waterjet model is demonstrated for local flow predictions for the DTMB 5594 high-speed sealift ship model for which ITTC waterjet model test data, including additional data for waterjet induced stern forces, are available. Correlations for the waterjet flow input variables are shown to be feasible using a combination of CFD and experimental data for the waterjet system for three different hulls. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Integral force/moment waterjet model for CFD simulations [texte imprimé] / Manivannan Kandasamy, Auteur ; Seng Keat Ooi, Auteur ; Pablo Carrica, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Mots-clés : force;  flow  (dynamics);  computational  fluid  dynamics;  engineering  simulation;  ships;  hull Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An integral force/moment waterjet model for computational fluid dynamics (CFD) is derived for ship local flow/powering predictions, including sinkage and trim. The waterjet induced reaction forces and moment and waterjet/hull interaction stern force replicate the effects of the waterjet without requiring detailed simulations of the waterjet system. The model extends the International Towing Tank Conference (ITTC) waterjet model for sinkage and trim by using an alternative control volume also appropriate for CFD and by including vertical forces and pitching moment in the waterjet/hull force/moment balance. The same grid is used for both without and with waterjet simulations. The CFD waterjet model requires limited waterjet geometry (inlet and outlet areas and locations, and weight of working fluid) and several waterjet flow (mass flow rate, inlet pressure force, inlet and outlet momentum correction factors and flow angles, and stern force and location) input variables. The CFD waterjet model can be used for local flow predictions by using waterjet flow input variables provided by ITTC waterjet model test data, including additional data for waterjet induced inlet pressure and stern forces. It can also be used for powering predictions once waterjet flow input variable correlations are available based on CFD for the waterjet system and/or experimental data. The CFD waterjet model is demonstrated for local flow predictions for the DTMB 5594 high-speed sealift ship model for which ITTC waterjet model test data, including additional data for waterjet induced stern forces, are available. Correlations for the waterjet flow input variables are shown to be feasible using a combination of CFD and experimental data for the waterjet system for three different hulls. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Numerical and experimental study on jet trajectories and mixing behavior of venturi-jet mixer / S. Sundararaj in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Titre : Numerical and experimental study on jet trajectories and mixing behavior of venturi-jet mixer Type de document : texte imprimé Auteurs : S. Sundararaj, Auteur ; V. Selladurai, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : momentum;  flow  (dynamics);  fluids;  turbulence;  trajectories  (physics);  equations;  venturi  tubes;  cross-flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An investigation of the jet trajectories and mixing behavior of venturi-jet mixers, in which turbulent jet injects fluid at an arbitrary angle to mix incompressible fluids, is described in this paper. Numerical results of an incompressible cross flow-jet mixing in venturi-jet mixers are presented and validated against experimental results. Jet trajectories, concentration decay of tracer jet, spatial unmixedness, and mixing length are computed for a range of injection angles (45 deg≤θo≤135 deg). Twenty-five cases are studied with five different initial injection angles, each with five different jet momentum ratios. As an example of practical insights that can be gained from such detailed analysis, the resulting flow field is used to obtain an equation for trajectory and tracer concentration in the mixer. The penetration of jet scales with the third root of the jet-to-mainstream momentum ratio and that of with square root of downstream distance. The decay of mean concentration scales with the inverse of axial distance and with the negative root of injection angle. The results show a consistency in the experimental data and simulation has provided a good insight into the flow details and has paved the way in optimization of the geometry based on jet injection angle to get a good mixing efficiency. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Numerical and experimental study on jet trajectories and mixing behavior of venturi-jet mixer [texte imprimé] / S. Sundararaj, Auteur ; V. Selladurai, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Mots-clés : momentum;  flow  (dynamics);  fluids;  turbulence;  trajectories  (physics);  equations;  venturi  tubes;  cross-flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An investigation of the jet trajectories and mixing behavior of venturi-jet mixers, in which turbulent jet injects fluid at an arbitrary angle to mix incompressible fluids, is described in this paper. Numerical results of an incompressible cross flow-jet mixing in venturi-jet mixers are presented and validated against experimental results. Jet trajectories, concentration decay of tracer jet, spatial unmixedness, and mixing length are computed for a range of injection angles (45 deg≤θo≤135 deg). Twenty-five cases are studied with five different initial injection angles, each with five different jet momentum ratios. As an example of practical insights that can be gained from such detailed analysis, the resulting flow field is used to obtain an equation for trajectory and tracer concentration in the mixer. The penetration of jet scales with the third root of the jet-to-mainstream momentum ratio and that of with square root of downstream distance. The decay of mean concentration scales with the inverse of axial distance and with the negative root of injection angle. The results show a consistency in the experimental data and simulation has provided a good insight into the flow details and has paved the way in optimization of the geometry based on jet injection angle to get a good mixing efficiency. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Unsteady peristaltic pumping in a finite length tube with permeable wall / Y. V. K. Ravi Kumar in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 04 p. Titre : Unsteady peristaltic pumping in a finite length tube with permeable wall Type de document : texte imprimé Auteurs : Y. V. K. Ravi Kumar, Auteur ; S. V. H. N. Krishna Kumari.P., Auteur ; M. V. Ramana Murthy, Auteur Année de publication : 2011 Article en page(s) : 04 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  wavelength;  fluids;  permeability;  Reynolds  number;  waves;  boundary-value  problems Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Peristaltic transport due to a sinusoidal wave traveling on the boundary of a tube filled with an incompressible fluid is presented. Solution is obtained under infinite wavelength and zero Reynolds number in a finite length tube which extends the study of and (1993, “Non-Steady Peristaltic Transport in Finite-Length Tubes,” J. Fluid Mech., 248, pp. 129–151). Boundary conditions are changed to include wall permeability. Analysis of pressure profile is described. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Unsteady peristaltic pumping in a finite length tube with permeable wall [texte imprimé] / Y. V. K. Ravi Kumar, Auteur ; S. V. H. N. Krishna Kumari.P., Auteur ; M. V. Ramana Murthy, Auteur . - 2011 . - 04 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 04 p. Mots-clés : pressure;  flow  (dynamics);  wavelength;  fluids;  permeability;  Reynolds  number;  waves;  boundary-value  problems Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Peristaltic transport due to a sinusoidal wave traveling on the boundary of a tube filled with an incompressible fluid is presented. Solution is obtained under infinite wavelength and zero Reynolds number in a finite length tube which extends the study of and (1993, “Non-Steady Peristaltic Transport in Finite-Length Tubes,” J. Fluid Mech., 248, pp. 129–151). Boundary conditions are changed to include wall permeability. Analysis of pressure profile is described. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Rotational and quasiviscous cold flow models for axisymmetric hybrid propellant chambers / Joseph Majdalani in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Titre : Rotational and quasiviscous cold flow models for axisymmetric hybrid propellant chambers Type de document : texte imprimé Auteurs : Joseph Majdalani, Auteur ; Michel Akiki, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  motion;  fuels;  Reynolds  number;  hybrid  engines;  vorticity;  approximation;  boundary-value  problems;  equations;  propellants Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this work, we present two simple mean flow solutions that mimic the bulk gas motion inside a full-length, cylindrical hybrid rocket engine. Two distinct methods are used. The first is based on steady, axisymmetric, rotational, and incompressible flow conditions. It leads to an Eulerian solution that observes the normal sidewall mass injection condition while assuming a sinusoidal injection profile at the head end wall. The second approach constitutes a slight improvement over the first in its inclusion of viscous effects. At the outset, a first order viscous approximation is constructed using regular perturbations in the reciprocal of the wall injection Reynolds number. The asymptotic approximation is derived from a general similarity reduced Navier–Stokes equation for a viscous tube with regressing porous walls. It is then compared and shown to agree remarkably well with two existing solutions. The resulting formulations enable us to model the streamtubes observed in conventional hybrid engines in which the parallel motion of gaseous oxidizer is coupled with the cross-streamwise (i.e., sidewall) addition of solid fuel. Furthermore, estimates for pressure, velocity, and vorticity distributions in the simulated engine are provided in closed form. Our idealized hybrid engine is modeled as a porous circular-port chamber with head end injection. The mathematical treatment is based on a standard similarity approach that is tailored to permit sinusoidal injection at the head end. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Rotational and quasiviscous cold flow models for axisymmetric hybrid propellant chambers [texte imprimé] / Joseph Majdalani, Auteur ; Michel Akiki, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Mots-clés : flow  (dynamics);  motion;  fuels;  Reynolds  number;  hybrid  engines;  vorticity;  approximation;  boundary-value  problems;  equations;  propellants Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this work, we present two simple mean flow solutions that mimic the bulk gas motion inside a full-length, cylindrical hybrid rocket engine. Two distinct methods are used. The first is based on steady, axisymmetric, rotational, and incompressible flow conditions. It leads to an Eulerian solution that observes the normal sidewall mass injection condition while assuming a sinusoidal injection profile at the head end wall. The second approach constitutes a slight improvement over the first in its inclusion of viscous effects. At the outset, a first order viscous approximation is constructed using regular perturbations in the reciprocal of the wall injection Reynolds number. The asymptotic approximation is derived from a general similarity reduced Navier–Stokes equation for a viscous tube with regressing porous walls. It is then compared and shown to agree remarkably well with two existing solutions. The resulting formulations enable us to model the streamtubes observed in conventional hybrid engines in which the parallel motion of gaseous oxidizer is coupled with the cross-streamwise (i.e., sidewall) addition of solid fuel. Furthermore, estimates for pressure, velocity, and vorticity distributions in the simulated engine are provided in closed form. Our idealized hybrid engine is modeled as a porous circular-port chamber with head end injection. The mathematical treatment is based on a standard similarity approach that is tailored to permit sinusoidal injection at the head end. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Experimental and numerical study of laminar round jet flows along a wall / K. F. K. Adane in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 10 p. Titre : Experimental and numerical study of laminar round jet flows along a wall Type de document : texte imprimé Auteurs : K. F. K. Adane, Auteur ; M. F. Tachie, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  measurement;  Reynolds  number;  jets;  vorticity Résumé : In the present study, both experimental and numerical techniques were employed to study three-dimensional laminar wall jet flows. The wall jet was created using a circular pipe of diameter 7×10−3 m and flows into an open water tank. The inlet Reynolds numbers based on the pipe diameter and jet exit velocity were 310 and 800. A particle image velocimetry (PIV) was used to conduct detailed measurements at various streamwise-transverse and streamwise-spanwise planes. The complete nonlinear incompressible Navier–Stokes equation was also solved using a collocated finite volume based in-house computational fluid dynamics (CFD) code. The computation was performed for three inlet Reynolds numbers, namely, 310, 420, and 800. From the PIV measurements and CFD results, velocity profiles and jet half-widths were extracted at selected downstream locations. It was observed that the numerical results are in reasonable agreement with the experimental data. The distributions of the velocities, jet spread rates, and vorticity were used to provide insight into the characteristics of three-dimensional laminar wall jet flows. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Experimental and numerical study of laminar round jet flows along a wall [texte imprimé] / K. F. K. Adane, Auteur ; M. F. Tachie, Auteur . - 2011 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 10 p. Mots-clés : flow  (dynamics);  measurement;  Reynolds  number;  jets;  vorticity Résumé : In the present study, both experimental and numerical techniques were employed to study three-dimensional laminar wall jet flows. The wall jet was created using a circular pipe of diameter 7×10−3 m and flows into an open water tank. The inlet Reynolds numbers based on the pipe diameter and jet exit velocity were 310 and 800. A particle image velocimetry (PIV) was used to conduct detailed measurements at various streamwise-transverse and streamwise-spanwise planes. The complete nonlinear incompressible Navier–Stokes equation was also solved using a collocated finite volume based in-house computational fluid dynamics (CFD) code. The computation was performed for three inlet Reynolds numbers, namely, 310, 420, and 800. From the PIV measurements and CFD results, velocity profiles and jet half-widths were extracted at selected downstream locations. It was observed that the numerical results are in reasonable agreement with the experimental data. The distributions of the velocities, jet spread rates, and vorticity were used to provide insight into the characteristics of three-dimensional laminar wall jet flows. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Stokes flow through a periodically grooved tube / Chiu-On Ng in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Titre : Stokes flow through a periodically grooved tube Type de document : texte imprimé Auteurs : Chiu-On Ng, Auteur ; Wang, C. Y., Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : pressure;  flow  (dynamics);  fluids;  electrical  resistance;  shear  (mechanics);  boundary-value  problems;  creeping  flow;  fins;  pressure  drop Résumé : This is an analytical study on Stokes flow through a tube of which the wall is patterned with periodic transverse grooves filled with an inviscid gas. In one period of the pattern, the fluid flows through an annular groove and an annular rib subject to no-shear and no-slip boundary conditions, respectively. The fluid may penetrate the groove to a certain depth, so there is an abrupt change in the cross section of flow through the two regions. The problem is solved by the method of domain decomposition and eigenfunction expansions, where the coefficients of the expansion series are determined by matching velocities, stress, and pressure on the domain interface. The effective slip length and pressure distributions are examined as functions of the geometrical parameters (tube radius, depth of fluid penetration into grooves, and no-shear area fraction of the wall). Particular attention is paid to the limiting case of flow through annular fins on a no-shear wall. Results are generated for the streamlines, resistance, and pressure drop due to the fins. It is found that the wall condition, whether no-shear or no-slip, will be immaterial when the fin interval is smaller than a certain threshold depending on the orifice ratio. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Stokes flow through a periodically grooved tube [texte imprimé] / Chiu-On Ng, Auteur ; Wang, C. Y., Auteur . - 2011 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Mots-clés : pressure;  flow  (dynamics);  fluids;  electrical  resistance;  shear  (mechanics);  boundary-value  problems;  creeping  flow;  fins;  pressure  drop Résumé : This is an analytical study on Stokes flow through a tube of which the wall is patterned with periodic transverse grooves filled with an inviscid gas. In one period of the pattern, the fluid flows through an annular groove and an annular rib subject to no-shear and no-slip boundary conditions, respectively. The fluid may penetrate the groove to a certain depth, so there is an abrupt change in the cross section of flow through the two regions. The problem is solved by the method of domain decomposition and eigenfunction expansions, where the coefficients of the expansion series are determined by matching velocities, stress, and pressure on the domain interface. The effective slip length and pressure distributions are examined as functions of the geometrical parameters (tube radius, depth of fluid penetration into grooves, and no-shear area fraction of the wall). Particular attention is paid to the limiting case of flow through annular fins on a no-shear wall. Results are generated for the streamlines, resistance, and pressure drop due to the fins. It is found that the wall condition, whether no-shear or no-slip, will be immaterial when the fin interval is smaller than a certain threshold depending on the orifice ratio. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Numerical prediction of impact force in cavitating flows / Hong Wang in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Titre : Numerical prediction of impact force in cavitating flows Type de document : texte imprimé Auteurs : Hong Wang, Auteur ; Baoshan Zhu, Auteur Année de publication : 2011 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  pressure;  flow  (dynamics);  cavitation;  bubbles;  numerical  analysis;  collapse;  equations Résumé : A numerical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamics is proposed for the prediction of the impact force caused by cavitation bubble collapse in cavitating flows. A large eddy simulation solver, which is incorporated with a macroscopic cavitation model, is applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles is determined by a microscopic cavitation model from the resolution of a Rayleigh–Plesset equation including the effects of the surface tension, the viscosity and compressibility of fluid, the thermal conduction and radiation, the phase transition of water vapor at the interface, and the chemical reactions. The cavitation flow around a hydrofoil is simulated to validate the macroscopic cavitation model. A good quantitative agreement is obtained between the prediction and the experiment. The proposed numerical method is applied to predict the impact force at cavitation bubble collapse on a KT section in cavitating flows. It is found that the shock pressure caused by cavitation bubble collapse is very high. The impact force is predicted qualitatively compared with the experimental data. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Numerical prediction of impact force in cavitating flows [texte imprimé] / Hong Wang, Auteur ; Baoshan Zhu, Auteur . - 2011 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 09 p. Mots-clés : force;  pressure;  flow  (dynamics);  cavitation;  bubbles;  numerical  analysis;  collapse;  equations Résumé : A numerical method including a macroscopic cavitation model based on the homogeneous flow theory and a microscopic cavitation model based on the bubble dynamics is proposed for the prediction of the impact force caused by cavitation bubble collapse in cavitating flows. A large eddy simulation solver, which is incorporated with a macroscopic cavitation model, is applied to simulate the unsteady cavitating flows. Based on the simulated flow field, the evolution of the cavitation bubbles is determined by a microscopic cavitation model from the resolution of a Rayleigh–Plesset equation including the effects of the surface tension, the viscosity and compressibility of fluid, the thermal conduction and radiation, the phase transition of water vapor at the interface, and the chemical reactions. The cavitation flow around a hydrofoil is simulated to validate the macroscopic cavitation model. A good quantitative agreement is obtained between the prediction and the experiment. The proposed numerical method is applied to predict the impact force at cavitation bubble collapse on a KT section in cavitating flows. It is found that the shock pressure caused by cavitation bubble collapse is very high. The impact force is predicted qualitatively compared with the experimental data. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Non-Newtonian drops spreading on a flat surface / A. Dechelette in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Titre : Non-Newtonian drops spreading on a flat surface Type de document : texte imprimé Auteurs : A. Dechelette, Auteur ; P. E. Sojka, Auteur ; C. R. Wassgren, Auteur Année de publication : 2011 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : force;  surface  tension;  flow  (dynamics);  viscosity;  Reynolds  number;  drops;  water Résumé : The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Non-Newtonian drops spreading on a flat surface [texte imprimé] / A. Dechelette, Auteur ; P. E. Sojka, Auteur ; C. R. Wassgren, Auteur . - 2011 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 07 p. Mots-clés : force;  surface  tension;  flow  (dynamics);  viscosity;  Reynolds  number;  drops;  water Résumé : The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren). DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Relationship between accuracy and number of velocity particles of the finite-difference lattice Boltzmann method in velocity slip simulations / Minoru Watari in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 11 p. Titre : Relationship between accuracy and number of velocity particles of the finite-difference lattice Boltzmann method in velocity slip simulations Type de document : texte imprimé Auteurs : Minoru Watari, Auteur Année de publication : 2011 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : momentum;  flow  (dynamics);  particulate  matter;  computer  simulation;  simulation;  relaxation  (physics);  equilibrium  (physics);  engineering  simulation;  equations;  simulation  results Résumé : Relationship between accuracy and number of velocity particles in velocity slip phenomena was investigated by numerical simulations and theoretical considerations. Two types of 2D models were used: the octagon family and the D2Q9 model. Models have to possess the following four prerequisites to accurately simulate the velocity slip phenomena: (a) equivalency to the Navier–Stokes equations in the N-S flow area, (b) conservation of momentum flow Pxy in the whole area, (c) appropriate relaxation process in the Knudsen layer, and (d) capability to properly express the mass and momentum flows on the wall. Both the octagon family and the D2Q9 model satisfy conditions (a) and (b). However, models with fewer velocity particles do not sufficiently satisfy conditions (c) and (d). The D2Q9 model fails to represent a relaxation process in the Knudsen layer and shows a considerable fluctuation in the velocity slip due to the model’s angle to the wall. To perform an accurate velocity slip simulation, models with sufficient velocity particles, such as the triple octagon model with moving particles of 24 directions, are desirable. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Relationship between accuracy and number of velocity particles of the finite-difference lattice Boltzmann method in velocity slip simulations [texte imprimé] / Minoru Watari, Auteur . - 2011 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 11 p. Mots-clés : momentum;  flow  (dynamics);  particulate  matter;  computer  simulation;  simulation;  relaxation  (physics);  equilibrium  (physics);  engineering  simulation;  equations;  simulation  results Résumé : Relationship between accuracy and number of velocity particles in velocity slip phenomena was investigated by numerical simulations and theoretical considerations. Two types of 2D models were used: the octagon family and the D2Q9 model. Models have to possess the following four prerequisites to accurately simulate the velocity slip phenomena: (a) equivalency to the Navier–Stokes equations in the N-S flow area, (b) conservation of momentum flow Pxy in the whole area, (c) appropriate relaxation process in the Knudsen layer, and (d) capability to properly express the mass and momentum flows on the wall. Both the octagon family and the D2Q9 model satisfy conditions (a) and (b). However, models with fewer velocity particles do not sufficiently satisfy conditions (c) and (d). The D2Q9 model fails to represent a relaxation process in the Knudsen layer and shows a considerable fluctuation in the velocity slip due to the model’s angle to the wall. To perform an accurate velocity slip simulation, models with sufficient velocity particles, such as the triple octagon model with moving particles of 24 directions, are desirable. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

Three-dimensional vortex method for the simulation of bubbly flow / Tomomi Uchiyama in Transactions of the ASME . Journal of fluids engineering, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Titre : Three-dimensional vortex method for the simulation of bubbly flow Type de document : texte imprimé Auteurs : Tomomi Uchiyama, Auteur ; Shoji Matsumura, Auteur Année de publication : 2011 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  simulation;  plumes  (fluid  dynamics);  bubbles;  vorticity;  bubbly  flow;  vortices;  equations Résumé : This study proposes a three-dimensional vortex method for the simulation of bubbly flow. The method discretizes the vorticity field by vortex elements. The behavior of the vortex element and the bubble motion are simultaneously analyzed with the Lagrangian approach to compute the time evolution of the flow. This study also applies the vortex method to the simulation of a bubble plume to demonstrate the validity of the method. In a tank containing water, small hydrogen bubbles are released from the bottom of the tank. The bubbles rise due to the buoyant force and induce the water flow around them. The simulation for the plume at the starting period highlights that the rising bubbles induce large-scale eddies at their top and that the bubbles are entrained into the eddies. The simulation for the developed plume demonstrates that large-scale eddies appear around the rising bubbles and that they cause the meandering behavior of the plume. Such three-dimensional features of the bubble plume are favorably compared with the experimental results, indicating the validity of the proposed vortex method. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...] [article] Three-dimensional vortex method for the simulation of bubbly flow [texte imprimé] / Tomomi Uchiyama, Auteur ; Shoji Matsumura, Auteur . - 2011 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 132 N° 10 (Octobre 2010) . - 08 p. Mots-clés : flow  (dynamics);  simulation;  plumes  (fluid  dynamics);  bubbles;  vorticity;  bubbly  flow;  vortices;  equations Résumé : This study proposes a three-dimensional vortex method for the simulation of bubbly flow. The method discretizes the vorticity field by vortex elements. The behavior of the vortex element and the bubble motion are simultaneously analyzed with the Lagrangian approach to compute the time evolution of the flow. This study also applies the vortex method to the simulation of a bubble plume to demonstrate the validity of the method. In a tank containing water, small hydrogen bubbles are released from the bottom of the tank. The bubbles rise due to the buoyant force and induce the water flow around them. The simulation for the plume at the starting period highlights that the rising bubbles induce large-scale eddies at their top and that the bubbles are entrained into the eddies. The simulation for the developed plume demonstrates that large-scale eddies appear around the rising bubbles and that they cause the meandering behavior of the plume. Such three-dimensional features of the bubble plume are favorably compared with the experimental results, indicating the validity of the proposed vortex method. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27433 [...]

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