Dépouillements

An aerodynamic investigation of an isolated stationary formula 1 wheel assembly / John Axerio-Cilies in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 17 p. Titre : An aerodynamic investigation of an isolated stationary formula 1 wheel assembly Type de document : texte imprimé Auteurs : John Axerio-Cilies, Auteur ; Emin Issakhanian, Auteur ; Juan Jimenez, Auteur Année de publication : 2012 Article en page(s) : 17 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Scale  stationary  Formula  1  Turbulence  modeling  techniques  Reynolds  averaged  Navier-Stokes  (URANS)  equations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel at a Reynolds number of 500,000 was computationally examined in order to assess the accuracy of different turbulence modeling techniques and confirm the existence of large scale flow features. A simplified and replica tire model that includes all brake components was tested to determine the sensitivity of the wake to cross flow within the tire hub along with the flow blockage caused by the brake assembly. The results of steady and unsteady Reynolds averaged Navier-Stokes (URANS) equations and a large eddy simulation (LES) were compared with the experimental data. The LES closure and the RANS closure that accounted for unsteadiness with low eddy viscosity (unsteady komega-SST) matched closest to the experimental data both in point wise velocity comparisons along with location and intensity of the strong counter-rotating vortex pair dominating the far wake of the tire. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] An aerodynamic investigation of an isolated stationary formula 1 wheel assembly [texte imprimé] / John Axerio-Cilies, Auteur ; Emin Issakhanian, Auteur ; Juan Jimenez, Auteur . - 2012 . - 17 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 17 p. Mots-clés : Scale  stationary  Formula  1  Turbulence  modeling  techniques  Reynolds  averaged  Navier-Stokes  (URANS)  equations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The flowfield around a 60% scale stationary Formula 1 tire in contact with the ground in a closed wind tunnel at a Reynolds number of 500,000 was computationally examined in order to assess the accuracy of different turbulence modeling techniques and confirm the existence of large scale flow features. A simplified and replica tire model that includes all brake components was tested to determine the sensitivity of the wake to cross flow within the tire hub along with the flow blockage caused by the brake assembly. The results of steady and unsteady Reynolds averaged Navier-Stokes (URANS) equations and a large eddy simulation (LES) were compared with the experimental data. The LES closure and the RANS closure that accounted for unsteadiness with low eddy viscosity (unsteady komega-SST) matched closest to the experimental data both in point wise velocity comparisons along with location and intensity of the strong counter-rotating vortex pair dominating the far wake of the tire. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Low pressure turbine relaminarization bubble characterization using Massively-parallel large Eddy simulations / Shriram Jagannathan in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 13 p. Titre : Low pressure turbine relaminarization bubble characterization using Massively-parallel large Eddy simulations Type de document : texte imprimé Auteurs : Shriram Jagannathan, Auteur ; Markus Schwänen, Auteur ; Andrew Duggleby, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Low  pressure  turbine  Large-eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The separation and reattachment of suction surface boundary layer in a low pressure turbine is characterized using large-eddy simulation at Ress = 69000 based on inlet velocity and suction surface length. Favorable comparisons are drawn with experiments using a high pass filtered Smagorinsky model for sub-grid scales. The onset of time mean separation is at s/so = 0.61 and reattachment at s/so = 0.81, extending over 20% of the suction surface. The boundary layer is convectively unstable with a maximum reverse flow velocity of about 13% of freestream. The breakdown to turbulence occurs over a very short distance of suction surface and is followed by reattachment. Turbulence near the bubble is further characterized using anisotropy invariant mapping and time orthogonal decomposition diagnostics. Particularly the vortex shedding and shear layer flapping phenomena are addressed. On the suction side, dominant hairpin structures near the transitional and turbulent flow regime are observed. The hairpin vortices are carried by the freestream even downstream of the trailing edge of the blade with a possibility of reaching the next stage. Longitudinal streaks that evolve from the breakdown of hairpin vortices formed near the leading edge are observed on the pressure surface. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Low pressure turbine relaminarization bubble characterization using Massively-parallel large Eddy simulations [texte imprimé] / Shriram Jagannathan, Auteur ; Markus Schwänen, Auteur ; Andrew Duggleby, Auteur . - 2012 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 13 p. Mots-clés : Low  pressure  turbine  Large-eddy  simulation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The separation and reattachment of suction surface boundary layer in a low pressure turbine is characterized using large-eddy simulation at Ress = 69000 based on inlet velocity and suction surface length. Favorable comparisons are drawn with experiments using a high pass filtered Smagorinsky model for sub-grid scales. The onset of time mean separation is at s/so = 0.61 and reattachment at s/so = 0.81, extending over 20% of the suction surface. The boundary layer is convectively unstable with a maximum reverse flow velocity of about 13% of freestream. The breakdown to turbulence occurs over a very short distance of suction surface and is followed by reattachment. Turbulence near the bubble is further characterized using anisotropy invariant mapping and time orthogonal decomposition diagnostics. Particularly the vortex shedding and shear layer flapping phenomena are addressed. On the suction side, dominant hairpin structures near the transitional and turbulent flow regime are observed. The hairpin vortices are carried by the freestream even downstream of the trailing edge of the blade with a possibility of reaching the next stage. Longitudinal streaks that evolve from the breakdown of hairpin vortices formed near the leading edge are observed on the pressure surface. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Computational fluid dynamic studies of vortex amplifier design for the nuclear industry / Francis, J. in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 12 p. Titre : Computational fluid dynamic studies of vortex amplifier design for the nuclear industry : II. transient conditions Type de document : texte imprimé Auteurs : Francis, J., Auteur ; Birch, M. J., Auteur ; Parker, D., Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Computational  fluid  dynamics  (CFD)  techniques  Vortex  amplifier  (VXA)  Nuclear  industry Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this paper computational fluid dynamics (CFD) techniques have been used to investigate the effect of changes to the geometry of a vortex amplifier (VXA) in the context of glovebox operations in the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established VXA design was reduced in scale. The study simulates the transient aspects of two effects: back-flow into the glovebox through the VXA supply ports, and the precessing vortex core in the amplifier outlet. A temporal convergence error study indicates that there is little to be gained from reducing the time step duration below 0.1 ms. Based upon this criterion, the results of the simulation show that the percentage imbalance in the domain was well below the required figure of 1%, and imbalances for momentum in all three axes were all below measurable values. Furthermore, there was no conclusive evidence of periodicity in the flow perturbations at the glovebox boundary, although good evidence of periodicity in the device itself and in the outlet pipe was seen. Under all conditions the modified geometry performed better than the control geometry with regard to aggregate reversed supply flow. The control geometry exhibited aggregate nonaxisymmetric supply port back-flow for almost all of the simulated period, unlike the alternative geometry for which the flow through the supply ports was positive, although still nonaxisymmetric, for most of the period. The simulations show how transient flow structures in the supply ports can cause flow to be reversed in individual ports, whereas aggregate flow through the device remains positive. Similar to the supply ports, flow through the outlet of the VXA under high swirl conditions is also nonaxisymmetric. A time-dependent reverse flow region was observed in both the outlet and the diffuser. It is possible that small vortices in the outlet, coupled with the larger vortex in the chamber, are responsible for the oscillations, which cause the shift in the axis of the precessing vortex core (and ultimately in the variations of mass flow in the individual supply ports). Field trials show that the modified geometry reduces the back-flow of oxygen into the glovebox by as much as 78%. At purge rates of 0.65 m3/h the modified geometry was found to be less effective, the rate of leakage from the VXA increasing by 16–20%. Despite this reduced performance, leakage from the modified geometry was still 63% less than the control geometry. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Computational fluid dynamic studies of vortex amplifier design for the nuclear industry : II. transient conditions [texte imprimé] / Francis, J., Auteur ; Birch, M. J., Auteur ; Parker, D., Auteur . - 2012 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 12 p. Mots-clés : Computational  fluid  dynamics  (CFD)  techniques  Vortex  amplifier  (VXA)  Nuclear  industry Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In this paper computational fluid dynamics (CFD) techniques have been used to investigate the effect of changes to the geometry of a vortex amplifier (VXA) in the context of glovebox operations in the nuclear industry. These investigations were required because of anomalous behavior identified when, for operational reasons, a long-established VXA design was reduced in scale. The study simulates the transient aspects of two effects: back-flow into the glovebox through the VXA supply ports, and the precessing vortex core in the amplifier outlet. A temporal convergence error study indicates that there is little to be gained from reducing the time step duration below 0.1 ms. Based upon this criterion, the results of the simulation show that the percentage imbalance in the domain was well below the required figure of 1%, and imbalances for momentum in all three axes were all below measurable values. Furthermore, there was no conclusive evidence of periodicity in the flow perturbations at the glovebox boundary, although good evidence of periodicity in the device itself and in the outlet pipe was seen. Under all conditions the modified geometry performed better than the control geometry with regard to aggregate reversed supply flow. The control geometry exhibited aggregate nonaxisymmetric supply port back-flow for almost all of the simulated period, unlike the alternative geometry for which the flow through the supply ports was positive, although still nonaxisymmetric, for most of the period. The simulations show how transient flow structures in the supply ports can cause flow to be reversed in individual ports, whereas aggregate flow through the device remains positive. Similar to the supply ports, flow through the outlet of the VXA under high swirl conditions is also nonaxisymmetric. A time-dependent reverse flow region was observed in both the outlet and the diffuser. It is possible that small vortices in the outlet, coupled with the larger vortex in the chamber, are responsible for the oscillations, which cause the shift in the axis of the precessing vortex core (and ultimately in the variations of mass flow in the individual supply ports). Field trials show that the modified geometry reduces the back-flow of oxygen into the glovebox by as much as 78%. At purge rates of 0.65 m3/h the modified geometry was found to be less effective, the rate of leakage from the VXA increasing by 16–20%. Despite this reduced performance, leakage from the modified geometry was still 63% less than the control geometry. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Computational fluid dynamics analysis of a hydrokinetic turbine based on oscillating hydrofoils / Thomas Kinsey in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 16 p. Titre : Computational fluid dynamics analysis of a hydrokinetic turbine based on oscillating hydrofoils Type de document : texte imprimé Auteurs : Thomas Kinsey, Auteur ; Guy Dumas, Auteur Année de publication : 2012 Article en page(s) : 16 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Hydrokinetic  turbine  Oscillating  hydrofoils  URANS  numerical  simulations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The performance of a new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is investigated using URANS numerical simulations. The numerical predictions are compared with experimental data from a 2 kW prototype, composed of two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. 3D computational fluid dynamics (CFD) predictions are found to compare favorably with experimental data especially for the case of a single-hydrofoil turbine. The validity of approximating the actual arc-circle trajectory of each hydrofoil by an idealized vertical plunging motion is also addressed by numerical simulations. Furthermore, a sensitivity study of the turbine's performance in relation to fluctuating operating conditions is performed by feeding the simulations with the actual time-varying experimentally recorded conditions. It is found that cycle-averaged values, as the power-extraction efficiency, are little sensitive to perturbations in the foil kinematics and upstream velocity. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Computational fluid dynamics analysis of a hydrokinetic turbine based on oscillating hydrofoils [texte imprimé] / Thomas Kinsey, Auteur ; Guy Dumas, Auteur . - 2012 . - 16 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 16 p. Mots-clés : Hydrokinetic  turbine  Oscillating  hydrofoils  URANS  numerical  simulations Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The performance of a new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is investigated using URANS numerical simulations. The numerical predictions are compared with experimental data from a 2 kW prototype, composed of two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. 3D computational fluid dynamics (CFD) predictions are found to compare favorably with experimental data especially for the case of a single-hydrofoil turbine. The validity of approximating the actual arc-circle trajectory of each hydrofoil by an idealized vertical plunging motion is also addressed by numerical simulations. Furthermore, a sensitivity study of the turbine's performance in relation to fluctuating operating conditions is performed by feeding the simulations with the actual time-varying experimentally recorded conditions. It is found that cycle-averaged values, as the power-extraction efficiency, are little sensitive to perturbations in the foil kinematics and upstream velocity. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Analysis and simulation of a micro hydrocyclone device for particle liquid separation / P. Bagdi in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 09 p. Titre : Analysis and simulation of a micro hydrocyclone device for particle liquid separation Type de document : texte imprimé Auteurs : P. Bagdi, Auteur ; P. Bhardwaj, Auteur ; A. K. Sen, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Micro  hydrocyclone  Three-dimensional  simulation  Bradley  model  Particle  liquid  separation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a three-dimensional simulation of a micro hydrocyclone for the separation of micron sized particles from liquid in a particulated sample. A theoretical analysis is performed to demonstrate the working principle of the micro hydrocyclone and develop design models. The geometry of the proposed device is designed based on the Bradley model, since it offers a lower cut-size, thus making it suitable for microfluidics applications. The operational parameters of the hydrocyclone are derived from a dimensional group model. The particle separation process inside the micro hydrocyclone is simulated by solving fluid flows using Navier-Stokes equations and particle dynamics using the Lagrangian approach in a Eulerean fluid. First, the numerical model is validated by comparing the simulation results with the experimental results for a macroscale hydrocyclone reported in the literature. Then, the micro hydrocyclone is simulated and the simulation results are presented and discussed in the context of the functioning of the micro hydrocyclone. Finally, the effects of inlet velocity, vortex finder diameter, particle size, and density on the separation efficiency are investigated. The proposed device can be easily integrated with micro-environments; thus, is suitable for lab-on-chip and microsystems development. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Analysis and simulation of a micro hydrocyclone device for particle liquid separation [texte imprimé] / P. Bagdi, Auteur ; P. Bhardwaj, Auteur ; A. K. Sen, Auteur . - 2012 . - 09 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 09 p. Mots-clés : Micro  hydrocyclone  Three-dimensional  simulation  Bradley  model  Particle  liquid  separation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a three-dimensional simulation of a micro hydrocyclone for the separation of micron sized particles from liquid in a particulated sample. A theoretical analysis is performed to demonstrate the working principle of the micro hydrocyclone and develop design models. The geometry of the proposed device is designed based on the Bradley model, since it offers a lower cut-size, thus making it suitable for microfluidics applications. The operational parameters of the hydrocyclone are derived from a dimensional group model. The particle separation process inside the micro hydrocyclone is simulated by solving fluid flows using Navier-Stokes equations and particle dynamics using the Lagrangian approach in a Eulerean fluid. First, the numerical model is validated by comparing the simulation results with the experimental results for a macroscale hydrocyclone reported in the literature. Then, the micro hydrocyclone is simulated and the simulation results are presented and discussed in the context of the functioning of the micro hydrocyclone. Finally, the effects of inlet velocity, vortex finder diameter, particle size, and density on the separation efficiency are investigated. The proposed device can be easily integrated with micro-environments; thus, is suitable for lab-on-chip and microsystems development. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Measurement of effective bulk modulus for hydraulic oil at low pressure / Sunghun Kim in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 10 p. Titre : Measurement of effective bulk modulus for hydraulic oil at low pressure Type de document : texte imprimé Auteurs : Sunghun Kim, Auteur ; Hubertus Murrenhoff, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Oil  properties  Hydraulic  components  Bulk  modulus  Mass-change  Volume-change  Sound-speed  method Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Oil properties are very important input parameters for the simulation of hydraulic components. Precise values of effective bulk modulus at low pressures are especially required to improve the simulation accuracy of the pumps suction side or of cavitation in pumps or valves. So far, theoretical equations to compute the effective bulk modulus of hydraulic oil have not been experimentally verified, and only poor measured data are available to calculate the effective bulk modulus at low pressure. Therefore in this paper, the theoretical equation was verified for effective bulk moduli based on measurements of pressure change as a function of volume change at low pressures, varying temperature, entrained air content, and type of state change. Furthermore, the comparison of effective bulk moduli calculated with three different methods (mass-change, volume-change, and sound-speed method) shows that the effective bulk modulus can be calculated well from the measurement results of all three methods. The calculated effective bulk moduli values show little variation among the methods. Additionally, the release pressure of dissolved air in oil and the change of the polytropic gas constant depending on the speed of volume change rate were identified in this study. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Measurement of effective bulk modulus for hydraulic oil at low pressure [texte imprimé] / Sunghun Kim, Auteur ; Hubertus Murrenhoff, Auteur . - 2012 . - 10 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 10 p. Mots-clés : Oil  properties  Hydraulic  components  Bulk  modulus  Mass-change  Volume-change  Sound-speed  method Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Oil properties are very important input parameters for the simulation of hydraulic components. Precise values of effective bulk modulus at low pressures are especially required to improve the simulation accuracy of the pumps suction side or of cavitation in pumps or valves. So far, theoretical equations to compute the effective bulk modulus of hydraulic oil have not been experimentally verified, and only poor measured data are available to calculate the effective bulk modulus at low pressure. Therefore in this paper, the theoretical equation was verified for effective bulk moduli based on measurements of pressure change as a function of volume change at low pressures, varying temperature, entrained air content, and type of state change. Furthermore, the comparison of effective bulk moduli calculated with three different methods (mass-change, volume-change, and sound-speed method) shows that the effective bulk modulus can be calculated well from the measurement results of all three methods. The calculated effective bulk moduli values show little variation among the methods. Additionally, the release pressure of dissolved air in oil and the change of the polytropic gas constant depending on the speed of volume change rate were identified in this study. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Continuous deposition of a liquid thread onto a moving substrate / S. Ubal in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 17 p. Titre : Continuous deposition of a liquid thread onto a moving substrate : numerical analysis and comparison with experiments Type de document : texte imprimé Auteurs : S. Ubal, Auteur ; B. Xu, Auteur ; B. Derby, Auteur Année de publication : 2012 Article en page(s) : 17 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Line  of  liquid  Moving  flat  solid  substrate  Numerical  analysis  Substrate-nozzle  gap  Flow  rate  parameter  space Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The printing of a thin line of liquid onto a moving flat solid substrate was studied numerically. For a fixed value of the Capillary number, the window of steady state deposition was explored in terms of the substrate-nozzle gap and flow rate parameter space for two nozzle configurations: a nozzle pointing vertically at the plate and a nozzle slightly tilted towards the substrate motion direction. A lower limit for the flow rate was found, below which no steady state solutions could be obtained. This minimum flow rate increases as the nozzle stand-off and the nozzle tilting do. Solutions near this lower flow rate boundary were stable under a flow rate perturbation. The process was also studied experimentally and the measurements were compared with the corresponding numerical simulations, giving a fairly good agreement, except in the advancing front deposition region. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Continuous deposition of a liquid thread onto a moving substrate : numerical analysis and comparison with experiments [texte imprimé] / S. Ubal, Auteur ; B. Xu, Auteur ; B. Derby, Auteur . - 2012 . - 17 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 17 p. Mots-clés : Line  of  liquid  Moving  flat  solid  substrate  Numerical  analysis  Substrate-nozzle  gap  Flow  rate  parameter  space Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The printing of a thin line of liquid onto a moving flat solid substrate was studied numerically. For a fixed value of the Capillary number, the window of steady state deposition was explored in terms of the substrate-nozzle gap and flow rate parameter space for two nozzle configurations: a nozzle pointing vertically at the plate and a nozzle slightly tilted towards the substrate motion direction. A lower limit for the flow rate was found, below which no steady state solutions could be obtained. This minimum flow rate increases as the nozzle stand-off and the nozzle tilting do. Solutions near this lower flow rate boundary were stable under a flow rate perturbation. The process was also studied experimentally and the measurements were compared with the corresponding numerical simulations, giving a fairly good agreement, except in the advancing front deposition region. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Influence of flow coefficient and flow structure on rotational cavitation in inducer / Naoki Tani in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 13 p. Titre : Influence of flow coefficient and flow structure on rotational cavitation in inducer Type de document : texte imprimé Auteurs : Naoki Tani, Auteur ; Nobuhiro Yamanishi, Auteur ; Yoshinobu Tsujimoto, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Cavitation  instability  Inducer  and  unsteady  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Cavitation instability is a major vibration source in turbopump inducers, and its prevention is a critical design problem in rocket-engine development. As reported by Kang et al., (2009, “Cause of Cavitation Instabilities in Three Dimensional Inducer,” Int. J. Fluid Mach. Syst., 2(3), pp. 206–214), the flow coefficient plays an important role in the onset of cavitation instabilities such as rotating and asymmetric cavitation. At high flow rates, various cavitation instabilities occur; on the other hand, as the flow coefficient is reduced, these cavitation instabilities either become absent or may change in character. The purpose of the present study is to investigate the relationship between rotating cavitation and flow coefficient through numerical simulations using the Combustion Research Unstructured Navier-stokes solver with CHemistry (CRUNCH) computational fluid dynamics (CFD) code (Ahuja et al., 2001, “Simulations of Cavitating Flows Using Hybrid Unstructured Meshes,” J. Fluids Eng.Trans ASME, 123(2), pp. 331–340), and to investigate the internal flow. As a first step, the interaction between the tip vortex and inducer blade was investigated through steady-state simulations. The tip vortex was identified by a vortex detection variable, i.e., the Q-function, a second invariant of the velocity tensor, and the distance between the blade and Q-function peak was measured. For a better understanding of cavitation instabilities, unsteady simulations were also performed for two different flow coefficients. The internal flow was carefully investigated, and the relation between cavity collapse/growth and the change in angle of attack was evaluated. The tip-vortex interaction is not a primary cause of unsteady cavitation, but the negative flow divergence caused by cavity collapse has a great influence on the flow angle. Moreover, changes in flow angle also introduce backflow from the tip clearance; these two factors are primary causes of cavitation instability. When the flow coefficient is large, the backflow is weak, and the interaction with the cavity collapse is strong. In contrast, as the flow coefficient decreases, stronger backflow occurs, and the interaction between backflow, cavity collapse, and flow angle weakens. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Influence of flow coefficient and flow structure on rotational cavitation in inducer [texte imprimé] / Naoki Tani, Auteur ; Nobuhiro Yamanishi, Auteur ; Yoshinobu Tsujimoto, Auteur . - 2012 . - 13 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 13 p. Mots-clés : Cavitation  instability  Inducer  and  unsteady  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Cavitation instability is a major vibration source in turbopump inducers, and its prevention is a critical design problem in rocket-engine development. As reported by Kang et al., (2009, “Cause of Cavitation Instabilities in Three Dimensional Inducer,” Int. J. Fluid Mach. Syst., 2(3), pp. 206–214), the flow coefficient plays an important role in the onset of cavitation instabilities such as rotating and asymmetric cavitation. At high flow rates, various cavitation instabilities occur; on the other hand, as the flow coefficient is reduced, these cavitation instabilities either become absent or may change in character. The purpose of the present study is to investigate the relationship between rotating cavitation and flow coefficient through numerical simulations using the Combustion Research Unstructured Navier-stokes solver with CHemistry (CRUNCH) computational fluid dynamics (CFD) code (Ahuja et al., 2001, “Simulations of Cavitating Flows Using Hybrid Unstructured Meshes,” J. Fluids Eng.Trans ASME, 123(2), pp. 331–340), and to investigate the internal flow. As a first step, the interaction between the tip vortex and inducer blade was investigated through steady-state simulations. The tip vortex was identified by a vortex detection variable, i.e., the Q-function, a second invariant of the velocity tensor, and the distance between the blade and Q-function peak was measured. For a better understanding of cavitation instabilities, unsteady simulations were also performed for two different flow coefficients. The internal flow was carefully investigated, and the relation between cavity collapse/growth and the change in angle of attack was evaluated. The tip-vortex interaction is not a primary cause of unsteady cavitation, but the negative flow divergence caused by cavity collapse has a great influence on the flow angle. Moreover, changes in flow angle also introduce backflow from the tip clearance; these two factors are primary causes of cavitation instability. When the flow coefficient is large, the backflow is weak, and the interaction with the cavity collapse is strong. In contrast, as the flow coefficient decreases, stronger backflow occurs, and the interaction between backflow, cavity collapse, and flow angle weakens. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Numerical simulation of low specific speed american petroleum institute pumps in part-load operation and comparison with test rig results / Helmut Benigni in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 09 p. Titre : Numerical simulation of low specific speed american petroleum institute pumps in part-load operation and comparison with test rig results Type de document : texte imprimé Auteurs : Helmut Benigni, Auteur ; Helmut Jaberg, Auteur ; Hoi Yeung, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Low  specific  speed  centrifugal  pump  Numerical  simulation  Deep  part-load  operation  Computational  fluid  dynamics  (CFD)  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A low specific speed centrifugal pump is investigated by means of numerical simulation, especially in deep part-load operation. The 3D computational fluid dynamics (CFD) model includes the front and back cavities, a 360 deg impeller and a double volute, as well as suction and pressure pipes. Stationary calculations show a strong clocking effect and lead to an overprediction of the head close to zero flow rate. A one-dimensional estimation of the head at the closed valve operation point is compared to the 3D CFD results and also a series of test rig results. In a second step, the whole head curve is calculated by a fully transient calculation using the shear stress transport–scale-adaptive simulation (SST–SAS) turbulence model. For the net positive suction head (NPSH) estimation, the histogram method is applied providing good correlation to the test rig measurement—as do the head curve and the efficiency. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Numerical simulation of low specific speed american petroleum institute pumps in part-load operation and comparison with test rig results [texte imprimé] / Helmut Benigni, Auteur ; Helmut Jaberg, Auteur ; Hoi Yeung, Auteur . - 2012 . - 09 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 09 p. Mots-clés : Low  specific  speed  centrifugal  pump  Numerical  simulation  Deep  part-load  operation  Computational  fluid  dynamics  (CFD)  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A low specific speed centrifugal pump is investigated by means of numerical simulation, especially in deep part-load operation. The 3D computational fluid dynamics (CFD) model includes the front and back cavities, a 360 deg impeller and a double volute, as well as suction and pressure pipes. Stationary calculations show a strong clocking effect and lead to an overprediction of the head close to zero flow rate. A one-dimensional estimation of the head at the closed valve operation point is compared to the 3D CFD results and also a series of test rig results. In a second step, the whole head curve is calculated by a fully transient calculation using the shear stress transport–scale-adaptive simulation (SST–SAS) turbulence model. For the net positive suction head (NPSH) estimation, the histogram method is applied providing good correlation to the test rig measurement—as do the head curve and the efficiency. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

A statistical method on meridional profiles of centrifugal pumps / Zou, Jun in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 05 p. Titre : A statistical method on meridional profiles of centrifugal pumps Type de document : texte imprimé Auteurs : Zou, Jun, Auteur ; Pengfei, Wang, Auteur ; Ruan, Xiaodong, Auteur Année de publication : 2012 Article en page(s) : 05 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Meridional  profile  Medial  axis  transform  (MAT)  Statistics  Pump  Whole Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A method based on the medial axis transform (MAT) theory is presented to explore the laws of meridional profiles versus specific speeds for centrifugal pumps. Through extracting each pump's MAT and transforming to two newly introduced variables, striking features emerge. Based on these features, statistics are carried out on the two variables versus specific speeds. A series of pumps is used to verify this method. According to the laws gained from the statistical results, the meridional profile at any specific speed within this series of pumps can be directly drawn through calculations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] A statistical method on meridional profiles of centrifugal pumps [texte imprimé] / Zou, Jun, Auteur ; Pengfei, Wang, Auteur ; Ruan, Xiaodong, Auteur . - 2012 . - 05 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 05 p. Mots-clés : Meridional  profile  Medial  axis  transform  (MAT)  Statistics  Pump  Whole Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : A method based on the medial axis transform (MAT) theory is presented to explore the laws of meridional profiles versus specific speeds for centrifugal pumps. Through extracting each pump's MAT and transforming to two newly introduced variables, striking features emerge. Based on these features, statistics are carried out on the two variables versus specific speeds. A series of pumps is used to verify this method. According to the laws gained from the statistical results, the meridional profile at any specific speed within this series of pumps can be directly drawn through calculations. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

Secondary instabilities in incompressible axisymmetric boundary layers / N. Vinod in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 04 p. Titre : Secondary instabilities in incompressible axisymmetric boundary layers : effect of transverse curvature Type de document : texte imprimé Auteurs : N. Vinod, Auteur ; Rama Govindarajan, Auteur Année de publication : 2012 Article en page(s) : 04 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Axial  flow  Incompressible  boundary  layer  Cylinder  Laminar  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The secondary instability of the incompressible boundary layer in the axial flow past a cylinder is studied. The laminar flow is shown to be always stable at high transverse curvatures to secondary disturbances. Because the primary mode is stable as well, (Tutty et al., 2002, “Boundary Layer Flow on a Long Thin Cylinder,”. Phys. Fluids, 14(2), pp. 628–637), this implies that the boundary layer on a thin long cylinder may undergo transition to turbulence by means very different from that on a flat plate. The azimuthal wavenumber of the least stable secondary modes (m±) are related to that of the primary (n) by m+ = 2n and m− = −n. The base flow is shown to be inviscidly stable at any curvature. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...] [article] Secondary instabilities in incompressible axisymmetric boundary layers : effect of transverse curvature [texte imprimé] / N. Vinod, Auteur ; Rama Govindarajan, Auteur . - 2012 . - 04 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 2 (Fevrier 2012) . - 04 p. Mots-clés : Axial  flow  Incompressible  boundary  layer  Cylinder  Laminar  flow Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The secondary instability of the incompressible boundary layer in the axial flow past a cylinder is studied. The laminar flow is shown to be always stable at high transverse curvatures to secondary disturbances. Because the primary mode is stable as well, (Tutty et al., 2002, “Boundary Layer Flow on a Long Thin Cylinder,”. Phys. Fluids, 14(2), pp. 628–637), this implies that the boundary layer on a thin long cylinder may undergo transition to turbulence by means very different from that on a flat plate. The azimuthal wavenumber of the least stable secondary modes (m±) are related to that of the primary (n) by m+ = 2n and m− = −n. The base flow is shown to be inviscidly stable at any curvature. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000002 [...]

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