Dépouillements

An experimental and analytical investigation of rectangular synthetic jets / Gopi Krishnan in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 11 p. Titre : An experimental and analytical investigation of rectangular synthetic jets Type de document : texte imprimé Auteurs : Gopi Krishnan, Auteur ; Kamran Mohseni, Auteur Année de publication : 2010 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  jets;  actuators;  turbulence;  deflection;  membranes;  modeling;  viscosity;  eddies  (fluid  dynamics);  diaphragms  (structural);  wire Résumé : In this paper the flow field of a rectangular synthetic jet driven by a piezoelectric membrane issuing into a quiescent environment is studied. The similarities exhibited by synthetic and continuous turbulent jets lead to the hypothesis that a rectangular synthetic jet within a limited region downstream of the orifice be modeled using similarity analysis just as a continuous planar jet. Accordingly, the jet is modeled using the classic two-dimensional solution to a continuous jet, where the virtual viscosity coefficient of the continuous turbulent jet is replaced with that measured for a synthetic jet. The virtual viscosity of the synthetic jet at a particular axial location is related to the spreading rate and velocity decay rate of the jet. Hot-wire anemometry is used to characterize the flow downstream of the orifice. The flow field of rectangular synthetic jets is thought to consist of four regions as distinguished by the centerline velocity decay. The regions are the developing, the quasi-two-dimensional, the transitional, and the axisymmetric regions. It is in the quasi-two-dimensional region that the planar model applies, and where indeed the jet exhibits self-similar behavior as distinguished by the collapse of the lateral time average velocity profiles when scaled. Furthermore, within this region the spanwise velocity profiles display a saddleback profile that is attributed to the secondary flow generated at the smaller edges of the rectangular orifice. The scaled spreading and decay rates are seen to increase with stroke ratio and be independent of Reynolds number. However, the geometry of the actuator is seen to additionally affect the external characteristics of the jet. The eddy viscosities of the synthetic jets under consideration are shown to be larger than equivalent continuous turbulent jets. This enhanced eddy viscosity is attributed to the additional mixing brought about by the introduction of the periodic vortical structures in synthetic jets and their ensuing break down and transition to turbulence. Further, a semi-empirical modeling approach is proposed, the final objective of which is to obtain a functional relationship between the parameters that describe the external flow field of the synthetic jet and the input operational parameters to the system. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] An experimental and analytical investigation of rectangular synthetic jets [texte imprimé] / Gopi Krishnan, Auteur ; Kamran Mohseni, Auteur . - 2010 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 11 p. Mots-clés : flow  (dynamics);  jets;  actuators;  turbulence;  deflection;  membranes;  modeling;  viscosity;  eddies  (fluid  dynamics);  diaphragms  (structural);  wire Résumé : In this paper the flow field of a rectangular synthetic jet driven by a piezoelectric membrane issuing into a quiescent environment is studied. The similarities exhibited by synthetic and continuous turbulent jets lead to the hypothesis that a rectangular synthetic jet within a limited region downstream of the orifice be modeled using similarity analysis just as a continuous planar jet. Accordingly, the jet is modeled using the classic two-dimensional solution to a continuous jet, where the virtual viscosity coefficient of the continuous turbulent jet is replaced with that measured for a synthetic jet. The virtual viscosity of the synthetic jet at a particular axial location is related to the spreading rate and velocity decay rate of the jet. Hot-wire anemometry is used to characterize the flow downstream of the orifice. The flow field of rectangular synthetic jets is thought to consist of four regions as distinguished by the centerline velocity decay. The regions are the developing, the quasi-two-dimensional, the transitional, and the axisymmetric regions. It is in the quasi-two-dimensional region that the planar model applies, and where indeed the jet exhibits self-similar behavior as distinguished by the collapse of the lateral time average velocity profiles when scaled. Furthermore, within this region the spanwise velocity profiles display a saddleback profile that is attributed to the secondary flow generated at the smaller edges of the rectangular orifice. The scaled spreading and decay rates are seen to increase with stroke ratio and be independent of Reynolds number. However, the geometry of the actuator is seen to additionally affect the external characteristics of the jet. The eddy viscosities of the synthetic jets under consideration are shown to be larger than equivalent continuous turbulent jets. This enhanced eddy viscosity is attributed to the additional mixing brought about by the introduction of the periodic vortical structures in synthetic jets and their ensuing break down and transition to turbulence. Further, a semi-empirical modeling approach is proposed, the final objective of which is to obtain a functional relationship between the parameters that describe the external flow field of the synthetic jet and the input operational parameters to the system. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Flow separation control on a race car wing with vortex generators in ground effect / Yuichi Kuya in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Titre : Flow separation control on a race car wing with vortex generators in ground effect Type de document : texte imprimé Auteurs : Yuichi Kuya, Auteur ; Kenji Takeda, Auteur ; Xin Zhang, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  separation  control;  vortex  generators Résumé : Flow separation control using vortex generators on an inverted wing in ground effect is experimentally investigated, and its performance is characterized in terms of forces and pressure distributions over a range of incidence and ride height. Counter-rotating and co-rotating rectangular-vane type vortex generators are tested on the suction surface of the wing. The effect of device height and spacing is investigated. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators on the wing deliver 23% and 10% improvements in the maximum downforce, respectively, compared with the clean wing, at an incidence of one degree, and delay the onset of the downforce reduction phenomenon. The counter-rotating sub-boundary layer vortex generators exhibit up to 26% improvement in downforce and 10% improvement in aerodynamic efficiency at low ride heights. Chordwise pressure measurement confirms that both counter-rotating vortex generator configurations suppress flow separation, while the co-rotating vortex generators exhibit negligible effectiveness. This work shows that a use of vortex generators, notably of the counter-rotating sub-boundary layer vortex generator type, can be effective at controlling flow separation, with a resultant improvement in downforce for relatively low drag penalty. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Flow separation control on a race car wing with vortex generators in ground effect [texte imprimé] / Yuichi Kuya, Auteur ; Kenji Takeda, Auteur ; Xin Zhang, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Mots-clés : flow  separation  control;  vortex  generators Résumé : Flow separation control using vortex generators on an inverted wing in ground effect is experimentally investigated, and its performance is characterized in terms of forces and pressure distributions over a range of incidence and ride height. Counter-rotating and co-rotating rectangular-vane type vortex generators are tested on the suction surface of the wing. The effect of device height and spacing is investigated. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators on the wing deliver 23% and 10% improvements in the maximum downforce, respectively, compared with the clean wing, at an incidence of one degree, and delay the onset of the downforce reduction phenomenon. The counter-rotating sub-boundary layer vortex generators exhibit up to 26% improvement in downforce and 10% improvement in aerodynamic efficiency at low ride heights. Chordwise pressure measurement confirms that both counter-rotating vortex generator configurations suppress flow separation, while the co-rotating vortex generators exhibit negligible effectiveness. This work shows that a use of vortex generators, notably of the counter-rotating sub-boundary layer vortex generator type, can be effective at controlling flow separation, with a resultant improvement in downforce for relatively low drag penalty. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Flow physics of a race car wing with vortex generators in ground effect / Yuichi Kuya in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 09 p. Titre : Flow physics of a race car wing with vortex generators in ground effect Type de document : texte imprimé Auteurs : Yuichi Kuya, Auteur ; Kenji Takeda, Auteur ; Xin Zhang, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : suction;  flow  visualization;  wakes;  vortices;  flow  (dynamics);  generators;  wings;  separation  (technology);  flow  separation;  physics Résumé : This paper experimentally investigates the use of vortex generators for separation control on an inverted wing in ground effect using off-surface flow measurements and surface flow visualization. A typical racing car wing geometry is tested in a rolling road wind tunnel over a wide range of incidences and ride heights. Rectangular vane type of sub-boundary layer and large-scale vortex generators are attached to the suction surface, comprising counter-rotating and corotating configurations. The effects of both device height and spacing are examined. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators suppress the flow separation at the center of each device pair, while the counter-rotating large-scale vortex generators induce horseshoe vortices between each device where the flow is separated. The corotating sub-boundary layer vortex generators tested here show little evidence of separation control. Increasing the spacing of the counter-rotating sublayer vortex generator induces significant horseshoe vortices, comparable to those seen in the counter-rotating large-scale vortex generator case. Wake surveys show significant spanwise variance behind the wing equipped with the counter-rotating large-scale vortex generators, while the counter-rotating sub-boundary layer vortex generator configuration shows a relatively small variance in the spanwise direction. The flow characteristics revealed here suggest that counter-rotating sub-boundary layer vortex generators can provide effective separation control for race car wings in ground effect. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Flow physics of a race car wing with vortex generators in ground effect [texte imprimé] / Yuichi Kuya, Auteur ; Kenji Takeda, Auteur ; Xin Zhang, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 09 p. Mots-clés : suction;  flow  visualization;  wakes;  vortices;  flow  (dynamics);  generators;  wings;  separation  (technology);  flow  separation;  physics Résumé : This paper experimentally investigates the use of vortex generators for separation control on an inverted wing in ground effect using off-surface flow measurements and surface flow visualization. A typical racing car wing geometry is tested in a rolling road wind tunnel over a wide range of incidences and ride heights. Rectangular vane type of sub-boundary layer and large-scale vortex generators are attached to the suction surface, comprising counter-rotating and corotating configurations. The effects of both device height and spacing are examined. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators suppress the flow separation at the center of each device pair, while the counter-rotating large-scale vortex generators induce horseshoe vortices between each device where the flow is separated. The corotating sub-boundary layer vortex generators tested here show little evidence of separation control. Increasing the spacing of the counter-rotating sublayer vortex generator induces significant horseshoe vortices, comparable to those seen in the counter-rotating large-scale vortex generator case. Wake surveys show significant spanwise variance behind the wing equipped with the counter-rotating large-scale vortex generators, while the counter-rotating sub-boundary layer vortex generator configuration shows a relatively small variance in the spanwise direction. The flow characteristics revealed here suggest that counter-rotating sub-boundary layer vortex generators can provide effective separation control for race car wings in ground effect. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Pulsating flow for mixing intensification in a twisted curved pipe / B. Timité in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 10 p. Titre : Pulsating flow for mixing intensification in a twisted curved pipe Type de document : texte imprimé Auteurs : B. Timité, Auteur ; M. Jarrahi, Auteur ; C. Castelain, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  pulsatile  flow;  pipes Résumé : This work concerns the manipulation of a twisted curved-pipe flow for mixing enhancement. Previous works have shown that geometrical perturbations to a curved-pipe flow can increase mixing and heat transfer by chaotic advection. In this work the flow entering the twisted pipe undergoes a pulsatile motion. The flow is studied experimentally and numerically. The numerical study is carried out by a computational fluid dynamics (CFD) code (FLUENT 6 ) in which a pulsatile velocity field is imposed as an inlet condition. The experimental setup involves principally a “Scotch-yoke” pulsatile generator and a twisted curved pipe. Laser Doppler velocimetry measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bends during the pulsation phase. These measurements were made for a range of steady Reynolds number (300≤Rest≤1200), frequency parameter (1≤α=r0⋅(ω/υ)1/2<20), and two velocity component ratios (β=Umax,osc/Ust). We observe satisfactory agreement between the numerical and experimental results. For high β, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter α increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. Experimental results also show that pulsating flow through a twisted curved pipe increases mixing over the steady twisted curved pipe. This mixing enhancement increases with β. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Pulsating flow for mixing intensification in a twisted curved pipe [texte imprimé] / B. Timité, Auteur ; M. Jarrahi, Auteur ; C. Castelain, Auteur . - 2010 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 10 p. Mots-clés : flow  (dynamics);  pulsatile  flow;  pipes Résumé : This work concerns the manipulation of a twisted curved-pipe flow for mixing enhancement. Previous works have shown that geometrical perturbations to a curved-pipe flow can increase mixing and heat transfer by chaotic advection. In this work the flow entering the twisted pipe undergoes a pulsatile motion. The flow is studied experimentally and numerically. The numerical study is carried out by a computational fluid dynamics (CFD) code (FLUENT 6 ) in which a pulsatile velocity field is imposed as an inlet condition. The experimental setup involves principally a “Scotch-yoke” pulsatile generator and a twisted curved pipe. Laser Doppler velocimetry measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bends during the pulsation phase. These measurements were made for a range of steady Reynolds number (300≤Rest≤1200), frequency parameter (1≤α=r0⋅(ω/υ)1/2<20), and two velocity component ratios (β=Umax,osc/Ust). We observe satisfactory agreement between the numerical and experimental results. For high β, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter α increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. Experimental results also show that pulsating flow through a twisted curved pipe increases mixing over the steady twisted curved pipe. This mixing enhancement increases with β. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Direct numerical simulations of the flow past a cylinder moving with sinusoidal and nonsinusoidal profiles / Osama A. Marzouk in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 09 p. Titre : Direct numerical simulations of the flow past a cylinder moving with sinusoidal and nonsinusoidal profiles Type de document : texte imprimé Auteurs : Osama A. Marzouk, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : oscillations;  flow  (dynamics);  computer  simulation;  cylinders;  displacement;  drag  fluid  dynamics);  vortex-induced  vibration Résumé : We perform direct numerical simulations of the flow past a circular cylinder undergoing a one-degree-of-freedom transverse oscillation. The displacement follows a sine function raised to an arbitrary integer power ranging from 1 to 8. When the displacement power is above 2, we have multifrequency oscillation, and the number of Fourier components in the oscillation increases with the power, but they are either odd or even multiples of the input (argument) frequency of the displacement function. We study the responses of the nondimensional lift and drag under these different oscillation profiles and the transfer of nondimensional mechanical energy due to the oscillation, and their trends as the power (hence the number of Fourier components in the oscillation) increases. For odd powers, the energy is transferred to the cylinder; whereas for even powers, it is transferred to the flow. A unity power (harmonic oscillation) corresponds to the maximum energy transfer to the cylinder, which can explain the occurrence of this profile in the case when the cylinder is free to oscillate due to the vortex-induced vibration (VIV) phenomenon. The lift exhibits a mean value only with even powers above 2. The results show that the lift is driven to a large extent by the acceleration of the oscillation rather than its velocity. This should be considered when modeling the fluid-structure coupling in reduced-order VIV models. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Direct numerical simulations of the flow past a cylinder moving with sinusoidal and nonsinusoidal profiles [texte imprimé] / Osama A. Marzouk, Auteur . - 2010 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 09 p. Mots-clés : oscillations;  flow  (dynamics);  computer  simulation;  cylinders;  displacement;  drag  fluid  dynamics);  vortex-induced  vibration Résumé : We perform direct numerical simulations of the flow past a circular cylinder undergoing a one-degree-of-freedom transverse oscillation. The displacement follows a sine function raised to an arbitrary integer power ranging from 1 to 8. When the displacement power is above 2, we have multifrequency oscillation, and the number of Fourier components in the oscillation increases with the power, but they are either odd or even multiples of the input (argument) frequency of the displacement function. We study the responses of the nondimensional lift and drag under these different oscillation profiles and the transfer of nondimensional mechanical energy due to the oscillation, and their trends as the power (hence the number of Fourier components in the oscillation) increases. For odd powers, the energy is transferred to the cylinder; whereas for even powers, it is transferred to the flow. A unity power (harmonic oscillation) corresponds to the maximum energy transfer to the cylinder, which can explain the occurrence of this profile in the case when the cylinder is free to oscillate due to the vortex-induced vibration (VIV) phenomenon. The lift exhibits a mean value only with even powers above 2. The results show that the lift is driven to a large extent by the acceleration of the oscillation rather than its velocity. This should be considered when modeling the fluid-structure coupling in reduced-order VIV models. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Unsteady velocity profiles in laminar and turbulent water hammer flows / Alireza Riasi in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Titre : Unsteady velocity profiles in laminar and turbulent water hammer flows Type de document : texte imprimé Auteurs : Alireza Riasi, Auteur ; Ahmad Nourbakhsh, Auteur ; Mehrdad Raisee, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  turbulence;  water  hammer;  pipes;  waves;  shear  (mechanics);  equations;  pressure  gradient;  stress Résumé : The behavior of unsteady velocity profiles in laminar and turbulent water hammer flows is numerically investigated. In this way, the governing equations for the quasitwo-dimensional equations of transient flow in pipe are solved by using the modified implicit characteristics method. A k-ω turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results for both steady and unsteady turbulent pipe flows are in good agreement with the experimental data. The results indicate that both decelerating and accelerating flows are produced in a wave cycle of water hammer. During deceleration of the flow, a region of reverse flows and also strong gradients is formed near to the pipe wall. In case of the turbulent water hammer, this region is very close to the pipe wall compared with the laminar water hammer. Moreover, point of inflection and also point of zero velocity are formed in the unsteady velocity profile due to the water hammer problem. The results show that the point of zero velocity does not move very far from its initial location, while the point of inflection moves rapidly from the wall. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Unsteady velocity profiles in laminar and turbulent water hammer flows [texte imprimé] / Alireza Riasi, Auteur ; Ahmad Nourbakhsh, Auteur ; Mehrdad Raisee, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Mots-clés : flow  (dynamics);  turbulence;  water  hammer;  pipes;  waves;  shear  (mechanics);  equations;  pressure  gradient;  stress Résumé : The behavior of unsteady velocity profiles in laminar and turbulent water hammer flows is numerically investigated. In this way, the governing equations for the quasitwo-dimensional equations of transient flow in pipe are solved by using the modified implicit characteristics method. A k-ω turbulence model which is accurate for two-dimensional boundary layers under adverse and favorable pressure gradients is applied. The numerical results for both steady and unsteady turbulent pipe flows are in good agreement with the experimental data. The results indicate that both decelerating and accelerating flows are produced in a wave cycle of water hammer. During deceleration of the flow, a region of reverse flows and also strong gradients is formed near to the pipe wall. In case of the turbulent water hammer, this region is very close to the pipe wall compared with the laminar water hammer. Moreover, point of inflection and also point of zero velocity are formed in the unsteady velocity profile due to the water hammer problem. The results show that the point of zero velocity does not move very far from its initial location, while the point of inflection moves rapidly from the wall. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Application of fractional scaling analysis to loss of coolant accidents / Ivan Catton in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Titre : Application of fractional scaling analysis to loss of coolant accidents : component level scaling for peak clad temperature Type de document : texte imprimé Auteurs : Ivan Catton, Auteur ; Wolfgang Wulff, Auteur ; Novak Zuber, Auteur Année de publication : 2010 Article en page(s) : 08 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Fractional  scaling  analysis;  nuclear  reactor Résumé : Fractional scaling analysis (FSA) is demonstrated here at the component level for depressurization of nuclear reactor primary systems undergoing a large-break loss of coolant accident. This paper is the third of a three-part sequence. The first paper by (2005, “Application of Fractional Scaling Analysis (FSA) to Loss of Coolant Accidents (LOCA), Part 1. Methodology Development,” Nucl. Eng. Des., 237, pp. 1593–1607) introduces the FSA method; the second by (2005, “Application of Fractional Scaling Methodology (FSM) to Loss of Coolant Accidents (LOCA), Part 2. System Level Scaling for System Depressurization,” ASME J. Fluid Eng., to be published) demonstrates FSA at the system level. This paper demonstrates that a single experiment or trustworthy computer simulation, when properly scaled, suffices for large break loss of coolant accident (LBOCAs) in the primary system of a pressurized water reactor and of all related test facilities. FSA, when applied at the system, component, and process levels, serves to synthesize the world-wide wealth of results from analyses and experiments into compact form for efficient storage, transfer, and retrieval of information. This is demonstrated at the component level. It is shown that during LBOCAs, the fuel rod stored energy is the dominant agent of change and that FSA can rank processes quantitatively and thereby objectively in the order of their importance. FSA readily identifies scale distortions. FSA is shown to supercede use of the subjectively implemented phenomena identification and ranking table and to minimize the number of experiments, analyses and computational effort by reducing the evaluation of peak clad temperature (PCT) to a single parameter problem, thus, greatly simplifying uncertainty analysis. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Application of fractional scaling analysis to loss of coolant accidents : component level scaling for peak clad temperature [texte imprimé] / Ivan Catton, Auteur ; Wolfgang Wulff, Auteur ; Novak Zuber, Auteur . - 2010 . - 08 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 08 p. Mots-clés : Fractional  scaling  analysis;  nuclear  reactor Résumé : Fractional scaling analysis (FSA) is demonstrated here at the component level for depressurization of nuclear reactor primary systems undergoing a large-break loss of coolant accident. This paper is the third of a three-part sequence. The first paper by (2005, “Application of Fractional Scaling Analysis (FSA) to Loss of Coolant Accidents (LOCA), Part 1. Methodology Development,” Nucl. Eng. Des., 237, pp. 1593–1607) introduces the FSA method; the second by (2005, “Application of Fractional Scaling Methodology (FSM) to Loss of Coolant Accidents (LOCA), Part 2. System Level Scaling for System Depressurization,” ASME J. Fluid Eng., to be published) demonstrates FSA at the system level. This paper demonstrates that a single experiment or trustworthy computer simulation, when properly scaled, suffices for large break loss of coolant accident (LBOCAs) in the primary system of a pressurized water reactor and of all related test facilities. FSA, when applied at the system, component, and process levels, serves to synthesize the world-wide wealth of results from analyses and experiments into compact form for efficient storage, transfer, and retrieval of information. This is demonstrated at the component level. It is shown that during LBOCAs, the fuel rod stored energy is the dominant agent of change and that FSA can rank processes quantitatively and thereby objectively in the order of their importance. FSA readily identifies scale distortions. FSA is shown to supercede use of the subjectively implemented phenomena identification and ranking table and to minimize the number of experiments, analyses and computational effort by reducing the evaluation of peak clad temperature (PCT) to a single parameter problem, thus, greatly simplifying uncertainty analysis. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Improving the spatial resolution and stability by optimizing compact finite differencing templates / Stephen A. Jordan in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 11 p. Titre : Improving the spatial resolution and stability by optimizing compact finite differencing templates Type de document : texte imprimé Auteurs : Stephen A. Jordan, Auteur Année de publication : 2010 Article en page(s) : 11 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : resolution  (optics);  optimization;  errors;  turbulence;  composite  materials;  flat  plates Résumé : Parameter optimization is an excellent path for easily raising the resolution efficiency of compact finite differencing schemes. Their low-resolution errors are attractive for resolving the fine-scale turbulent physics even in complex flow domains with difficult boundary conditions. Most schemes require optimizing closure stencils at and adjacent to the domain boundaries. But these constituents can potentially degrade the local resolution errors and destabilize the final solution scheme. Current practices optimize and analyze each participating stencil separately, which incorrectly quantifies their local resolution errors. The proposed process optimizes each participant simultaneously. The result is a composite template that owns consistent spatial resolution properties throughout the entire computational domain. Additionally, the optimization technique leads to templates that are numerically stable as understood by an eigenvalue analysis. Finally, the predictive accuracy of the optimized schemes are evaluated using four canonical test problems that involve resolving linear convection, nonlinear Burger wave, turbulence along a flat plate, and circular cylinder wall pressure. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Improving the spatial resolution and stability by optimizing compact finite differencing templates [texte imprimé] / Stephen A. Jordan, Auteur . - 2010 . - 11 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 11 p. Mots-clés : resolution  (optics);  optimization;  errors;  turbulence;  composite  materials;  flat  plates Résumé : Parameter optimization is an excellent path for easily raising the resolution efficiency of compact finite differencing schemes. Their low-resolution errors are attractive for resolving the fine-scale turbulent physics even in complex flow domains with difficult boundary conditions. Most schemes require optimizing closure stencils at and adjacent to the domain boundaries. But these constituents can potentially degrade the local resolution errors and destabilize the final solution scheme. Current practices optimize and analyze each participating stencil separately, which incorrectly quantifies their local resolution errors. The proposed process optimizes each participant simultaneously. The result is a composite template that owns consistent spatial resolution properties throughout the entire computational domain. Additionally, the optimization technique leads to templates that are numerically stable as understood by an eigenvalue analysis. Finally, the predictive accuracy of the optimized schemes are evaluated using four canonical test problems that involve resolving linear convection, nonlinear Burger wave, turbulence along a flat plate, and circular cylinder wall pressure. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Experimental measurement of laminar axisymmetric flow through confined annular geometries with sudden inward expansion / Afshin Goharzadeh in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 12 (Décembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 04 p. Titre : Experimental measurement of laminar axisymmetric flow through confined annular geometries with sudden inward expansion Type de document : texte imprimé Auteurs : Afshin Goharzadeh, Auteur ; Peter Rodgers, Auteur Année de publication : 2010 Article en page(s) : 04 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : flow  (dynamics);  measurement;  eddies  (fluid  dynamics);  Reynolds  number;  laminar  flow;  particulate  matter Résumé : In this paper, separating and reattaching aqueous laminar flows produced by a sudden inward expansion within confined annular geometries are experimentally studied. The test geometries are based on a previous numerical study. The fluid flow structure at the expansion region is experimentally characterized using particle image velocimetry combined with refractive index matching. The detailed measurements of the velocity field, reattachment length, and relative eddy intensity are obtained for two different expansion ratios, 1.4 and 1.6. For both expansion ratios, the reattachment length is found to vary nonlinearly with the Reynolds number (50 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Experimental measurement of laminar axisymmetric flow through confined annular geometries with sudden inward expansion [texte imprimé] / Afshin Goharzadeh, Auteur ; Peter Rodgers, Auteur . - 2010 . - 04 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 12 (Décembre 2009) . - 04 p. Mots-clés : flow  (dynamics);  measurement;  eddies  (fluid  dynamics);  Reynolds  number;  laminar  flow;  particulate  matter Résumé : In this paper, separating and reattaching aqueous laminar flows produced by a sudden inward expansion within confined annular geometries are experimentally studied. The test geometries are based on a previous numerical study. The fluid flow structure at the expansion region is experimentally characterized using particle image velocimetry combined with refractive index matching. The detailed measurements of the velocity field, reattachment length, and relative eddy intensity are obtained for two different expansion ratios, 1.4 and 1.6. For both expansion ratios, the reattachment length is found to vary nonlinearly with the Reynolds number (50 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse