Documents disponibles écrits par cet auteur

High rayleigh number natural convection inside 2D porous enclosures using the lattice Boltzmann method / Ramanathan Vishnampet in Journal of heat transfer, Vol. 133 N° 6 (Juin 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [062501/1-9] Titre : High rayleigh number natural convection inside 2D porous enclosures using the lattice Boltzmann method Type de document : texte imprimé Auteurs : Ramanathan Vishnampet, Auteur ; Arunn Narasimhan, Auteur ; V. Babu, Auteur Année de publication : 2011 Article en page(s) : pp. [062501/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Natural  convection  Porous  media  Lattice  Boltzmann  Numerical  Enclosure  convection  Convection  correlation Index. décimale : 536 Chaleur. Thermodynamique Résumé : Lattice Boltzmann method (LBM) is employed to investigate natural convection inside porous medium enclosures at high Rayleigh numbers. Volume averaged porous medium model is coupled with the lattice Boltzmann formulation of the momentum and energy equations for fluid flow. A parallel implementation of the single relaxation time LBM is used, which allows the porous medium modified Rayleigh number Ram to be as high as 108. Heat transfer results in the form of the enclosure averaged Nusselt number Nu are obtained for higher modified Rayleigh numbers 104<=Ram<=108. The Nu values are compared with values in the absence of the form drag term. The form drag due to the porous medium is found to influence Nu considerably. The effect of the form drag on Nu is studied by using a form drag modified Rayleigh number RaC (extended from Ram). Utilizing the results for Nu in the high Ram range, a correlation is proposed between Nu and RaC for Darcy numbers 10−6<=Da<=10−2, encompassing the non-Darcy flow regime. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] High rayleigh number natural convection inside 2D porous enclosures using the lattice Boltzmann method [texte imprimé] / Ramanathan Vishnampet, Auteur ; Arunn Narasimhan, Auteur ; V. Babu, Auteur . - 2011 . - pp. [062501/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [062501/1-9] Mots-clés : Natural  convection  Porous  media  Lattice  Boltzmann  Numerical  Enclosure  convection  Convection  correlation Index. décimale : 536 Chaleur. Thermodynamique Résumé : Lattice Boltzmann method (LBM) is employed to investigate natural convection inside porous medium enclosures at high Rayleigh numbers. Volume averaged porous medium model is coupled with the lattice Boltzmann formulation of the momentum and energy equations for fluid flow. A parallel implementation of the single relaxation time LBM is used, which allows the porous medium modified Rayleigh number Ram to be as high as 108. Heat transfer results in the form of the enclosure averaged Nusselt number Nu are obtained for higher modified Rayleigh numbers 104<=Ram<=108. The Nu values are compared with values in the absence of the form drag term. The form drag due to the porous medium is found to influence Nu considerably. The effect of the form drag on Nu is studied by using a form drag modified Rayleigh number RaC (extended from Ram). Utilizing the results for Nu in the high Ram range, a correlation is proposed between Nu and RaC for Darcy numbers 10−6<=Da<=10−2, encompassing the non-Darcy flow regime. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Natural convection inside a bidisperse porous medium enclosure / Arunn Narasimhan in Journal of heat transfer, Vol. 132 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 1 (Janvier 2010) . - pp. [012502-1/9] Titre : Natural convection inside a bidisperse porous medium enclosure Type de document : texte imprimé Auteurs : Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur Article en page(s) : pp. [012502-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Confined  flow  Finite  volume  methods  Flow  simulation  Flow  through  porous  media  Natural  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Bidisperse porous medium (BDPM) consists of a macroporous medium whose solid phase is replaced with a microporous medium. This study investigates using numerical simulations, steady natural convection inside a square BDPM enclosure made from uniformly spaced, disconnected square porous blocks that form the microporous medium. The side walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The bidispersion effect is generated by varying the number of blocks (N2), macropore volume fraction (phiE), and internal Darcy number (DaI) for several enclosure Rayleigh numbers (Ra). Their effect on the BDPM heat transfer (Nu) is investigated. When Ra is fixed, the Nu increases with an increase in both DaI and DaE. At low Ra values, Nu is strongly affected by both DaI and phiE. When N2 is fixed, at high Ra values, the porous blocks in the core region have negligible effect on the Nu. A correlation is proposed to evaluate the heat transfer from the BDPM enclosure, Nu, as a function of Raphi, DaE, DaI, and N2. It predicts the numerical results of Nu within ±15% and ±9% in two successive ranges of modified Rayleigh number, RaphiDaE. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Natural convection inside a bidisperse porous medium enclosure [texte imprimé] / Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur . - pp. [012502-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 1 (Janvier 2010) . - pp. [012502-1/9] Mots-clés : Confined  flow  Finite  volume  methods  Flow  simulation  Flow  through  porous  media  Natural  convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Bidisperse porous medium (BDPM) consists of a macroporous medium whose solid phase is replaced with a microporous medium. This study investigates using numerical simulations, steady natural convection inside a square BDPM enclosure made from uniformly spaced, disconnected square porous blocks that form the microporous medium. The side walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The bidispersion effect is generated by varying the number of blocks (N2), macropore volume fraction (phiE), and internal Darcy number (DaI) for several enclosure Rayleigh numbers (Ra). Their effect on the BDPM heat transfer (Nu) is investigated. When Ra is fixed, the Nu increases with an increase in both DaI and DaE. At low Ra values, Nu is strongly affected by both DaI and phiE. When N2 is fixed, at high Ra values, the porous blocks in the core region have negligible effect on the Nu. A correlation is proposed to evaluate the heat transfer from the BDPM enclosure, Nu, as a function of Raphi, DaE, DaI, and N2. It predicts the numerical results of Nu within ±15% and ±9% in two successive ranges of modified Rayleigh number, RaphiDaE. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Resonance of natural convection inside a bidisperse porous medium enclosure / Arunn Narasimhan in Journal of heat transfer, Vol. 133 N° 4 (Avril 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042601/1-9] Titre : Resonance of natural convection inside a bidisperse porous medium enclosure Type de document : texte imprimé Auteurs : Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur Année de publication : 2011 Article en page(s) : pp. [042601/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Natural  convection  Resonance  Bidisperse  Monodisperse  Porous  media  Numerical  simulations  Scale  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : An enclosure filled with blocks made of a microscale porous medium, separated by macrosize pores, can be treated as a bidisperse porous medium (BDPM) enclosure. This study investigates natural convection resonance inside such a BDPM enclosure subjected to time-periodic heat flux at a side wall, with the opposite wall kept isothermal while the top and bottom walls are adiabatic. The BDPM enclosure is made from uniformly spaced, disconnected, square, porous blocks that form the microporous medium saturated with a fluid of Pr=0.7. For Rayleigh numbers, Ra=108 and 107, the pulsating wall heat flux is varied over a frequency range of 0.01<=f<=0.1, and the bidispersion effect is induced by varying both the internal (micropore) Darcy number (DaI) and external (macropore) Darcy number DaE. Natural convection resonance is observed in the BDPM enclosure and the resonance heating frequency fr increases with Ra, DaI, and DaE. However, fr of the BDPM enclosure is always less than that of the corresponding clear fluid enclosure limit (at DaI-->[infinity]). Predictions of fr using a modified scale analysis incorporating BDPM effects agree well with that arrived by numerical methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...] [article] Resonance of natural convection inside a bidisperse porous medium enclosure [texte imprimé] / Arunn Narasimhan, Auteur ; B. V. K. Reddy, Auteur . - 2011 . - pp. [042601/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 4 (Avril 2011) . - pp. [042601/1-9] Mots-clés : Natural  convection  Resonance  Bidisperse  Monodisperse  Porous  media  Numerical  simulations  Scale  analysis Index. décimale : 536 Chaleur. Thermodynamique Résumé : An enclosure filled with blocks made of a microscale porous medium, separated by macrosize pores, can be treated as a bidisperse porous medium (BDPM) enclosure. This study investigates natural convection resonance inside such a BDPM enclosure subjected to time-periodic heat flux at a side wall, with the opposite wall kept isothermal while the top and bottom walls are adiabatic. The BDPM enclosure is made from uniformly spaced, disconnected, square, porous blocks that form the microporous medium saturated with a fluid of Pr=0.7. For Rayleigh numbers, Ra=108 and 107, the pulsating wall heat flux is varied over a frequency range of 0.01<=f<=0.1, and the bidispersion effect is induced by varying both the internal (micropore) Darcy number (DaI) and external (macropore) Darcy number DaE. Natural convection resonance is observed in the BDPM enclosure and the resonance heating frequency fr increases with Ra, DaI, and DaE. However, fr of the BDPM enclosure is always less than that of the corresponding clear fluid enclosure limit (at DaI-->[infinity]). Predictions of fr using a modified scale analysis incorporating BDPM effects agree well with that arrived by numerical methods. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&smode=strresults& [...]