Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session LW: Mini-Symposium: High Rayleigh Number Convection: Is there an ultimate regime? |
Hide Abstracts |
Chair: Detlef Lohse, University of Twente, The Netherlands Room: 004 |
Monday, November 24, 2008 3:35PM - 4:01PM |
LW.00001: Nusselt and Reynolds numbers for turbulent convection at very large Rayleigh numbers Invited Speaker: This talk will present a brief review of available Nusselt- and Reynolds-number measurements relevant to the issue of the transition to the ``ultimate'' regime of turbulent Rayleigh-Benard convection discussed by Kraichnan. It will then examine the expected signature of such a transition in the dependence of the Nusselt number on the Rayleigh and Prandtl numbers. Finally it will discuss future prospects for new measurements at very large Rayleigh numbers that will be potentially relevant to the transition. [Preview Abstract] |
Monday, November 24, 2008 4:01PM - 4:27PM |
LW.00002: Comparative study of the hot and cold thermal boundary layers in turbulent Rayleigh-Benard convection Invited Speaker: We report a comprehensive series of measurements of the mean temperature profiles in turbulent Rayleigh-Benard convection of air in a cylindrical cell with aspect ratio one and Rayleigh numbers in the range 10$^{11}$ to 10$^{12}$. The measurements differ from those reported in the paper du Puits et al [J. Fluid Mech., vol. 572 (2007), pp. 231-254] in that the profiles are taken simultaneously at the heating and the cooling plates and that we can directly measure the local heat flux at the heating plate. In the present communication we will discuss the results of these measurements and compare them to previous ones as well as to recent predictions about the asymptotic shape of the mean temperature profiles derived by Hoelling and Herwig [Int. J. Heat Mass Transf., vol. 49 (2006) pp. 1129-1136]. In collaboration with Christian Resagk and Ronald du Puits, Ilmenau University of Technology. [Preview Abstract] |
Monday, November 24, 2008 4:27PM - 4:53PM |
LW.00003: Temperature Oscillations and Flow Dynamics in Turbulent Thermal Convection Invited Speaker: We report an experimental study of three-dimensional structure of the low-frequency temperature oscillations in a cylindrical Rayleigh-B\'{e}nard (RB) convection cell of aspect ratio one. It is found that the hot and cold thermal plumes are not emitted periodically nor alternatively, but continuously and randomly, from the top and bottom plates. We further found that the oscillation of the temperature field does not originate from boundary layers, but rather is a result of the horizontal motion of the hot ascending and cold descending fluids being modulated by the twisting oscillation near the top and bottom plates and the off-center oscillation in the bulk flow field. Evidence will also be presented to show that the off-center oscillation in the bulk flow field is a manifestation of the twisting motion of fluid near the top and bottom plates. In collaboration with Heng-Dong Xi, Quan Zhou, and Sheng-Qi Zhou, The Chinese University of Hong Kong. [Preview Abstract] |
Monday, November 24, 2008 4:53PM - 5:19PM |
LW.00004: The Heat Transport Law In Thermal Convection Invited Speaker: This talk will survey the outstanding elements of the heat transport law in thermal convection. It will particularly focus on the author's work on this problem carried out in collaboration with a number of his colleagues and students. From a combination of experimental and numerical studies, which have pushed the limits of Rayleigh (Ra) and Prandtl (Pr) numbers, we deduce the dependence of the Nusselt number (Nu) on Ra and Pr. These studies include the consideration of non-Boussinesq effects, imperfect boundary conditions, the role of aspect ratio, and so forth. Our conclusion is that Nu is proportional to the one-third power of Ra for large Ra, and that the so-called asymptotic form, which stipulates a 1/2 power instead of the 1/3, does not arise in thermal convection in the presence of solid boundaries. Some remarks will be made also about the dependence of Nu on Pr. [Preview Abstract] |
Monday, November 24, 2008 5:19PM - 5:45PM |
LW.00005: Numerical simulations of thermal convection at high Prandtl numbers Invited Speaker: Direct numerical simulations of thermal convection are conducted for a cylindrical cell of aspect ratio $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $. The Prandtl number (Pr) varies from 10$^{0}$ to 10$^{4}$ and the Rayleigh numbers (Ra) are moderate (10$^{5} \quad <$ Ra $<$ 10$^{9})$. This study is motivated by the fact that the role of the Prandtl number in convective heat transport is not yet fully understood. The three-dimensional behaviors of the temperature and velocity fields, of the viscous and thermal dissipation fields, and of the diffusive and convective heat fluxes are explored. In the ranges of Pr and Ra considered, we find steady, periodic and chaotic regimes, and large-scale structures which are more complex than the single recirculation cell filling the whole volume. Multiple flow structures are found to be associated with a given set of conditions. The multiple solutions seem to be more probable at higher Pr numbers and could explain the scatter in some data trends. In collaboration with Katepalli Raju Sreenivasan, The Abdus Salam International Centre for Theoretical Physics - Trieste, and Roberto Verzicco, DIM, Universit\`a degli Studi di Roma Tor Vergata - Roma. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700