Author: Emily S.C. Ching Publisher: Springer Science & Business Media ISBN: 9814560235 Category : Technology & Engineering Languages : en Pages : 71
Book Description
This Brief addresses two issues of interest of turbulent Rayleigh-Bénard convection. The first issue is the characterization and understanding of the statistics of the velocity and temperature fluctuations in the system. The second issue is the revelation and understanding of the nature of the scaling behavior of the velocity temperature structure functions. The problem under the Oberbeck-Boussinesq approximation is formulated. The statistical tools, including probability density functions (PDF) and conditional statistics, for studying fluctuations are introduced, and implicit PDF formulae for fluctuations obeying certain statistical symmetries are derived. Applications of these PDF formulae to study the fluctuations in turbulent Rayleigh-Bénard convection are then discussed. The phenomenology of the different types of scaling behavior: the Bolgiano-Obhukov scaling behavior when buoyancy effects are significant and the Kolmogorov-Obukhov-Corrsin scaling behavior when they are not, is introduced. A crossover between the two types of scaling behavior is expected to occur at the Bolgiano length scale above which buoyancy is important. The experimental observations are reviewed. In the central region of the convective cell, the Kolmogorov-Obukhov-Corrsin scaling behavior has been observed. On the other hand, the Bolgiano-Obukhov scaling remains elusive only until recently. By studying the dependence of the conditional temperature structure functions on the locally averaged thermal dissipation rate, evidence for the Bolgiano-Obukhov scaling has recently been found near the bottom plate. The different behaviors observed in the two regions could be attributed to the different size of the Bolgiano scale. What physics determines the relative size of the Bolgiano scale remains to be understood. The Brief is concluded by a discussion of these outstanding issues.
Author: Andrés Alonso Castillo-Castellanos Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
One outstanding feature of the Rayleigh-Bénard problem which concerns a horizontal fluid layer heated from below and cooled from above, is the spontaneous establishment of spatial ordering and the formation of a coherent large-scale circulation. How different factors, such as the domain geometry and boundary conditions, influence the sizes and shapes of the large-scale flow remains an open question. Despite its apparent simplicity, Rayleigh-Bénard convection exhibits some incredibly rich and complex large-scale dynamics such as torsional modes, rotation, sloshing, and cessations, which often coexist and compete to each other. One approach, commonly used in the study of cessations is to constrain the large scale circulation to a plane by restricting the fluid domain to a (2-D) square cell or to a slim rectangular cell of small aspect ratio in the transversal direction. However, it is not entirely clear whether the 2-D and (quasi-)2-D reversals correspond to the same phenomenon. The present document is dedicated to the study of the large-scale flow patterns in turbulent Rayleigh-Bénard convection, and of the influence exerted by different factors on the flow structures and on their temporal evolution. The proposed characterization combines a statistical analysis with a physical approach relying on the angular momentum as well as the kinetic and potential energies to highlight the underlying physical mechanisms. We subsequently attempt to tie these mechanisms together to each of the distinctive flow patterns observed and to their evolution.
Author: David Goluskin Publisher: Springer ISBN: 3319239414 Category : Science Languages : en Pages : 73
Book Description
This Brief describes six basic models of buoyancy-driven convection in a fluid layer: three configurations of internally heated convection and three configurations of Rayleigh-Bénard convection. The author discusses the main quantities that characterize heat transport in each model, along with the constraints on these quantities. This presentation is the first to place the various models in a unified framework, and similarities and differences between the cases are highlighted. Necessary and sufficient conditions for convective motion are given. For the internally heated cases only, parameter-dependent lower bounds on the mean fluid temperature are proven, and results of past simulations and laboratory experiments are summarized and reanalyzed. The author poses several open questions for future study.
Author: Yichao Xie Publisher: ISBN: Category : Heat Languages : en Pages : 114
Book Description
Turbulent thermal convection is of tremendous importance to many areas of science, technology as well as the environment. In this thesis, the dynamics of the large-scale circulation (LSC) in turbulent Rayleigh-Bénard convection, which is an idealised model to study turbulent thermal convection problem, is investigated using the multi-thermal probe technique in the high Prandtl number Pr regime.
Author: G. F. Nellis Publisher: Cambridge University Press ISBN: 110717953X Category : Mathematics Languages : en Pages : 1027
Book Description
Equips students with the essential knowledge, skills, and confidence to solve real-world heat transfer problems using EES, MATLAB, and FEHT.
Author: Emily S.C. Ching
Author: Mohammad Shah Emran
Author: Mohammad Shah Emran
Author: Andrés Alonso Castillo-Castellanos
Author: A. A. R. Townsend
Author: N. O. Weiss
Author: Yin Wang
Author: David Goluskin
Author: Yichao Xie
Author: G. F. Nellis