by Lui Siu Lung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 132-136). / by Lui Siu Lung. / Abstract --- p.i / Acknowledgements --- p.ii / Table of Contents --- p.iii / List of Figures --- p.v / Chapter / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- The Parameters --- p.1 / Chapter 1.2 --- The Stories of Turbulent Convection --- p.2 / Chapter 1.3 --- The Models: Plumes with no Flow or a Flow with no Plumes? --- p.3 / Chapter 1.4 --- Building up the Picture --- p.5 / Chapter 1.5 --- Starting Point of the Experiment --- p.6 / Chapter 2. --- Setup of the Experimental Environment --- p.8 / Chapter 2.1 --- The Convection Cell --- p.8 / Chapter 2.2 --- The Temperature Probe --- p.12 / Chapter 2.3 --- The Thermistors --- p.15 / Chapter 2.4 --- The Large Scale Circulation and the Plumes --- p.19 / Chapter 2.5 --- Building up the Convection --- p.22 / Chapter 3. --- Hard Turbulence Properties and Scalings in the Normal Cell --- p.27 / Chapter 3.1 --- Heat Transfer Efficiency --- p.27 / Chapter 3.2 --- Thermal Boundary Layer --- p.32 / Chapter 3.3 --- The RMS Temperature Fluctuation --- p.39 / Chapter 3.4 --- Temperature Time Series --- p.42 / Chapter 3.5 --- Histograms --- p.48 / Chapter 3.6 --- Power Spectrum --- p.53 / Chapter 3.7 --- Summary on the Normal Cell --- p.56 / Chapter 4. --- Horizontal-Position-Dependent Thermal Boundary Layer --- p.58 / Chapter 4.1 --- Orientation --- p.59 / Chapter 4.2 --- Along the Large Scale Circulation --- p.60 / Chapter 4.3 --- Perpendicular to the Large Scale Circulation --- p.70 / Chapter 4.4 --- Horizontal Measurement for the A = 2 Cell --- p.78 / Chapter 4.5 --- Summary on the Horizontal Measurement --- p.81 / Chapter 5. --- Sphere in the Cell --- p.84 / Chapter 5.1 --- Heat Transfer Efficiency --- p.84 / Chapter 5.2 --- Thermal Boundary Layer --- p.86 / Chapter 5.3 --- The RMS Temperature Fluctuation --- p.87 / Chapter 5.4 --- Temperature Time Series --- p.88 / Chapter 5.5 --- Histograms --- p.92 / Chapter 5.6 --- Summary on the Sphere Cell --- p.94 / Chapter 6. --- Fingers in the Cell --- p.96 / Chapter 6.1 --- The Gear Cell --- p.96 / Chapter 6.1.1 --- Heat Transfer Efficiency --- p.96 / Chapter 6.1.2 --- Thermal Boundary Layer --- p.98 / Chapter 6.1.3 --- Flow Pattern in the Gear Cell --- p.100 / Chapter 6.1.4 --- Temperature Time Series --- p.104 / Chapter 6.1.5 --- Histograms --- p.109 / Chapter 6.1.6 --- Power Spectrum --- p.110 / Chapter 6.2 --- The Finger Cell --- p.117 / Chapter 6.2.1 --- Heat Transfer Efficiency --- p.117 / Chapter 6.2.2 --- Temperature Time Series --- p.120 / Chapter 6.2.3 --- Histograms --- p.122 / Chapter 6.2.4 --- Power Spectrum --- p.125 / Chapter 6.3 --- Summary on the Finger Cells --- p.127 / Chapter 7. --- Conclusions --- p.129 / References --- p.132 / Appendix --- p.137

Rayleigh-Bénard convection has been extensively studied in literature owing to its ubiquitous nature. However, most of the studies have been confined to geometries where the aspect ratio of the cylinder was less than 1. Here we study the motion of fluid in geometries with aspect ratio greater than 1, with particular application to use of such motion to actuate biochemical reactions, such as the polymerase chain reaction. We show that it is possible to accelerate the rate of reaction by using a geometry that promotes chaotic motion versus a geometry that promotes quasi- periodic motion. We also simulate chemical kinetics using the fluid motion as a starting point and we prove that chaotic motion indeed enhances the rate of the reaction. We also provide qualitative and quantitative measures for chaotic motion in a fluid flow, which helps to distinguish between different types of fluid motion. We highlight the transitions between different types of flow that are possible with Rayleigh-Bénard convection. Finally, we compare our simulations against experimental data obtained from particle image velocimetry, laser induced fluorescence and optical microscopic visualization.

Numerical simulations of combined buoyant and surface tension driven flow, also known as Rayleigh-Bénard-Marangoni (RBM) convection are conducted for heated fluid layers of small aspect ratio (defined as the ratio of the horizontal extent of the domain divided by the depth of the fluid) in square cross-section containers. A particular non-dimensionalization of the governing equations is developed in which the aspect ratio of the domain appears as a continuous parameter. The simulations extend and enhance existing experimental studies of the RBM convection phenomenon by mapping continuous solution branches in aspect ratio and Marangoni number parameter space. Key implementation aspects of the development of the adaptive mesh refinement (AMR) library libMesh are discussed, and a series of simulations of the RBM problem with a stick-slip boundary condition demonstrate the suitability of AMR for computing these flows. / text

The transport of a species in complex flow fields is an important phenomenon related to many areas in science and engineering. There has been significant progress theoretically and experimentally in understanding active transport in steady, periodic flows such as a chain of vortices but many open questions remain for transport in complex and chaotic flows. This thesis investigates the active transport in a three-dimensional, time-dependent flow field characterized by a spatiotemporally chaotic state of Rayleigh-Be?nard convection. A nonlinear Fischer-Kolmogorov-Petrovskii-Piskunov reaction is selected to study the transport within these flows. A highly efficient, parallel spectral element approach is employed to solve the Boussinesq and the reaction-advection-diffusion equations in a spatially-extended cylindrical domain with experimentally relevant boundary conditions. The transport is quantified using statistics of spreading and in terms of active transport characteristics like front speed and geometry and are compared with those results for transport in steady flows found in the literature. The results of the simulations indicate an anomalous diffusion process with a power law 2 < ? < 5/2 a result that deviates from other superdiffusive processes in simpler flows, and reveals that the presence of spiral defect chaos induces strongly anomalous transport. Additionally, transport was found to most likely occur in a direction perpendicular to a convection roll in the flow field. The presence of the spiral defect chaos state of the fluid convection is found to enhance the front perimeter by t^3/2 and by a perimeter enhancement ratio r(p) = 2.3. / Master of Science

Kwok Chun-yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves [121]-122). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Experimental data --- p.7 / Chapter 2.1 --- Turbulent Convection using Helium --- p.7 / Chapter 2.2 --- Turbulent Convection using water --- p.8 / Chapter 3 --- Probability Distribution and Scaling behavior --- p.9 / Chapter 3.1 --- PDF of YT --- p.9 / Chapter 3.1.1 --- Helium Convection --- p.10 / Chapter 3.1.2 --- Water Convection --- p.26 / Chapter 3.1.3 --- Comparison between helium data and Water data --- p.34 / Chapter 3.2 --- T -dependence of the moments of XT --- p.39 / Chapter 3.2.1 --- Helium Convection --- p.39 / Chapter 3.2.2 --- Water Convection --- p.47 / Chapter 4 --- Hierarchical Moment Relation --- p.50 / Chapter 4.1 --- Method of Analysis --- p.50 / Chapter 4.2 --- Results and Discussion --- p.53 / Chapter 4.2.1 --- Helium Convection --- p.53 / Chapter 4.2.2 --- Water Convection --- p.81 / Chapter 5 --- Discussion and Conclusion --- p.95 / Chapter 5.1 --- Passive Scalar --- p.96 / Chapter 5.2 --- Comparison between Turbulent Convection and Passive Scalar --- p.99 / Chapter 5.3 --- Scaling behavior for length scale above and below the Bolgiano scale for turbulent convection using Helium gas --- p.100 / Chapter 5.4 --- Conclusions --- p.107 / Chapter A --- The lognormal model --- p.108 / Chapter B --- Definition of XT --- p.110 / Chapter C --- Reasons for analysis of (xTp) for p≤ 12 --- p.112 / Chapter D --- Functional form of μp implied by the hierarchical relation --- p.119 / Bibliography --- p.122

Zhou Sheng-qi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 66-70). / Text in English; abstracts in English and Chinese. / Zhou Sheng-qi. / Abstract (in Chinese) --- p.i / Abstract (in English) --- p.ii / Acknowledgement --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vi / List of Tables --- p.viii / Chapter / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Turbulence: a Universal Problem --- p.1 / Chapter 1.2 --- Rayleigh-Benard Convection --- p.2 / Chapter 1.2.1 --- The History of Rayleigh-Benard Convection --- p.2 / Chapter 1.2.2 --- The Dimensionless Parameters --- p.4 / Chapter 1.2.3 --- The Physical Picture of Turbulent Convection --- p.5 / Chapter 1.3 --- Motivation of This Study --- p.8 / Chapter 2. --- Theoretical Base and Experimental Setup --- p.11 / Chapter 2.1 --- The Rayleigh-Benard problem --- p.11 / Chapter 2.1.1 --- The Boussinesq approximation --- p.11 / Chapter 2.1.2 --- The Convection Equation --- p.13 / Chapter 2.2 --- Experimental Setup and Measurement --- p.14 / Chapter 2.2.1 --- The Convection Cell --- p.14 / Chapter 2.2.2 --- The Power Supply and the Refrigerated Recirculator --- p.19 / Chapter 2.2.3 --- The Temperature Probes --- p.19 / Chapter 2.2.4 --- The Temperature Measurement System --- p.20 / Chapter 2.2.5 --- Building up the Convection State --- p.25 / Chapter 3. --- Temperature Power Spectra and the Viscous Boundary Layer in the Thermal Turbulence --- p.27 / Chapter 3.1 --- The Power Spectra Method --- p.27 / Chapter 3.2 --- The Suspicions of the Power Spectra Method --- p.30 / Chapter 3.3 --- Discussion of the Experimental Results --- p.32 / Chapter 3.4 --- Summary --- p.39 / Chapter 4. --- The Correlation Function of Temperature --- p.40 / Chapter 4.1 --- Preparation of Experiment --- p.41 / Chapter 4.1.1 --- Apparatus --- p.41 / Chapter 4.1.2 --- Definition of correlation function --- p.41 / Chapter 4.2 --- Results and Discussion --- p.44 / Chapter 4.2.1 --- The Delay Time (¡’0) --- p.47 / Chapter 4.2.2 --- The Maximum Correlation Coefficient (R) --- p.52 / Chapter 4.2.3 --- The Half Width (¡’h) --- p.58 / Chapter 4.3 --- Summary --- p.61 / Chapter 5. --- Conclusions --- p.63 / References --- p.66

Xi Hengdong = 關於熱羽流和Rayleigh-Bénard對流中大尺度環流形成的實驗研究 / 郗恒東. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 71-75). / Text in English; abstracts in English and Chinese. / Xi Hengdong = Guan yu re yu liu he Rayleigh-Bénard dui liu zhong da chi du huan liu xing cheng de shi yan yan jiu / Xi Hengdong. / Table of Contents --- p.v / List of Figures --- p.xi / List of Tables --- p.xii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Rayleigh-Benard System --- p.1 / Chapter 1.1.1 --- Physical Picture --- p.1 / Chapter 1.1.2 --- Characteristic Parameters --- p.2 / Chapter 1.2 --- Plume and Large Scale Circulation --- p.4 / Chapter 2 --- Experimental Setup and Techniques --- p.8 / Chapter 2.1 --- Apparatus --- p.8 / Chapter 2.1.1 --- Convection Cell --- p.8 / Chapter 2.1.2 --- Other Apparatus --- p.12 / Chapter 2.2 --- Visualization --- p.14 / Chapter 2.3 --- PIV technique --- p.17 / Chapter 2.3.1 --- Image Capture System --- p.20 / Chapter 2.3.2 --- Image Analysis system --- p.26 / Chapter 3 --- Properties of Laminar Plume --- p.30 / Chapter 3.1 --- Shadowgraph and Temperature measurement --- p.30 / Chapter 3.2 --- Velocity Measurement --- p.35 / Chapter 4 --- Onset of Large-scale circulation in turbulent thermal convec- tion --- p.48 / Chapter 5 --- Convection in Rectangular cell --- p.60 / Chapter 6 --- Conclusion --- p.69 / Chapter 6.1 --- Conclusion --- p.69 / Chapter 6.2 --- Perspective for further investigation --- p.71 / Bibliography --- p.72

Cheung Yin Har = 瑞利-柏納德湍流對流中Nusselt與縱橫比的關係以及邊界層性質的研究 / 張燕霞. / Thesis submitted in: October 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 115-119). / Text in English; abstracts in English and Chinese. / Cheung Yin Har = Ruili-Bonade tuan liu dui liu zhong Nusselt yu zong heng bi de guan xi yi ji bian jie ceng xing zhi de yan jiu / Zhang Yanxia. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgments --- p.iv / Contents --- p.v / List of Figures --- p.vii / List of Tables --- p.x / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background of turbulence --- p.1 / Chapter 1.2 --- Rayleigh-Benard convection --- p.3 / Chapter 1.3 --- Theoretical background --- p.4 / Chapter 1.3.1 --- The convection equations --- p.4 / Chapter 1.3.2 --- Characteristic parameters --- p.6 / Chapter 1.3.3 --- Reynolds equations --- p.8 / Chapter 1.4 --- Recent developments --- p.10 / Chapter 1.4.1 --- Heat transport --- p.10 / Chapter 1.4.2 --- Large scale flow and thermal plumes --- p.11 / Chapter 1.4.3 --- Boundary layers --- p.12 / Chapter 1.5 --- Motivation --- p.14 / Chapter 1.5.1 --- Nusselt measurements --- p.14 / Chapter 1.5.2 --- Boundary layer properties measurements --- p.14 / Chapter 1.6 --- Synopsis of this thesis --- p.15 / Chapter Chapter 2 --- Experimental setup and measurement techniques --- p.17 / Chapter 2.1 --- The turbulent convection system --- p.17 / Chapter 2.1.1 --- The convection cells --- p.18 / Chapter 2.1.2 --- The temperature probe --- p.21 / Chapter 2.1.3 --- The thermistors --- p.23 / Chapter 2.2 --- Particle Image Velocimetry (PIV) --- p.25 / Chapter 2.2.1 --- Image capture system --- p.27 / Chapter 2.2.2 --- Image analysis system --- p.36 / Chapter Chapter 3 --- Aspect ratio dependence of heat transport and the flow field --- p.39 / Chapter 3.1 --- Motivation for this experiment --- p.39 / Chapter 3.2 --- Heat transfer efficiency measurements --- p.40 / Chapter 3.3 --- Heat correction --- p.44 / Chapter 3.3.1 --- Temperature correction --- p.44 / Chapter 3.3.2 --- Heat current density J correction --- p.45 / Chapter 3.3.3 --- Finite conductivity of plate --- p.50 / Chapter 3.4 --- Aspect ratio dependence --- p.51 / Chapter 3.4.1 --- Without correction of finite conductivity --- p.51 / Chapter 3.4.2 --- With correction of finite conductivity --- p.59 / Chapter 3.5 --- Time-averaged velocity field --- p.65 / Chapter 3.6 --- Summary --- p.70 / Chapter Chapter 4 --- Local temperature and velocity measurements near the boundary layers --- p.71 / Chapter 4.1 --- Motivation for this experiment --- p.71 / Chapter 4.2 --- Temperature profile measurement --- p.72 / Chapter 4.2.1 --- Temperature and fluctuation profiles --- p.73 / Chapter 4.2.2 --- Thermal boundary thickness --- p.77 / Chapter 4.2.3 --- Temperature time series --- p.79 / Chapter 4.2.4 --- PDF --- p.83 / Chapter 4.3 --- Velocity profile measurement --- p.86 / Chapter 4.3.1 --- 2D velocity and fluctuation profiles --- p.86 / Chapter 4.3.2 --- Scaling properties --- p.93 / Chapter 4.4 --- Shear stress --- p.98 / Chapter 4.4.1 --- Viscous and Reynolds stresses --- p.99 / Chapter 4.4.2 --- Laminar or Turbulent? --- p.101 / Chapter 4.5 --- Summary --- p.104 / Chapter Chapter 5 --- Conclusion --- p.106 / Chapter 5.1 --- Heat flux measurement --- p.106 / Chapter 5.2 --- Boundary layers --- p.107 / Chapter 5.3 --- Perspective for further investigation --- p.108 / Appendix A Heat flux measurement for high Prandtl number --- p.109 / Chapter I. --- Experimental conditions --- p.110 / Chapter II. --- Result and discussion --- p.112 / Chapter III. --- Summary and perspective for further investigation --- p.114 / Bibliography --- p.115

A distinct feature of Rayleigh-Benard(RB) convection is the existence of a self-organized large-scale circulatory flow(LSC), also known as the "mean wind" of turbulence. This thesis is an experimental investigation of this LSC by using the particle image velocimetry and multi-thermal probe method. We studied the various aspects of the LSC, including the azimuthal motion, the flow cessation and reversal and the reorientation of the LSC, in aspect ratio(Gamma) 1, 1/2 and 1/3 cells, where Gamma is the ratio between the diameter and the height of the cylindrical convection cells. Also studied in the thesis are the different flow modes and the flow mode transitions for these different geometries. / It is found in Gamma = 1 cells the azimuthal motion consists of erratic fluctuations and a time-periodic oscillation. While in Gamma = 1/2 cells, this kind of oscillation is missing. An intriguing dynamic feature of the LSC is the apparently erratic large orientational change of its nearly vertical circulation plane, which is called reorientation. The occurrence of the reorientations are both Poisson process for the Gamma = 1 and 1/2 geometries. We found that the azimuthal motion of LSC is more confined in larger Gamma geometry, and this property can be used to interpret the so-called bimodality of heat transport. / The reversal of the flow direction of the LSC in RB system resembles a lot of reversal phenomena and is the interest of several theoretical models. We found, in Gamma = 1/2 geometry, that there are an order of magnitude more cessations and reversals than that in Gamma = 1 geometry, which contrasts sharply to the finding in Gamma = 1 geometry. Thus in Gamma = 1/2 cells a statistically significant number of unambiguously identified pure reversal events are obtained, which allow us to analyze several important properties of pure reversal events. It is found that the occurrence of reversals is a Poisson process and that a stronger rebound of the flow strength after a reversal/cessation leads to a longer period of stability of the LSC. Several properties of reversals/cessations in this system are found to be statistically similar to those of geomagnetic reversals. / We found in all the aspect ratios explored(Gamma = 1, 1/2 and 1/3) both single circulating roll flow structure and two vertically stacked counter-rotating rolls structure exist. The average percentage of time that the flow spends in the single-roll mode (SRM) is decreasing with Gamma while that of the double-roll mode (DRM) is increasing with Gamma. Several routes of transitions among the different flow modes are identified. We also show direct evidence that the SRM is more efficient for heat transfer than the DRM. It is also found that the time interval between successive flow mode transitions has an exponential distribution, suggesting a Poisson process for the underlying dynamics. / Xi, Hengdong = 熱湍流中的大尺度環流 / 郗恒東. / "July 2007." / Adviser: Ke-Qing Xia. / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0386. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 144-153). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307. / Xi, Hengdong = Re tuan liu zhong de da chi du huan liu / Xi Hengdong.

Chan, Tak Shing = 粗糙表面的熱湍流對流的Nusselt數和雷諾數的測量 / 陳德城. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 63-67). / Abstracts in English and Chinese. / Chan, Tak Shing = Cu cao biao mian de re tuan liu dui liu de Nusselt shu he Leinuo shu de ce liang / Chen Decheng. / Table of Contents --- p.v / List of Figures --- p.xi / List of Tables --- p.xii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What is turbulence ? --- p.1 / Chapter 1.2 --- Rayleigh Benard convection system --- p.3 / Chapter 1.2.1 --- Oberbeck-Boussinesq approximation and equations of Rayleigh- Benard system --- p.5 / Chapter 1.2.2 --- Some coherent structures of Rayleigh-Benard convection system --- p.7 / Chapter 1.3 --- Motivation --- p.8 / Chapter 2 --- Experimental methods and setups --- p.12 / Chapter 2.1 --- Convection cell --- p.12 / Chapter 2.2 --- Temperature measurement --- p.15 / Chapter 2.3 --- Experimental techniques --- p.16 / Chapter 2.3.1 --- Heat leakage prevention --- p.16 / Chapter 2.3.2 --- Water absorption of Dipropylene Glycol --- p.21 / Chapter 2.3.3 --- Particle Image Velocimetry --- p.22 / Chapter 3 --- Heat flux measurement --- p.25 / Chapter 3.1 --- Water Results --- p.26 / Chapter 3.1.1 --- Experimental procedures --- p.26 / Chapter 3.1.2 --- Heat leakage/ heat absorption estimation --- p.27 / Chapter 3.1.3 --- Results and discussions --- p.29 / Chapter 3.2 --- Dipropylene Glycol Results --- p.32 / Chapter 3.2.1 --- Experimental procedures --- p.32 / Chapter 3.2.2 --- Heat leakage/ heat absorption estimation --- p.33 / Chapter 3.2.3 --- Result and discussions --- p.34 / Chapter 3.3 --- More discussion --- p.41 / Chapter 4 --- Large scale circulation and Reynolds number measurement --- p.44 / Chapter 4.1 --- Flow pattern of turbulent Rayleigh-Benard convection over rough plates --- p.46 / Chapter 4.2 --- Reynolds number measurement --- p.48 / Chapter 4.2.1 --- Reynolds number determined from oscillation of temper- ature signals --- p.48 / Chapter 4.2.2 --- Reynolds number determined from velocity measurement near sidewall --- p.55 / Chapter 5 --- Conclusion --- p.61 / Chapter 5.1 --- Conclusion --- p.61 / Bibliography --- p.63