The observation of turbulence in the Florida Current is presented with the use of velocity measurements collected with an Acoustic Doppler Current Profiler (ADCP). The research is conducted through application of the theories of Taylor and Kolmogorov and related derivations, and processing tools of MATLAB software to this Eulerian observation of flow [1]. The velocity profile of the Florida Current is deduced in terms of its turbulent character with shear, acceleration, gradient, Reynolds Number, Reynolds Stress, Welch power spectrum density of current velocity, wavenumbers of Taylor’s hypothesis and Kolmogorov, wavenumber spectrum, eddy diameters, diapycnal diffusivity, and the Richardson Number. Processing methods are validated with results of other research conducted in the Florida Current with the use of a Multi-Scale Profiler, and an Advanced Microstructure Profiler for determination of shear, dissipation, diffusivity, and estimates of turbulent eddy diameters based on Taylor’s Hypothesis [1][4]. A spectral analysis is developed and is compared with Kolmogorov’s -5/3-Law. The process and the results of the analysis are described. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Qiu, Can = / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 82-87). / Abstracts in English and Chinese. / Qiu, Can = / Abstract --- p.i / 摘要 --- p.ii / Acknowledge --- p.iii / Table of Contents --- p.iv / List of Figures --- p.v i i / List of Tables --- p.xi / Chapter Chapters I --- Introduction --- p.1 / Chapter 1.1 --- Turbulence --- p.1 / Chapter 1.2 --- Rayleigh-Benard convection --- p.3 / Chapter 1.2.1 --- Physics picture-Motion in the convection cell --- p.4 / Chapter 1.2.2 --- The governing equations and parameters --- p.6 / Chapter 1.2.3 --- Multilayer convection --- p.9 / Chapter 1.2.4 --- The Nu scaling --- p.9 / Chapter 1.2.5 --- Boundary layers --- p.11 / Chapter 1.3 --- Present work and the organization of the thesis --- p.14 / Chapter II --- Experimental Setup --- p.16 / Chapter 2.1 --- The convection cell --- p.16 / Chapter 2.2 --- The thermistors --- p.20 / Chapter 2.2.1 --- Calibration --- p.20 / Chapter 2.3 --- The multimeter --- p.21 / Chapter 2.4 --- Thermostat box --- p.22 / Chapter 2.5 --- Visualization --- p.23 / Chapter 2.6 --- Motorized translation stage --- p.24 / Chapter 2.7 --- AC Wheatstone Bridge and Lock in amplifier --- p.24 / Chapter 2.8 --- Test different heaters --- p.26 / Chapter III --- "Heat flux, boundary layer and Reynolds number measurement of one-layer FC77 thermal convection" --- p.30 / Chapter 3.1 --- Heat flux measurement with correction --- p.30 / Chapter 3.1.1 --- Sidewall correction --- p.31 / Chapter 3.1.2 --- Bottom plate correction --- p.31 / Chapter 3.1.3 --- Post correction --- p.31 / Chapter 3.2 --- The Nu result --- p.32 / Chapter 3.3 --- Boundary layer measurement --- p.34 / Chapter 3.4 --- The Pr dependence of the Reynolds number Re --- p.37 / Chapter 3.5 --- Summary --- p.40 / Chapter IV --- "Heat transfer, thermal boundary layer and flow property measurement of multilayer immiscible fluid turbulent thermal convection" --- p.41 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Experiment --- p.44 / Chapter 4.3 --- The temperature and temperature fluctuation across the interface --- p.46 / Chapter 4.3.1 --- The temperature near the interface --- p.46 / Chapter 4.3.2 --- Position and temperature of the interface --- p.47 / Chapter (a) --- Using the profile to get the temperature of the interface --- p.47 / Chapter (b) --- Using the traveling microscope to get the absolute position of the interface --- p.50 / Chapter 4.4 --- The Nu result --- p.50 / Chapter 4.5 --- Boundary layer thickness and scaling --- p.54 / Chapter 4.6 --- Statistical properties of the temperature field across the interface --- p.58 / Chapter 4.6.1 --- Temperature time series and the corresponding histogram of the interface --- p.58 / Chapter 4.6.2 --- "The mean, root mean square, skewness, time derivative skewness and flatness of the temperature profiles across the interface" --- p.64 / Chapter 4.6.3 --- Scaling of the temperature fluctuation in two-layer system --- p.71 / Chapter 4.7 --- The temperature oscillation --- p.74 / Chapter 4.8 --- Passive scalar and active scalar --- p.77 / Chapter 4.9 --- Summary --- p.79 / Chapter V --- Conclusion --- p.80 / Chapter 5.1 --- One-layer thermal convection --- p.80 / Chapter 5.2 --- Two-layer thermal convection --- p.80 / Chapter 5.3 --- Future works --- p.81 / References --- p.82

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.

Graduation date: 2006

Bibliography: leaves ix-xiii / viii, 171, ix-xiii leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1992

Turbulent flow measurements were performed in the wake of a slender axisymmetric body in the presence of a flat plate strut and an image plane representing the "rigid lid" approximation to a free surface. The tests were performed in a wind tunnel at a nominal Reynolds number of 6.0 x 10⁵. All turbulent flow parameters were measured at three streamwise stations. A Yawhead probe was used for the mean flow measurements, and a Constant Temperature Anemometer System with a 'x'-wire probe was used to obtain the turbulent flow characteristics. The presence of the image plane was found to increase the velocity defect and the static pressure as the image plane was approached. A redistribution among the various components of velocity fluctuations was noted near the "rigid lid" plane. The transverse component was enhanced at the expense of the normal component. The image plane also was found to influence the magnitudes and radial spread of turbulence intensities and Reynolds stresses. Some interactions between the wake of the axisymmetric body and that of the plate strut were observed. Overall, the mean velocities and the turbulence quantities indicated symmetry about the image plane throughout the wake. / M.S.

M. S.

An analysis is presented for hot wire/film anemometer measurement of mean velocities and turbulent stresses in a three dimensional flow field with a predominant flow direction. The experimental data can be taken with an automated traverse under the control of a digital data acquisition system which has been modified for this particular application. / Master of Science

Experimental results of hot-·wire measurements of turbulence in a supersonic shear layer are presented. A multiple-overheat single-wire method based on high-speed, computer-controlled sampling was used in order to obtain large sample sets in short time intervals. The Mach 3 main stream had a total pressure of 95 psia and a Re/cm of 2 x 10⁶. The Mach 1.7 secondary stream was injected parallel to the main flow at 10.7 psia, resulting in a slightly overexpanded flow. The injection slot had a height of 1.2 cm. The flow was monitored at four streamwise stations (x/H = .25, 4, 10, 20). The total temperature of the injected stream was varied from 300 K (equal to that of the main stream) to 420 K. The effects on the flow of these changes in density, velocity and temperature was investigated. Measured quantities included the mean and rms levels of the mass flux and total temperature. Nanosecond Shadowgraphs and spark Schlieren photographs were taken. The Favre-averaged velocity fluctuation, u^H, was also calculated. Small increases in absolute turbulence levels were seen in the heated flow, and the location of the maximum turbulence shifted significantly. Heating greatly enhanced the mixing in the shear layer and in the injected flow by the last station. An investigation of shock interaction with the shear layer generally resulted in elevated turbulence, but had little effect on. The measurement technique and reduction method proved accurate in the unheated flow, but greater uncertainty was found for the heated injection case. / Master of Science

Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen 5° increments. Stereo PIV measurements of the instantaneous velocity field were recorded at four locations for each angle. Tilted wakes are described in terms of the average streamwise velocity field, wall-normal velocity field, Reynolds stresses, and mean vertical transport of kinetic energy. Conditional sampling is used to quantify the importance of sweep vs. ejection events and thus downwards vs. upwards momentum transfer. Additionally, wake center displacement and changes in net power are presented and compared to existing models. The results demonstrate large variations in wake velocity and vertical displacement with enhanced vertical energy and momentum transfer for negative tilt angles. Simulation models accurately predict wake deflection while analytic models deviate considerably highlighting the difficulties in describing tilt phenomena. Negative angles successfully produce crashing wakes and improve the availability of kinetic energy thereby improving the power output of the wind plant.