Ji and Wang (2010) propose that the dominant source of sound from a forward facing step is the stream wise dipole on the face of the step and that sources acting normal to the flow are negligible. Sound radiation normal to flow of forward facing steps has been measured in wind tunnel experiments previously by Farabee and Casarella (1986, 1991) and Catlett (2010). A method for evaluating sound radiation from surface roughness proposed in Glegg and Devenport (2009) has been adapted and applied to flow over a forward facing step which addresses the sound normal to the flow that was previously unaccounted for. Far-field radiation predictions based on this method have been compared with wind tunnel measurements and show good agreement. A second method which evaluates the forcing from a vortex convected past surface roughness using RANS calculations and potential flow information is also evaluated. / by Benjamin Skyler Bryan. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

This dissertation will consider the sound radiation from forward-facing steps and a three dimensional cylindrical embossment of very low aspect ratio mounted on a plate. Glegg et al (2014) outlined a theory for predicting the sound radiation from separated flows and applied the method to predicting the sound from forward-facing steps. In order to validate this theory it has been applied to the results of Catlett et al (2014) and Ji and Wang (2010). This validation study revealed that the original theory could be adjusted to include a mixed scaling which gives a better prediction. RANS simulations have been performed and used to support the similarities between the forward-facing step and the cylindrical embossment. The simulations revealed that the cylindrical embossment exhibits a separation zone similar to that of the forward-facing step. This separation zone has been shown to be the dominant source of noise on the forward-facing step in previous works and therefore was expected to be the major source of sound from the cylindrical embossment. The sensitivity of this separation zone to the different parameters of the flow has been investigated by performing several simulations with different conditions and geometries. The separation zone was seen to be independent of Reynolds number based on boundary layer thickness but was directly dependent on the height of the cylinder. The theory outlined in Glegg et al (2014) was then reformulated for use with a cylindrical embossment and the predictions have been compared with wind tunnel measurements. The final predictions show good agreement with the wind tunnel measurements and the far-field sound shows a clearly defined directionality that is similar to an axial dipole at low frequencies. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Boundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of the turbulence with uncorrelated sheets of vorticity. Both aerodynamic and acoustic results are compared to experimental measurements of the flow. The CFD simulation of the flow returns consistent results but would benefit from a refinement of the grid. The surface pressure spectrum presents a slope in the high frequencies close to the experimental spectrum. The far field noise spectrum has a 5dB difference to the experiments. / by Jean-Baptiste Blanc. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

The flow field behavior of axial flow turbines is of great importance, especially in modern designs that may operate at a low Reynolds number. At these low Reynolds numbers, the efficiency loss is significantly augmented compared to higher Reynolds number flows. A detailed incompressible numerical study of a single stage axial-flow turbine at a low Reynolds number is investigated with the use of multiple eddy-viscosity turbulence models. The study includes epistemic uncertainty quantification as a form of numerical error estimation. The numerical results show good qualitative and quantitative agreement with experimental data. It was found that the shear stress transport (SST) k - ω turbulence model with rotation/curvature correction and inclusion of transition modeling is most capable at predicting the mean velocity distribution, which is further enhanced when the URANS formulation is employed. However, all the cases indicate a large variation in the prediction of the root-mean-squared of the turbulent velocity fluctuations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Tam Wai Shing = 穩態環流的熱傳送與縱橫比之關係及其與湍流狀態的瑞利-伯纳德對流之聯繫 / 譚偉誠. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 59-61). / Text in English; abstracts in English and Chinese. / Tam Wai Shing = Wen tai huan liu de re chuan song yu zong heng bi zhi guan xi ji qi yu tuan liu zhuang tai de Ruili-Bonade dui liu zhi lian xi / Tan Weicheng. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Review of the theoretical studies of heat transport by turbulent convection --- p.5 / Chapter 2.1 --- The marginal stability arguments --- p.7 / Chapter 2.2 --- Chicago mixing zone model --- p.7 / Chapter 2.3 --- Shraiman and Siggia theory --- p.10 / Chapter 2.4 --- Grossmann and Lohse Theory --- p.12 / Chapter 2.4.1 --- Estimation of the kinetic dissipation --- p.13 / Chapter 2.4.2 --- Estimation of the thermal dissipation --- p.14 / Chapter 2.4.3 --- The four regimes --- p.15 / Chapter 3 --- Aspect-ratio dependence: The problem studied --- p.19 / Chapter 3.1 --- The velocity field --- p.21 / Chapter 3.1.1 --- Incompressible flow --- p.21 / Chapter 3.1.2 --- Large-scale circulating flow --- p.21 / Chapter 3.1.3 --- No-slip boundary conditions --- p.22 / Chapter 3.2 --- The functions f(x) and g(y) --- p.23 / Chapter 3.3 --- Boundary conditions for the temperature field --- p.23 / Chapter 3.4 --- Important parameters in the numerical calculation --- p.24 / Chapter 4 --- The numerical calculations --- p.31 / Chapter 5 --- Results and discussions --- p.34 / Chapter 5.1 --- Nu-Г Relationship --- p.38 / Chapter 5.2 --- Nu - Pe Relationship --- p.41 / Chapter 6 --- Implications for heat transport by Rayleigh-Benard convection --- p.49 / Chapter 6.1 --- Nu-Ra relationship --- p.50 / Chapter 6.2 --- Comparison with recent experimental results --- p.52 / Chapter 7 --- Conclusions --- p.57 / Bibliography --- p.59

Direct real-space multi-point measurements of the velocity and temperature fields were carried out in various places of the convection cell. In the central region of the cell it is found that both velocity and temperature exhibit the same scaling behavior that one would find for the velocity and for a passive scalar in homogeneous and isotropic Navier-Stokes turbulence. Near the cell's sidewall where thermal plumes abound, vertical velocity and temperature exhibit different scalings. A model, taking into account both buoyancy and energy dissipation, is proposed and its predictions agree well with the sidewall experimental results. / This thesis aims to address three key issues in convectioe thermal turbulence: heat transport, statistics of turbulent fluctuations of the velocity and temperature fields, and flow dynamics. / Through measurement of 2D velocity at different cross sections of the cylindrical cell with Gamma = 1, we investigate the 3D flow structures and dynamics of turbulent thermal convection. Our result reveals how thermal plumes synchronize their emissions and organize their motions spatially between the top and bottom plates, leading to an oscillatory motion in the bulk region of the fluid. In Gamma = 0.5 small cell, we successfully identified the relationship between 2D instantaneous velocity map and the time-averaged 3D flow pattern. This experiment also showed that a particular value of Nu can be unambiguously associated with a specific large-scale flow mode in the convection cell. By taking into account the effects of the evolution in the circulation path of the mean wind and of the counterflow, we provide a solution to the riddle about the scaling exponent dispersion of the Reynolds number Re with Ra and show that the scaling exponent has a universal value of 0.5. / To study the confinement effect on heat transport at high levels of turbulence, we conducted high precision measurements of the Nusselt number Nu as a function of the Rayleigh number Ra in a 1 m diameter cylindrical cell filled with water with aspect ratio Gamma = 0.67, l, 2, 5, 10, 20. The measurements were conducted at the Prandtl number Pr ≃ 4 with Ra varying from 1 x 10 7 to 5 x 1012. It is found that Nuinfinity can be described by a combination of two power laws for all aspect ratios, and that the asymptotic large Gamma behavior may have been reached for Gamma ≥ 10. By studying the statistics of temperature fluctuations inside the conducting plates, we found that the product of temperature skewness and the skewness of temperature time derivative may be used to quantify the intensity of plume emissions. / Sun Chao = 熱湍流對流的實驗研究 / 孙超. / "July 2006." / Adviser: Keqing Xia. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1697. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 132-140). / 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. / School code: 1307. / Sun Chao = Re tuan liu dui liu de shi yan yan jiu / Sun Chao.

Qi, Pengfei = 湍流熱對流中速度場結構函數和流動循環的實驗研究 / 齊鵬飛. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 65-69). / Abstracts in English and Chinese. / Qi, Pengfei = Tuan liu re dui liu zhong su du chang jie gou han shu he liu dong xun huan de shi yan yan jiu / Qi Pengfei. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgements --- p.iii / Contents --- p.iv / List of Figures --- p.vi / List of Tables --- p.X / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What is turbulence? --- p.1 / Chapter 1.2 --- Why study turbulence and experimentally? --- p.2 / Chapter 1.3 --- Turbulent Rayleigh-Benard convection --- p.4 / Chapter 1.4 --- Basic equations and characteristic parameters --- p.S / Chapter 1.4.1 --- Continuity equation --- p.5 / Chapter 1.4.2 --- Momentum equation (Navier-Stokes equation) --- p.5 / Chapter 1.4.3 --- Energy equation --- p.7 / Chapter 1.4.4 --- Averaged equations --- p.9 / Chapter 1.4.5 --- Characteristic parameters --- p.10 / Chapter 1.5 --- Statistical properties in small-scale turbulence --- p.13 / Chapter 1.5.1 --- Phenomenological description and Kolmogorov hypotheses --- p.14 / Chapter 1.5.2 --- Local structure of the velocity fluctuations --- p.15 / Chapter 1.6 --- Large-scale circulation --- p.17 / Chapter 1.7 --- Motivation and Organizations of this thesis --- p.19 / Chapter 1.7.1 --- B059 scaling --- p.19 / Chapter 1.7.2 --- Large-scale circulation --- p.19 / Chapter 1.7.3 --- Organization of the thesis --- p.20 / Chapter 1.8 --- Some words to my experiment and further expectation --- p.21 / Chapter Chapter 2 --- Experimental apparatus and techniques --- p.27 / Chapter 2.1 --- Rectangle cell --- p.27 / Chapter 2.2 --- The power supply and cooler --- p.28 / Chapter 2.3 --- Thermistor and multimeter --- p.29 / Chapter 2.4 --- Particle image velocimetry (PIV) technology --- p.30 / Chapter 2.4.1 --- Seeding particles --- p.31 / Chapter 2.4.2 --- Light source and light-sheet optics --- p.33 / Chapter 2.4.3 --- Imaging system --- p.34 / Chapter 2.4.4 --- Control system --- p.34 / Chapter 2.4.5 --- Analysis method --- p.35 / Chapter Chapter 3 --- Small-scale properties in rectangular cell --- p.37 / Chapter 3.1 --- Introduction --- p.37 / Chapter 3.2 --- Experimental condition --- p.37 / Chapter 3.3 --- Homogeneity --- p.39 / Chapter 3.4 --- Isotropy --- p.40 / Chapter 3.5 --- Scaling of structure function --- p.42 / Chapter Chapter 4 --- Large-scale circulation --- p.51 / Chapter 4.1 --- Introduction --- p.51 / Chapter 4.2 --- Experimental condition and limitation --- p.54 / Chapter 4.3 --- Statistical properties of large-scale circulation period --- p.56 / Chapter 4.4 --- Scaling of the Reynolds number --- p.59 / Chapter 4.5 --- Oscillation period --- p.60 / Chapter Chapter 5 --- Conclusion --- p.63 / Chapter 5.1 --- Small-scale properties in rectangular cell --- p.63 / Chapter 5.2 --- Large-scale circulation --- p.63 / Reference --- p.65

Bibliography: leaves 184-190 / viii, 190 leaves : ill ; 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 Applied Mathematics, 1987

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