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This thesis presents a study of tidal flow interaction with headland and island features. Wake development in the lee of topographic features can generate complex two- and three-dimensional flow structures. The primary objectives of the research are to (i) determine the suitability of traditional numerical modelling techniques for application in the coastal environment, (ii) elucidate the development of wake features in the coastal environment, and (iii) illustrate the impact of wake features on tidal mixing and dispersion processes. A numerical finite-difference model has been developed using standard methods to solve the two-dimensional Shallow Water Equations. The model has undergone an extensive validation and verification exercise. Comparisons of model output with field data and output from other numerical simulations presented in the literature confirms the suitability of the numerical model for investigating wake and eddy development in the coastal environment. The sequence of events necessary for a wake eddy to develop from flow separation through to eddy shedding has been elucidated using idealised numerical modelling cases. Simulation and interpretation of test cases obtained from the literature has confirmed these findings. Important differences between eddy shedding events in headland and island wakes have been identified. Symmetry of the governing equations has been confirmed as the source of numerical models' failure to reproduce eddy shedding around symmetrical islands. Mixing and dispersion around a headland in a deterministic tidal flow field is simulated. Lagrangian analysis techniques are required to properly interpret transport processes. The significant impact of transient eddy features generated by the headland is indicated by the mixing and dispersion diagrams presented. A defined front between the well mixed and unmixed regions of flow is apparent. This indicates the extent of the mixing zone. Dispersion of individual patches around the headland is described using a three stage process.

A experimental study of the two-phase flow inside a lean premixed prevaporised combustor has been carried out in order to evaluate the capabilities of large eddy simulations applied to engineering applications. To this end, a existing LPP design was modified in order to simplify the injection mechanisms involved and gain a optimum optical access if the critical injection region. The liquid and the gas phase inside the LPP module are then characterised with the help of non-invasive laser techniques, namely PDA for the liquid phase, LDA for the airstream and PLIF for the vapour phase. Relevant information regarding droplet sizes, droplet velocity, airstream velocity and fuel placement have thus been collected. The measurements are then evaluated against flow solutions computed by a Eulerian-Lagrangian ite-volume solver. A hybrid RANS/LES modelling strategy has been adopted for the gas phase and the Lagrangian tracking procedure has been updated to predict the influence of the gas turbulence on the droplet dispersion, and the heat penetrating the droplet during its evaporation. This simulation is finally matched against ZD and 3D steady RANS solution in a attempt to demonstrate the superiority of the time dependent approach.

本論文主要通過衛星遙感觀測資料和海洋數值模式的方法，來研究南海海洋上層對颱風西馬侖（2006）的回應過程，以及南海水平方向的渦度熱通量的年變化過程。 / 通過衛星海表溫度資料和氣候態海洋溫度資料反演颱風西馬侖引起的混合層加深的問題。反演結果顯示，2006年11月3日，對應海表溫度降低了4.4度，混合層則由颱風前的43.2米加深了104.5米，該結果與一維混合層模型(GOTM)的類比結果一致。此外，颱風引起的海表面溫度梯度可用來計算斜壓地轉流場和渦度。負渦度顯示了反氣旋斜壓迴圈在混合層底部最強，在50米水深處地轉流速可達到0.2米每秒。2006年11月3日，颱風西馬侖在最大的海表溫度降低的附近，向西南方向轉彎，此時行進速度比較緩慢(1.7 米每秒)進而導致在亞臨界條件弗勞德數(颱風的平移速度與第一斜壓相速度的比值)為0.6，在颱風尾區因缺少慣性重力波從而促進了海表溫度冷卻和混合層加深。通過比較Argo浮標觀測資料和氣候態資料的溫度剖面，混合層加深程度估算的誤差在10米以內。 / 三維海洋數值模型ROMS 用來研究颱風期間海洋物理動力和生態回應。海表溫度類比值同衛星觀測值比對得到的相關係數高達84%以上，表明ROMS基本上可以模擬在颱風期間南海的海表面溫度變化情況。但是深入研究發現由於垂向混合強度不夠，模式結果低估了海表面溫度冷卻和混合層加深，混合層深度被低估。通過增加波致混合效應(Bv)改進KPP混合方案，可以提高海表面溫度冷卻和混合層加深的模擬精度。類比結果顯示在颱風尾區，葉綠素的大規模爆發則發生在颱風經過的1周以後。透光層葉綠素濃度由颱風前的0.1 mg m⁻³ 增加到11月9日的1.9 mg m⁻³。衛星觀測顯示在颱風尾區，葉綠素濃度在11月16日仍高達0.85 mg m⁻³。 / 高度計的海表面高度異常值與海表面溫度的衛星觀測資料可以用來計算南海渦度熱通量。南海表層渦度熱通量的年變化趨勢表明，在南海西邊的熱通量表現出北向輸送特徵，其強度甚至與黑潮延伸區域的強熱通量相當。渦熱通量在冬季最強，熱量由南海南部流入，並且從呂宋海峽流出，甚至通過臺灣海峽進入東海海域。冬季熱通量的輻合帶主要分佈在南海東部近呂宋海峽附近海域和越南東南海域，而夏季主要集中在越南東南海域。研究表明，冬季和夏季的海表面渦度熱通量對海洋上層熱收支平衡的調整有顯著影響。 / This dissertation focuses on the investigation of the upper ocean response to typhoon Cimaron (2006) and annual variations of horizontal eddy fluxes in the South China Sea (SCS) through the methods both of satellite remote sensing and numerical ocean modeling. / The mixed layer deepening induced by typhoon Cimaron is derived based on satellite observed sea surface temperature (SST) and climatological temperature profiles in the SCS. Corresponding to the SST drop of 4.4ÅC on November 3, 2006, the mixed-layer deepened by 104.5 m relative to the undisturbed depth of 43.2 m, which is consistent with the simulation results from the one-dimensional mixed-layer model (GOTM). Furthermore, baroclinic geostrophic velocity and vorticity are calculated from the surface temperature gradient caused by the typhoon. The negative vorticity, associated with the typhoon cooling, indicated an anti-cyclonic baroclinic circulation strongest at the base of the mixed-layer, and at the depth of 50 m, the geostrophic speed reached as high as 0.2 m s⁻¹. Typhoon Cimaron proceeded slowly (1.7 m s⁻¹) when it was making a southwestward turn on November 3, 2006, resulting in a subcritical condition with a Froude number (the ratio of typhoon translation speed to first baroclinic mode speed) of 0.6 around the maximum SST drop location and facilitating high SST cooling and mixed-layer deepening due to absence of inertial-gravity waves in the wake of the typhoon. Comparison of Argo buoy data with the climatological temperature suggests that the average uncertainty in the mixed-layer deepening estimation caused by the difference between Argo and climatological temperature profiles is less than 10 m. / The physical dynamic and biological responses to typhoon Cimaron are investigated through a three-dimensional ocean model, the Regional Ocean Modeling System (ROMS). The correlation between simulated sea surface temperature (SST) and the satellite observations is over 84%, which indicates ROMS can generally simulate the sea surface temperature in the South China Sea during typhoon process. However, detailed analysis shows that the ROMS model underestimates the sea surface temperature cooling and mixed layer deepening because of insufficient mixing in the modeling. The wave-induced mixing term (Bv) added into the nonlocal K-Profile Parameterization (KPP) scheme can increase the simulation accuracy of surface temperature cooling and mixed layer depth deepening in response to the typhoon forcing. The simulation results show that the blooming of phytoplankton in the wake of storm appeared one week later after typhoon’s passage. The concentration of chlorophyll is 0.1 mg m⁻³ at pre-typhoon time and increase to 1.9 mg m⁻³ on November 9. Satellite Observation indicates the concentration of chlorophyll in wake of typhoon Cimaron was also in a high value of 0.85 mg m⁻³ on November 16. / The eddy heat flux in the SCS is derived from the satellite data including the altimeter surface height anomalies and optimally interpolated sea surface temperature. The long term heat flux shows a northward heat transport on the west side of the SCS, comparable to that in other strong flux regions such as the Kuroshio extension. The eddy flux becomes the strongest in winter with the inflow flux in the south and the outflow through the Luzon, and the eddy heat can flux through the Taiwan Strait into the East China Sea. The convergence of the flux indicates that heat accumulation in the eastern SCS close to Luzon Strait in winter and also to southeast of Vietnam in winter and summer. The eddy heat flux is more significant in adjusting the ocean upper layer heat budget flux in winter and summer. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Sun, Yujuan. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 101-111). / Abstracts also in Chinese. / Abstract --- p.ii / 摘要 --- p.v / Acknowledgements --- p.vii / Table of Contents --- p.viii / List of Tables --- p.x / List of figures --- p.xi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Ocean responses to typhoons (or tropical storms and hurricanes) --- p.4 / Chapter 1.2 --- Eddy Heat Transport --- p.9 / Chapter 2. --- The one-dimension remote sensing model (the mixed-layer deepening) --- p.11 / Chapter 2.1 --- Introduction --- p.11 / Chapter 2.2 --- Data and Methodology --- p.11 / Chapter 2.3 --- Results --- p.16 / Chapter 2.4 --- One-dimensional mixed-layer model --- p.17 / Chapter 2.5 --- Discussions --- p.20 / Chapter 2.5.1 --- Horizontal baroclinic pressure gradient and vorticity --- p.20 / Chapter 2.5.2 --- Effects of subsurface temperature variation on the mixed-layer deepening --- p.22 / Chapter 2.6 --- Summary --- p.28 / Chapter 3. --- Three-dimensional numerical ocean model --- p.29 / Chapter 3.1 --- Model description --- p.29 / Chapter 3.1.1 --- Physical model --- p.30 / Chapter 3.1.2 --- Biological model --- p.34 / Chapter 3.2 --- Model setting --- p.40 / Chapter 3.2.1 --- Initial and lateral boundary conditions --- p.41 / Chapter 3.2.3 --- Bio-module setting --- p.47 / Chapter 3.3 --- Model result validation --- p.51 / Chapter 3.3.1 --- Satellite observations --- p.51 / Chapter 3.3.2 --- Validations of observations and simulations --- p.54 / Chapter 3.4 --- Model results analysis --- p.56 / Chapter 3.4.1 --- Ocean temperature --- p.56 / Chapter 3.4.2 --- Ocean current --- p.62 / Chapter 3.4.3 --- bio-results of simulation --- p.70 / Chapter 3.4.4 --- Effect of the wave-induced mixing --- p.77 / Chapter 3.5 --- summary --- p.83 / Chapter 4. --- Annual Variations of Horizontal Eddy Heat Flux in the South China Sea --- p.84 / Chapter 4.1 --- Introduction --- p.84 / Chapter 4.2 --- Methodology and data --- p.86 / Chapter 4.3 --- Results --- p.89 / Chapter 4.4 --- Summary --- p.96 / Chapter 5. --- Conclusion --- p.97 / Chapter 6. --- Future work --- p.100 / Bibliography --- p.101

Graduation date: 2000

Remote field eddy current (RFEC) testing is an eddy current non-destructive test method that has become widely used for the examination of carbon steel tubes, such as those found in heat exchangers and boilers. RFEC testing relies on the use of very low intensity electromagnetic fields on the exciting probe. The defect detection is carried out considering the phase difference between the exciting and pickup signals. However, various testing effects were produced because the affection of different electromagnetic characteristics of tubes and types of defects The purpose of this study is to analyze the influential factors of RFEC testing accuracy by means of the finite element method (FEM). In order to investigate the numerical simulation, the researcher used the finite element software package FEMLAB to create an electromagnetic model of RFEC testing. Then he applied the mathematics software package MATLAB to plot the voltage plane diagram and defect-phase difference diagram. After the comparison of the simulation with experiments, the researcher confirmed the reliability of electromagnetic simulation. As a result, this study provides the variations in RFEC testing result diagrams for the influential factors. Over all, this study has successfully established an FEM RFEC electromagnetic model. After the FEM simulation, this method can provide many comparable data for experimenter. This study may remedy the different types of defects and reduce assessing error. Therefore, the accuracy and reliability of testing of RFEC can be accessed.

Eddy current testing is a non-destructive testing method, which is usually used for an examination of thin metal material. It can acquire the coil impedance variety between the eddy current magnetic field and the coil magnetic field by electromagnetic induction. By prognosticating its phase angle, testing can exam the influence of the examination through the impedance plane diagram. However, the eddy current testing is usually influenced by different types of the defects and factors of examination. The purpose of this study is to analyze the examination factors of eddy current testing accuracy by means of the finite element method (FEM). This study is to create two dimensional axial symmetry model of simplification in eddy current testing by finite element software package Femlab. After that, the researcher applied the mathematics software package Matlab to plot the impedance plane diagram and evaluation curve. Furthermore, the researcher analyzed the impedance plane diagram and evaluation curve in different examination factors. After the FEM simulation in different types of the defects and the examination factors, this study can provide many comparable data for experimentalists, to judge the condition of the defects more correctly and to reduce testing errors more effectively in the eddy current testing.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xxii, 177 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 151-154) and index.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xiv, 259 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 252-259).