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An alternative method to overcome the high cost and time required for the design, analysis, construction and operating of a conventional water control structure is an inflatable dam. The basic aim of this project is to study both theoretically and experimentally the behaviour and performance of inflatable dams under hydrostatic and hydrodynamic conditions and to develop a design method. A finite element approach is developed in order to analyse air, water and a combination of air and water inflated dams to determine the shape and tension of the membrane of the dam under hydrostatic and hydrodynamic conditions. A series of models of inflatable dams were constructed and tested under hydrostatic and hydrodynamic conditions. The shapes of these models were compared with the theoretical shapes obtained from the theoretical analysis. The comparison shows there was a good relationship between the experimental and theoretical shapes. A new formula was derived for calculating the rate of flow over the air, water and air/water inflated dams theoretically. This develops the potential for applying an inflatable dam as a device for measuring discharge. A design technique for a dam was developed to design air, water and air/water inflated dams under hydrostatic conditions. This,technique can be used for the design of dams with different geometry of base length. computer programs were written for the analysis and design of the dams based on the finite element approach and considerable efforts were undertaken to simplify the input data and the output results. A sub-program was developed to provide the results in graphic form if required.

Philosophiae Doctor - PhD / Using two hydrodynamic galaxy formation simulations from the Mufasa project that I helped develop, we aim to better understand the relationship between galaxy evolution and its cold gas content commonly known as the neutral hydrogen or Hi. We first look at the environmental properties of the simulated galaxies and compare to those that are available observationally. As a proxy, we specifically quantify the so-called galactic conf ormity, which is the concordance between the properties of galaxies neighbouring the primaries, in chapter 2. We show that the Hi, the specific star formation rate (sSFR) and the colour of galaxies show galactic conformity in qualitative agreement with previous observed data, i.e. the Hi-rich primary galaxies are surrounded by Hi-richer galaxies than the Hi-poor primary galaxies, and similarly for the sSFR and the colour. We find that environment, quantified by the number of neigbouring galaxies within a fixed aperture, stellar age and molecular hydrogen (H2) also show conformity. Galactic conformity also depends on the dark matter halo mass of the primary galaxy. The galactic conformity signal from the primaries of smaller haloes is weak but extends out to several virial radii of those structures, whereas the signal is very strong for high mass haloes but lowers quickly with distances from the primaries. We also find the galactic conformity only emerges in the later half of cosmic evolution. We next quantify the gas content and star formation depletion timescales in chapter 3. We use two carefully chosen groups of simulated galaxies and find that timescales are affected by both the mass of the virialised structure of the first infall and the galaxy stellar mass at infall: the higher the halo mass or the stellar mass the shorter the timescale. The gas or Hi depletion timescale is concordant to that of the star formation quenching, indicative of direct decrease of SFR due to depletion of the extended cold gas reservoir. The neutral atomic or molecular hydrogen consumption timescale depends on the Hubble time. Galaxies tend to form stars more efficiently at lower redshift. While the halo mass of infall affects the consumption timescale of the Hi, it does not correlate with the H2. We lastly develop machine learning tools to use galaxy photometric data to predict a galaxy’s Hi mass in chapter 4, to allow predictions for Hi from much larger optical photometric surveys. The training and testing of the algorithms are done first with the simulated data from Mufasa. We show that our model performs better than previously done with ad hoc data fitting approaches. Random Forest (RF) followed by the Deep Neural Networks (DNN) perform best among the explored machine learning techniques. Extending the trained models to observed data, namely the Arecibo Legacy Fast ALFA (ALFALFA) and REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey data, we show the overall performance is slightly reduced relative to the simulated testing set owing to the small inconsistency between definition of galaxy properties between simulation and observational data, and DNN perfoms the best in this case. The application of our methods is useful for galaxy-by-galaxy predictions and anticipated to correct for incompletness in the upcoming Hi deep surveys done with MeerKAT and eventually the Square Kilometre Array (SKA).

This thesis presents results from experimental and numerical investigations of the hydrodynamic forces on a rigid cylinder moving with prescribed orbits in uniform flow. The hydrodynamic forces are measured in both in-line (IL) and cross- ow (CF) directions. The measurements are processed to nd excitation and added mass coeffcients at discrete frequencies. The numerical simulations are used to illustrate the vortex shedding modes and are compared with the experimental results. The hydrodynamic coeffcients obtained from the harmonic forced motion experiments of a rigid cylinder do not always represent forces on a cross section of a exible beam. The orbits used in the forced motion experiments are therefore extracted from the measured motions of cross sections of a exible pipe under uniform and shear flows. Both periodic and observed orbits within a time window are applied as prescribed motions. Higher order displacement components are present in such orbits. IL response amplitudes from combined IL and CF response are larger than pure IL response amplitudes. The hydrodynamic coefficients obtained from the periodic experiments are often larger than those obtained from the pure IL tests. Higher order displacement components are more common in the IL direction than in the CF direction, and higher order IL displacement components will cause larger hydrodynamic forces in both directions. The hydrodynamic coefficients obtained from periodic motion tests are adequate for representing quasi-periodic observed motions. For chaotic observed motions, periodic orbits will yield hydrodynamic coefficients with larger uncertainties. Results from numerical analyses using large eddy simulation (LES) indicate that this method can be used to identify vortex shedding patterns and predict hydrodynamic forces under certain Re numbers and orbits.

Abstract The tool wear characteristics of the hydrodynamic polishing process under various lubricating conditions are examined in this study. Both the experimental and theoretical studies will be done in this paper. In the experimental study, the relationships between tool wear and its possible influential factors will be examined. In the theoretical study, the mathematical model will be established to interpret the qualitative and quantitative relationships between tool wear characteristics and various operating parameters. For the experimental study, a series of experiments will be done to investigate the effect of various factors on the tool wear and machining rate, under non-contact or semi-contact lubricating condition. The factors may include the tool¡¦s angular speed, the applied load, the tool¡¦s surface irregularities, the slurry viscosity, and the properties of tool, workpiece and abrasive particle (such as surface energy). To establish the mathematical model, the principle of dynamics, law of minimum potential energy and elasto-hydrodynamic lubricating theorem of hydrodynamic polishing process are adopted to derive the removal rate model of a particle under differential contact conditions or under various material parameters (such as surface energies or speed constants) from the energy point of view. In addition, the wear rate of tool is to be analyzed. To deal with the random nature of tool¡¦s surface irregularities, the probability theory is applied to calculate the average wear rate of tool, under semi-contact or non-contact condition or under various material parameters. It is shown that both the tool waviness and radius of tool curvature changed and had specific trends in the wear process. Especially, the wear rate of tool under semi-contact lubricating condition was not necessarily large than that under the non-contact one. The experimental data indicated that the effects of tool wear on machining rate highly depended on the lubricating condition of tool. The trend of machining rate versus accumulated machining time under non-contact lubricating condition was very different from that under the semi-contact one. A mathematical model relating the removal capability of an abrasive particle at the tool¡¦s or workpiece¡¦s surface and various operating parameters are proposed. The qualitative properties of removal capability the under different material parameters and various contact conditions are obtained by the computer simulations. The analysis indicates that the relationships between the removal capability and various material parameters (such as surface energies of adhesion or operating conditions) are not monotonic. Under the contact condition, it is shown that the tool¡¦s surface energy of adhesion and the speed constant has a negative effect on the removal capability at tool¡¦s surface. On the other hand, the surface energy of adhesion on work and the speed constants have a positive effect on the removal capability at tool¡¦s surface. For the workpiece, the converse implications are also true. Three types of patterns for removal capability at tool¡¦s surface due to the degree of embedding of a particle were obtained. There are increase or first increase then decrease or decrease directly, respectively. Under non-contact condition, it is shown that the removal capability has a negative relationship with local film thickness. In addition, a mathematical model relating the tool or work piece wear rate and various operating parameters are also proposed. The qualitative properties of tool wear rate under various lubricating conditions are obtained by the simple statistic analysis. The analysis indicates that the relationships between tool and workpiece wear rate and various parameters are also not monotonic. Under non-contact condition, the tool or workpiece wear rate will first increase then decrease due to the tool periphery speed increase. The magnitude of wear rate will decrease or increase due to the material parameters. Under the semi-contact condition, the up-and-down trend is also occurred in the relationship between tool or workpiece wear rate and the tool periphery speed. Accordingly, the relationships between wear rate and tool periphery speed, in a lubricating range covering the non-contact and semi-contact conditions, will reveal a twin-peak pattern. Generally, the workpiece wear rate under the semi-contact condition is not less than the non-contact one. However, the tool wear rate under the semi-contact condition is not necessarily large than the non-contact one. For a specific condition, under the semi-contact condition, the magnitude of the tool wear rate under different speed will increase or decrease by choosing different tool¡¦s surface adhesive energy and speed constant and the relationship between tool wear rate and tool speed will become complex. The wear rate could increase or decrease significantly. In other word, the tool wear rate under the semi-contact condition may be smaller or large than the non-contact one. Hence, a tool with large surface adhesive energy and speed constant should have a lower tool wear rate or higher work wear rate under certain lubricating regime. Finally, the experimental study tests that the proposed model is closely related with the experimental data. The study showed that the qualitative trends of experimental data are consistent with the analytical predictions. Some of the qualitative relationships between tool wear and machining rate could be properly explained from the elasto-hydrodynamic lubrication theorem and the proposed wear theorem for hydrodynamic polishing process.

Floating LNG terminals are a relatively new concept with the first such terminal in the world installed this year. The hydrodynamic interaction effects between the terminal and a LNG carrier in a side-by-side offloading arrangement is investigated. The side-byside arrangement is compared with each body floating alone to identify the interaction effects. The hydrodynamic coefficients are obtained using the Constant Panel Method and the analysis of body motions, mooring line tensions are done in time domain. The relative motion between the two bodies is analyzed using WAMIT in frequency domain and WINPOST in time domain to ascertain the offloading operability of the terminal under 1 year storm condition.