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No description available.

No description available.

No description available.

No description available.

This study investigates the turbulent mixing within gravity currents preceding backdrafts and validates the ability of the computational fluid dynamics (CFD) software Fire Dynamics Simulator version 4 (FDS) to simulate these flows. Backdrafts are rapid deflagrations, which occur after the introduction of oxygen into compartments containing unburned gaseous fuel. They may form large fireballs out of the compartment opening and present a significant hazard to the safety of fire-fighters. Gravity currents which precede backdrafts are responsible for the formation of flammable gas mixtures required for ignition. Scale saltwater modelling is used to generate Boussinesq, fully turbulent gravity currents for five different opening geometries, typical of fire compartments. Width-integrated concentration fields and two-dimensional velocity fields are generated using the non-intrusive light attenuation (LA) and particle tracking velocimetry (PTV) flow visualisation techniques respectively. Numerical simulations are carried out with FDS to replicate these flows. The experimental and numerical results are compared directly. Front velocities are shown to be governed directly by local buoyancy conditions, in the later stages of the flows, and therefore the initial conditions associated with the opening geometries only influence the front velocities indirectly. The internal concentration structure, internal velocity structure and location of potential flammable regions are found to be highly opening geometry dependent. In general, the results of the numerical simulations are quantitatively similar to those from experiment, which suggests that the numerical model realistically predicted the experimental flows. However, the numerical concentration fields appear slightly lumpier than those from the experiments, possibly due to unresolved turbulence on scales smaller than the numerical grid (0.01H, where H = compartment height).

This thesis addresses the open questions of providing a cosmological model describing an accelerated expanding Universe without violating the energy conditions or a model that contributes to the physical interpretation of the dark energy. The former case is analyzed considering a closed model based on a regular lattice of black holes using the Einstein equation in vacuum. In the latter case I will connect the dark energy to the Shan-Chen equation of state. A comparison between these two proposals is then discussed. As a complementary topic I will discuss the motion of test particles in a general relativistic spacetime undergoing friction effects. This is modeled following the formalism of Poynting-Robertson whose link with the Stokes’ formula is presented. The cases of geodesic and non-geodesic motion are compared and contrasted for Schwarzschild, Tolman, Pant-Sah and Friedman metrics respectively.

This thesis investigates the problems within quantum mechanics for the Bohm model caused by Lorentz invariance and the existence of photons. A model describing the electromagnetic interactions of fermions is produced which does not use photons and avoids these problems. It is then shown how these techniques can be extended to linearised gravitational interactions. Finally semi-classical gravity and the possibility of gravitationally induced collapse are considered. In the first part of the thesis two modifications to the Bohm model are proposed. One takes account of Lorentz invariance, and the other is capable of describing photons. The main part of the thesis is devoted to describing interactions in a way which does not need extra gauge particles, and so is in the same spirit as the Bohm model. Electromagnetic interactions are formed using a 4-potential operator which is calculated directly, without imposing commutation relations on the 4-potential. This leads to an expression for the 4-potential in terms of the Dirac field, and results in there being no photon states. There are various ways of constructing the theory and the scattering matrix of standard QED is compared to the scattering matrix of the version which appears to be most similar. Considering only the matrix elements between fermion states, they are found to be in agreement at the order e(^2), but disagree at the order e(^4). It follows that this model, which otherwise appears to be a self consistent theory of QED, cannot agree with experiment. The same techniques can be used to quantise General Relativity when it is linearised about the Minkowski metric. The metric operator is calculated in terms of the Dirac field. The interaction is similar to that of electrodynamics, being of order 4 in the Dirac field. Finally issues relating to gravitational collapse are discussed.

The 1995 Sandwell & Smith WGI7.2 satellite gravity map has been compared with high quality ship gravity data offshore Sabah. The standard deviation of the differences between gravity profiles interpolated from WGI7.2 and the ship survey was 5.7 mGal. Spectral analysis indicated that WGI7.2 resolves features with half-wavelengths greater than 10 km. Three hundred new gravity stations, including ten base stations tied to IGSN71, were established during a survey of Sabah and were merged with two previous surveys to complete the gravity coverage of the state at reconnaissance level. New gravity maps of Sundaland, compiled from the Sabah and WGI7.2 gravity data sets have been interpreted. ' Subtraction from these data sets of the long wavelength GEM-T3 gravity anomaly field, which is dominated by the effects of the subducted proto-South China Sea and the ongoing subduction of the Australian, Indian and Philippine Sea Plates, achieved a simple 'regional-residual' separation and the isolation of crustal-scale anomalies. 5' x 5' maps of the depth to Moho, crustal thickness and β (crustal extension) factor beneath the Sunda Shelf and the South China Sea have been produced by 1-D geometric manipulation of the marine gravity field using sediment isopach and bathymetry control data. The average difference between the new Moho map and seismic refraction depth-to-Moho estimates at the south China margin was 0.2 ± 2.0 km. The Moho rises from an average depth of 29 km beneath the Sunda Shelf to a depth of about 16 km beneath the South China Sea oceanic basin. It is estimated that approximately 1100 km of oceanic crust of the proto-South China Sea was subducted at the northwest Borneo margin. Gravity modelling independently confirmed the average 35 mm/yr spreading rate prediction for the southwestern subbasin of the South China Sea oceanic basin from magnetic lineation interpretation. Quantitative interpretation indicates that Sabah is underlain by thick continental crust, and gravity modelling of the Maliau Basin predicts a minimum sediment thickness of 8 km. The ophiolite bodies at Telupid and Darvel Bay are separated by a gravity low and there is no evidence that the two are related. The crustal root of the Crocker Ranges extends to a depth of ~49 km below sea level. In order to reach this present day crustal thickness, the turbiditic sediments forming the Crocker Ranges must have been compressed to less than half of their original lateral extent during the Sabah Orogeny.

Petroleum research is responsible for making previously unusable reservoirs economically viable and for limiting the environmental impact of petroleum development. Microfluidics, the study of fluid flow at the micro-scale, is predominantly used to study biological phenomena. Adapting microfluidics to study petroleum requires the use of materials and methods not commonly used. This thesis focuses on applying microfluidics to the study of petrochemical fluid flow at high-pressure and high-temperature. The first problem addressed is the study of fluids during alkaline steam assisted gravity drainage (alkaline SAGD). The addition of an alkaline additive is found to improve the bitumen production rate by 35-67%. Secondly, two high-pressure, high-temperature, solvent resistant microfluidic interfaces for glass chips are designed to be operated up to 140 bar and 70 degrees Celsius. Lastly, a novel method for fabricating solvent resistant microfluidic devices from Teflon film is demonstrated by measuring the viscosity of toluene-heavy oil blends.