This dissertation examines the suitability of Computational Fluid Dynamics (CFD) modelling for the production of realistic flowfields and temperature fields within a series of vortex combustion chambers of differing geometries and operating under various conditions. Initial validation of the CFD predictions was obtained through modelling of a series of isothermal vortex chambers for which a comprehensive set of experimental data was available. It was observed that CFD did indeed produce representative flowfield predictions for chambers of various geometries and operating conditions. A vortex unit used for the incineration of sewage sludge (US Navy Waste Incinerator) was subsequently investigated, and it was shown that due to the high moisture content of the waste material used, temperature profiles obtained with a modified coal combustion model were similar to those obtained with a more straightforward and computationally less expensive spray drier model. Results from both models were similar to experimentally observed conditions. However, comprehensive validation was not possible. In order that full validation could be provided for a CFD model of a vortex combustion unit, a model was developed of a commercial thermal oxidiser used for the incineration of liquid and gaseous wastes. CFD temperature predictions for the BASF Thermal Oxidiser were validated by a series of experimental measurements obtained from the operating unit. In general, it was found that the Reynolds Stress Model for turbulence produced the most representative velocity flowfields, with the less computationally demanding k-e model being applicable only under certain limited circumstances. Furthermore, insufficient grid refinement resulted in significantly distorted velocity profiles.

The unsteady vortex-lattice method is used to calculate the pressure coefficients on thick and thin airfoils in steady and unsteady flowfields. The parameters which affect the results, such as time step and aspect ratio, are studied. The effects of Reynolds number and thickness of a wing in steady state and in oscillation are investigated. The present computed results for thick and thin wings are in close agreement with the experimental data. The numerical results obtained from a lifting-surface approximation are also in close agreement with the experimental data for a wing as thick as 18%. The lift and moment coefficients are affected by the thickness of a wing in oscillation and this effect is more noticeable for the moment coefficient. But to illustrate this it is necessary to go as high as 27% thickness. A wing in steady flight near a wavy surface, such as in the case of a large transoceanic wingship, is simulated by a wing oscillating in heave near a flat surface. In accord with the wingship, small aspect ratios and slight camber are considered. The numerical simulation predicts that the mean aerodynamic loads on a wing executing a simple-harmonic heaving motion are higher than the corresponding loads on the same wing in steady flight at the mean height and the same angle of attack. The increases are about the same for all heights. Hence, these preliminary results suggest that it would be beneficial to fly near the waves; that doing so would improve the aerodynamic efficiency. Also included in the present results are numerical simulation of the wakes that show the strong influences of the ground and the oscillations on their behavior. The unsteady vortex-lattice method is further used to investigate the effect of trailing vortices from a large leading wing on a trailing aircraft. The aerodynamic response of the trailing aircraft is examined by calculating the lift and drag forces and the pitch and roll moments. Furthermore, the aerodynamic response and the behavior of the wakes of the crossing wings are investigated. / Ph. D.

An experimental and computational study was made of a single circular jet impinging onto a flat ground board. A 1/2' nozzle running at a fixed nozzle pressure ratio of 1.05 was used in the experimental phase (giving an nozzle exit Reynolds number of 90xlO'), the nozzle to ground plane separation being varied between 2 and 10 nozzle diameters. Measurements were performed in the free and wall jets using single and cross-wire hot-wire anemometry techniques and pitot pressure probes in order to detemine mean velocity and normal and shear stress distributions. Some analysis is also presentedo f earlier measurementso n high pressurer atio impinging jets. Nozzle height was found to effect the initial thickness of the wall jet leaving the impingement region, increasing nozzle to ground plane separation increasing the wall jet thickness, although this separation distance did not seem to affect the rate at which the wall jet grew. Nozzle height was also found to have a large effect on the peak level of turbulence found in the wall jet up to a radial distan ce from the jet axial centre line of 4.5 nozzle diameters, after which the profiles become self-similar. Lowering the nozzle tended to increase the peak level measured in all the turbulent stresses within this development region. The production of turbulent kinetic energy in the wall jet, which is an indication of the amount of work done against the mean flow by the turbulent flow was found to increase dramatically with decreasing nozzle height. This was attributed to greater shearing of the flow at lower nozzle heights due to a thinner wall jet leaving the impingement region. A moving impingement surface was found to cause separation of the wall jet inner boundary layer on the 'approach' side leading to very rapid decay of peak velocity. The point of separation was found to occur at radial positions in the region of 7.0 to 8.0 nozzle diameters, this reducing slightly for lower nozzle heights. A parametric investigation was performed using the k-e turbulence model and the PHOENICS CFD code. It was found that due to inadequacies in the model, it failed to predict accurately the growth of the wall jet, both in terms of its initial thickness and the rate of growth. It did, however, predict an increase in wall jet thickness with both increasing nozzle height and exit turbulence intensity and decreasing nozzle pressure ratio. Modifications were made to the constants in the model to try and improve the predictions,w ith a limited degreeo f successT. he low Reynoldsn umber k-F-t urbulence model was shown to give a slightly improved non-dimensional wall jet profile, although this did not improve the predicted rate of growth of the wall jet.

An experimental and computational study was made of a single circular jet impinging onto a flat ground board. A 1/2" nozzle running at a fixed nozzle pressure ratio of 1.05 was used in the experimental phase (giving an nozzle exit Reynolds number of 90xlO'), the nozzle to ground plane separation being varied between 2 and 10 nozzle diameters. Measurements were performed in the free and wall jets using single and cross-wire hot-wire anemometry techniques and pitot pressure probes in order to detemine mean velocity and normal and shear stress distributions. Some analysis is also presentedo f earlier measurementso n high pressurer atio impinging jets. Nozzle height was found to effect the initial thickness of the wall jet leaving the impingement region, increasing nozzle to ground plane separation increasing the wall jet thickness, although this separation distance did not seem to affect the rate at which the wall jet grew. Nozzle height was also found to have a large effect on the peak level of turbulence found in the wall jet up to a radial distan ce from the jet axial centre line of 4.5 nozzle diameters, after which the profiles become self-similar. Lowering the nozzle tended to increase the peak level measured in all the turbulent stresses within this development region. The production of turbulent kinetic energy in the wall jet, which is an indication of the amount of work done against the mean flow by the turbulent flow was found to increase dramatically with decreasing nozzle height. This was attributed to greater shearing of the flow at lower nozzle heights due to a thinner wall jet leaving the impingement region. A moving impingement surface was found to cause separation of the wall jet inner boundary layer on the 'approach' side leading to very rapid decay of peak velocity. The point of separation was found to occur at radial positions in the region of 7.0 to 8.0 nozzle diameters, this reducing slightly for lower nozzle heights. A parametric investigation was performed using the k-e turbulence model and the PHOENICS CFD code. It was found that due to inadequacies in the model, it failed to predict accurately the growth of the wall jet, both in terms of its initial thickness and the rate of growth. It did, however, predict an increase in wall jet thickness with both increasing nozzle height and exit turbulence intensity and decreasing nozzle pressure ratio. Modifications were made to the constants in the model to try and improve the predictions,w ith a limited degreeo f successT. he low Reynoldsn umber k-F-t urbulence model was shown to give a slightly improved non-dimensional wall jet profile, although this did not improve the predicted rate of growth of the wall jet.

The Multidisciplinary University Research Initiative (MURI) research at Texas A and M University is concerned with the experimental characterization of non-thermal and non-chemical equilibrium systems in hypersonic (Mach greater than 5) flowfields using experimental diagnostics, and is an interdisciplinary collaboration between the Chemistry and Aerospace Engineering departments. Hypersonic flight conditions often lead to non-thermochemical equilibrium (NTE) state of air, where the timescale of reaching a single (equilibrium) Boltzmann temperature is much longer than the timescale of the flow, meaning that certain molecular modes such as vibrational modes, may be much more excited than the translational or rotational modes of the molecule leading to thermal-nonequilibrium. A nontrivial amount of energy is therefore contained within the vibrational mode, and this energy cascades into the flow as thermal energy, affecting flow properties through the process of various vibrational-vibrational (V-V) and vibrational-translational (V-T) energy exchanges between the flow species. The research is a fundamental experimental study of these NTE systems and involves the application of advanced laser and optical diagnostics towards hypersonic flowfields. The research is broken down into two main categories: the application and adaptation of existing laser and optical techniques towards characterization of NTE, and the development of new molecular tagging velocimetry techniques which have been demonstrated in an NTE flowfield, but may be extended towards a variety of flowfields.