Presented here are observations, analysis and interpretation of five Fanaroff-Riley class I radio galaxies. Total intensity and polarised emission was observed in each source at 6 and 3 cm at angular resolutions of 16 to 2 arc seconds. These sources have a flux density greater than 1 Jy at 843 MHz, are 10-30 arc minutes in total angular extent, have redshifts between 0.011 and 0.035, are south of declination –43 degrees and have bright prominent jet structure. Images of the distribution of total intensity, polarised intensity and magnetic field configuration are presented and analysed. Physical properties in the jets and lobe are estimated using a number of different techniques. The observations have revealed a wide variety of structures, which imply many types of physical processes occurring in these sources, and different types of environments the jets travel through. The surface brightness distribution of some FR I radio galaxies with some characteristics of FR II galaxies are found to be consistent with the jets traveling through flat pressure gradients possibly caused by the presence of a cocoon surrounding the source. Analytical model imply jets with Mach numbers of 1-5, and jet velocities of approximately 1,000-20,000 km s-1 along most of the jets but mildly relativistic velocities 0.1-0.5c are indicated by Doppler boosting models at the base of most of the jets / Doctor of Philosophy (PhD)

A new buoyant jet model is presented in this thesis to simulate the trajectory and dilution of a fluid from a single port or line source. The new features include: A generalised derivation of the governing equations so that buoyant jets discharged from a source of any shape can be modelled within the one framework, and the effects of high-frequency internal waves on the motion of the buoyant jet. Past buoyant jet models were constructed for specific cases and their application is necessarily restricted. In this thesis, a new model is developed in a Lagrangian framework that can be applied to buoyant jet discharges at any angle into ambient waters that may be stratified or unstratified, flowing or stagnant. The model is validated using both laboratory and field data. Furthermore, the model is applicable to the continuous discharge of a buoyant jet from line, axisymmetric or elliptic sources and to the instantaneous discharge of a spherical puff. No previously published model is capable of unifying and solving all of these problems within the one framework. Transforming the governing equations to their non-dimensional form shows that the trajectory and dilution of discharges from line or axisymmetric sources or of spherical puffs into a flowing, stratified ambient environment are uniquely specified using three parameters. These are: the non-dimensional size of the outlet port, the relative importance of the initial fluxes of momentum and buoyancy, and the number of orthogonal planes through which entrainment can occur. This is a significant advance in the understanding of the processes affecting buoyant jets. When high-frequency internal waves are present in the receiving waters they can have significant effects on the buoyant jet. These effects are incorporated into the present model. Using data obtained from an experiment conducted off Sydney the effects of internal waves on the height of rise and dilution of the buoyant jet were found to exceed a factor of two. Consequently, it is important that the effects of internal waves (when present) be incorporated into any buoyant jet model.

Research into the fluidic precessing jet, used in industrial burners, has been carried out within the School of Mechanical Engineering at the University of Adelaide for over a decade. The flow field generated by the fluidic precessing jet (FPJ) is extremely complex, and there are many questions yet to be answered about the mechanisms by which precession influences the mixing of the jet and ambient fluid, and hence combustion. Some may be answered by studying a non-reacting precessing jet. The mechanical precessing jet (MPJ) nozzle generates a precessing jet for which the exit conditions are well known, unlike the fluidic precessing jet. The non-reacting flow from this 'mechanical analogue' of the FPJ forms the basis of the current study. The MPJ provides a means of controlling and changing the structure of turbulence in a precessing jet by varying its precessional frequency. The characteristics of the MPJ flow are primarily determined by a Strouhal number of precession, and may be categorised as belonging to either a 'low Strouhal number' or 'high Strouhal number' regime of behaviour. The fundamental aim of studying the mechanical precessing jet flow is to determine the influence of the structure of turbulent motions, and in particular the large scale motions, on jet mixing. The analyses presented in this thesis lead to a better understanding of the underlying mechanisms of precession-enhanced turbulent mixing and combustion. Simultaneously collected phase-averaged velocity and concentration fields of the MPJ flow are presented, and correlations between the fields analysed, for one low and one high Strouhal number. Additionally, because the turbulent flow produced by the MPJ nozzle is unsteady in nature and instantaneous realisations of the flow may differ significantly from the mean flow patterns, planar velocity and concentration measurements which show instantaneous flow structure over the entire field are presented. The phase-averaged velocity and concentration field data have enabled new analytical models of the MPJ trajectory to be developed, and the behaviour of the major flow features, including the stability of the counter-rotating vortex pair, to be studied. The strong entrainment and mixing characteristics of the MPJ flow are also illustrated. The data and analysis strongly suggest that the initial trajectory of the jet is essentially radial, during which the jet experiences axial compression. At larger radius the jet experiences axial stretching. A counter- rotating vortex pair is seen to form approximately two potential core lengths from the jet exit, where the jet appears to bend sharply towards the axis of rotation. These vortices dominate the jet motion in the near field and eventually merge in the transition region of the flow. The inner vortex of the counter-rotating vortex pair mixes at approximately half the rate of the outer vortex, thus delivering a rich fuel mixture to the transition region when the MPJ is used as a burner. This may explain in part earlier observations of highly radiant, fuel-rich flames in the transition region. This study also outlines the development of an experimental technique for the simultaneous measurement of velocity and concentration in a plane. The medium is air, and the technique combines Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) of acetone vapour in a unique manner. / Thesis (Ph.D.)--School of Mechanical Engineering, 2004.

One microfilm reel (16 mm.) in pocket / Bibliography: leaves 194-201 / xiii, 212, 6 leaves, [9] leaves of plates : ill. (some col.) ; 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 Mechanical Engineering, 1987

A plane jet is a statistically two-dimensional flow, with the dominant flow in the streamwise (x) direction, spread in the lateral (y) direction and zero entrainment in the spanwise (z) direction respectively (see Figure 1). A plane jet has several industrial applications, mostly in engineering environments, although seldom is a jet issuing through a smooth contoured nozzle encountered in real life. Notably, the Reynolds number and boundary conditions between industrial and laboratory environments are different. In view of these, it is important to establish effects of nozzle boundary conditions as well as the influence of Reynolds number, on jet development. Such establishments are essential to gain an insight into their mixing field, particularly relevant to engineering applications. To satisfy this need, this thesis examines the influence of boundary conditions, especially those associated with the formation of the jet and jet exit Reynolds number, on the flow field of a turbulent plane air jet by measuring velocity with a hot wire anemometer. A systematic variation is performed, of the Reynolds number Re over the range 1,500≤Re ≤16,500, the inner-wall nozzle contraction profile r* over the range 0≤r*≤3.60 and nozzle aspect ratio AR over the range 15≤AR≤72 (see notation for symbols). An independent assessment of the effect of sidewalls on a plane jet is also performed. Key outcomes are as follows: (1) Effects of Reynolds number Re: Both the mean and turbulence fields show significant dependence on Re. The normalized initial mean velocity and turbulence intensity profiles are Re-dependent. An increase in the thickness of boundary layer at the nozzle lip with a decrease in Re is evident. This dependence appears to become negligible for Re ≥10,000. The centerline mean velocity decay and jet spreading rates are found to decrease as Re is increased. Furthermore, the mean velocity field appears to remain sensitive to Reynolds number at Re = 16,500. Unlike the mean velocity field, the turbulent velocity field has a negligible Re-dependence for Re ≥10,000. An increase in Reynolds number leads to an increase in the entrainment rate in the near field but a reduced rate in the far field. The centerline skewness and the flatness factors show a systematic dependence on Reynolds number too. (2) Effects of the inner-wall nozzle exit contraction profile r*: The inner-wall nozzle exit contraction profile r* influences the initial velocity and turbulence intensity profiles. Saddle-backed mean velocity profiles are evident for the sharp-edged orifice configuration (r* ≈ 0) and top hat profiles emerge when r* ≥1.80. As r* is increased from 0 to 3.60, both the near and the far field decay and the spreading rates of the plane jet are found to decrease. Hence, the sharp-edged orifice-jet (r* ≈ 0) decays and spreads more rapidly than the jet through a radially contoured configuration (r* ≈ 3.60). The asymptotic values of the center-line turbulence intensity, skewness and flatness factors of the velocity fluctuations increase as r* tends toward zero. The non-dimensional vortex shedding frequency of StH ≈ 0.39, is higher for the sharp-edged orifice nozzle (r*≈ 0), than for the radially contoured (r* ≈ 3.60) nozzle whose StH ≈ 0.24. Thus, the vortex shedding should be strongly dependent on flow geometry and on nozzle boundary conditions. (3) Effects of nozzle aspect ratio AR: The initial velocity and turbulence intensity profiles are slightly dependent on nozzle aspect ratio of the plane air jet. It is believed that a coupled influence of the nozzle aspect ratio and sidewalls produce changes in the initial flow field. The axial extent over which a statistically 'two-dimensional' flow is achieved, is found to depend upon nozzle aspect ratio. This could be possibly due to the influence of the evolving boundary layer on the sidewalls or due to increased three-dimensionality, whose influence becomes significantly larger as nozzle aspect ratio is reduced. A statistically two dimensional flow is only achieved over a very limited extent for AR = 15. In the self-similar region, the rates of centreline velocity decay, spreading of the mean velocity field and jet entrainment increase with an increase in nozzle aspect ratio. An estimate of the critical jet aspect ratio, where three-dimensional effects first emerge and its axial location is made. Results show that the critical aspect ratio increases with nozzle aspect ratio up to AR <30. For AR≥30, the critical aspect ratio based on jet half width, attains a constant value of about 0.15. Thus, it appears that when the width of the flow approximately equals the spacing between the sidewalls, the plane air jet undergoes a transition from 2-D to 3-D. A distinct hump of the locally normalized turbulence intensity at an axial distance between 10 to 12 nozzle widths downstream, characterizes the centerline turbulence intensity for all nozzle aspect ratios. This hump is smaller when nozzle aspect ratio is larger. (4) Effects of the sidewalls: A jet issuing from a nozzle of AR = 60 and measured at Re = 7,000 is tested with sidewalls, i.e. plane-jet and without sidewalls, i.e. free-rectangular-jet. It is found that the entire flow field behaves differently for the two cases. The initial velocity profiles are top hat for both jets. The free rectangular jet decays and spreads more rapidly in both the near and far field. It is found that the free rectangular jet behaves statistically two-dimensional up to a shorter axial distance (x/H = 70) as opposed to the plane jet whose two-dimensional region extends up to x/H = 160. Also noted are that the axial extent of the two-dimensional region depends strongly on nozzle aspect ratio. Beyond the 2-D region, the free rectangular jet tends to behave, statistically, like a round jet. The locally normalized centerline turbulence intensity also depend on sidewalls. Turbulence intensity for the plane jet asymptotes closer to the nozzle (around x/H = 30) whereas for the free rectangular jet, turbulence intensity varies as far downstream as x/H = 100, and then asymptotes. A constant StH of 0.36 is found for the free rectangular jet whereas an StH of 0.22 is obtained for the plane jet. It is noted that the effects of jet exit Reynolds number, inner-wall nozzle exit contraction profile, nozzle aspect ratio and sidewalls on the plane air jet are all non-negligible. The effect of viscosity is expected to weaken with increased Reynolds number and this may contribute to the downstream effects on the velocity field. Both the nozzle contraction profile and nozzle aspect ratio provide different exit boundaries for the jet. Such boundary conditions not only govern the formation of the initial jet but also its downstream flow properties. Hence, the initial growth of the shear layers and the structures within these layers are likely to evolve differently with different boundary conditions. Thus, the interaction of the large-scale structures with the surroundings seems to depend on nozzle boundary conditions and consequently, influences the downstream flow. In summary, the present study supports the notion that the near and far fields of the plane jet are strongly dependent on Reynolds number and boundary conditions. Therefore, the present thesis contains immensely useful information that will be helpful for laboratory-based engineers in selection of appropriate nozzle configurations for industrial applications. / Thesis (Ph.D.)--School of Mechanical Engineering, 2005.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Dans le cadre de l'approximation MLLA de la Chromodynamique Quantique, nous calculons analytiquement, pour des jets hadroniques à très haute énergie, les distributions inclusives en fonction de l'impulsion transverse du hadron émergent, ainsi que les corrélations à 2 particules. Dans un premier temps, nous obtenons, pour le spectre inclusif et pour les corrélations, les solutions exactes des équations d'évolution partoniques, qui sont ensuites calculées à petit x dans l'approximation du ``spectre limite''. La méthode du col nous permet enfin de généraliser les résultats précédents au delà de cette limite. Nos résultats pour les distributions inclusives sont en très bon accord avec les données expérimentales (Tevatron), et améliorent très sensiblement ceux obtenus dans les travaux antérieurs pour les corrélations. La comparaison avec les données à venir (Tevatron, LHC) fournira un test supplémentaire de l'hypothèse de dualité locale parton-hadron, ainsi que de la nécessité éventuelle d'inclure des corrections d'ordre supérieur (next-to-MLLA).

<p>Two types of mesoscale wind-speed jet and their effects on boundary-layer structure were studied. The first is a coastal jet off the northern California coast, and the second is a katabatic jet over Vatnajökull, Iceland. Coastal regions are highly populated, and studies of coastal meteorology are of general interest for environmental protection, fishing industry, and for air and sea transportation. Not so many people live in direct contact with glaciers but properties of katabatic flows are important for understanding glacier response to climatic changes. Hence, the two jets can potentially influence a vast number of people.</p><p>Flow response to terrain forcing, transient behavior in time and space, and adherence to simplified theoretical models were examined. The turbulence structure in these stably stratified boundary layers was also investigated. Numerical modeling is the main tool in this thesis; observations are used primarily to ensure a realistic model behavior.</p><p>Simple shallow-water theory provides a useful framework for analyzing high-velocity flows along mountainous coastlines, but for an unexpected reason. Waves are trapped in the inversion by the curvature of the wind-speed profile, rather than by an infinite stability in the inversion separating two neutral layers, as assumed in the theory. In the absence of blocking terrain, observations of steady-state supercritical flows are not likely, due to the diurnal variation of flow criticality.</p><p>In many simplified models, non-local processes are neglected. In the flows studied here, we showed that this is not always a valid approximation. Discrepancies between simulated katabatic flow and that predicted by an analytical model are hypothesized to be due to non-local effects, such as surface inhomogeneity and slope geometry, neglected in the theory. On a different scale, a reason for variations in the shape of local similarity scaling functions between studies is suggested to be differences in non-local contributions to the velocity variance budgets.</p>

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 124-128).

Two types of mesoscale wind-speed jet and their effects on boundary-layer structure were studied. The first is a coastal jet off the northern California coast, and the second is a katabatic jet over Vatnajökull, Iceland. Coastal regions are highly populated, and studies of coastal meteorology are of general interest for environmental protection, fishing industry, and for air and sea transportation. Not so many people live in direct contact with glaciers but properties of katabatic flows are important for understanding glacier response to climatic changes. Hence, the two jets can potentially influence a vast number of people. Flow response to terrain forcing, transient behavior in time and space, and adherence to simplified theoretical models were examined. The turbulence structure in these stably stratified boundary layers was also investigated. Numerical modeling is the main tool in this thesis; observations are used primarily to ensure a realistic model behavior. Simple shallow-water theory provides a useful framework for analyzing high-velocity flows along mountainous coastlines, but for an unexpected reason. Waves are trapped in the inversion by the curvature of the wind-speed profile, rather than by an infinite stability in the inversion separating two neutral layers, as assumed in the theory. In the absence of blocking terrain, observations of steady-state supercritical flows are not likely, due to the diurnal variation of flow criticality. In many simplified models, non-local processes are neglected. In the flows studied here, we showed that this is not always a valid approximation. Discrepancies between simulated katabatic flow and that predicted by an analytical model are hypothesized to be due to non-local effects, such as surface inhomogeneity and slope geometry, neglected in the theory. On a different scale, a reason for variations in the shape of local similarity scaling functions between studies is suggested to be differences in non-local contributions to the velocity variance budgets.