The Background Oriented Schlieren (BOS) technique is a method that has been developed recently for easily and inexpensively visualizing density gradient variations in compressible flows. In this thesis, the applications of this technique in the Drummond tunnel and the T4 free-piston reflected shock tunnel are presented. The BOS technique was first tested in the Drummond tunnel then used during four test campaigns to qualitatively visualize the flow over scramjet models and components of scramjets in the T4 shock tunnel. The results demonstrate that a simple optical arrangement, that does not need high quality windows in the test section and model, can be used to detect the locations of shock waves, expansion fans and shear layers. At present, the resolution and quality of the images is not as high as can be achieved using conventional Schlieren techniques.

A field system capable of making high-resolution measurements of rainfall is described. The system incorporates a disdrometer, an array of high-resolution raingauges, a general-purpose data acquisition system and ancillary equipment. In an evaluation of the disdrometer, a theory allowing calculation of the effects of windspeed on detection efficiency is presented which has wide applicability. The raingauges are an improved design allowing 10-s temporal resolution of rainfall intensity and 100 m spatial resolution of rain-patch size when used in the array. An extensive data base of measurements made using the field system is described. Duration of rainfall is shown to be approximately log-normal and is consistent with a log-normal distribution of precipitation region size. The fractional duration of rainfall above a threshold intensity varies considerably between rain periods, a result which may be important for electromagnetic attenuation models. Estimation of the shapes of rain patches using the raingauge array is demonstrated and shows considerable promise. Raindrop fallspeeds, measured using the disdrometer, generally show much less deviation from stagnant air terminal velocities than indicated by previously reported results. Much of the spread in the results is shown to be consistent with instrumentation errors although significant residual deviations are still apparent; the fallspeeds are generally slower than stagnant air values would suggest. Measurements of the arrival rate of raindrops at the disdrometer indicate clustering of drops rather than the often assumed Poisson distribution. The clustering is associated with small drops and has reasonable correlation with rainfall intensity. Examination of the cross-correlation of arrival rates of different sized drops show results in contradiction to previous results; small drops are found to lead other sized drops. Using a normalisation method, the shapes of raindrop size distributions measured are shown to be depressed in the mid-radius region.

Introduction: In this chapter the present status of our understanding of the interaction of five and fewer nucleons will be briefly summarized. Some of the gaps in our knowledge will be pointed out, making clear the motivation for the experimental work described in the remainder of the thesis. Since most of the experimental effort by the author has been directed towards scattering of neutrons by protons, the nucleon - nucleon problem will be considered in greater detail. In speaking of this, the simplest problem in nuclear physics, M.L. Goldberger made the following remarks at the 1960 Midwest Conference on Theoretical Physics: "There are few problems in modern theoretical physics which have attracted more attention than that of trying to determine the fundamental interaction between two nucleons. It is also true that scarcely ever has the world of physics owed so little to so many .. . . . . . In general, in surveying the field, one is oppressed by the unbelievable confusion and conflict that exists. It is hard to believe that many of the authors are talking about the same problem, or in fact that they know what the problem is."

A field system capable of making high-resolution measurements of rainfall is described. The system incorporates a disdrometer, an array of high-resolution raingauges, a general-purpose data acquisition system and ancillary equipment. In an evaluation of the disdrometer, a theory allowing calculation of the effects of windspeed on detection efficiency is presented which has wide applicability. The raingauges are an improved design allowing 10-s temporal resolution of rainfall intensity and 100 m spatial resolution of rain-patch size when used in the array. An extensive data base of measurements made using the field system is described. Duration of rainfall is shown to be approximately log-normal and is consistent with a log-normal distribution of precipitation region size. The fractional duration of rainfall above a threshold intensity varies considerably between rain periods, a result which may be important for electromagnetic attenuation models. Estimation of the shapes of rain patches using the raingauge array is demonstrated and shows considerable promise. Raindrop fallspeeds, measured using the disdrometer, generally show much less deviation from stagnant air terminal velocities than indicated by previously reported results. Much of the spread in the results is shown to be consistent with instrumentation errors although significant residual deviations are still apparent; the fallspeeds are generally slower than stagnant air values would suggest. Measurements of the arrival rate of raindrops at the disdrometer indicate clustering of drops rather than the often assumed Poisson distribution. The clustering is associated with small drops and has reasonable correlation with rainfall intensity. Examination of the cross-correlation of arrival rates of different sized drops show results in contradiction to previous results; small drops are found to lead other sized drops. Using a normalisation method, the shapes of raindrop size distributions measured are shown to be depressed in the mid-radius region.

Introduction: In this chapter the present status of our understanding of the interaction of five and fewer nucleons will be briefly summarized. Some of the gaps in our knowledge will be pointed out, making clear the motivation for the experimental work described in the remainder of the thesis. Since most of the experimental effort by the author has been directed towards scattering of neutrons by protons, the nucleon - nucleon problem will be considered in greater detail. In speaking of this, the simplest problem in nuclear physics, M.L. Goldberger made the following remarks at the 1960 Midwest Conference on Theoretical Physics: "There are few problems in modern theoretical physics which have attracted more attention than that of trying to determine the fundamental interaction between two nucleons. It is also true that scarcely ever has the world of physics owed so little to so many .. . . . . . In general, in surveying the field, one is oppressed by the unbelievable confusion and conflict that exists. It is hard to believe that many of the authors are talking about the same problem, or in fact that they know what the problem is."

The Background Oriented Schlieren (BOS) technique is a method that has been developed recently for easily and inexpensively visualizing density gradient variations in compressible flows. In this thesis, the applications of this technique in the Drummond tunnel and the T4 free-piston reflected shock tunnel are presented. The BOS technique was first tested in the Drummond tunnel then used during four test campaigns to qualitatively visualize the flow over scramjet models and components of scramjets in the T4 shock tunnel. The results demonstrate that a simple optical arrangement, that does not need high quality windows in the test section and model, can be used to detect the locations of shock waves, expansion fans and shear layers. At present, the resolution and quality of the images is not as high as can be achieved using conventional Schlieren techniques.

A field system capable of making high-resolution measurements of rainfall is described. The system incorporates a disdrometer, an array of high-resolution raingauges, a general-purpose data acquisition system and ancillary equipment. In an evaluation of the disdrometer, a theory allowing calculation of the effects of windspeed on detection efficiency is presented which has wide applicability. The raingauges are an improved design allowing 10-s temporal resolution of rainfall intensity and 100 m spatial resolution of rain-patch size when used in the array. An extensive data base of measurements made using the field system is described. Duration of rainfall is shown to be approximately log-normal and is consistent with a log-normal distribution of precipitation region size. The fractional duration of rainfall above a threshold intensity varies considerably between rain periods, a result which may be important for electromagnetic attenuation models. Estimation of the shapes of rain patches using the raingauge array is demonstrated and shows considerable promise. Raindrop fallspeeds, measured using the disdrometer, generally show much less deviation from stagnant air terminal velocities than indicated by previously reported results. Much of the spread in the results is shown to be consistent with instrumentation errors although significant residual deviations are still apparent; the fallspeeds are generally slower than stagnant air values would suggest. Measurements of the arrival rate of raindrops at the disdrometer indicate clustering of drops rather than the often assumed Poisson distribution. The clustering is associated with small drops and has reasonable correlation with rainfall intensity. Examination of the cross-correlation of arrival rates of different sized drops show results in contradiction to previous results; small drops are found to lead other sized drops. Using a normalisation method, the shapes of raindrop size distributions measured are shown to be depressed in the mid-radius region.

Granulation is an industrial process where fine particles are bound together into larger granules. The process has numerous applications including the manufacture of pharmaceuticals and the production of cosmetics, chemicals, detergents and fertilisers. This thesis studies aspects of wet granulation which involves the application of a viscous binder, usually in the form of a spray, to an agitated bed of powder particles. Individual powder particles may adhere together, joined by small quantities of binder fluid called liquid bridges. By a process of collision and adherence additional particles may join the newly formed agglomerates. Agglomerates may also coalesce together which is a process that leads to granule formation. On the completion of this process, granules are typically dried.This thesis studies wet granulation on three different levels. First, micro-level investigations of liquid bridges between two and three particles are performed. For the two-particle case, the fluid profile of static (stationary) and dynamic (moving) liquid bridges is investigated. For the static case, a numerical solution to the Young-Laplace equation is obtained; this relates the volume of binder fluid to liquid bridge properties such as the inter-particle force. An analytic solution is also obtained, providing the liquid bridge profile in terms of known mathematical functions. For both solutions, the radii of the (spherical) primary particles may be different. The dynamic case is then studied using the Navier-Stokes equations with the low Reynolds number approximation. The motion of the approaching particles is shown to be damped by the viscosity of the liquid bridge. Static liquid bridges between three equally sized primary particles are then studied. Symmetry of the problem is used to obtain a numerical solution to the Young-Laplace equation. Liquid bridge properties are calculated in terms of the binder fluid volume. Experimental agreement is provided.Secondly, a model to estimate the stickiness (fractional wet surface area) of agglomerates is proposed. Primary particles are approximated as spheres and are added one at a time in a closely packed arrangement. The model includes parameters to control the inter-particle separation distance and the fluid saturation state. Computational geometry is used to obtain results which relate the number of particles and the volume of binder fluid to the stickiness of the agglomerates.Finally, a population balance model for wet granulation is developed by extending an earlier model to incorporate the effects of binder fluid. Functions for the inter-particle collision rate and drying rate are proposed, including functions which are derived from the geometric model, described above, for the case of maximum particle consolidation. The model is solved numerically for a range of coalescence kernels and results are presented which show the effect of binder volume and the drying rate.

Entre l'enfournement des matières premières sur le bain liquide et le verre la sortie du four, on peut s'interroger sur les étapes par lesquelles le mélange vitrifiable passe avant d'être transformé en un liquide homogène. D'un point de vue chronologique, l'élaboration du verre peut être considérée en trois étapes : l'état initial du mélange granulaire avant réaction ; l'étape de réaction chimique entre les différents constituants ; un liquide avec ses inclusions gazeuses et solides (bulles et quartz résiduel). Chacune de ces étapes concerne un domaine spécifique, avec un fort couplage entre physique et chimie. Aborder la façon dont réagissent ces matières premières ensemble et comment la microstructure peut influencer le chemin réactionnel suivi globalement par le mélange est indispensable pour savoir a chaque moment de la transformation quels mécanismes sont mis en jeu. Cela permettrait de corriger certains problèmes liés à l'élaboration d'un verre industriel (bulles piégé es dans le liquide, grains de quartz non incorporés au liquide, hétérogénéité chimique du liquide). La variété de phénomènes possibles lors de la fusion d'un mélange vitrifiable industriel nous poussera à simplifier le système un maximum, afin d'être capable de relier l'évolution de la microstructure à celle de la chimie du matériau. C'est la raison pour laquelle nous avons décidé d'étudier le système SiO2-Na2CO3. Nous avons de plus utilisé des grains tamisés dans des tranches précises, afin de pouvoir relier la transformation chimique du mélange à la répartition spatiale initiale du mélange granulaire.

Introduction: This thesis is an account of the design, construction and testing of a particle accelerator which represents a minor variation on the now-familiar theme of the tandem van de Graaff. The machine has been very briefly described elsewhere (Naylor 1968).