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Turbidity currents are turbulent particle suspensions that are the primary mechanism for transporting terrestrial sediments to the deep marine, and generate some of the largest depositional features on Earth. However the fluid-particle interactions that sustain these currents are poorly understood, principally due to the technical challenges posed by obtaining accurate velocity and density measurements, which are critical for describing flow behavior and depositional characteristics. Numerous studies have bypassed these issues by using saline density currents, but this negates the ability to link flow processes with depositional features, and it is unclear whether their density structures are representative of particle gravity flows. Consequently, numerous questions remain over the flow conditions that build up a significant part of the deep-marine geologic record. In this thesis I reports on the flow processes and depositional features of sediment-gravity currents across a broad range of particle sizes and concentrations. The technical challenges of obtaining reliable density data are overcome by running the experimental flows through a medical grade computed tomography (CT) scanner, and pair this data with three-dimensional velocity measurements using an ultrasonic Doppler velocity profiler (UDVP-3D) to get one of the first glimpses of the internal structure of turbidity currents. Unlike previous studies where flow processes are described in terms of the velocity field, this thesis demonstrates that fluid-particle interactions are controlled by momentum characteristics, and that the velocity field is determined largely by the current’s density structure. Moreover, the density structure also exerts a first order control on the morphology of their deposits.

The effect of turbulence damping polymer additive on the fluid flow structure near the wall region of a circular pipe was made visible using real-time laser holographic interferometry. The interference fringes were recorded by high-speed motion photography. The gross flow behaviour of dilute solutions of Polyox WSR 301 in distilled water was studied in a 2.63 cm pipe. It was observed that (i) The onset of drag reduction occurred at a critical value of wall shear stress and Reynolds number. (ii) The fluid property parameter, δ, which governs the drag reduction capacity of the solution, had a power-law dependence on polymer concentration given by [23] [ Formula omitted ] Motion pictures of real-time holographic fringe displays for pure solvent and polymer solution were appraised qualitatively. Under similar flow conditions turbulent eddies in drag-reducing flow were observed (i) to show less small scale structure than those in the pure solvent, and (ii) to burst from the wall region into the bulk flow with a lower frequency. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The propagation of a shock wave into a general inhomo-geneous flow field is studied. The equations for the shock velocity through such a region are developed in a general manner. A consequence of these equations is the development of the shock wave as a probe into unknown flow fields. The shock velocity is measured and the initial parameters ahead of the shock are calculated. The unique advantage of the shock probe is that it does not perturb the gas ahead of the front. An experimental application is described in which the shock probe is used to analyze the unknown flow field created by a constricted arc light source. The flow field is subsequently identified as a radiation front at the Chapman-Jouguet point. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis investigates different examples of action at a distance, namely the interaction of two circular cylinders of different diameters and the interaction of a cylinder with a wall in various arrangements. Action at a distance modifies both the lift and drag of each one of the objects. The fluid flow interaction between a circular cylinder (of diameter D) with a wall, and a circular cylinder with a smaller (¼D) circular cylinder at Reynolds numbers of ≈ 10,000 were of interest. Manifestations of the interactions include mutual changes in the lift and drag forces, phase, onset and frequency of vortex shedding on the circular cylinders/wall. A novel force measurement device for lift and drag of circular cylinders and a data acqusition system was built to realize the above experiments in a water towing tank. The system was capable of simultaneously measuring lift and drag on two circular cylinders with time resolution and correlating these measurements with flow field pictures. Measurements of the lift and drag and phase, onset and frequency of vortex shedding were taken on the large and small cylinder simultaneously as a function of the relative position between itself and the smaller cylinder as the two are towed. These measurements make it possible to map out the areas within the cylinders' sphere of influence and measure the intensity of this influence as a function of the distance between the two cylinders. Every quantity that was mutually altered by the presence of another cylinder is used as measurements of the area of influence for a circular cylinder. It was found in general that the forces act up to a distance of about 3 diameters in the lateral direction. It was also noted that pressure fluctuations at the vortex shedding frequency penetrate into the laminar flow region up to about 3D in the lateral direction. The results agree with existing results for wall/cylinder proximity experiments and flow interference between identical circular cylinders. A novel method to trigger the onset of vortex shedding for towing tanks was also discovered. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new viscous-inviscid semi-inverse (VISI) interaction method has been developed for predicting the flow field arising from a combination of inviscid potential flow and viscous flow. The technique involves matching the bounding velocities for each region by iteratively solving for the displacement thickness, δ*(x). The formula used to update δ*(x) after each iteration is generated by linearly perturbing the governing equations. Application of the VISI procedure to predict the unseparated flow past a flat plate gives excellent results, producing numerical solutions essentially indistinguishable from the appropriate analytical solution in less than 0.5 seconds of CPU time on an Amdahl 5850 computer. Application of the technique to external flow over a backward facing step (BFS) indicates that the region of strong interaction between the viscous and inviscid flows is much larger than reported for internal flow. Calculated reattachment lengths, LR, are clearly influenced by the thickness of the boundary layer upstream of the step, thicker boundary layers producing longer reattachment lengths. Good accuracy is achieved for a relatively coarse distribution of control points, and rapid convergence (< 2 seconds on the Amdahl 5850) usually occurs. Finite-difference predictions using an elliptic code (TEACH-T), modified at the outer boundary to simulate external flow, have also been made for the BFS, largely as a basis of comparison for the VISI results. Comparison of results for the two models (VISI and TEACH) gives similar trends in LR as a function of Rh and x₈, (a measure of the displacement thickness at the step). The values of LR obtained with the VISI method, however, are 15-80% longer than those from TEACH. Direct comparison with experiments is difficult because the experimental data does not clearly identify the effects of x₈, in the resulting values of LR. Trends appear to be the same for all computed and observed cases however. Disagreement between the VISI and TEACH results is thought to be due to a combination of neglecting velocities in the recirculation region in the VISI model, and numerical error and inaccurate boundary conditions in the TEACH code. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

This dissertation describes two experimental studies of a vibrofluidized granular medium and a preliminary study of two-phase fluid flow in a porous medium using Nuclear Magnetic Resonance (NMR). The first study of granular medium is to test a scaling law of the rise in center of mass in a three-dimensional vibrofluidized granular system. Our granular system consisted of mustard seeds vibrated vertically at 40 Hz from 0g to 14g. We used Magnetic Resonance Imaging (MRI) to measure density profile in vibrated direction. We observed that the rise in center of mass scaled as ν 0α/Nlβ with α = 1.0 ± 0.2 and β = 0.5 ± 0.1, where ν 0 is the vibration velocity and Nl is the number of layers of grains in the container. A simple theory was proposed to explain the scaling exponents. In the second study we measured both density and velocity information in the same setup of the first study. Pulsed Field Gradient (PFG)-NMR combined with MRI was used to do this measurement. The granular system was fully fluidized at 14.85g 50 Hz with Nl ≤ 4. The velocity distributions at horizontal and vertical direction at different height were measured. The distributions were nearly-Gaussian far from sample bottom and non-Gaussian near sample bottom. Granular temperature profiles were calculated from the velocity distributions. The density and temperature profile were fit to a hydrodynamic theory. The theory agreed with experiments very well. A temperature inversion near top was also observed and explained by additional transport coefficient from granular hydrodynamics. The third study was the preliminary density measurement of invading phase profile in a two-phase flow in porous media. The purpose of this study was to test an invasion percolation with gradient (IPG) theory in two-phase flow of porous media. Two phases are dodecane and water doped with CuSO4. The porous medium was packed glass beads. The front tail width σ and front width of invading phase were extracted from fitting of the invading front profile. The front tail scaled as σ∞Ca −α, where Ca is capillary number and α is 0.4 ± 0.08. The result is very close to IPG predication 0.25.