This study aims to describe and quantify the important sedimentary processes which control the dispersal and accumulation of sediment in the Dwyryd Estuary, adjacent to Tremadog Bay in West Wales. It is shown that sedimentation in the estuary is dominantly control by fast tidal currents, and in the bay by weak tidal currents. Landward transport of coastal sediments by tidal currents is the residual sediment transport path. The spatial distribution of textural parameters of the estuarine sediments is related to the strength of tidal currents as well as the morphology and bathymetry of the study area. The estuarine sediments, predominantly sand, are very similar in texture and mineralogy to the adjacent beach sediments but markedly different to the river sediments. However, the beach sediments are slightly coarser and more poorly sorted than the estuarine sediments. In contrast, sediment in the deeper parts of Tremadog Bay are finer than both the estuarine and beach sediments due to the presence of substantial admixture of mud. The grain size distributions of most of the sediments are neither lognormal nor log-hyperbolic reflecting the great variability of hydrodynamic conditions in the study area. Using previously published flume data, a new sediment transport rate formula in the form of a power law has been developed for computation of total sediment load from the bed mean grain size and flow parameters: Uc The exponent n varies from 2.7 (for 0.93 mm sand) to 4.18 (for 0.19 mm sand). This is in contrast to the Bagnold (1966) formula which regards the exponent value (equal to 3) as constant for all grain sizes. Sediment transport patterns depend on the asymmetry between flood and ebb tidal currents due to distortion of the tidal wave on entering the estuary. Estimates of sediment budgets from surveyed profiles suggest that large amounts of sand have been transported from coastal areas into the estuary, supporting the mineralogical evidence. The estimates are of the same order of magnitude as estimates using flow velocity data and the above sediment transport formula.

No description available.

The aim of this investigation was to study the hydraulic behaviour of small circular openings in plastic water pipes. According to the theoretical orifice equation, the flow through an orifice is proportional to the square root of the pressure. However, a number of field studies have shown that this exponent can be considerably larger than 0.5, and typically varies between 0.5 and 2.79 with a median of 1.15 (Farley and Trow 2003). The implication is that water losses are substantially more sensitive to pressure than originally thought. Van Zyl and Clayton (2005) proposed four categories of factors that may be responsible for the observed behaviour: leak hydraulics, pipe material behaviour, soil hydraulics and water demand. The aim of this study was to investigate the hydraulics of small circular holes in water distribution systems to determine their behaviour under various conditions. Variables studied in this investigation include pipe material, leak size, surrounding media and pressure fluctuations. Boundary conditions need to be established to accurately simulate the conditions that a pipe in a water network experiences. The author designed and built the apparatus to provide these constant boundary conditions. The apparatus consists of six major components. These are the frame, casing, sample, pressure vessel, constant pressure regulators and measuring equipment. The frame provides structural stability to the apparatus during testing. The casing’s purpose is to house the material that surrounds the sample while being tested; it also creates the constant boundary conditions necessary for the experiments. 1mm and 2mm holes are drilled into the uPVC and HDPE pipes. This serves as the test samples. The pressure vessel is used to enable constant pressure with better pressure control. Constant pressure regulators help to provide the required conditions within the casing. The measuring equipment records that data from the experiments. The data is then processed into interpretable information. It was found that leaks discharging into air show good correlation with the theory, but differ significantly from the behaviour of leaks discharging into water or glass beads. Other findings of the study include that pressure fluctuations do not have a significant effect on the leak behaviour, the classification of the opening (as an orifice, tube or pipe) is important and that a discontinuity in the pressure leakage relationship occurs in holes classified as tubes. It is suspected that the discontinuity is caused by separation of the fluid stream from the tube wall, effectively changing it into an orifice. / Prof. J.E. Van Zyl Prof. C.R.I. Clayton

No description available.

A bench-scale, two-dimensional multi-compartmentalized fluidized reactor was designed and studies of hydrodynamic behavior of fluidization of struvite pellets were performed. Also size growth distribution tests were analyzed qualitatively. The study validated a previously-proposed theory, concerning the relationship between dynamic pressure drop and upflow velocity as well the experimental protocol to determine the minimum fluidization velocity. Findings indicated that the mixture of two-sized particles would behave rather independently of each other, before the bed expansion. It was suggested that bed height measurement could be another promising method to pinpoint minimum fluidization velocity as there is a sharp bed surface "waking episode" during the process of a packed bed being gradually fluidized. Bed expansion equations for the prediction of void fraction as a function of superficial upflow velocity or vice versa, have been established for 4 groups of monosize particles, as well as two mixtures of two-sized particles. The equation constants did not agree well with previously established ones. The two layers of segregated mixture bed had congruent linear relationships between the logarithmic void fraction and logarithmic upflow velocity. It was found that a mixture does not always go through segregation, but only when the size difference is large enough. Size growth distribution tests were performed under different hydrodynamic configurations as well as seeding conditions. Conclusions can be made that a bed with uniformly- distributed particle void fractions and higher mixing energy input (upflow velocity), normally has better performance of struvite growth in size. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

On the thesis that the lateral frictional stresses should play an important part in determining the horizontal circulation in landlocked bodies of water, a mathematical model of the circulation in an inlet is developed. The circulation is described by a fourth order differential equation [formula omitted] where Ψ is a stream function. A solution representing a commonly observed circulation is obtained for a rectangular bay. The significance of Coriolian, frictional, and mass field forces in maintaining such a circulation is discussed. The theoretical model is tested by means of data available for Burrard Inlet. The data indicate the existence of two net circulations, one at 50 feet which has been attributed to the tides, and the other at the surface which is influenced strongly by the influx of brackish water from the Fraser River. Relaxation methods are introduced to test the current fields for verification of the differential equation. Despite the more complex boundaries of Burrard Inlet as compared with the rectangular bay investigation, the actual circulation in Burrard Inlet is found to satisfy the fourth order differential equation within the limit of observational error. This agreement suggests that the lateral frictional stresses do play an important part in the circulation in inlets. Further applications of relaxation methods are urged for oceanographic studies. Suggestions are made as to where oceanographic observations should be taken for a study of lateral circulations in inlets or bays. The reasonable agreement of the mathematical model and prototype suggests that lateral effects can be described by the mathematical theory. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Five symmetrical wye branches of conventional and spherical types were tested for hydraulic losses under symmetrical and unsymmetrical flow conditions. Results are presented graphically. A wide variation in loss factor was observed depending on the type of wye and on flow condition. For a given wye the minimum wye loss coefficient does not necessarily occur under conditions of symmetrical flow. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This thesis examines buoyancy driven steady flows in mouths of sea straits and around coastal protrusions. At high latitudes, the Coriolis force keeps these currents banked against the coast even around relatively sharp re-entrant (convex) corners with radii of curvature that are comparable to the width of the current. On the other hand, if the radius of curvature of the corner is much smaller than the width of the current, the current may leave the coast at the apex of the corner. A central part of the thesis is the solution of the nonlinear problem of a steady inviscid reduced gravity flow in a wedge, 0<θ<π/a (with a>l/2), around a sharp corner on an f-plane. An exponential upper layer upstream depth profile, h=Hexp(-x/X) (where x and X are the offshore distance and the current width scale, respectively), is combined with conservation of potential vorticity, Bernoulli and transport equations. The resulting nonlinear equations are expanded in a Rossby number ∈=V/fX (where f is the Coriolis parameter and V is the upstream boundary value of velocity). The 0(1) and 0(∈) equations are solved. First, they are simplified via transformations of the transport streamfunction variables: ⍦₀=p⁴ʹ³ and ⍦₁=2p¹ʹ³q. By modifying the results of Bromwich's (1915) and Whipple's (1916) diffraction theory, the 0(1) solution is expressed in a compact integral form, [formula omitted] The 0(∈) contribution q is calculated using an approximate Green's function method. The wedge of an angle 3π/2 (a=2/3) is used as an example to show details of the solution. The results exhibit the relative importance of the centrifugal, Coriolis and pressure gradient forces. Centrifugal upwelling (surfacing) of the interface occurs very close to the apex. For a rounded re-entrant corner, the upwelling is important only if the radius of curvature is much smaller than the lateral scale X. liorever, for re-entrant corners, the flow is supercritical within an arc, whose size depends upon the Rossby number and the angle of the wedge. Using two or more corner solutions, plausible flow streamlines can be generated in more complicated domains, as long as no two corners are closer than the Rossby radius of deformation. This procedure is illustrated with two examples: (a) circulation in a channel mouth and (b) flow around a square bump in a coastline. Finally, baroclinic circulation is modeled for boundaries that approximate coastlines near the mouth of Hudson Strait. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The problem of the dynamics of a flexible offshore structure in either a regular or random sea is considered in this thesis. A simple single degree of freedom model of the structure is assumed and the relative velocity formulation of the Morison equation is used to describe the fluid force. The resulting equation of motion is a nonlinear ordinary differential equation with either harmonic or stochastic forcing depending on the wave description. Solutions are obtained for regular deterministic waves by numerical integration, various linearization methods and a new perturbation method developed in this thesis. The numerical solution is used to assess the accuracy of each of the approximate solution methods. Of these, the perturbation method is found to give the best approximation to the numerical solution over the complete frequency range of interest. For random seas the response spectrum and the mean square response are obtained by various linearization methods, the method of equivalent linearization, and by the new perturbation method. The perturbation method and the method of equivalent linearization are very similar in that they both yield the same values of effective damping. Comparison of the results obtained by a numerical simulation method with the results of the perturbation method and the widely used method of equivalent linearization shows that the perturbation method gives a better estimate of the response mean square value than does the method of equivalent linearization. For all of the approximate solution methods that are discussed it was found that the use of Hermite polynomials to represent the solution is very effective in obtaining various expected values required in the computational procedure. In addition to the average response statistics, such as the response mean square value, the probability density of the response is also considered. It is well known that the response of a linear system to Gaussian forcing is itself Gaussian. The wave force given by the Morison equation is non-Gaussian and therefore the response is also non-Gaussian but of unknown form. The hypothesis that for a linear equation, the probability density of the response is of the same form as the probability density of forcing, even for the case of non-Gaussian forcing, is investigated and verified using the results of numerical simulations. Design considerations of interest which follow from the response probability density are also discussed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The salt expulsion caused by the freezing of seawater and the drainage of brine from the ice creates a convectively mixed layer, which extends to the bottom in shallow coastal regions. This buoyancy flux at the surface was simulated in laboratory experiments by percolating salt water through a porous membrane into a tank. Shadowgraph images show that a down-slope flow is induced when the bottom of the tank is set at an angle. Velocity maxima in the slope flow, measured from the movement of injected dye ranged from 0.09 to 0.66 cm/s. Fluid densities were determined using thermistors and small-volume conductivity micro-cells developed for this purpose. For bottom slope angles between 2.2° and 5.5°, and at computed salt fluxes between 1.82★10⁻⁵ and 1.63★10⁻⁶ g/cm²/s, the salinity profiles showed slope flow depths between 7 and 17 mm with a rise in salinity of 0.24 to 0.92 ppt above those in the mixed layer. Entrainment at a density interface without shear, using this experimental arrangement, agreed closely with predicted results by Bo Pedersen. Using the entrainment model for a turbulent gravity current, entrainment factors computed from the data of the slope flow experiments were up to two orders of magnitude larger than those predicted for flows in a quiescent environment. This is contrary to visual evidence of the experiments or to Arctic field data, which indicate low rates of entrainment. This suggests that a different model is required to explain the interaction between such flows and the turbulent environment. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate