No description available.

No description available.

Much research activity is carried out to reduce water consumption for domestic purposes. This leads to the possibility of reducing the amount of water introduced into building drainage systems. However, an accurate estimation of the flow attenuation within building drainage pipes is of great importance to prevent solid eposition and subsequent blockage. The research is focused on the field of subcritical flow in partially-filled pipes. Experimental and numerical investigations have been carried out to study the wave attenuation in the following configurations encountered in drainage pipe systems: i) A simple pipe, ii) A pipe subject to one concentrated lateral inflow, iii) A pipe with gate fixed at the downstream section, generating an interaction between wave and backwater profiles. In the present study the Saint-Venant equations are derived in their general and characteristic forms. A number of numerical procedures for solution of the Saint-Venant equations are reviewed, and the rectangular grid characteristics method, diffusing scheme and Strelkoff's implicit method are chosen to solve the equations. The stability of the finite-difference methods used is investigated for free-outfall and controlled outfall boundary conditions. An experimental installation consisting of 0.105 m diameter uPVC pipe is used to investigate the characteristics of the flow and to form test cases for the numerical methods. Comparisons between computed and observed depth hydrographs, peak depths and depth variations along the pipe are made for subcritical flow in a pipe of slope 1/300. The rectangular-grid characteristics method and the diffusing scheme are also applied to supercritical flow. Flow tests are undertaken for supercritical flow in a pipe of slope 1/200 to validate the use of these methods. The investigation revealed that the attenuation rate of peak depths is affected by the volume of the waves. The implicit method is the most suitable method, dealing efficiently with most problems encountered in drainage pipe systems of flat slope. The diffusing scheme can model the attenuation of supercritical flow within building drainage pipes.

No description available.

No description available.

No description available.

Melt blending of polyethylene, in particularly HDPE and LLDPE, have been shown to be a major success, especially in the film markets. In this thesis studies are reported on the stress rupture performance of pipes produced from selected polyethylene materials blended to a chosen MDPE pipe grade. The pipes were tested, notched or unnotched, at a single temperature of 80oC and at internal pressures designed to induce slit-mode failure. Results showed the simple concept of increasing the stress rupture performance of a pipe material by the addition of a higher molecular weight polymer was invalidated when applied to the blends system used in these studies. However molecular weight does have an influence to some degree as was illustrated by the addition of a very low molecular weight material, which produced the poorest stress rupture properties of the additives used. Charaterization techniques, including Differential Scanning Calorimetry and Dynamic Mechanical Thermal Analysis, showed good compatibility of the blends at all addition levels studied, illustrating that there was no seperation of the polyethylene phases. Fracture analysis of pipe failures showed variations between the blends, except for a MDPE additive which had similar molecular characteristics to the base resin. Some of the blends fracture surfaces were found to vary in fibre height and distribution from the bore region to the outside of the pipe. On the morphological front spherulites from pipe samples were found to be a poor indication of stress rupture behaviour. Pipe blends were produced which had fine/featureless morphologies but whose 80oC stress rupture behaviour was found to be good and poor in comparison to the control MDPE pipe resin which had a spherulitic structure much larger than all the blends studied. Models presented here infer that a number of mechanisms may be operating in producing these changes in stress rupture properties. One may be due to a dilution of a polyethylene system by materials of varying molecular weight and molecular weight distributions. This was evident in MDPE-AlMDPE-P blends (MDPE-P being a high molecular weight, low branch length additive), where the stress rupture performance initially decreased and then increased after addition levels of 10wt%. The main mechanisms for this system was postulated to be the initial dilution of octene branching levels within the MDPE-A blend causing a reduction in the ability of the branches to sterically hinder crack propagation under stress, to one of chain entanglement after sufficient levels of the additive was present in the blend to contribute to increasing the stress rupture behaviour. It was found that good blending can be produced using materials with similar branching types and distributions (especially in the high molecular weight tail), similar molecular weights and distributions and comparable crystallization temperatures.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 147-152). / Microfiche. / xviii, 152 leaves, bound ill. 29 cm

Thesis (M.S.)--Rochester Institute of Technology, 1990. / Includes bibliographical references (leaf 80).

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Civil Engineering, 1986. / Includes bibliographical references (leaves 53-57).