The present thesis is a comparative study of the hydrodynamic effects of a few deterministic microasperity shapes in a thrust slider application. Numerical study based on finite difference methods is used to find the trend of important tribological properties such as friction and leakage. Also, this work utilizes a distinctive and practical approach for comparison by considering constant load conditions, instead of constant film thickness, as is expected in an operating thrust bearing. The results are encouraging and clearly reveal the existence of a transition point for asperity area fraction where a reversal in trends for both the coefficient of friction and leakage is observed. The shapes of asperities affect leakage but, have a negligible effect on coefficient of friction; however, the size and the type of asperity (positive or negative) do influence it. The effects of orientation, on the other hand, are found both on the coefficient of friction and leakage. Triangular asperities exhibit an advantage over the other shapes in terms of leakage. In general, the impact of shapes is distinguishable, more at higher asperity area fractions in accordance with the geometrical differences.

This thesis is concerned with the interactions of oils with surfactants. The understanding of these interactions is important for a number of practical applications which include perfume delivery in fabric softeners. Both non-ionic surfactants, of the general formula H( CH2)n( OCH2CH2)m-OH, and lome surfactants, of the general formula CnH2n+lW(CH3)3Br were used in the study. Oils of varying polarity were investigated from non-polar alkane oils to moderately polar perfume oils.Initially, the work of adhesions of the perfume oils with water were studied to establish where these oils 'fitted-in' to a range of oils of varying polarity. It was found that the three perfume oils studied (linalool, cineole and eugenol) all exhibited adhesion properties which were fairly typical of moderately polar oils. In order to obtain the enthalpies and entropies of adhesion of the perfume oils with water the surface tensions and interfacial tensions with water were measured as a function of temperature. The enthalpy of adhesion for linalool with water is consistent with values obtained for the enthalpy of hydration of the hydroxyl group.The co-surfactant nature of the perfume oils was investigated by tension measurements of their adsorption to the heptane-water interface. Linalool and eugenol show reasonably high surface activity at this interface and could therefore be expected to act as cosurfactants in systems that contain conventional surfactants.The phase behaviour of the CgE5 + water + octane micro emulsion system was investigated to determine the effect of adding different concentrations of perfume oil on the size, shape and position of the three phase region. It was found that linalool reduces the size of this three phase region and also reduces the temperature at which the three phase region occurs. Although not conclusive, this behaviour suggests the system is approaching a triclitical point.It is of interest also to understand the adsorption of oils at planar surfactant mono layers and then attempt to relate the adsorption data to bulk phase solubilisation of the oils in micelles. The adsorption at a planar interface was attained by measuring the surface pressure of the oil at different activities. The surface concentration of the oils was then calculated from the Gibbs adsorption equation. By measuring these surface pressures as a function of activities at various temperatures, it was possible to derive the adsorption enthalpies and entropies with use of a form of the Van't Hoff equation. It was found that alkane adsorption increases with decreasing alkane chain length and the isotherms show a greater curvature upwards for the shorter chain length alkanes suggesting that the adsorption becomes more favourable as more alkane is added to the mixed alkane/surfactant film.Headspace analysis was employed to measure the solubilisation of oils in bulk surfactant solutions. The results obtained with this technique were preliminary although early indications suggest that more alkane oil is solubilised in bulk aggregates with curved monolayers than is adsorbed at planar monolayer interfaces. However, solubilisation of oil in bulk solutions may either be in the curved monolayer or they could form a 'core' of oil inside the aggregate.

Thesis (M.Sc. (Chemical Engineering)) -- University of Pretoria, 2007. / Includes bibliographical references.

Thesis (M.Sc.)(Chemistry)--University of Pretoria, 2004. / Summaries in English and Afrikaans. Includes bibliographical references.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: lubrication; rupture; journal bearings; Reynolds equation; thin films; cavitation. Includes bibliographical references (p. 72-76).

Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / Jiri Janata, Committee Member ; Shreyes Melkote, Committee Member ; Steven Danyluk, Committee Chair. Includes bibliographical references.

Thesis (Ph. D.)--Columbia University, 1933. / Vita.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Salant, Richard F.; Committee Member: Bair, Scott; Committee Member: Cowan, Richard S; Committee Member: Danyluk, Steven; Committee Member: Scott, Waymond R. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

A lubrication-flow model for a free film in a corner is presented. The model, written in the hyperbolic coordinate system ξ = x² – y², η = 2xy, applies to films that are thin in the η direction. The lubrication approximation yields two coupled evolution equations for the film thickness and the velocity field which, to lowest order, describes plug flow in the hyperbolic coordinates. A free film in a corner evolving under surface tension and gravity is investigated. The rate of thinning of a free film is compared to that of a film evolving over a solid substrate. Viscous shear and normal stresses are both captured in the model and are computed for the entire flow domain. It is shown that normal stress dominates over shear stress in the far field, while shear stress dominates close to the corner.