Fluid retention in textured surfaces under shear flow conditions

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Capello, Colin James

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The ability of a surface to retain water or oil has oil-gas flow assurance applications like hydrocarbon deposition prevention, oil-water separation and core annular flows. This dissertation examines the ability of textured aluminum surfaces to retain water or oil. The surface texture is obtained by an acid treatment of aluminum; the high surface energy and the porous texture (resulting from the chemical etching) together creates a surface which can wick liquid into its interior. Strong adhesion between the surface and liquid is expected to lead to a stable film, even in the presence of liquid shear. This dissertation presents preliminary experimental results that are the first step towards understanding the ability of textured surfaces in retaining liquid under shear flow conditions. A custom built recirculating flow loop is used to measure the ability of the surface to retain oil and water under the action of water and oil shear flow respectively. It is seen that the surface can retain oil films under water flows as high as 0.26 m/s (Reynolds number of 9900). The surface showed loss of water films under an oil flow velocity of 0.13 m/s (Reynolds number of 500); additional experiments are needed to determine the utility of such surfaces in retaining water at lower speeds. Similarly, oil loss from the surface was observed under the action of water jet impingement. Additionally, this work examined the chemical resistance of the textured aluminum surface by exposure to five liquid media. It was observed that static tap water does not degrade the performance of the surface, which validates the use of such surfaces in a wide variety of operating conditions. High temperature water exposure can degrade surface performance due to bubbling-induced fluid loss from the textures. The surfaces show performance degradation under concentrated acidic and basic media exposure; however, they are expected to offer more resistance in lower concentrations that approach real world conditions. Overall, this work provides preliminary assessments and a starting point for an understanding of the interfacial phenomena involved in liquid retention on textured surfaces. Follow-up studies will ultimately enable the development of surface architectures for trapping fluids for various oil-gas applications.


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