ePrints@IIScePrints@IISc Home | About | Browse | Latest Additions | Advanced Search | Contact | Help

Time dependent superhydrophobicity of drag reducing surfaces

Bobji, Musuvathi S and Balan, Ganesh and Govardhan, Raghuraman N (2011) Time dependent superhydrophobicity of drag reducing surfaces. In: 3rd Micro and Nano Flows Conference (MNF2011), 22-24 August 2011, Thessaloniki, Greece.

[img] PDF
Micr_Nan_Flow_Con_1_2011.pdf - Published Version
Restricted to Registered users only

Download (1MB) | Request a copy
Official URL: http://bura.brunel.ac.uk/handle/2438/6804


Air can be trapped on the crevices of specially textured hydrophobic surfaces immersed in water. This heterogenous state of wetting in which the water is in contact with both the solid surface and the entrapped air is not stable. Diffusion of air into the surrounding water leads to gradual reduction in the size and numbers of the air bubbles. The sustainability of the entrapped air on such surfaces is important for many underwater applications in which the surfaces have to remain submersed for longer time periods. In this paper we explore the suitability of different classes of surface textures towards the drag reduction application by evaluating the time required for the disappearance of the air bubbles under hydrostatic conditions. Different repetitive textures consisting of holes, pillars and ridges of different sizes have been generated in silicon, aluminium and brass by isotropic etching, wire EDM and chemical etching respectively. These surfaces were rendered hydrophobic with self-assembled layer of fluorooctyl trichlorosilane for silicon and aluminium surfaces and 1-dodecanethiol for brass surfaces. Using total internal reflection the air bubbles are visualized with the help of a microscope and time lapse photography. Irrespective of the texture, both the size and the number of air pockets were found to decrease with time gradually and eventually disappear. In an attempt to reverse the diffusion we explore the possibility of using electrolysis to generate gases at the textured surfaces. The gas bubbles are nucleated everywhere on the surface and as they grow they coalesce with each other and get pinned at the texture edges.

Item Type: Conference Paper
Publisher: Brunel University
Additional Information: Copyright of this article belongs to Brunel University.
Keywords: Superhydrophobic Surfaces; Drag Reduction; Surface Texturing; Underwater Hydrophobicity
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 06 May 2013 12:03
Last Modified: 06 May 2013 12:03
URI: http://eprints.iisc.ac.in/id/eprint/46294

Actions (login required)

View Item View Item