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Effect of absolute pressure on flow through a textured hydrophobic microchannel

Dilip, D and Bobji, MS and Govardhan, Raghuraman N (2015) Effect of absolute pressure on flow through a textured hydrophobic microchannel. In: MICROFLUIDICS AND NANOFLUIDICS, 19 (6). pp. 1409-1427.

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Official URL: http://dx.doi.org/10.1007/s10404-015-1655-4

Abstract

The potential of textured hydrophobic surfaces to provide substantial drag reduction has been attributed to the presence of air bubbles trapped on the surface cavities. In this paper, we present results on water flow past a textured hydrophobic surface, while systematically varying the absolute pressure close to the surface. Trapped air bubbles on the surface are directly visualized, along with simultaneous pressure drop measurements across the surface in a microchannel configuration. We find that varying the absolute pressure within the channel greatly influences the trapped air bubble behavior, causing a consequent effect on the pressure drop (drag). When the absolute pressure within the channel is maintained below atmospheric pressure, we find that the air bubbles grow in size, merge and eventually detach from the surface. This growth and subsequent merging of the air bubbles leads to a substantial increase in the pressure drop. On the other hand, a pressure above the atmospheric pressure within the channel leads to gradual shrinkage and eventual disappearance of trapped air bubbles. We find that in this case, air bubbles do cause reduction in the pressure drop with the minimum pressure drop (or maximum drag reduction) occurring when the bubbles are flush with the surface. These results show that the trapped air bubble dynamics and the pressure drop across a textured hydrophobic microchannel are very significantly dependent on the absolute pressure within the channel. The results obtained hold important implications toward achieving sustained drag reduction in microfluidic applications.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the SPRINGER HEIDELBERG, TIERGARTENSTRASSE 17, D-69121 HEIDELBERG, GERMANY
Keywords: Textured hydrophobic surface; Trapped air bubbles; Pressure drop; Drag reduction
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Depositing User: Id for Latest eprints
Date Deposited: 02 Jan 2016 07:29
Last Modified: 02 Jan 2016 07:29
URI: http://eprints.iisc.ac.in/id/eprint/52995

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