Sustainability of apparent slip in micro-channel flows

Govardhan, Raghuraman N and Pawar, Pradeep S and Bobji, Musuvathi S (2011) Sustainability of apparent slip in micro-channel flows. In: 3rd Micro and Nano Flows Conference, 22-24 August 2011, Thessaloniki, Greece.

PDF Mic_Nan_Flow_Con_1_2011.pdf - Published Version Restricted to Registered users only Download (462kB) | Request a copy

Abstract

In the present work, we experimentally study the flow of water over textured hydrophobic surfaces in a micro-channel. Shear stress measurements are done along with direct visualization of trapped air pockets on the hydrophobic surface. The trapped air pockets on such surfaces are known to be responsible for apparent slip at these surfaces and hence in significant drag reduction. In typical circumstances, the apparent slip reduces over time as seen, for example, from our shear stress measurements. This implies that the drag reduction will not be sustained. We have performed extensive visualizations of the trapped air pockets while varying flow parameters like the flow rate and the pressure. We present here direct visualizations that show that under some conditions, the air pockets can grow with time. The variation of the air pocket size with time is found to change qualitatively and quantitatively as the flow rate is varied. These measured changes in the air pocket size with time have a direct bearing on the sustainability of apparent slip in micro-channel flows.

Item Type:	Conference Paper
Publisher:	Brunel University
Additional Information:	Copyright of this article belongs to Brunel University.
Keywords:	Hydrophobic Surface; Apparent Slip; Drag Reduction; Air Pockets
Department/Centre:	Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	04 May 2013 10:19
Last Modified:	04 May 2013 10:19
URI:	http://eprints.iisc.ac.in/id/eprint/46293

Actions (login required)

View Item