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Behaviour of rarefied gas flow near the junction of a suddenly expanding tube

DSpace at IIT Bombay

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Title Behaviour of rarefied gas flow near the junction of a suddenly expanding tube
 
Creator VARADE, V
AGRAWAL, A
PRADEEP, AM
 
Subject micro-/nano-fluid dynamics
non-continuum effects
rarefied gas flow
REYNOLDS-NUMBER FLOW
GASEOUS SLIP-FLOW
PRESSURE-DROP
FRICTION CHARACTERISTICS
LONG MICROCHANNELS
AREA CHANGES
EXPANSION
MICROTUBES
REGIME
COEFFICIENT
 
Description This paper presents an experimental study of isothermal rarefied gas flow through a tube with sudden expansion in the slip flow regime. The measurements reported here are for nitrogen flowing at low pressures in conventional tubes with sudden expansion area ratios of 1.48, 3.74, 12.43 and 64. The flow is dynamically similar to gas flow in a microchannel as the Knudsen number (0.0001 < Kn < 0.075) falls in the slip flow regime; the Reynolds number in the smaller section (Re-s) ranges between 0.2 and 837. The static pressure along the wall is measured for different mass flow rates controlled by a mass flow controller and analysed to understand the flow behaviour. The velocity profiles are obtained through a momentum balance and using the pressure measurements. A discontinuity in the slope of pressure at the sudden expansion junction is noted and given special attention. The absence of flow separation is another key feature observed from the measurements. The streamlines are found to be concave near the junction. It is demonstrated that the flow 'senses' the oncoming sudden expansion junction and starts adjusting itself much before reaching the junction; this interesting behaviour is attributed to an increased axial momentum diffusion and wall slip. The additional acceleration of the central core of the gas flow causes an increase in the wall shear stress and a larger pressure drop as compared with a straight tube. These results are not previously available and should help in improving understanding of gaseous slip flows.
 
Publisher CAMBRIDGE UNIV PRESS
 
Date 2014-12-28T12:08:32Z
2014-12-28T12:08:32Z
2014
 
Type Article
 
Identifier JOURNAL OF FLUID MECHANICS, 739363-391
0022-1120
1469-7645
http://dx.doi.org/10.1017/jfm.2013.615
http://dspace.library.iitb.ac.in/jspui/handle/100/16446
 
Language English