Imperial College London

Emeritus ProfessorGeoffreyHewitt

Faculty of EngineeringDepartment of Chemical Engineering

Emeritus Professor
 
 
 
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Contact

 

+44 (0)20 7594 5562g.hewitt

 
 
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Assistant

 

Mrs Sarah Payne +44 (0)20 7594 5567

 
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Location

 

507aACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Zadrazil:2012:10.1016/j.ces.2011.12.044,
author = {Zadrazil, I and Bismarck, A and Hewitt, GF and Markides, CN},
doi = {10.1016/j.ces.2011.12.044},
journal = {Chemical Engineering Science},
pages = {142--154},
title = {Shear Layers in the Turbulent Pipe Flow of Drag Reducing Polymer Solutions},
url = {http://dx.doi.org/10.1016/j.ces.2011.12.044},
volume = {72},
year = {2012}
}

RIS format (EndNote, RefMan)

TY  - JOUR
AB - A range of high molecular weight polymers (polyethylene oxide) was dissolved at very low concentrations – in the order of few wppm – in a solvent (water). The Newtonian character of the polymer solutions was confirmed by rheological measurements. The polymer solutions were then pumped through a long horizontal pipe section in fully developed turbulent conditions. The flow experienced a reduction in frictional drag when compared to the drag experienced by the equivalent flow of the pure solvent. Specifically, drag reduction was measured at Reynolds numbers ranging from 3.5×10^4 to 2.1×10^5 in a pressure driven flow facility with a circular tube section of internal diameter 25.3 mm. The turbulent flow was visualized by Particle Image Velocimetry and the resulting data were used to investigate the effect of the drag reducing additives on the turbulent pipe flow. Close attention was paid to the mean and instantaneous velocity fields, as well as the two-dimensional vorticity and streamwise shear strain rate. The results indicate that drag reduction is accompanied by the appearance of “shear layers” (i.e. thin filament-like regions of high spatial velocity gradients) that act as interfaces separating low-momentum flow regions near the pipe wall and high-momentum flow regions closer to the centerline. The shear layers are not stationary. They are continuously formed close to the wall at a random frequency and move towards the pipe centerline until they eventually disappear, thus occupying or existing within a “shear layer region”. It is found that the mean thickness of the shear layer region is correlated with the measured level of drag reduction. The shear layer region thickness is increased by the presence of polymer additives when compared to the pure solvent, in a similar way to the thickening of the buffer layer. The results provide valuable insights into the characteristics of the turbulent pipe flow of a solvent contai
AU - Zadrazil,I
AU - Bismarck,A
AU - Hewitt,GF
AU - Markides,CN
DO - 10.1016/j.ces.2011.12.044
EP - 154
PY - 2012///
SP - 142
TI - Shear Layers in the Turbulent Pipe Flow of Drag Reducing Polymer Solutions
T2 - Chemical Engineering Science
UR - http://dx.doi.org/10.1016/j.ces.2011.12.044
UR - http://www3.imperial.ac.uk/people/c.markides
UR - http://www.elsevier.com/
UR - http://hdl.handle.net/10044/1/14330
VL - 72
ER -