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REVIEW ARTICLES

Effect of Polymeric Additives on Turbulent Flow in Opposed Jets

[+] Author and Article Information
A. J. Müller, A. E. Saez

Grupo de Polimeros USB, Departamentos de Thermodinámica y Ciencia de los Materiales, Universidad Simón Bolívar, PO Box 89000, Caracas 1080-A, Venezuela

J. P. Tatham, J. A. Odell

HH Wills Physics Laboratory, University of Bristol, Royal Fort, Tyndall Avenue, Bristol BS8 1TL, United Kingdom

Appl. Mech. Rev 48(11S), S216-S221 (Nov 01, 1995) doi:10.1115/1.3005075 History: Online April 29, 2009

Abstract

In this work we study the effect of polymeric additives on the transition to turbulence in opposed-jets flow. In this type of flow, the transition to turbulence for Newtonian fluids is characterized by a decrease in the rate of change of pressure drop with flow rate. We have used various polymers whose equilibrium molecular conformation in aqueous solution is different: poly (ethylene oxide), which exists in a conformation close to a random coil, hydroxypropyl guar, which adopts an expanded coil conformation, and hydrolyzed polyacrylamide, whose conformation is close to a random coil in the presence of an electrolyte (sodium chloride) but it changes to an expanded coil in distilled water. The results show that small amounts of either flexible or semi-rigid polymers induce a delay in the critical Reynolds number at which turbulence sets in. This delay seems to be a result of the suppression of flow instabilities in a region close to the stagnation point, which is linked to macromolecular orientation. Since, for Newtonian fluids, this flow has an increase of drag with flow rate that is slower in the turbulent flow regime than in the laminar regime, the addition of polymer causes a substantially higher pressure drop in turbulent flow with respect to that of the pure solvent. Therefore, polymer addition causes, in this particular case, a drag increase in turbulent flow, as opposed to the commonly observed drag reduction in turbulent flow through pipes.

Copyright © 1995 by The American Society of Mechanical Engineers
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