Lowering mechanical degradation of drag reducers in turbulent flow
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Taruna Reddy Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302, India
Ram P. Singh Office of the Vice Chancellor, University of Lucknow, Lucknow 226 007, India
Leslie White Laboratory of Advanced Polymers & Optimized Materials (LAPOM), Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203-5310 (Received 26 April 2006; accepted 3 August 2006)
Drag reduction (DR) agents are used in several ppm concentrations to accelerate significantly the flow through conduits in oil pipelines, oil well operations, flood water disposal, fire fighting, field irrigation, transport of suspensions and slurries, sewage systems, water heating and cooling systems, airplane tank filling, marine systems, and also in biomedical systems including blood flow. The drag reduction agents are typically high molecular mass polymers; in industrial applications they undergo mechanical degradation in turbulent flow. We provide an equation that describes quantitatively the degradation, thus predicting drag reduction as a function of time and of the concentration of the drag reduction agent. We report how grafting a polymer on the backbone of a different polymer affects the drag reduction efficacy. Our grafted polymer undergoes degradation by flow turbulence more slowly and also provides high levels of drag reduction efficacy at much lower concentrations than homopolymers do. I. INTRODUCTION
Drag reduction (DR) as defined in the above abstract has many applications in a variety of fields.1–4 To give an example, large urban agglomerations in India (and by no means only in India) find their sewer systems inadequate in the face of doubled or tripled populations. An alternative to digging out the entire municipal sewer system and replacing it by pipes with larger diameters is the use of DR agents. This is not just a much faster and cheaper solution. Larger diameter sewage pipes would have to be replaced periodically by still larger ones. By contrast, when the population continues to grow still more as it always does, a DR agent at increasing concentrations can continue to keep the sewer situation under control for a much longer time, provided a sewer network exists. DR has been discovered as occurring ‘by itself’ in human and animal blood flow5,6 and consequences of this fact are of staggering proportions. Without DR, humans and animals would have to eat multiple amounts of food compared with their current food consumption. Otherwise the blood circulation would be far from adequate and living a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0003 56
http://journals.cambridge.org
J. Mater. Res., Vol. 22, No. 1, Jan 2007 Downloaded: 10 Jul 2014
organisms other than plants would disappear. The fact that we know about DR occurrence in blood makes possible atherosclerosis prevention.5,6 In industrial applications (such as the Alaska pipeline) we have typically mechanical degradation in flow (MDF); DR decreases with time—a consequence of scission o
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