Role of molecular aggregates in liquid drag reduction by polymers

Cox, Liam R.; Dunlop, Eric H.; North, Alastair M.

doi:10.1038/249243a0

Cited by 44 publications

(37 citation statements)

References 5 publications

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“…Vlachogiannis and Hanratty (2004) observed similar processes of polymer filamentation in their study of wall-injected polymer in a channel flow. They concluded that the presence of polymer filamentation resulted in enhanced drag reduction, and this, in turn may be due to the formation of polymer aggregates, as previously suggested by Cox et al (1974). As discussed above, it is likely that there is substantial aggregation of the injected polymer solutions.…”

Section: Filamentation Of High Concentration Polymer Solutionssupporting

confidence: 49%

High Reynolds Number Micro-Bubble and Polymer Drag Reduction Experiments

Ceccio¹,

Dowling²,

Perlin³

et al. 2008

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Background: This effort was a continuation of the joint ONR and DARPA programs of the PI and Co-PI's initiated as part of the DARPA Friction Drag Reduction Program (ATO/TTO). The purpose of the investigation was to examine the physics and engineering of friction drag reduction methods for turbulent boundary layers (TBL) found in hydrodynamic flows. Three methods of friction drag reduction (FDR) were examined:" Polymer Drag Reduction-solutions containing extensible, long-chain molecules ' are injected into a TBL. The polymer molecules interact with the underlying turbulent flow and lead to a reduction of the correlated velocity fluctuations and, hence, a reduction of the turbulent transport of momentum across the TBL. This leads to local drag reduction of up to -70% for a TBL flow over smooth surfaces compared to a flow without polymer injection.* Micro-bubble Drag Reduction-air is injected into the TBL with the aim of producing a large volume of small bubbles in the near-wall region of the TBL. The presence of the bubbles reduces the bulk density of the fluid near the wall and possibly alters the turbulent velocity fluctuations. These effects can combine to locally reduce the friction drag over 80%." Air Layer Drag Reduction-air is injected into the TBL with the aim of creating a stable gas layer of very high void fraction (> 80% void fraction), separating the liquid flow from the solid surface. This results in friction drag reductions of over 80% compared to the friction drag of an unmodified TBL. DISTRIBUTION STATEMENT A 20080131 272 Approved for Public ReleaseDistribution UnlimitedThese FDR methods have been studied for some time on the laboratory scale, yielding a great deal of information on their engineering potential and underlying methods. However, the flow physics responsible for FDR does not easily scale from the laboratory to full-scale hydrodynamic applications. Hence, our effort focused on conducting a series of experiments at both large size scales and high Reynolds numbers in order to further explore the flow physics and practicality of these FDR methods.Our experiments were performed on a canonical TBL flow formed on a flat plate, zeropressure gradient boundary layer. The maximum length of the test model was -10 m, and the maximum velocity of the flow was -20 m/s, making the Reynolds number based on maximum length -200 million. Our experiments were conducted in the William B.Morgan Large Cavitation Channel (LCC), owed and operated by the Naval Surface Warfare Center-Carderock Division of the U. S. Navy.During this portion of our research program, three rounds of testing in the LCC were conducted:* Phase III (Polymer FDR) * Phase IV (MBDR/ALDR) * Phase V (Polymer FDR).Two additional rounds of testing were conducted under the first portion of ONR and DARPA support: Phase I was a baseline test of the model, and Phase II was on MBDR. Also, a portion of Phase V was devoted to examining the influence of roughness on Polymer FDR and ALDR. This portion of the effort was supported under DARPA contract "...

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Section: Filamentation Of High Concentration Polymer Solutionssupporting

confidence: 49%

High Reynolds Number Micro-Bubble and Polymer Drag Reduction Experiments

Ceccio¹,

Dowling²,

Perlin³

et al. 2008

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“…As a result, the formation of aggregates, which plays an important role in the drag reduction phenomenon, is improved as reported by Cox et al (1947) and Vlachogiannis et al (2003).…”

Section: Effect Of Pdra Molecular Weight On Drag Reductionmentioning

confidence: 58%

“…Increasing the PDRA concentration enhances the formation of aggregates which play a very significant role in the drag reduction phenomenon as reported by Cox et al (1947).…”

Section: Effect Of Pdra Concentration On Drag Reductionmentioning

confidence: 87%

Effect of drag reducing polymers on oil–water flow in a horizontal pipe

Al-Yaari

Soleimani

Abu-Sharkh

et al. 2009

International Journal of Multiphase Flow

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“…[2] One example of its industrial importance is its ability to reduce friction between surfaces. [3,4] This ability has been shown to be linked to the tendency of PEG to aggregate in aqueous solution. [5,6] An early study showed that aggregation is not an inherent property of PEG-water system.…”

Section: Introductionmentioning

confidence: 99%