Turbulent diffusion and degradation of polymer molecules in a pipe and boundary layer

Sedov, L. I.; Ioselevich, V. A.; Pilipenko, V. N.; Vasetskaya, N. G.

doi:10.1017/s002211207900118x

Cited by 12 publications

(1 citation statement)

References 9 publications

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“…Moreover, there is a correspondence between local conditions in pipe flow, turbulent flow in a square channel, and turbulent flow in a developing boundary layer that yields an expectation that results from the former geometry will be locally applicable to the latter geometries. [20][21][22] Molecular weight, polymer concentration, solvent quality, turbulent intensity, and flow geometry have been identified as important factors influencing polymer degradation in turbulent pipe flows. [7][8][9][10][11]23 In particular, it has been reported that high molar mass polymers break preferentially relative to low molar mass chains 8,9,11 and that scission occurs predominantly at the chain midpoint.…”

Section: Introductionmentioning

confidence: 99%

Scission-induced bounds on maximum polymer drag reduction in turbulent flow

2005

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We report the direct quantification of molar mass degradation in the drag-reducing polymers polyethylene oxide ͑PEO͒ and polyacrylamide ͑PAM͒ in turbulent pipe flows with an upstream tapered contraction. We find that entrance effects associated with the upstream contraction dominate the polymer degradation. Quantifying degradation according to the scaling relationship ␥ w ϰ M ws −n , the exponent n is determined to be −2.20± 0.21 and −2.73± 0.18 for PEO and PAM, respectively. Here M ws is the steady-state ͑or limiting͒ weight-average scission molar mass. A methodology is devised to circumvent polymer degradation due to the upstream contraction and thereby conduct degradation experiments in which only the turbulent flow in the pipe is responsible for chain scission. In this case, the scission-scaling relationship for PEO is ␥ w ϰ M w −3.20±0.28. Here M w is the degraded weight-average molar mass after one pass through the 1.63-m length of pipe. Based on these scaling relationships we obtain a new upper limit for polymer drag reduction that is determined by chain scission rather than the maximum drag reduction asymptote.

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Section: Introductionmentioning

confidence: 99%

Scission-induced bounds on maximum polymer drag reduction in turbulent flow

2005

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Recent studies of polymer reactions caused by stress

Porter

Casale²

1985

Polymer Engineering & Sci

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A singular class of polymer reactions can be caused by mechanical stress. Sufficient storage of mechanical energy to break chemical bonds in the main chain is generally possible only on deformation of polymers of high molecular weight. The corresponding appropriate conditions of high stress may occur in both polymer processing and use. This review summarizes reports of such polymer stress reactions published principally after 1980. The survey is organized by polymer type and by analysis technique.

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