Velocity and turbulent fluctuation fields in water containing low concentrations of high-molecular substances

Khabakhpasheva, E. M.; Pereplitsa, B. V.

doi:10.1007/bf00828543

Cited by 11 publications

(1 citation statement)

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“…Turbulenzintensitgtsmessungen in Rohren mit quadratischem Querschnitt [14][15][16] zeigen im Vergleich zu solchen am reinen L6sungsmittel ein Anwachsen der mit der Schubspannungsgeschwindigkeit u~= ~ normierten Turbulenzintensit,it in StrSmungsrichtung in der N~ihe der Wand. Dies wird bei Kreisrohren indessen nicht gefunden [17][18][19] [23,24].…”

Section: Widerstandsverminderung Bei Polymerl~sungenunclassified

Heterogene Widerstandsverminderung bei turbulenten Rohrstr�mungen

Bewersdorff

1984

Rheol Acta

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Experiments in which a viscoelastic fluid is injected along the axis of a fully developed pipe flow of a Newtonian fluid are described. For relatively high polymer concentrations the injected polymer solution forms a thread, which remains intact down the entire length of the pipe. Under these conditions remarkable drag reduction is also observed, although the polymer has not diffused noticeably into the layers near the wall.The dependence of the local drag reduction along the pipe on the total polymer concentration in the pipe, the concentration of the injected polymer solution and the Reynolds number was investigated. Furthermore, velocity profiles, turbulence intensities and Reynolds shear stresses were measured and compared with those for the solvent and a premixed homogeneous polymer solution with the same effective concentration.The shape of the velocity profiles and the Reynolds shear stresses demonstrate that the structure of turbulence in the transition or buffer layer between the viscous sublayer and the turbulent core is markedly different in the injection experiments from that in a premixed homogeneous polymer solution. The size of this region is significantly larger than in a Newtonian fluid or a homogeneous polymer solution *) Von der Abteilung Chemietechnik der Universit~it Dortmund genehmigten Dissertation; auszugsweise vorgetragen auf der Jahrestagung der Deutschen Rheologischen Gesellschaft in Berlin vom 11.-13. Mai 1981 und der Ersten Europ~tischen Rheologen-Konferenz in Graz vom 14.-16. April 1982. 979 Bewersdorff, Heterogene Widerstandsverminderung bei turbulenten RohrstrSmungen 523 and the Reynolds shear stresses are drastically reduced. From details of the structure of the turbulence and the rheological properties of the injected polymer solution it may be concluded that the large-scale structures in the pipe are influenced by the polymer thread. It seems that their motion is restricted leading to a reduced transport of energy to the dissipating small eddies and thus to the occurrence of drag reduction.

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