Velocity distributions and normal stresses in viscoelastic turbulent pipe flow

Astarita, Gianni; Nicodemo, L.

doi:10.1002/aic.690120316

Cited by 30 publications

(11 citation statements)

References 6 publications

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“…The sensor was a conical probe having a diameter of about 0.50 mm in the region of the heated film, and was located 349 pipe diameters from the pump. Pitot tubes were not used to measure mean velocity profiles in the polymer flows, because viscoelastic effects tend to distort the tube response in the regions of pronounced shear [1]. However, a 1.80 mm I.D.…”

Section: Experimental Techniquementioning

confidence: 99%

Turbulent Characteristics Of Drag-Reducing Flows

Alonso

Klaus²,

Wylie

1976

Journal of Hydraulic Research

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Turbulence measurements were made in water and in a polyethylene oxide aqueous solution, using hot-film anemometry. Mean velocities, turbulence intensities, energy spectra and energy-dissipation rates were measured in a turbulent smooth-pipe flow. Mean flow structure showed that the mean velocity follows Virk's interactive-layer profile, and that the wall shear velocity is the proper velocity scale for polymer flows. Using Lumley's concept of an effective viscosity, the polymer spectra were cast into universal form and compared with Newtonian spectra. Results coincide reasonably well with the universal equilibrium theory. The major effect of the polymer additive appears to be an increase of the dissipative scales of the turbulence without significantly altering the basic structure of the flow, except near the wall.Resume L'étude présentée a comporté des mesures des différentes caractéristiques de la turbulence dans des écoulements d'eau, et d'une solution aqueuse d'oxyde de polyethylene, effectuées par la methode d'ané-mométrie a fil chaud. Ces mesures, exécutées dans une conduite comportant des parois lisses, ont porté sur les vitesses moyennes, les intensités de turbulence, les spectres énergétiques, et enfin, les taux de dissipation d'énergie. Il est ressorti de la structuration moyenne de l'ecoulement que Ia vitesse moyenne évolue selon Ie profil a couches inter-actives défini par Virk, et d'autre part, que la vitesse de cisaillement a la paroi représente l'échelle des vitesses a prendre en compte en ce qui concerne l'écoulement des liquides a base de polymères. En partant de la notion d'une viscosité efficace, proposée par Lumley, les spectres polymériques ont été établis sous une forme universelle, et confrontés aux spectres newtoniens. Les résultats obtenus s'accordent assez bien avec la theorie d'équilibre universel. L'influence prépon-dérante du produit additif a base de polymère se manifeste apparemment sous la forme d'une augmentation des echelles de dissipation de la turbulence, sans toutefois modifier de maniere significative la structure fondamentale de l'écoulement, sauf au voisinage de la paroi.

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Section: Experimental Techniquementioning

confidence: 99%

Turbulent Characteristics Of Drag-Reducing Flows

Alonso

Klaus²,

Wylie

1976

Journal of Hydraulic Research

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“…Wells et al considered the equation of motion in the form DV/Dt = -(l/p) grad P (3) assuming no shear stresses and no deviatoric normal stresses and an incompressible, nonconducting fluid. To Eq.…”

Section: Generalization Of the Wells Harkness And Meyer Equationmentioning

confidence: 99%

Measurement of Turbulence Intensities with Piezoelectric Probes in Viscoelastic Fluids

Rodriguez

Patterson

Zakin

1971

Journal of Hydronautics

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The piezoelectric impact probe of Wells et al. was used to compare measurements of turbulence intensity in a pipe of purely viscous solvents with viscoelastic polymer solutions and to compare with measurements made with hot-film anemometer probes. An equation was derived which shows the form of normal and shear stress contributions to measured fluctuating impact pressure in viscoelastic fluids. The equation indicated that for viscoelastic fluids, low values of intensities of turbulence can be obtained by neglecting normal and shear stress effects. Experimental measurements showed that turbulence intensities measured at the pipe center with the piezoelectric probe were the same as those measured with a hot-film wedge probe for viscoelastic solutions, but that as the wall was approached, the piezoelectric probe values were low for the viscoelastic solutions. Nomenclature e x = unit vector in the axial direction in cylindrical coordinates e r = unit vector in the radial direction in cylindrical coordinates £0 = unit vector in the tangential direction in cylindrical coordinates g(x) = function of the shear stress fluctuations I = displacement vector p f -fluctuating component of pressure P = pressure P = time-averaged value of P P p = pressure measured by impact tube pt = fluctuating component of pressure measured by piezoelectric probe Pt = total pressure measured by piezoelectric probe Pt = time-averaged value of P t P w = static pressure at the wall r = radial coordinate R = tube radius u f = fluctuating velocity component in the axial direction U_ = velocity in the axial direction U = time-averaged value of U v' = fluctuating velocity component in the radial direction V = velocity vector in cylindrical coordinates x = longitudinal coordinate X c = characteristic time of the flow p = density AI = viscosity (Tl • = deviatoric normal stress aii = time-averaged deviatoric normal stress

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“…Comme il a été indiqué, les premières constatations expérimentales de ces effets ont eu lieu au cours des mesures des profils des vitesses dans les conduites. Des écarts importants, de l'ordre de 10 à 15 %, entre les débits calculés par intégration des vitesses et ceux mesurés indépendamment sont apparus [17,18].…”

Section: Comportement Des Prises De Pression Totaleunclassified

“…Au cours d'essais dans des conduites il a été constaté par différents auteurs [16,17,18], des écarts entre les débits obtenus par intégration des vitesses mesurées au moyen de tubes de Pitot, et ceux mesurés par pesée ou par volumétrie. Il s'agit là, en fait, de la mise en évidence globale d'un phéno-mène qui prend naissance au point d'arrêt des sondes, et sur lequel peu d'études systématiques ont été effectuées jusqu'à présent.…”

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