Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Influence of Reynolds number on characteristics of turbulent wall boundary layers (1984)
    Springer
    Experiments in fluids 2 (1984), S. 7-16 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hot-wire anemometer measurements, using two types of probes, are reported for wall boundary layer flows with particular attention being given to the near-wall region and to measurements at high Reynolds numbers up to Rϕ≈ 15,000. To obtain accurate near-wall measurements, the influence of wall proximity on hot-wire readings was eliminated by using a highly insulating wall material. Measurements were carried out with a single hot-wire boundary layer probe to obtain the longitudinal velocity informatemperature-wake sensor for the cross flow tion and a hot-wire, information. The results provided in the paper include measurements of averaged properties like mean velocity, rms-quantities of velocity fluctuations, probability density distributions etc. Conditional averages are also provided in order to yield information related to coherent flow structures present in boundary layer flows. It is shown that these structure remain present up to the highest Reynolds number investigated in the present study. The conditionally averaged data provide quantitative information on the mechanisms that are involved in the production of turbulence in boundary-layer flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266313
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Steady ellipsoidal vortex rings with finite cores (1981)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 32 (1981), S. 156-169 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung Die vorliegende Arbeit beschreibt numerische Berechnungen von Wirbelringen, die Lösungen der Navier-Stokes-Gleichungen in einem gewählten elliptischen Gebiet darstellen. Die berechneten Wirbelringe haben einen begrenzten Kern, innerhalb dessen die Wirbelstärke von Null verschieden ist. Die Wirbelstärkenverteilung erfüllt die Navier-Stokes-Gleichungen und bestimmt die Form des Wirbelkernes. Die Theorie impliziert, daß sich die Form des Wirbelringes nicht ändert, wenn er stetig in einem nichtviskosen, unendlichen Fluid fortschreitet. Grenzfälle der beschriebenen Wirbelringe sind Hill's Kugelwirbelringe und O'Briens elliptische Wirbelringe, deren physikalische Eigenschaften mit den numerischen Ergebnissen der beschriebenen Wirbelringe verglichen werden. Weitere Vergleiche werden mit experimentellen Ergebnissen von Sullivan, Widnall und Ezekiel durchgeführt.
    Notes: Abstract The present paper provides explicit numerical descriptions of vortex rings that are exact solutions to the Navier-Stokes equations inside of the chosen ellipsoidal boundaries. It is a particular feature of the resulting rings that they have finite cores within which the vorticity is nonzero whereas outside the cores no vorticity exists. The vorticity distribution is in agreement with the Navier-Stokes equations and yield the shape of the vortex ring core as a result of the described predictions. The theoretical approach implies that the shape of the resulting rings does not change as the rings propagate steadily through an inviscid and unbounded fluid. Hill's spherical vortex and O'Brien's ellipsoidal vortices are limiting cases of the vortex rings described in this paper. Analytical expressions for their properties are provided and results computed from these expressions are compared with values numerically obtained for the range of vortex rings described by the authors. Further comparisons are made with experimental results by Sullivan, Widnall and Ezekiel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00946745
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Die Charakterisierung viskoelastischer Fluide mit Hilfe ihrer Strömungseigenschaften in Kugelschüttungen (1982)
    Springer
    Rheologica acta 21 (1982), S. 150-166 
    Details
    ISSN: 1435-1528
    Keywords: Viscoelasticity ; elongational flow ; dilute polymer solution ; porous media flow ; dumbbell suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Abstract The viscoelastic flow behaviour of dilute macromolecular solutions is investigated experimentally using the flow through randomly packed beds composed of glass beads with a narrow size distribution. The concept of the Deborah number is applied to describe the observed polymer effects. To model the polymeric liquids and to derive extensional viscosity equations the kinetic theory of dilute dumbbell solutions is used treating the macromolecules as finite extendable, nonlinear-elastic dumbbells. In this way two parameters (b, τ H) are obtained which characterize the behaviour of the macromolecules when these are stretched in elongational flow fields. The flow through porous media can be classified as such an extensional flow. The viscoelastic behaviour and the relaxation times of various polymer solutions are investigated by systematically varying the fluid velocity and bed characteristics of the porous media and the polymer-solvent-temperature conditions of the used polymer solutions. The experimental results are in good agreement with the theoretical predictions obtained by the dilute dumbbell theory.
    Notes: Zusammenfassung Das viskoelastische Verhalten verdünnter makromolekularer Lösungen wird anhand von Strömungen durch Zufallsschüttungen mit einheitlichem Kugeldurchmesser untersucht. Zur Beschreibung der experimentell beobachteten Polymereffekte wird das Konzept einer repräsentativen Deborahzahl angewandt, die sich für die Porenströmung als Produkt aus der Relaxationszeit der Polymerflüssigkeit und der effektiven Dehnrate im Porenraum ergibt. Zur Modellierung der polymeren Flüssigkeit und zur Ableitung von Dehnviskositätsgleichungen werden Modellvorstellungen herangezogen, die auf der kinetischen Theorie verdünnter Hantelsuspensionen basieren. Für endlich dehnbare, nichtlinear-elastische Hanteln als Modellmoleküle erhält man für die Modellflüssigkeit ein Zweiparametersystem (b, τ H), welches unmittelbar in die viskoelastischen Kenngrößen einer reinen Dehnströmung eingeht. Die Porenströmung wird als eine solche Dehnströmung modelliert. Experimentelle Ergebnisse aus Porenströmungen zeigen, daß der Einfluß aller maßgebenden strömungsmechanischen und physikalisch-chemischen Parameter, die das viskoelastische Verhalten von verdünnten Polymerlösungen bestimmen, von den theoretisch abgeleiteten Endbeziehungen korrekt beschrieben wird.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01736414
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Dehnströmungen mit verdünnten Polymerlösungen: Ein theoretisches Modell und seine experimentelle Verifikation (1981)
    Springer
    Rheologica acta 20 (1981), S. 179-192 
    Details
    ISSN: 1435-1528
    Keywords: Elongational flow ; macromolecular model ; porous media flow ; FENE dumbbell ; polymer solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary The present paper summarizes theoretical considerations regarding the elongation of flexible macromolecules in simple steady elongational flows. The macromolecules are treated as FENE(finite extensible, nonlinear elastic)-dumbbells. Equations for extensional viscosity are given for flows of dilute polymer solutions applicable at low and high elongation rates. The present paper compares the derived theoretical relationships with experimental results. These results were obtained in porous media flows, which exhibit strong elongational rates. It can be shown on the basis of the experimental investigations, that all fluid mechanic and physico-chemical parameters that influence the measured pressure losses responded as predicted by the theory.
    Abstract: Schlüsselwörter Dehnströmung, Makromolekülmodell, Porenströmung, EDNE-Hantelmodell, Polymerlösung
    Notes: Zusammenfassung Es werden theoretische Überlegungen zusammenfassend dargestellt, welche die Streckung und Ausrichtung von flexiblen Makromolekülen in stationären einfachen Dehnströmungen beschreiben. Die Makromoleküle werden hierbei als EDNE-(endlich dehnbare, nichtlinear elastische) Hanteln modelliert. Für den Fall niedriger bzw. hoher Dehnungsraten werden Dehnviskositätsgleichungen für Strömungen mit verdünnten Polymerlösungen angegeben. Die Arbeit vergleicht die abgeleiteten theoretischen Gleichungen mit experimentellen Ergebnissen, welche für Porenströmungen erhalten wurden; Porenströmungen weisen Dehnströmungen auf. Anhand der durchgeführten experimentellen Untersuchungen, in denen alle die den Druckverlust maßgebend beeinflussenden strömungsmechanischen und physikalisch-chemischen Parameter variiert wurden, kann gezeigt werden, daß sich die aufgezeigten theoretischen Zusammenhänge quantitativ bestätigen lassen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01513060
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Viscoelastic flow of dilute polymer solutions in regularly packed beds (1982)
    Springer
    Rheologica acta 21 (1982), S. 566-571 
    Details
    ISSN: 1435-1528
    Keywords: Porous media flow ; viscoelasticity ; polymer solution ; dumbbell model ; elongational flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01534349
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Laminar and turbulent flows of dilute polymer solutions: A physical model (1982)
    Springer
    Rheologica acta 21 (1982), S. 572-577 
    Details
    ISSN: 1435-1528
    Keywords: Drag reduction ; porous media flow ; elongational viscosity ; dilute polymer solution ; macromolecule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01534350
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 3125-3149 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Experimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ-conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...