The Effect of Viscous Shear on Transients in Liquid Lines

Holmboe, E. L.; Rouleau, W. T.

doi:10.1115/1.3609549

Cited by 115 publications

(49 citation statements)

References 6 publications

(12 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This assumption is satisfactory for slow transients where the wall shear stress has a quasi-steady behaviour. Experimental validation of steady friction models for rapid transients [1,2,3,4,5] previously has shown significant discrepancies in attenuation and phase shift of pressure traces when the computational results are compared to the results of measurements. The discrepancies are introduced by a difference in velocity profile, turbulence and the transition from laminar to turbulent flow.…”

Section: Introductionmentioning

confidence: 99%

Developments in unsteady pipe flow friction modelling

Bergant

Simpson

Vìtkovsk

2001

Journal of Hydraulic Research

278

121

View full text Add to dashboard Cite

This paper reviews a number of unsteady friction models for transient pipe flow. Two distinct unsteady friction models, the Zielke and the Brunone models, are investigated in detail. The Zielke model, originally developed for transient laminar flow, has been selected to verify its effectiveness for "low Reynolds number" transient turbulent flow. The Brunone model combines local inertia and wall friction unsteadiness. This model is verified using the Vardy's analytically deduced shear decay coefficient C* to predict the Brunone's friction coefficient k rather than use the traditional trial and error method for estimating k. The two unsteady friction models have been incorporated into the method of characteristics water hammer algorithm. Numerical results from the quasi-steady friction model and the Zielke and the Brunone unsteady friction models are compared with results of laboratory measurements for water hammer cases with laminar and low Reynolds number turbulent flows. Conclusions about the range of validity for the three friction models are drawn. In addition, the convergence and stability of these models are addressed. RESUMELe papier passe en revue un certain nombre de modeles de friction non permanente en ecoulement transitoire en conduite. Deux modeles de friction non permanente, celui de Zielke et celui de Brunone sont investigues en details. Le modele de Zielke, developpe a l'origine pour les ecoulements transitoires laminaires, a ete selectionne pour tester l'efficacite du modele pour les ecoulements transitoires turbulents a faible nombre de Reynolds. Le modele de Brunone combine la variation de l'inertie locale et de la friction de paroL Ce modele est verifie en utilisant Ie coefficient C* d'amortissement du cisaillement de Vardy dCduit analytiquement pour predire Ie coefficient de friction k de Brunone, plutot que la method traditionnelle par essais et erreurs pour estimer k. Les deux modeles de friction non permanente ont ete incorpores dans un algorithme de calcul du coup de belier par la methode des caracteristiques. Les resultats numeriques obtenus a partir d'un modele de friction quasi permanente et a partir des modeles non permanents de Zielke et de Brunone sont compares avec des resultats de mesures en laboratoire pour des ecoulements laminaires ou turbulents a faible nombre de Reynolds. Des conclusions sont tirees sur les domaines de validite des trois modeles de friction. En complement, la convergence et la stabilite des modeles sont abordees. IntroductionTraditionally the steady or quasi-steady friction terms are incorporated into the standard water hammer algorithms. This assumption is satisfactory for slow transients where the wall shear stress has a quasi-steady behaviour. Experimental validation of steady friction models for rapid transients [1,2,3,4,5] previously has shown significant discrepancies in attenuation and phase shift of pressure traces when the computational results are compared to the results of measurements. The discrepancies are introduced by a difference in ve...

show abstract

Section: Introductionmentioning

confidence: 99%

Developments in unsteady pipe flow friction modelling

Bergant

Simpson

Vìtkovsk

2001

Journal of Hydraulic Research

278

121

View full text Add to dashboard Cite

show abstract

“…Jeszcze innym modelem dynamicznym przewodu hydraulicznego jest linia o rezystancji zależnej od częstotliwości [3,4,8]. W tym przypadku uwzględniona jest zmiana profilu prędkości w przekroju przewodu w zależności od częstotliwo-ści fal ciśnienia i natężenia przepływu wzdłuż przewodu i wpływ tej zmiany na zmianę rezystancji (efektu tarcia lepkiego) w funkcji częstotliwości.…”

Section: Modele Przepływu Cieczy Roboczej W Linii Hydraulicznejunclassified

Właściwości Dynamiczne Linii Hydraulicznych Lotniczych Napędów Hydraulicznych

Ułanowicz

2008

Research Works of Air Force Institute of Technology

View full text Add to dashboard Cite

WŁAŚCIWOŚCI DYNAMICZNE LINII HYDRAULICZNYCH LOTNICZYCH NAPĘDÓW HYDRAULICZNYCHSłowa kluczowe: napęd hydrauliczny, wydajność pompy, natężenie przepływu, pulsacja ciśnienia, linia hydrauliczna, ściśliwość oleju hydraulicznego, tarcie lepkie oleju hydraulicznego, oporność hydrauliczna, inertancja, kapacitancja, równanie ciągłości płynu, równanie zachowania ilości ruchu, uderzenie hydrauliczne. WstępNowoczesne lotnicze napędy hydrauliczne powinny charakteryzować się dużą szybkością działania, wysoką dokładnością i optymalnym wykorzystaniem energii. Dla zapewnienia tych własności niezbędne jest opracowanie metod projektowania uwzględniających, m.in. przy analizie i syntezie napędów, ich właściwości dynamiczne.Lotnicze napędy hydrauliczne są projektowane w następujący sposób: -odbiornik hydrauliczny (siłownik lub silnik hydrauliczny) wraz z elementami sterującymi i układem zasilania stanowią jeden zwarty zespół (rozwiązanie stosowane w śmigłowcach), -odbiornik hydrauliczny znajduje się w pewnej, często znacznej odległości od elementów sterujących i układu zasilającego (rozwiązanie stosowane w samolotach).

show abstract

“…Brown and Nelson [1965] developed an approximate method for analysis of laminar compressible flow subject to pressure and flow step inputs. Holmboe and Rouleau [1967] extended the work of D'Souza and Oldenburger [1964] and Brown [1962]. In particular, the premise that wall shear stress in unsteady flow is a function of both frequency of disturbance and mean velocity was examined.…”

Section: Conclusion For Laminar and Transitional Monotonic Flowmentioning

confidence: 99%

The study of unsteady pipe flow and non-uniform channel flow by the use of laser doppler anemometry

Johnson¹

View full text Add to dashboard Cite

Steady fluid flow within circular pipelines has been the subject of very extensive research for well over 100 years. However, unsteady flows, particularly those at transitional and higher Reynolds Numbers, have not been nearly so well analyzed.Consequently, although there is now an essentially complete description of the hydraulic and fluids mechanics aspects of steady flow, the understanding of turbulent unsteady flow phenomena is much less certain.The major difficulty in working in the unsteady flow area is the inherent nature of the flow. That is, the unsteadiness of the velocity vector requires a measurement device that does not rely upon time-averaging techniques to produce estimates of the velocity magnitude. For this reason alone, the laser-Doppler anemometer (LDA) is an ideal instrument for analysis of unsteady flows. In addition, it is non-intrusive and so does not affect the structure of the flow during the measurement process.Experimental procedures were developed successfully to enable the accurate measurement of mean velocity and turbulence intensity in monotonically varying unsteady pipe flow. Previous research at the University of Queensland had produced unexpected results in relation to this class of flow, and it was considered that a more detailed experimental analysis would yield important information.More specifically, the concept of quasi-steadiness of the flow was examined. In parallel with the experimental program, theoretical analyses were undertaken to derive methods for determining whether flow at a particular time instant is quasi-steady in nature. A modified simple power law was developed, which enables the flow rate and velocity profile in a steady turbulent flow to be estimated accurately from a single measurement of the centreline velocity. From the same velocity measurement, a law of the wall was used to derive estimates of the friction velocity and hence turbulence intensities over the entire cross-section. niIt was found that velocity profiles in monotonically unsteady turbulent flow were indistinguishable from the corresponding profiles for steady flow at the equivalent Reynolds Number. However, turbulence intensities, in flow under the effect of an acceleration transient, were shown to be significantly smaller than quasi-steady. This is consistent with a lagging process. Under these conditions, it was also found that the onset of laminar-turbulent transition was very significantly delayed (to Re in excess of 100 X 10^). The behaviour around the time of transition was examined in detail, with the conclusion that transition to fully developed turbulent flow occurred much more rapidly in accelerating flow than under steady flow conditions. The LDA was also used to study the behaviour within an open channel flow transition, where the flow area remains constant throughout the transition, but the aspect ratio varies continuously. The channel chosen was such that the width of flow converged as the bed level fell away. Previous research has shown that this form of channel exhib...

show abstract

The Effect of Viscous Shear on Transients in Liquid Lines

Cited by 115 publications

References 6 publications

Developments in unsteady pipe flow friction modelling

Developments in unsteady pipe flow friction modelling

Właściwości Dynamiczne Linii Hydraulicznych Lotniczych Napędów Hydraulicznych

The study of unsteady pipe flow and non-uniform channel flow by the use of laser doppler anemometry

Contact Info

Product

Resources

About