Small-Amplitude Frequency Behavior of Fluid Lines With Turbulent Flow

Brown, F. T.; Margolis, Donald L.; Shah, Rasool

doi:10.1115/1.3571209

Cited by 45 publications

(20 citation statements)

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“…10 (Loureiro andRamos 2003, Abreu andAlmeida 2004). The k P coefficient can be linked to the momentum correction factor, β, by k P ≈ β−1 for low frequency disturbances (Brown et al, 1969). The coefficient k A may be interpreted as the extra frictional damping due to the unsteady shear stress.…”

Section: Modelmentioning

confidence: 99%

Systematic Evaluation of One-Dimensional Unsteady Friction Models in Simple Pipelines

et al. 2006

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In this paper, basic unsteady flow types and transient event types are categorised, and then Additionally, numerical errors arising from the approximate implementation of the instantaneous acceleration-based model are determined, suggesting some previous good fits with experimental data are due to numerical error rather than the unsteady friction model.The convolution-based model is successful for all transient event types. Both approaches are tested against experimental data from a laboratory pipeline.

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Section: Modelmentioning

confidence: 99%

Systematic Evaluation of One-Dimensional Unsteady Friction Models in Simple Pipelines

et al. 2006

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“…Funk and Wood [1974] utilized a method previously developed for monotonic turbulent flow (Wood and Funk [1970]) to study small amplitude frequency response. It was found that this boundary layer theory was able to reproduce Brown at al's [1969] results excellently. Lu et al [1975] carried out detailed measurements of time-averaged and instantaneous parameters, in pulsating turbulent pipe flow.…”

Section: Conclusion For Monotonically Varying Turbulent Pipe Flowmentioning

confidence: 76%

“…It is only relatively recently that detailed studies of either monotonically varying (Daily et al [1956]) or periodically varying (Brown et al [1969]) turbulent flow have appeared.…”

Section: Unsteadiness In Laminar and Turbulent Pipe Flow -Literatumentioning

confidence: 99%

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

Johnson¹

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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...

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“…where f is the well-documented friction factor (15). The weighting function w can be approximated by the summation of first-order lag terms in the same way as for laminar flow.…”

Section: Turbulent Frictionmentioning

confidence: 99%

Modelling of transient flow in hydraulic pipelines

Taylor

Johnston

Longmore

1997

Proceedings of the Institution of Mechanical Engineers, Part I:

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This paper describes a method of modelling time-varying flow in hydraulic pipelines which may be incorporated into time domain simulations of hydraulic systems operating with variable time steps. A previously reported finite element method is extended. New approximations to frequency-dependent friction for laminar and turbulent flow are presented. These are applicable to this finite element method as well as the method of characteristics and finite difference methods. Simulation results are compared against theory and excellent agreement is found.

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Small-Amplitude Frequency Behavior of Fluid Lines With Turbulent Flow

Cited by 45 publications

References 0 publications

Systematic Evaluation of One-Dimensional Unsteady Friction Models in Simple Pipelines

Systematic Evaluation of One-Dimensional Unsteady Friction Models in Simple Pipelines

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

Modelling of transient flow in hydraulic pipelines

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