Studies of the wall shear stress in a turbulent pulsating pipe flow

Mao, Zugang; Hanratty, Thomas J.

doi:10.1017/s0022112086001015

Cited by 96 publications

(67 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Experimental studies on pulsating turbulent flow were conducted actively [1][2][3][4][5][6][7][8][9][10]. All of the measurements were made for fully developed flows with small oscillating velocity amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

Wang¹,

Zhang²

2005

International Journal of Heat and Mass Transfer

105

View full text Add to dashboard Cite

Convection heat transfer in pulsating turbulent flow with large velocity oscillating amplitudes in a pipe at constant wall temperature is numerically studied. A low-Reynolds-number (LRN) k-e turbulent model is used in the turbulence modeling. The model analysis indicates that Womersley number is a very important parameter in the study of pulsating flow and heat transfer. Flow and heat transfer in a wide range of process parameters are investigated to reveal the velocity and temperature characteristics of the flow. The numerical calculation results show that in a pulsating turbulent flow there is an optimum Womersley number at which heat transfer is maximally enhanced. Both larger amplitude of velocity oscillation and flow reversal in the pulsating turbulent flow also greatly promote the heat transfer enhancement.

show abstract

Section: Introductionmentioning

confidence: 99%

Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

Wang¹,

Zhang²

2005

International Journal of Heat and Mass Transfer

105

View full text Add to dashboard Cite

show abstract

“…Concern about its accuracy is justified because the measured rms value of s~ has been reported to be 0.35-0.36 Sx (Fortuna and Hanratty 1971;Mao and Hanratty 1986). In addition, s x has a large positive skewness so that large positive excursions of the order of S~ are observed.…”

Section: Introductionmentioning

confidence: 99%

Application of an inverse mass transfer method to the measurement of turbulent fluctuations in the velocity gradient at the wall

Mao¹,

Hanratty

1991

Experiments in Fluids

View full text Add to dashboard Cite

Abstract. The frequency response of the concentration boundarylayer is often a concern when flush mounted mass transfer probes are used to measure turbulent fluctuations in the velocity gradient at a wall. Present practice involves the use of a solution of the mass balance equation which is linear in the fluctuating quantities. An inverse mass transfer method is explored in this paper, which avoids the linearization assumption. Improved measurements of the amplitude probability distribution and of the frequency spectrum of the streamwise component of the fluctuating velocity gradient are presented. In particular, values of rms level, skewness and flatness of 0.37, 0.96, 4.2 are obtained, in good agreement with a recent study

show abstract

“…Basically, this consisted of measuring steady state flow conditions at a number of different Re for fully turbulent flow conditions. However, in the method of analysis used, there was no allowance for any response lag in unsteady flow as other researchers (Mao and Hanratty [1986]) have attempted to apply for similar types of probes. A numerical model developed by Acharya and Reynolds [1975] was used to predict flow parameters.…”

Section: 2) Dymentioning

confidence: 99%

“…One other interesting aspect of this study was the authors' recognition that the indirect method of shear stress evaluation was inherently inaccurate. Mao and Hanratty [1986] used a flush-mounted platinum wall probe in a electrochemical solution to determine wall shear stress in a small amplitude pulsating turbulent flow. By measuring the mass transfer coefficient at the electrode, the velocity gradient at the wall was derived.…”

Section: 2) Dymentioning

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

Studies of the wall shear stress in a turbulent pulsating pipe flow

Cited by 96 publications

References 31 publications

Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

Numerical analysis of heat transfer in pulsating turbulent flow in a pipe

Application of an inverse mass transfer method to the measurement of turbulent fluctuations in the velocity gradient at the wall

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

Contact Info

Product

Resources

About