Fully developed periodic turbulent pipe flow. Part 2. The detailed structure of the flow

The main experimental results of the study of periodic turbulent pipe flow have been described in Part 1 of this report. In this second part, these experimental data are examined in greater detail to understand the effect of imposed oscillation on the flow structure, at moderate to large oscillation frequencies. Data on phase and amplitude and energy spectrum are used to study the effect of the imposed oscillation on the turbulence structure at these interactive frequencies of oscillation. Additional experiments which were performed to study the effect of oscillation frequency on the flow structure are also reported. Based on the present observations as well as on the data from other sources, it is inferred that turbulent shear flows respond very differently from laminar shear flows to imposed unsteadiness. A turbulent Stokes number relevant for characterizing the unsteady turbulent shear flows is identified and used to classify such flows.

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On Turbulence Structure and Mixing Mechanism in Free Turbulent Shear Flows

Turbulent Mixing in Nonreactive and Reactive Flows ◽

10.1007/978-1-4615-8738-5_21 ◽

1975 ◽

pp. 381-409 ◽

Cited By ~ 24

Author(s):

H. E. Fiedler

Keyword(s):

Shear Flows ◽

Turbulent Shear ◽

Turbulence Structure ◽

Turbulent Shear Flows

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Fully developed periodic turbulent pipe flow. Part 1. Main experimental results and comparison with predictions

Journal of Fluid Mechanics ◽

10.1017/s0022112083002281 ◽

1983 ◽

Vol 137 ◽

pp. 31-58 ◽

Cited By ~ 84

Author(s):

S. W. Tu ◽

B. R. Ramaprian

Keyword(s):

Experimental Data ◽

Pipe Flow ◽

Shear Flows ◽

Volumetric Flow Rate ◽

Intermediate Frequency ◽

Turbulent Pipe Flow ◽

Experimental Results ◽

Turbulent Shear ◽

Relevant Parameter ◽

Flow Modulation

The present paper is the first part of a two-part report on a detailed investigation of periodic turbulent pipe flow. In this investigation, experimental data on instantaneous velocity and wall shear stress were obtained at a mean Reynolds number of 50000 in a fully developed turbulent pipe flow in which the volumetric flow rate was varied sinusoidally with time around the mean. Two oscillation frequencies at significant levels of flow modulation were studied in detail. The higher of these frequencies was of the order of the turbulent bursting frequency in the flow, and the other can be regarded as an intermediate frequency at which the flow still departed significantly from quasi-steady behaviour. While a few similar experiments have been reported in the recent literature, the present study stands out from the others in respect of the flow regimes investigated, the magnitude of flow modulation, the detailed nature of the measurements and most importantly the identification of a relevant parameter to characterize unsteady shear flows. The present paper contains the main experimental results and comparisons of these results with the results of a numerical calculation procedure which employs a well-known quasi-steady turbulence closure model. The experimental data are used to study the manner in which the time-mean, the ensemble-averaged and the random flow properties are influenced by flow oscillation at moderate to high frequencies. In addition, the data are also used to bring out the capability and limitations of quasi-steady turbulence modelling in the prediction of unsteady shear flows. A further and more detailed analysis of the experimental data, results of some additional experiments and a discussion on the characterization of turbulent shear flows are provided in Part 2 (Ramaprian & Tu 1983).

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