Measurements of the Periodic Velocity Oscillations Near the Wall in Unsteady Turbulent Channel Flow

Binder, G.; Kueny, Jean-Louis

doi:10.1007/978-3-642-95410-8_2

Cited by 14 publications

(17 citation statements)

References 5 publications

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“…Considerable work was done (Mao and Hanratty, 1984) of the velocity field very close to the wall by and by Binder, et al (1982) It is to be noted that the medium frequency of the turbulence is oj /15 = 0.004. Thus, the effect discussed above appears to occur when the imposed oscillation is equal to or greater than the dominant frequency of the turbulence.…”

Section: Numerical Results •mentioning

confidence: 99%

Studies of the Wall Shear Stress in a Turbulent Pulsating Pipe Flow

Mao

Hanratty

1984

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Section: Numerical Results •mentioning

confidence: 99%

Studies of the Wall Shear Stress in a Turbulent Pulsating Pipe Flow

Mao

Hanratty

1984

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“…12-15͒. Based on l s , a similarity parameter that was independently introduced by Ronneberger and Ahrens 12 and by Binder and Kueny 16,17 is the viscous Stokes length, l s + = ͑l s u / ͒, where u is the wall-friction velocity. It should be noted that the forcing frequency scaled in inner variables can also be directly expressed in terms of l s + as + = ͓2 / ͑l s + ͒ 2 ͔.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of unsteady flow in channel with rough walls

Bhaganagar

2008

Physics of Fluids

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A fundamental study has been performed to understand the effect of unsteady forcing on turbulence statistics in channel flow with rough walls using direct numerical simulation. Unsteady flows have been generated by applying an unsteady nonzero mean forcing in the form of time varying pressure gradient such that the amplitude of oscillations is between 19% and 26% of mean centerline velocity and covering a range of forcing frequencies. The analysis has revealed unsteady forcing, depending on the forcing frequency, results in enhanced roughness compared to steady channel flow. The rough-wall flow dynamics have been categorized into high-, intermediate-, and low-frequency regimes. In the regime of high-frequency forcing, unsteadiness alters the mean velocity and turbulence intensities only in the inner layer of the turbulent boundary layer. Further, the turbulence intensities are out of phase with each other and also with the external forcing. In the regime of intermediate-frequency forcing, mean velocity and turbulence intensities are altered beyond the inner layer. In the inner layer, the turbulence intensities are out of phase with each other. The Reynolds stress is in phase with the external forcing in the inner layer, but it is out of phase in the outer layer. In the regime of low-frequency forcing, the mean velocity and turbulence intensities are significantly altered throughout the turbulent boundary layer.

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“…The studies of Mizushina et al (1973Mizushina et al ( , 1975 have addressed issues of stuctural information concerning these flows. Also, effects of periodic through-flow rates in fully-developed channel flow have been studied by Acharya & Reynolds (1975), Binder et al (1985) and Tardu, Binder & Blackwelder ( 1987).…”

Section: Introductionmentioning

confidence: 99%

Response of a turbulent boundary layer to sinusoidal free-stream unsteadiness

1990

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In this paper, selected findings of a detailed experimental investigation are reported concerning the effects of forced free-stream unsteadiness on a turbulent boundary layer. The forced unsteadiness was sinusoidal and was superimposed locally on an otherwise-steady mainstream, beyond a turbulent boundary layer which had developed under constant-pressure conditions. Within the region over which free-stream unsteadiness was induced, the sinusoidal variation in pressure gradient was between extremes of zero and a positive value, with a positive average level. The local response of the boundary layer to these free-stream effects was studied through simultaneous measurements of the u- and v-components of the velocity fieldAlthough extensive studies of unsteady, turbulent, fully-developed pipe and channel flow have been carried out, the problem of a developing turbulent boundary layer and its response to forced free-stream unsteadiness has received comparatively little attention. The present study is intended to redress this imbalance and, when contrasted with other studies of unsteady turbulent boundary layers, is unique in that: (i) it features an appreciable amplitude of mainstream modulation at a large number of frequencies of forced unsteadiness, (ii) its measurements are both detailed and of high spatial resolution, so that the near-wall behaviour of the flow can be discerned, and (iii) it allows local modulation of the mainstream beyond a turbulent boundary layer which has developed under the well-known conditions of steady, two-dimensional, constant-pressure flowResults are reported which allow comparison of the behaviour of boundary layers under the same mean external conditions, but with different time dependence in their free-stream velocities. These time dependences correspond to: (i) steady flow, (ii) quasi-steadily varying flow, and (iii) unsteady flow at different frequencies of mainstream unsteadiness. Experimental results focus upon the time-averaged nature of the flow; they indicate that the mean structure of the turbulent boundary layer is sufficiently robust that the imposition of free-stream unsteadiness results only in minor differences relative to the mean character of the steady flow, even at frequencies for which the momentary condition of the flow departs substantially from its quasi-steady state. Mean levels of turbulence production are likewise unaffected by free-stream unsteadiness and temporal production of turbulence appears to result only from modulation of the motions which contribute to turbulence production as a time-averaged measure.

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Measurements of the Periodic Velocity Oscillations Near the Wall in Unsteady Turbulent Channel Flow

Cited by 14 publications

References 5 publications

Studies of the Wall Shear Stress in a Turbulent Pulsating Pipe Flow

Studies of the Wall Shear Stress in a Turbulent Pulsating Pipe Flow

Direct numerical simulation of unsteady flow in channel with rough walls

Response of a turbulent boundary layer to sinusoidal free-stream unsteadiness

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