Acoustically Induced Enhancement of Widening and Fluctuation Intensity in a Two-Dimensional Turbulent Jet

The enhancement of widening rate and turbulence intensity in a turbulent plane jet, due to an acoustic disturbance are considered. Detailed data at a representative Strouhal number suggest a well organized symmetric structural array in the initial region of the flow. These highly organized flow structures act as efficient agents in the transport of energy to the fine-grained turbulence, leading to greater diffusivity, enhanced turbulence and an increase in widening. The data also suggest significant differences in the underlying structure of the natural and excited jet flows, hence putting in jeopardy any generalization of coherent motions especially excited to facilitate their study.

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Interaction of an Acoustic Disturbance and a Two-Dimensional Turbulent Jet: Experimental Data

Journal of Fluids Engineering ◽

10.1115/1.3240952 ◽

1983 ◽

Vol 105 (2) ◽

pp. 134-139 ◽

Cited By ~ 5

Author(s):

F. O. Thomas ◽

V. W. Goldschmidt

Keyword(s):

Turbulent Jet ◽

Vortical Flow ◽

Energy Spectra ◽

Flow Structures ◽

Two Dimensional ◽

Frequency Range ◽

Initial Region ◽

Acoustic Disturbance ◽

Turbulent Flow Structure ◽

The Mean

An experimental study was performed to determine the effects a periodic acoustic disturbance had upon a two-dimensional turbulent jet in both the initial and similarity regions. Correlation and energy spectra measurements in the initial region indicate that acoustic forcing within a certain frequency range is capable of restructuring the flow in this region. In particular, these measurements suggest the presence of vortical flow structures arranged symmetrically with respect to the jet centerline. Measurements of the mean and turbulent flow structure in the similarity region of the jet indicate strong acoustically induced effects. Evidence suggests that the interaction effects observed in the similarity region are intimately related to those in the initial region.

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Signal Transit Velocities in a Turbulent Plane Jet

Journal of Fluids Engineering ◽

10.1115/1.3448357 ◽

1976 ◽

Vol 98 (3) ◽

pp. 443-446

Author(s):

A. K. Stiffler

Keyword(s):

Nozzle Exit ◽

Flow Direction ◽

Turbulent Jet ◽

Measured Signal ◽

Centerline Velocity ◽

Pressure Gradients ◽

Periodic Pressure ◽

Turbulent Plane ◽

Plane Jet ◽

Signal Time

A turbulent jet is perturbed transverse to the flow direction by periodic pressure gradients near the nozzle exit. Transit velocities are defined in terms of the measured signal time delay for stations 8, 12, 16 nozzle widths downstream of the nozzle exit. Excitation frequencies to 800 cps are considered. Transit velocities are found to be much less than the jet centerline velocity. The results are related to the convection velocity of turbulence.

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FLOW VISUALIZATION OF SUBMERGED JETS IN NARROW CHANNELS

Modern Physics Letters B ◽

10.1142/s0217984909018448 ◽

2009 ◽

Vol 23 (03) ◽

pp. 377-380

Author(s):

JIAN-HONG SUN ◽

CHIN-TSAU HSU

Keyword(s):

Reynolds Numbers ◽

Narrow Channel ◽

Laser Induced Fluorescence ◽

Turbulent Jet ◽

Narrow Channels ◽

Submerged Jets ◽

Flow Motion ◽

Turbulent Plane ◽

Plane Jet ◽

Turbulent Water

In order to study the effect of wall on the flow pattern of a submerged turbulent water jet in narrow channels, the flow field was visualized by a laser-induced fluorescence (LIF) system at different Reynolds numbers. Those images showed that flow motion in a narrow channel is different from that of a turbulent plane jet without narrow channels. There are three flow patterns in narrow channels: stable impinging, stable jet with recirculation vortices and flapping turbulent jet.

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A time-domain evaluation of the large-scale flow structure in a turbulent jet

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1979.0083 ◽

1979 ◽

Vol 367 (1729) ◽

pp. 193-218 ◽

Cited By ~ 8

Keyword(s):

Flow Structure ◽

Time Domain ◽

Large Scale ◽

Reynolds Numbers ◽

Turbulent Jet ◽

Flow Structures ◽

Jet Flows ◽

Hot Wire ◽

Potential Core ◽

Large Scale Flow

This paper describes an investigation of the large-scale flow processes which occur in turbulent circular jet flows ( Re > 10 5 ). The existence of regular large-scale flow structures at low and moderate Reynolds numbers ( Re < 5 x 10 4 ) has clearly been demonstrated by flow-visualization experiments, but visual evidence for order in jet turbulence becomes ambiguous at a Reynolds number around 7 x 10 4 . A new time-domain technique for the study of two-dimensional large-scale flow structures has been developed by Bruun (1977). In this paper this technique is extended to the study of three-dimensional large-scale flow structures by the inclusion of X hot-wire and circumferential eductions. The evaluated large-scale structures in the turbulent jet ( Re = 2 x 10 5 ) are shown to deviate considerably from the axi-symmetric flow structures which occurs at low and moderate Reynolds numbers ( Re < 5 x 10 4 ). We observe a much smaller deformation rate of the semi-regular flow structure in the potential core in the turbulent jet case, and also the circumferential eductions reveal a rapid radial decrease in the circumferential coherence of the related large-scale flow structure in the mixing region. Further-more, combining these results with the X hot-wire eductions in the mixing region proved that the major contributions to the shear stress uv is caused by circumferentially-narrow tongues of ‘fast moving ejected’ and ‘slow moving entrained ’fluid, similar to the ‘burst’ and ‘sweep’ events observed previously in turbulent wall boundary layers.

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