Characteristics of small-scale motions in a dual-plane jet flow

A two-dimensional air jet, heated at a density ratio of 0.8, under external forcing by flexible wires is investigated experimentally. In each shear layer of the hot jet flow, a wire of diameter 0.23 mm (0.015 jet width) is flexibly mounted along the spanwise direction. By flow visualization, temperature measurements, and spectral analysis, the study demonstrates that the wires have quite different effects on the jet flow depending on that the wires are motionless or vibrating in the flow, and the shear layers of the heated plane jet can be manipulated by means of flexible wires.

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Simultaneous measurements of all three components of velocity and vorticity vectors in a lobed jet flow by means of dual-plane stereoscopic particle image velocimetry

Physics of Fluids ◽

10.1063/1.1481741 ◽

2002 ◽

Vol 14 (7) ◽

pp. 2128 ◽

Cited By ~ 15

Author(s):

Hui Hu ◽

Tetsuo Saga ◽

Toshio Kobayashi ◽

Nubuyuki Taniguchi

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Jet Flow ◽

Stereoscopic Particle Image Velocimetry ◽

Dual Plane ◽

Simultaneous Measurements ◽

Image Velocimetry ◽

Lobed Jet ◽

Three Components

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Assessment of local isotropy using measurements in a turbulent plane jet

Journal of Fluid Mechanics ◽

10.1017/s0022112086002331 ◽

1986 ◽

Vol 163 ◽

pp. 365-391 ◽

Cited By ~ 57

Author(s):

R. A. Antonia ◽

F. Anselmet ◽

A. J. Chambers

Keyword(s):

Large Scale ◽

Spatial Organization ◽

Structure Functions ◽

Small Scale ◽

Temperature Structure ◽

Local Isotropy ◽

Large Scale Motion ◽

Turbulent Plane ◽

Scale Motion ◽

Plane Jet

Following a review of the difficulties associated with the measurement and interpretation of statistics of the small-scale motion, the evidence for and against local isotropy is assessed in the light of measurements in a turbulent plane jet at moderate values of the Reynolds and Péclet numbers. These measurements include spatial derivatives with respect to different spatial directions of the longitudinal velocity fluctuation and of the temperature fluctuation. Relations between mean-square values of these derivatives suggest strong departures from local isotropy for both velocity and temperature. In contrast, the locally isotropic forms of the vorticity and temperature dissipation budgets are approximately satisfied. Possible contamination of the fine-scale measurements by the anisotropic large-scale motion is assessed in the context of the measured structure functions of temperature and of the measured skewness of the streamwise derivative of temperature. Structure functions are, within the framework of local isotropy, consistent with the average frequency and amplitude of temperature signatures that characterize the quasi-organized large-scale motion. Conditional averages associated with this motion account, in an approximate way, for the skewness of the temperature derivative but make negligible contributions to the skewness of velocity derivatives. The degree of spatial organization of the fine structure is inferred from conditional statistics of temperature derivatives.

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Acoustic Experiment and Numerical Simulation on Unheated Supersonic Jet Flow for a Small-scale Nozzle

AIAA Scitech 2020 Forum ◽

10.2514/6.2020-0002 ◽

2020 ◽

Author(s):

Seung Hoon Kang ◽

HyunShik Joo ◽

Sang Joon Shin ◽

Taeyoung Park ◽

Won-Suk Ohm ◽

...

Keyword(s):

Numerical Simulation ◽

Supersonic Jet ◽

Jet Flow ◽

Small Scale

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A note on the conservation of the axial momentum of a turbulent jet

Journal of Fluid Mechanics ◽

10.1017/s002211207800292x ◽

1978 ◽

Vol 87 (1) ◽

pp. 55-63 ◽

Cited By ~ 26

Author(s):

Nikolas E. Kotsovinos

Keyword(s):

Conservation Law ◽

Momentum Flux ◽

Pressure Field ◽

Jet Flow ◽

Experimental Results ◽

Turbulent Jet ◽

Ambient Fluid ◽

Induced Flow ◽

Plane Jet ◽

Direction Opposite

The conservation law for the flux of axial momentum in a turbulent jet is examined. The examination discloses that for a plane jet out of a wall the momentum flux is reduced appreciably because the induced flow towards the jet has a component in the direction opposite to the main jet flow and because of the pressure field generated in the ambient fluid. Existing experimental results confirm this conclusion.

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On the noise sources of the unsuppressed high-speed jet

Journal of Fluid Mechanics ◽

10.1017/s002211207100243x ◽

1971 ◽

Vol 50 (1) ◽

pp. 21-31 ◽

Cited By ~ 65

Author(s):

K. A. Bishop ◽

J. E. Ffowcs Williams ◽

W. Smith

Keyword(s):

Reynolds Number ◽

High Speed ◽

Large Scale ◽

Jet Noise ◽

Jet Flow ◽

Scale Model ◽

Small Scale ◽

Noise Sources ◽

Supersonic Transport ◽

Scale Turbulence

The paper describes an interpretation of jet-noise theory and scale-model experiments to highlight physical properties of jet-noise sources at very high speed. The study is prompted by current efforts to suppress the noise of supersonic transport aircraft.The principal noise sources are shown to be very large-scale wave-like undulations of the jet flow that travel downstream at supersonic speed for a distance of several jet diameters. These motions are relatively well ordered and are probably more akin to recognizable instabilities of a laminar flow than the confused small-scale turbulence. Because of this we postulate a model of the noise generating motions as the instability products of a jet flow of low equivalent Reynolds number. This Reynolds number is based on an eddy viscosity and can be further reduced by artificially increasing the small-scale turbulence level. This step would tend to stabilize the flow and inhibit the formation of large-scale noise producing eddies.

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Turbulent Features in the Coherent Central Region of a Plane Water Jet Issuing Into Quiescent Air

Journal of Fluids Engineering ◽

10.1115/1.4026924 ◽

2014 ◽

Vol 136 (8) ◽

Cited By ~ 3

Author(s):

Can Kang ◽

Haixia Liu

Keyword(s):

Central Region ◽

Reynolds Shear Stress ◽

Water Jet ◽

Small Scale ◽

General Tendency ◽

Mean Flow ◽

Cross Sectional ◽

Uniform Distributions ◽

Non Gaussian ◽

Plane Jet

A plane water jet issuing into quiescent air at a Reynolds number of 2.5 × 105 is experimentally studied using phase Doppler anemometry (PDA). The plane water jet contains a coherent central region, which is situated immediately downstream of the nozzle exit. Particular emphasis is placed upon the distinctive attributes of such a region. Both mean flow pattern and turbulent features are obtained statistically based upon instantaneous velocity data. The central region is overwhelmingly dominated by uniformly distributed velocity, and remarkably high velocity gradient is present near the boundary of this region. Evidence shows that self-preservation is not satisfied in the central region. Explicit energy dissipation mechanisms in the central region are appreciated from cross-sectional uniform distributions of Kolmogorov length scales. Turbulent kinetic energy increases as the plane jet progresses, which is opposite to the general tendency associated with self-preservation. Although the central region is filled with near-zero Reynolds shear stress, distributions of skewness and flatness in this region are non-Gaussian and the instability caused by small-scale flow structures is thereby substantiated.

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