Journal ArticleDOI
Upstream nozzle shaping effects on near field flow in round turbulent free jets
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TLDR
In this paper, the effects of upstream nozzle shaping on near field jet evolution experimentally were studied using hot-wire anemometry and a pitot-static tube to obtain the measured quantities which included the mean streamwise velocity, the turbulent Reynolds normal and shear stresses, the autocorrelation coefficients and one-dimensional energy spectra of the fluctuating stream-wise velocity and the mean static pressure.Abstract:
Isothermal, incompressible round turbulent free jets of air, issuing from a sharp-edged orifice and from a contoured nozzle into still air surroundings, have been used to study the effects of upstream nozzle shaping on near field jet evolution experimentally. The Reynolds number, based on the diameter of the orifice or the nozzle, was 1.84 × 10 5 in both jets. Hot-wire anemometry and a pitot-static tube were used to obtain the measured quantities which included the mean streamwise velocity, the turbulent Reynolds normal and shear stresses, the autocorrelation coefficients and one-dimensional energy spectra of the fluctuating streamwise velocity and the mean static pressure. The mean streamwise velocity decay on the jet centerline and the jet half-velocity widths were obtained from the mean streamwise velocity data. To the extent that the results showed that mixing in the sharp-edged orifice round jet was higher than in the contoured nozzle round jet, upstream nozzle shaping was found to affect jet evolution in the near flow field. The distribution of the autocorrelation coefficients of the streamwise fluctuating velocity showed a marked difference in the evolution of the two jets, one of which had a uniform, and the other a non-uniform, exit plane mean streamwise velocity profile. The one-dimensional energy spectra results and also those of the distribution of the autocorrelation coefficients indicated the presence of coherent structures in the near field of the jets and the sharp-edged orifice jet was found to be more “energetic” than the contoured nozzle jet.read more
Citations
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Journal ArticleDOI
The flow field in turbulent round free jets
TL;DR: A critical review of both experimental and computational studies of round turbulent jets is provided, beginning with the work of Tollmien (1926). as discussed by the authors traces the history, major advances, and various stages that the research community went through over the past 85-odd years, from statistical analyses through to the use of conditional sampling, proper orthogonal decomposition and structural eduction methods.
Journal ArticleDOI
Reynolds number effects within the development region of a turbulent round free jet
TL;DR: In this article, the effect of the Reynolds number on the near and intermediate-fields region (0,⩽,x/D, ⩽ 25) of a round free jet was investigated.
Journal ArticleDOI
Statistical properties of turbulent free jets issuing from nine differently-shaped nozzles
TL;DR: In this article, the centerline evolutions of turbulent statistical properties in nine air jets issuing from differently-shaped nozzles into still air surroundings were reported, showing that the loss of jet-axisymmetry at the exit generally causes the mean velocity decaying faster, and the fluctuating intensity growing, in the near field, thus indicating the increased overall entrainment rate.
Journal ArticleDOI
PIV measurements of a turbulent jet issuing from round sharp-edged plate
TL;DR: In this paper, an experimental investigation of a turbulent jet issuing from a round sharp-edged orifice plate (OP) into effectively unbounded surroundings was conducted using Particle Image Velocimetry (PIV) in near and transition regions.
Journal ArticleDOI
Experimental study of the near field and transition region of a free jet issuing from a sharp-edged elliptic orifice plate
TL;DR: In this paper, the mixing characteristics of an isothermal, incompressible, free jet of air issuing from a sharp-edged elliptic orifice plate of aspect ratio 2 into still air surroundings have been studied experimentally using hot-wire anemometry and a pitot-static tube.
References
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Book
Boundary layer theory
TL;DR: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part, denoted as turbulence as discussed by the authors, and the actual flow is very different from that of the Poiseuille flow.
Journal ArticleDOI
Orderly Structure in Jet Turbulence
S. C. Crow,F. H. Champagne +1 more
TL;DR: In this paper, the authors show that a large-scale orderly pattern may exist in the noiseproducing region of a round subsonic jet by observing the evolution of orderly flow with advancing Reynolds number.
Journal ArticleDOI
Some measurements in the self preserving jet
Israel Wygnanski,H. E. Fiedler +1 more
TL;DR: In this paper, the axisymmetric turbulent incompressible and isothermal jet was investigated by use of linearized constant-temperature hot-wire anemometers and the quantities measured include mean velocity, turbulence stresses, intermittency, skewness and flatness factors, correlations, scales, low-frequency spectra and convection velocity.
Journal ArticleDOI
Coherent structures—reality and myth
TL;DR: In this article, a definition of coherent structures in turbulent shear flows is proposed and its implications discussed, and the characteristic coherent structure properties are identified and the analytical and experimental constraints in the eduction of coherent structure are examined.
Journal ArticleDOI
Turbulence measurements in axisymmetric jets of air and helium. I - Air jet. II - Helium jet
TL;DR: In this paper, the authors used x-wire hot-wire probes mounted on a moving shuttle and a composite probe consisting of an interference probe of the Way-Libby type and an x-probe.