An experimental investigation of the near-field region of free turbulent round central and annular jets

Warda, H. A.; Kassab, Sadek Z.; Elshorbagy, Kamel A.; Elsaadawy, Ehab

doi:10.1016/s0955-5986(98)00042-9

Cited by 45 publications

(21 citation statements)

References 12 publications

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“…In fact, it has been shown that an increase in Reynolds number can lead to a decrease in the rate of jet entrainment as a result of a decrease in the streamwise mean velocity decay, which in turn engenders an increase in the potential core of the jet (i.e. an increase in x 0 ) [32]. Furthermore, the values of C 1 and x 0 for the triangular jet are not in agreement with those of Quinn [19] whose values are 5.10 and 0.389D e , respectively, at a Reynolds number of 184,000.…”

Section: Mean Streamwise Centerline Velocity Decay Without Quarlmentioning

confidence: 99%

Effect of Sudden Expansion on Entrainment and Spreading Rates of a Jet Issuing from Asymmetric Nozzles

Iyogun

Birouk

2008

Flow Turbulence Combust

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Turbulent free jets issuing from five different nozzle geometries; smooth pipe, contracted circular, rectangular, triangular, and square, are experimentally investigated by using TSI 2-D laser Doppler velocimetry (LDV) to assess the effect of nozzle geometry and quarl (i.e. a cylindrical sudden expansion) on jet entrainment and spreading. The centerline mean velocity decay and the jet half-velocity width, which are indicators of jet entrainment and spreading rates, are determined for each nozzle's flow configuration, i.e. with and without sudden expansion. Furthermore, turbulence quantities, such as the flow mean velocities and their mean fluctuating components, as well as Reynolds shear stresses, are all measured along the centerline plane of the jet to facilitate understanding the extent of the effect of nozzle's geometry (i.e. nozzle's orifice shape and sudden expansion) on jet's entrainment and spreading. The main results show that the jet flow with the presence of sudden expansion exhibits higher rates of entrainment and spreading than without. In addition, these results reveal that sudden expansion exercises a greater effect on the asymmetric jet characteristics, especially for the triangular and rectangular nozzles compared to their axisymmetric counterparts (i.e. circular contracted nozzle).

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Section: Mean Streamwise Centerline Velocity Decay Without Quarlmentioning

confidence: 99%

Effect of Sudden Expansion on Entrainment and Spreading Rates of a Jet Issuing from Asymmetric Nozzles

Iyogun

Birouk

2008

Flow Turbulence Combust

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“…1,2 Second, the bluff body can serve as a fuel injection device in non-or partially premixed combustion, either using cross-flow 3,4 or co-flow injection. [5][6][7] One widely used type of bluff-body combustor is the annular jet. An annular jet can be seen as the limiting case of a coaxial jet with a velocity ratio (ratio between the velocity of the outer and the inner jet) of infinity.…”

Section: Introductionmentioning

confidence: 99%

Symmetry breaking and vortex precession in low-swirling annular jets

et al. 2014

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In this paper, the flow dynamics in the wake of a turbulent annular jet is studied using Time-Resolved Stereoscopic Particle Image Velocimetry and Proper Orthogonal Decomposition (POD). In this wake, a central recirculation zone is present which, under certain conditions, shows a low-frequency precessing motion. POD analysis of the measured velocity data shows that at zero swirl, an asymmetry is present in the wake, which motion is random in time. This asymmetry originates from a bifurcation of the flow once a threshold Reynolds number is exceeded. For low-swirl numbers, ranging from 0 < S < 0.12, the asymmetry is still present and its motion becomes structured into a well defined precession. For S > 0.12, the precession is gone and the motion of the asymmetric wake is again random in time, similar like the non-swirling jet. In this paper, a model is developed to describe the influence of swirl on the wake dynamics. The model assumes that perturbations in the inner shear layer near the bluff body wall are convected towards the stagnation point. These perturbations cause a shift in the stagnation points position. This shift is convected back to the inner shear layer through convection in the recirculating flow. The dynamics of this feedback mechanism can be modeled by the nonlinear delayed saturation model. In this paper, the model is adapted for swirling flow and simulations show that good agreement is found with the experiments.

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“…Wilcox [7] published results from different CFD simulations for the straight turbulent free jet from a round nozzle outlet and compares this data to experimental values initially elaborated by Bradbury in the year 1965. Warda et al [8] performed a more detailed experimental assessment of the three-dimensional flow in the near-field region of a round turbulent jet. Ashforth-Frost and co-worker [9] published research on the influence of nozzle design and confinement on the core region of turbulent free jets.…”

Section: Introductionmentioning

confidence: 99%

CFD simulation of straight and slightly swirling turbulent free jets using different RANS-turbulence models

Miltner

Jordan

Harasek

2015

Applied Thermal Engineering

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An experimental investigation of the near-field region of free turbulent round central and annular jets

Cited by 45 publications

References 12 publications

Effect of Sudden Expansion on Entrainment and Spreading Rates of a Jet Issuing from Asymmetric Nozzles

Effect of Sudden Expansion on Entrainment and Spreading Rates of a Jet Issuing from Asymmetric Nozzles

Symmetry breaking and vortex precession in low-swirling annular jets

CFD simulation of straight and slightly swirling turbulent free jets using different RANS-turbulence models

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