On the deformation of the rectangular turbulent jet cross-section

Abramovich, G. N.

doi:10.1016/0017-9310(82)90111-9

Cited by 34 publications

(13 citation statements)

References 3 publications

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“…As far as the distance of the line source is concerned, different lengths at the same Reynolds number were found in [3][4]. The deformation of a three-dimensional rectangular jet was investigated in [5] where the line-source of the jet was upstream the slot exit, independently from the Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of mass transfer and fluid flow evolution of a rectangular free jet of air

Venuta

Petracci

Angelino

et al. 2018

International Journal of Heat and Mass Transfer

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The paper presents the Large Eddy Simulation (LES) of mass transfer and fluid flow evolution of a submerged rectangular free jet of air in the range of Reynolds numbers from Re = 3400 to Re = 22,000, with the Reynolds number, Re, defined with the hydraulic diameter of the rectangular slot, of height H. The numerical simulation is 3D for Re=3400 and 6800, while 2D for Re=10,400 and 22,000 to reduce computational time costs. The average and instant LES numerical simulations compare concentration visualizations, obtained with the Particle Image Velocimetry (PIV) technique, and fluid dynamics variables, velocity and turbulence, measured with the Hot Film Anemometry (HFA). In the numerical simulations, the Schmidt number is equal to 100 to compare the air concentration PIV experiments, while the turbulence on the exit of the slot is equal to the value measured experimentally, ranging between 1% and 2%. The average 2-3D LES simulations are in agreement with the concentration and fluid dynamics experimental results in the Undisturbed Region of Flow (URF) and in the Potential Core Region (PCR), while the vortex breakdown is captured only by the 3D approach. As far as the instant flow evolution is concerned, the 2-3D LES simulations reproduce the Negligible Disturbances Flow (NDF), where the jet height maintains constant, and the Small Disturbances Flow (SDF), where the jet height oscillates, with contractions and enlargements, but without the vortex formation. Average and instant velocity and turbulence numerical simulations on the centreline are in good agreement to the experimental measurements. Keywords: 2-3D Large Eddy Simulations; Transitional to turbulent flow; Numerical concentration fields and comparisons with PIV visualizations; Numerical fluid dynamics variables and comparison with HFA measurements; Confirmation of the URF in the average flow and NDF, SDF in the instant flow. Nomenclature Latin D diameter E turbulent energy spectrum

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of mass transfer and fluid flow evolution of a rectangular free jet of air

Venuta

Petracci

Angelino

et al. 2018

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

show abstract

“…As far as the distance of the line source is concerned, Bradbury (1965) found a length L S = À3H, while Gutmark and Wygnanski (1976) measured a length L S = À2H at Re H = 30,000. The deformation of a three-dimensional rectangular jet was investigated by Abramovich (1982) who declared that the line-source of the jet was upstream the slot exit at L S = À4.5 H, independently from the Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Reynolds number on the instant flow evolution of a turbulent rectangular free jet of air

Gori

Petracci

Angelino

2014

International Journal of Heat and Fluid Flow

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“…In perfect axial-symmetry conditions, these two estimates would give exactly the same result, so that deviations must be ascribed to the specific geometry of the nozzle: Experimental uncertainties are calculated based on the standard error on the mean entropy production, i.e. the mean square differences among instantaneous and mean values as expressed in Equation (10). This leads to an error from 2% to 4% depending on the Reynolds number and on the specific jet geometry.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…The main reason for axis switching seems to be the asymmetric pressure distribution due to non-uniform curvature of the nozzle on different axes [9]. In addition, the different growth rates of shear layers on the short and long sides of the nozzle is another reason leading to a crossover point at which both growth rates become equal and axis switching takes place [10]. Therefore, the combination of non-circular nozzles with sharp-edged orifices could result in mixing enhancement due to the combination of axis-switching and vena-contracta phenomena especially in the jet near field.…”

mentioning

confidence: 96%

An experimental investigation on mixing enhancements in non-circular sharp-edged nozzles using the entropy production concept

Hashiehbaf

Romano

2014

Journal of Turbulence

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An experimental study on mixing enhancement in free jets, issuing from sharp-edged nozzles of different geometry, is performed by using particle image velocimetry. The attention is focused on the jet near-field and interaction zones (0 < X/D < 18, where X is the axial coordinate and D the diameter of the equivalent circular jet). The mixing efficiency is evaluated and quantified using the definition of entropy production derived from the velocity field. The effect of Reynolds number is also discussed by performing measurements at Re = 8000 and Re = 35,000. The results are compared to circular nozzle data to evaluate the change in mixing efficiency among axisymmetric and nonsymmetric nozzles. While the effect of Reynolds number on mixing is small, at least for the values tested here, the change in geometry is rather crucial. In terms of entropy production, the rectangular and elliptical nozzles show higher mixing for X/D< 7, whereas the other ones attain the best results for larger distances. This behaviour is basically related to the axis-switching phenomenon observed in elongated jets. Different variables are tested and compared as possible velocity and length scales to derive a meaningful non-dimensional entropy production.

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On the deformation of the rectangular turbulent jet cross-section

Cited by 34 publications

References 3 publications

Numerical simulation of mass transfer and fluid flow evolution of a rectangular free jet of air

Numerical simulation of mass transfer and fluid flow evolution of a rectangular free jet of air

Influence of the Reynolds number on the instant flow evolution of a turbulent rectangular free jet of air

An experimental investigation on mixing enhancements in non-circular sharp-edged nozzles using the entropy production concept

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