Mixing in turbulent free jets issuing from isosceles triangular orifices with different apex angles

Azad, Mohammad; Quinn, W. R.; Groulx, Dominic

doi:10.1016/j.expthermflusci.2012.01.028

Cited by 32 publications

(7 citation statements)

References 22 publications

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“…Non-circular jets have been experimentally and numerically studied by various researchers because of their potential to enhance mixing between jets and the ambient fluid (Ho & Gutmark 1987;Hussain & Husain 1989;Quinn 1989Quinn , 2005Grinstein et al 1995;Miller et al 1995;Mi et al 2000). Considerable research efforts have also been made to understand the effects of nozzle geometry on mixing performance and turbulence characteristics of turbulent jets in the near-field (Hussain & Husain 1989;Mi et al 2001;Quinn 2005;Mi & Nathan 2010;Azad et al 2012;Hashiehbaf & Romano 2013;Quinn et al 2013;Xu et al 2013aXu et al , 2013bAleyasin et al 2017). In general, it has been found that the loss of axisymmetry of the orifice nozzle configuration increases the decay rate of mean and RMS velocities in the near-field, from which higher entrainment into the jet may be concluded (Mi et al 2001).…”

Section: Introductionmentioning

confidence: 99%

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Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets

Nejatipour

Khorsandi

2021

Water Science and Technology

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The effect of nozzle geometry on the dynamics and mixing of turbulent jets is experimentally investigated. The jets with a Reynolds number of 13,000 were issued from four different pipes with circular, elliptical, square and triangular cross sections. The velocity field was measured in the self-similar region of the jets using an acoustic Doppler velocimeter. Statistical parameters, such as the mean velocities, velocity variances, spreading rates, mass flow rates, and entrainment rates are presented. The results show that despite having approximately similar decay rates for the mean centerline velocities, the radial profiles of the axial mean velocity varied in jets with different nozzle cross sections and were widest for elliptical jets and narrowest for the triangular ones. On the other hand, velocity variances were greatest for the triangular jet when compared to the jets released from cross sections of other geometries. Furthermore, the spreading rate, mass flow rate, and entrainment rate were highest for the elliptical jet, and lowest for the triangular jet. From this it can be inferred that the elliptical jet has the highest mixing and dilution. The results of this study could help to improve the initial mixing of pollutants by optimizing the initial conditions.

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Section: Introductionmentioning

confidence: 99%

“…It has also been claimed that the statistics in the self-similar region may depend on the initial conditions (George & Arndt 1989). Furthermore, many of the past studies only focused on the mean velocity and turbulence intensities along the centerline (Mi et al 2000;Mi & Nathan 2010;Azad et al 2012;Quinn et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets

Nejatipour

Khorsandi

2021

Water Science and Technology

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“…In addition, the effective expansion characteristic of the water jet in the horizontal water jet field is also an important indicator of the water jet performance, which represents the effective impact area of the water jet. Given that the numerical model in this study is axisymmetric, the extension distance of the Y-axis was calculated according to the method of Azad et al [33], specifically by selecting the data with a velocity attenuation within 15% of the target distance of 100 mm, which can be used as the second quantitative evaluation index of water jet performance.…”

Section: Construction Features and Principlementioning

confidence: 99%

Design and Optimization of High-Pressure Water Jet for Coal Breaking and Punching Nozzle Considering Structural Parameter Interaction

et al. 2022

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The technology of increasing coal seam permeability by high-pressure water jet has significant advantages in preventing and controlling gas disasters in low-permeability coal seam. The structural parameters of a nozzle are the key to its jet performance. The majority of the current studies take strike velocity as the evaluation index, and the influence of the interaction between the nozzle’s structural parameters on its jet performance is not fully considered. In practice, strike velocity and strike area will affect gas release in the process of coal breaking and punching. To further optimize the structural parameters of coal breaking and punching nozzle, and improve water jet performance, some crucial parameters such as the contraction angle, outlet divergence angle, and length-to-diameter ratio are selected. Meanwhile, the maximum X-axis velocity and effective Y-axis extension distance are used as evaluation indexes. The effect of each key factor on the water jet performance is analyzed by numerical simulation using the single factor method. The significance and importance effect of each factor and their interaction on the water jet performance are quantitatively analyzed using the orthogonal experiment method. Moreover, three optimal combinations are selected for experimental verification. Results show that with an increase in contraction angle, outlet divergence angle, and length-to-diameter ratio, the maximum X-axis velocity increases initially and decreases thereafter. The Y-direction expansion distance of the jet will be improved significantly with an increase in the outlet divergence angle. Through field experiments, the jet performance of the improved nozzle 3 is the best. After optimization, the coal breaking and punching diameter of the nozzle is increased by 118%, and the punching depth is increased by 17.46%.

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“…The selected sharp-edged orifice shapes are circular and rectangular. This choice let us investigate and compare a symmetric and a clearly non-symmetric condition, with the latter that represents the best solution in term of mixing properties for free jets (Gutmark and Grinstein 1999) (Aleyasin et al 2017a) (Azad et al 2012) (Aleyasin et al 2017b). The orifice cross area is the same for both plates, so that an equivalent diameter of length 0.02 m is defined and used to evaluate the Reynolds number.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…Indeed, it is possible to increase mixing between jet flow and the environment by choosing a non-circular shape for the jet outlet. In particular, rectangular and elliptic jets were reported to have the highest entrainment rate compared to round, triangular, daisy or two-dimensional jets thanks to a phenomenon called "axis switching" (on large-scale) and higher azimuthal instability modes (on small-scale) (Gutmark and Grinstein 1999) (Aleyasin et al 2017a) (Azad et al 2012) (Aleyasin et al 2017b). The axis switching is an apparent 90° rotation of the free jet cross section which is observed for non-symmetric jets and it is ascribed to a different growth rate of the shear layers in the major and minor axis plane owing to the natural roll-up of the vortex rings with a non-uniform azimuthal curvature (Gutmark and Grinstein 1999) (Zaman 1995).…”

Section: Introductionmentioning

confidence: 99%

Entrainment and Mixing in Circular and Rectangular Bended Plunging Jets

Moscato

Romano

2022

Preprint

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In the present work we study the topology, mixing properties, turbulence quantities, dependence on the outlet geometry of a sharp-edged orifice plunging jet which first issues horizontally in air and then plunges in a water pool. The investigated orifices shapes are circular and rectangular. Data are acquired at different Reynolds numbers in the range 11000 ÷ 25000, based on the orifice diameter (equal to 2 cm) and on the average exit velocity, as derived from flow rate measurements. A planar time-resolved PIV technique is implemented to derive the velocity field of the jets in vertical and horizontal planes. Results show a clear asymmetry of the cross-velocity profiles both in circular and rectangular cases, with the latter that revealed a shape which is Reynolds number dependent. Axial velocity decays, potential core lengths and spreading rates highlight an opposite trend between the two jet geometries, thus suggesting a higher mixing for the lowest circular Reynolds number and the highest rectangular ones. However, axial velocity rms profiles show an overall greater turbulent production for the highest Reynolds number circular jet. Ambient mass entrainment points out the different interactions of the two plunging jets with the ambient flow: in circular case, it entrains fluid from the surroundings, from horizontal to vertical planes in streamwise direction, while in rectangular one it ejects flow from vertical to horizontal planes. Finally, circular lowest Reynolds number jet findings suggest it is the most promising in terms of mixing.

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Mixing in turbulent free jets issuing from isosceles triangular orifices with different apex angles

Cited by 32 publications

References 22 publications

Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets

Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets

Design and Optimization of High-Pressure Water Jet for Coal Breaking and Punching Nozzle Considering Structural Parameter Interaction

Entrainment and Mixing in Circular and Rectangular Bended Plunging Jets

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