An experimental investigation of the near-field region of a free turbulent coaxial jet using LDA

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

doi:10.1016/s0955-5986(98)00041-7

Cited by 30 publications

(26 citation statements)

References 15 publications

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“…The velocity variation along the jet axis is shown in Figure 10 for different jet velocities. It shows that the extent of potential core is of length about four times of the nozzle diameter 4D, this is in consistency with results from previous work [14,15]. The extent of the potential core is defined as the distance from the nozzle exit plane to the point of intersection of the constant, issuing velocity in the air jet axis and the curve of the hyperbolic decrease of the centerline velocity.…”

Section: Grid Independency and Turbulence Model Selectionsupporting

confidence: 90%

Effect of sand particles on flow structure of free jet from a nozzle

Al-Dulaimi

Hamad

Rasool

et al. 2019

JMES

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The Characteristics of single and two- phase flow from a circular turbulent free jet from a nozzle of 10 mm diameter were investigated experimentally and numerically. The measurements were conducted for ReJ = 10007 - 31561. The velocity was measured at location from the nozzle y/D (0-8) in axial and radial directions. The two phase measurement were done by using natural construction sand as a solid phase of sizes (220,350,550) µm and loading ratios (mass flow ratio of sand to mass flow rate of air) in the range (0.18-1.38). Two phase air velocity of jet showed that the introducing of natural sand particles gives lower jet velocity attributed to momentum transfer to particles. The smaller particle size leads to lower values of velocity. The velocity found to be decreased with loading ratio increase. The numerical simulation was performed for single and two phase jet flow. RNG K-ε turbulence model was used to simulate the flow of fluid and the discrete phase model to simulate the particles flow. The results form numerical simulation showed a good agreement with experimental results.

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Section: Grid Independency and Turbulence Model Selectionsupporting

confidence: 90%

Effect of sand particles on flow structure of free jet from a nozzle

Al-Dulaimi

Hamad

Rasool

et al. 2019

JMES

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“…Indeed, precise numerical methods, a wellresolved regular mesh and direct numerical simulations are used. The price to pay is that the Reynolds number for our simulations ͑Re D 1 = 3000͒ is lower than the values usually encountered in the experimental studies ͑see, i.e., Rehab et al, 6 Warda, Kassab, Elshorbagy, and Elsaadawy, 14 Buresti, Petagna, and Talamelli 15 ͒. Furthermore, to properly discretize the velocity gradient, relatively large values of 01 and 02 have to be considered.…”

Section: Numerical Methods and Computational Parametersmentioning

confidence: 98%

The near field of coaxial jets: A numerical study

Balarac

Métais

2005

Physics of Fluids

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The near-field behavior of coaxial jets is studied through direct numerical simulation ͑DNS͒ with a particular focus on the influence of the inner shear layer steepness characterized by its momentum thickness 01 thus mimicking the variation in the lip thickness of a real jet nozzle. We investigate the two distinct jet regimes r u Ͼ r uc for which a recirculation bubble is present near the jet inlet and r u Ͻ r uc without any recirculation bubble, r u being the velocity ratio between the outer jet and inner jet velocities. It is shown that small values of 01 lead to a fast transition to turbulence. The various mechanisms leading to this transition are investigated in detail: the three-dimensionality growth, the appearance of secondary vortices superimposed on the main ring vortices, and the subsequent longitudinal stretching of streamwise vortices. This stretching mechanism is shown to play a dominant role in the transition processes towards a fully developed turbulent state. For high enough values of r u , a pinching of the jet is observed near the inlet and it is shown that this pinching phenomenon lasts on a shorter downstream distance for small values of 01 due to a more efficient turbulent mixing. In the r u Ͼ r uc case, variations of 01 strongly affect the shape and the downstream extent of the recirculation bubble. The DNS allow to show the strong dependency of the inner and outer potential core lengths and of the critical value r uc on the jet inlet velocity profile. We finally revisit the theoretical model originally proposed by Rehab, Villermaux, and Hopfinger ͓"Flow regimes of large-velocity-ratio coaxial jets," J. Fluid Mech. 345, 357 ͑1997͔͒ first aimed at the prediction of the variations of various jet characteristics as a function of r u . The model is extended to determine the dependency of the jet characteristics with 01 . A very good correspondence between the theoretical predictions and the numerical results is obtained.

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“…As the lip thickness increases the turbulence intensity behind the nozzle wall increases. 9) The result for lip thickness 0:2D p co-flowing jet is shown in Fig. 14(a).…”

Section: Contours Of Turbulent Viscosity Ratiomentioning

confidence: 99%

“…2) Beginning from Olsen and Karchmer, 3) a large number of investigations indicate the effect of lip thickness on altering the characteristics of co-flowing jets in an incompressible flow regime such as static pressure rise (which is constant for co-flowing jets with minimum values of lip thickness), turbulence intensity variation in the near field, etc. [4][5][6][7][8][9][10][11] A large recirculation zone was recognized behind the lip region for large values of lip thicknesses, for co-flowing jets with incompressible flow fields at low subsonic Mach numbers ranging from 0.1 to 0.3. 12) Additionally the centerline velocity decay and the intensity of the turbulence were profoundly affected by co-flowing jets with large values of lip thickness.…”

Section: Introductionmentioning

confidence: 99%

Numerical Characterization of Lip Thickness on Subsonic and Correctly Expanded Sonic Co-flowing Jets

Shankar

Thanigaiarasu

Rathakrishnan

2016

Trans. Japan Soc. Aero. S Sci.

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Characteristics of co-flowing jets at subsonic and correctly expanded sonic Mach numbers were investigated numerically for three different lip thicknesses namely, 0.2D p , 1.0D p and 1.5D p (where D p is the exit diameter of the primary nozzle which is 10 mm). Comparisons of numerical flow-field characteristics were made with experimental data. Lip thickness is defined as the thickness of the wall separating primary jet and the secondary jet. It has been found that co-flow with 0.2D p lip thickness retards the mixing of the primary jet, leading to potential core elongation. For 1.0D p and 1.5D p lip thickness, the presence of lip thickness creates a recirculation zone between the primary jet and the secondary jet, which increases turbulence intensity in the near-field region of the co-flowing jet thereby influencing the properties in the nearfield, such as potential core length reduction, static pressure rise, etc. Variation in Mach number has less significance in the flow-field characteristics of co-flowing jet.

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An experimental investigation of the near-field region of a free turbulent coaxial jet using LDA

Cited by 30 publications

References 15 publications

Effect of sand particles on flow structure of free jet from a nozzle

Effect of sand particles on flow structure of free jet from a nozzle

The near field of coaxial jets: A numerical study

Numerical Characterization of Lip Thickness on Subsonic and Correctly Expanded Sonic Co-flowing Jets

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