Special Section Papers

Nozzle Geometry Effect on Stratified Layer Erosion by Vertical Turbulent Jet

[+] Author and Article Information
L. Ishay, G. Ziskind

Heat Transfer Laboratory,
Department of Mechanical Engineering,
Ben-Gurion University of the Negev,
P.O.B. 653,
Beer-Sheva 84105, Israel

U. Bieder

Gif sur Yvette 91191, France

A. Rashkovan

Physics Department,
P.O.B. 9001,
Beer-Sheva 84190, Israel
e-mail: rashbgu@gmail.com

1Corresponding author.

Manuscript received September 18, 2016; final manuscript received January 3, 2017; published online May 25, 2017. Assoc. Editor: Ilan Yaar.

ASME J of Nuclear Rad Sci 3(3), 030902 (May 25, 2017) (11 pages) Paper No: NERS-16-1105; doi: 10.1115/1.4035693 History: Received September 18, 2016; Revised January 03, 2017

Knowledge of the nuclear power plants (NPPs) containment atmosphere composition in the course of a severe accident is crucial for the effective design and positioning of the hydrogen explosion countermeasures. This composition strongly depends on containment flows which may include turbulent jet mixing in the presence of buoyancy, jet impingement onto the stratified layer, stable stratification layer erosion, steam condensation on the walls of the containment, condensation by emergency spray systems and other processes. Thus, in modeling of containment flows, it is essential to correctly predict these effects. In particular, a proper prediction of the turbulent jet behavior before it reaches the stably stratified layer is critical for the correct prediction of its mixing and impingement. Accordingly, validation study is presented for free neutral and buoyancy-affected turbulent jets, based on well-known experimental results from the literature. This study allows for the choice of a proper turbulence model to be applied for containment flow simulations. Furthermore, the jet behavior strongly depends on the issuing geometry. A comparative study of erosion process for the conditions similar to the ones of international benchmark exercise (IBE-3) is presented for different jet nozzle shapes.

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Fig. 1

Numerical model overview: (a) computational domain for free nozzle jet simulations and (b) grid at the nozzle outlet. Left: fine high y+ grid and right: coarse high y+ grid.

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Fig. 2

Contraction nozzle jet centerline velocity decay rate

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Fig. 3

Contraction nozzle jet normalized turbulent kinetic energy

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Fig. 4

Geometry of an axisymmetric computational domain for free turbulent jet issuing from a contraction nozzle

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Fig. 5

Concentration distribution—comparison with experiments by Dowling and Dimotakis [20]: (a) radial concentration for x/d = 30, (b) normalized radial concentration: comparison with additional experiments, and (c) centerline concentration

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Fig. 6

Geometry of an axisymmetric computational domain for positively buoyant jets. Dimensions are scaled for d = 0.75 cm.

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Fig. 7

Calculated results of EXP23 from Papanicolaou and List [26]. Turbulence model impact on: (a) jet centerline nondimensional velocity and (b) jet centerline nondimensional concentration.

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Fig. 8

Buoyancy-affected turbulent jets—predictions with C1ε = 1.52 for different initial jet buoyancy and momentum fluxes (see Table 3 for a key to the legend): (a) jet centerline nondimensional velocity and (b) jet centerline nondimensional concentration

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Fig. 9

Time history of helium concentration for ten measuring points along the jet axis. Pipe jet—dashed lines, nozzle jet—solid lines.

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Fig. 10

Erosion rate—time to reach helium mole fraction of 0.2

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Fig. 11

Average axial velocity profiles

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Fig. 12

Contours of velocity and helium mole fraction at t = 110 s: (a) Velocity magnitude, m/s. Pipe (right) and nozzle (left) jets and (b) helium mole fraction. Pipe (right) and nozzle (left) jets.




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