Mechanism of air entrainment by a disturbed liquid jet

2000 ◽  
Vol 12 (7) ◽  
pp. 1710-1714 ◽  
Author(s):  
C. D. Ohl ◽  
H. N. Og̃uz ◽  
A. Prosperetti
Keyword(s):  
Air Entrainment ◽  
Liquid Jet

Initial Impact of Liquid Jets and Entrainment of Air Bubbles: A Numerical Study

2011 ◽  
Author(s):  
Xiaoliang Qu ◽  
Lyes Khezzar ◽  
Zhenlin Li
Keyword(s):  
Focal Point ◽  
Numerical Study ◽  
Fluid Model ◽  
Air Entrainment ◽  
Liquid Jet ◽  
Maximum Height ◽  
Air Cavity ◽  
Subsequent Formation ◽  
Vof Model ◽  
Jet Impact

This paper presents a three-dimensional unsteady numerical simulation of a turbulent plunging liquid jet without artificial surface disturbance impinging on a quiecent liquid pool. The focal point of the study is the initial impact and air entrainment process. The multiphase, Volume of Fluid Model is used in combination with the Reynolds Averaged k-ε turbulence model. The process of the initial impact of the jet on the free surface, the subsequent formation of an air cavity and the subsequent break-down of the cavity into small bubbles are captued and analyzed. These simulations show clearly and in detail the process of air carryunder by the liquid-liquid jet. The air cavity caused by the intial jet impact stretches deeply under the pool surface untill break down due to the shear created by a torroidal vortex. The predicted maximum height of the developing air cavity shows very good agreement with existing semi-empirical correlations from the literature and experiments. The velocity of the front of the air cavity is equal to about half the jet valocity at impact as shown by previous works and the predicted penetration depth shows acceptable agreement with previous correlations. The VOF model shows a strong capability of tracking the interface between two phases.

Experimental investigation of air entrainment by vertical plunging liquid jet

2018 ◽  
Vol 181 ◽  
pp. 251-263 ◽  
Author(s):  
Shuichiro Miwa ◽  
Takahiro Moribe ◽  
Kohei Tsutstumi ◽  
Takashi Hibiki
Keyword(s):  
Experimental Investigation ◽  
Air Entrainment ◽  
Liquid Jet

scholarly journals Effect of Primary Variables on A Confined Plunging Liquid Jet Reactor

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 764 ◽  
Author(s):  
Bader S. Al-Anzi
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Liquid Jet ◽  
Entrainment Rate ◽  
Activated Sludge Process ◽  
Gas Entrainment ◽  
Air Entrainment Rate ◽  
Aeration Process

The effects of operating conditions including a novel downcomer geometry on the gas/air entrainment rate, Qa, were investigated for a local vertical confined plunging liquid jet reactor (CPLJR) as an alternative aeration process that is of interest to Kuwait and can be used in various applications, such as in wastewater treatment as an aerobic activated sludge process, fermentation, brine dispenser, and gas–liquid reactions. Operating conditions, such as various downcomer diameters (Dc = 45−145 mm), jet lengths (Lj = 200–500 mm), nozzle diameters (dn = 3.5–15 mm), and contraction angles (Ɵ =20–80°), were investigated. A newly designed downcomer with various mesh openings/pores (Dm = 0.25ʺ (6.35 mm)–1ʺ (25.4 mm)) was also investigated in the current study. The air entrainment results showed that these were the primary parameters for the measured air entrainment rate in confined systems. The highest gas entrainment rates were achieved when the ratio of the downcomer diameter (Dc) to the nozzle diameter (dn) was greater than approximately 5, as long as the liquid superficial velocity was sufficient to carry bubbles downward. Furthermore, a downcomer with mesh openings (Dm) less or equal to 0.5ʺ (12.7 mm) provided a higher entrainment rate than that of conventional downcomer (without a mesh).

A Two-Way Coupled Polydispersed Two-Fluid Model for the Simulation of Air Entrainment Beneath a Plunging Liquid Jet

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Jingsen Ma ◽  
Assad A. Oberai ◽  
Donald A. Drew ◽  
Richard T. Lahey
Keyword(s):  
Two Phase Flow ◽  
Transport Model ◽  
Waste Water Treatment ◽  
Critical Role ◽  
Experimental Studies ◽  
Air Entrainment ◽  
Liquid Jet ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluid

Plunging liquid jets are commonly encountered in nature and are widely used in industrial applications (e.g., in waterfalls, waste-water treatment, the oxygenation of chemical liquids, etc.). Despite numerous experimental studies that have been devoted to this interesting problem, there have been very few two-phase flow simulations. The main difficulty is the lack of a quantitative subgrid model for the air entrainment process, which plays a critical role in this problem. In this paper, we present in detail a computational multiphase fluid dynamics (CMFD)-based approach for analyzing this problem. The main ingredients of this approach are a comprehensive subgrid air entrainment model that predicts both the rate and location of the air entrainment and a two-fluid transport model, in which bubbles of different sizes are modeled as a continuum fluid. Using this approach, a Reynolds-averaged Navier Stokes (RaNS) two-way coupled two-phase flow simulation of a plunging liquid jet with a diameter of 24 mm and a liquid jet velocity around 3.5 m/s was performed. We have analyzed the simulated void fraction and bubble count rate profiles at three different depths beneath the average free surface and compared them with experimental data in literature. We observed good agreement with data at all locations. In addition, some interesting phenomena on the different movements of bubbles with different sizes were observed and discussed.

A Two-Way Coupled Polydispersed Simulation of Bubbly Flow Beneath a Plunging Liquid Jet

2010 ◽  
Author(s):  
Jingsen Ma ◽  
Assad A. Oberai ◽  
Donald A. Drew ◽  
Richard T. Lahey
Keyword(s):  
Two Phase Flow ◽  
Transport Model ◽  
Waste Water Treatment ◽  
Critical Role ◽  
Experimental Studies ◽  
Air Entrainment ◽  
Industrial Applications ◽  
Liquid Jet ◽  
Phase Flow ◽  
Two Phase

Plunging liquid jets are commonly encountered in nature and are widely used in industrial applications (e.g., in waterfalls, waste-water treatment, the oxygenation of chemical liquids, etc.). Despite numerous experimental studies that have been devoted to this interesting problem, there have been very few two-phase flow simulations. The main difficulty is the lack of a quantitative model to simulate the air entrainment process, which plays a critical role in this problem. In this paper, we present a computational multiphase fluid dynamics (CMFD) approach for solving this problem. The main ingredients of this approach are a comprehensive subgrid air entrainment model that predicts the rate and location of the air entrainment and a two-fluid transport model in which bubbles of different sizes are modeled as a continuum fluid. Using this approach, a Reynolds-averaged Navier Stokes (RaNS) two-way coupled two-phase flow simulation of a plunging liquid jet with a diameter of 24mm and a liquid jet velocity around 3.5m/s was performed. We analyzed the simulated void fraction and bubble count rate profiles at three different depths beneath the average free surface, and compared them with experimental data. We observed good agreement at all locations.

Experimental investigation of air entrainment in a vertical liquid jet flowing down onto a rotating roll

2000 ◽  
Vol 55 (5) ◽  
pp. 931-942 ◽  
Author(s):  
Masato Yamamura ◽  
Satoshi Suematsu ◽  
Toshihisa Kajiwara ◽  
Kitaro Adachi
Keyword(s):  
Experimental Investigation ◽  
Air Entrainment ◽  
Liquid Jet

The role of surface disturbances in the entrainment of bubbles by a liquid jet

1998 ◽  
Vol 372 ◽  
pp. 189-212 ◽  
Author(s):  
HASAN N. OGUZ
Keyword(s):  
Bubble Size ◽  
Air Entrainment ◽  
Boundary Integral ◽  
Liquid Jet ◽  
Air Pocket ◽  
Boundary Layer Instability ◽  
The Right ◽  
Air Pockets ◽  
Pocket Formation ◽  
Surface Disturbances

In this paper, air entrainment by a liquid jet is studied. The size of bubbles entrained by jets plunging into a liquid can be consistently decreased to the 50–100 μm range, and their number increased in a highly controllable fashion, by surrounding a mm-size jet by a hollow cap with a slightly larger inner diameter. When the right amount of air is supplied to the cap, small air bubbles detach from a steady annular cavity that forms around the jet and are entrained into the liquid. The fluid mechanical principles underlying this interesting and useful effect are investigated experimentally and theoretically in this paper. It is shown that a key aspect of the process is the jet surface roughness, which is studied quantitatively and explained in terms of the boundary layer instability inside the nozzle. The maximum bubble size is found to be nearly equal to one quarter of the wavelength of the jet surface disturbances, consistent with a breakup process of relatively large air pockets around the jet, as suggested by close-up pictures. The average bubble size downstream of the cap increases proportionally to the air to water flow ratio. Boundary integral simulations of the air pocket formation are carried out. The results are found to be useful in explaining important characteristics of the experiment such as the threshold for entrainment and cavity size.

THE ANALYSIS OF.A PLUNGING LIQUID JET—THE AIR ENTRAINMENT PROCESS

1994 ◽  
Vol 130 (1) ◽  
pp. 11-29 ◽  
Author(s):  
F. BONETTO ◽  
D. DREW ◽  
R.T. LAHEY
Keyword(s):  
Air Entrainment ◽  
Liquid Jet ◽  
Entrainment Process

Effect of Nozzle Contraction Angle on Air Entrainment Rate of a Vertical Plunging Liquid Jet.

2000 ◽  
Vol 33 (5) ◽  
pp. 805-807 ◽  
Author(s):  
Kazuaki Yamagiwa ◽  
Akira Ito ◽  
Kei Tajima ◽  
Masanori Yoshida ◽  
Akira Ohkawa
Keyword(s):  
Air Entrainment ◽  
Liquid Jet ◽  
Entrainment Rate ◽  
Air Entrainment Rate ◽  
Contraction Angle
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