Development of Bubble Characteristics on Chute Spillway Bottom

Bai, Ruidi; Liu, Chang; Feng, Bingyang; Liu, Shanjun; Zhang, Faxing

doi:10.3390/w10091129

Cited by 4 publications

(4 citation statements)

References 22 publications

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“…e CFD-PBM coupled model is of high value for applications in the gas-liquid twophase flow in hydraulic engineering, and the accuracy and reliability were validated through the physical model experiments of Bai et al [7,28]. e experiments were conducted in a 0.25 m wide rectangular chute with a bottom slope of 14°.…”

Section: Computational Model Layoutmentioning

confidence: 99%

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Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

Lei

Zhang

2021

Mathematical Problems in Engineering

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The aerator can reduce erosion by mixing a large amount of air into the water in the solid wall area. The effectiveness of erosion reduction is mainly based on air concentration and its bubble size distribution. However, simultaneous simulation of the air concentration and its bubble size distribution in numerical simulations is still a hot and difficult area of research. Aiming at the downstream aerated flow of hydraulic aeration facilities, several numerical models, such as VOF, mixture, Euler, and Population Balance Model (PBM), are compared and verified by experiments. The results show that the CFD-PBM coupled model performs well compared to other conventional multiphase models. It can not only obtain the evolution law of the bubble distribution downstream of the aerator but also accurately simulate the recombination and evolution process of bubble aggregation and breakage. The Sauter mean diameter of the air bubbles in the aerated flow decreases along the way and eventually reaches a stable value. The bubble breakage is the main process in the development of the bubbles. It reveals the aeration law that the small air bubbles are closer to the bottom plate, while the large bubbles float up along the aerated flow, which provides a powerful support for the basic research on the mechanism of aeration and erosion reduction.

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Section: Computational Model Layoutmentioning

confidence: 99%

“…Small bubbles support to alleviate cavitation erosion, even at the same air concentration. Bai et al [7] measured and analyzed the development of bubble characteristics downstream of the spillway aeration facility by using a conductivity probe. It was found that the chord length of bubbles decreased sharply in the impact zone.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

Lei

Zhang

2021

Mathematical Problems in Engineering

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“…Under normal atmospheric pressure, researchers have conducted extensive research on using air entrainment to alleviate cavitation. Research directions mainly encompass the mechanisms of using air entrainment to alleviate cavitation [10,11], the characteristics of forced aeration in water flow [12][13][14][15], the design of aeration devices [16], the downstream bubble characteristics of aeration devices [17], and the scale effects of aeration ratios [18,19]. The ventilation volume is an important parameter for measuring the effectiveness of air entrainment devices.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Decreased Atmospheric Pressure on Forced Aeration of Discharged Flow

Guo,

Zhang,

et al. 2024

Water

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To account for changes in the performance of spillway aerator structures of high-altitude dams, depressurization generalized model experiments and theoretical analyses were conducted in this study. Measurements were taken for ventilation hole air velocity, cavity subpressure, cavity length, and air concentration in crucial regions. The study proposed correction formulas for the aeration coefficient and water air concentration in aerator devices operating under low atmospheric pressure. The pressure range of the experiments was between 26.3 kPa and 101.3 kPa. The results indicated that with decreasing atmospheric pressure, ventilation hole air velocity, ventilation volume, cavity subpressure, and water air concentration all showed a decreasing trend. For every 15 kPa decrease in pressure, ventilation hole air velocity decreased by approximately 24%. When the atmospheric pressure dropped from 101.3 kPa to 26.3 kPa, the cavity subpressure decreased and eventually approached zero. The maximum reduction in air concentration was 14.9% in the cavity backwater area, 38.5% at the cavity end, and 38.3% in the downstream bubble escape segment. The proposed correction formulas could be used for a rapid estimation of ventilation volume and air concentration in low-pressure environments. This research provides a scientific basis for the design of aeration devices in water projects located in high-altitude regions.

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“…Juan César Luna-Bahena et al [12] studied the combined effect of the top pier and bottom aeration facilities of a smooth spillway. Bai et al [13][14][15] studied the characteristics of microscopic bubbles near the bottom of a drain tank, revealed the flow characteristics of air and water at the bottom, and proposed a self-similar relationship between air concentration and bubble frequency in various regions. Bai et al [16] proposed a method to estimate the air entrainment rate of a slot bed by considering the effective air cavity length and the influence of air escaping the jet.…”

Section: Introductionmentioning

confidence: 99%

Study on the Shape of the Aerator of High-Head Discharge Tunnel with Mild Bottom Slope

Zhang

Song

2021

Water

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Due to the high flow velocity and easy cavitation of high-head drainage tunnels, it is usually necessary to set up aeration facilities. In particular, when the bottom slope of the tunnel is mild, the aeration facilities often have problems such as difficulty with air intake, short cavity, and serious water accumulation, which aggravate the risk of cavitation damage. In this paper, based on the Rumei hydropower station and the Gushui hydropower station, a method combining theoretical analysis and model testing is used to solve the connection problem between the aeration facility and the 3% mild bottom slope of a tunnel body, and the aeration facility shape of “lifting ridge + flat (mild) slope + steep slope” is put forward. The research shows that the steep slope section can smoothly connect the water flow over the cantilever, reduce the jet impact angle, prevent the water from backtracking, and produce a long and stable cavity in the flat (mild) slope section. The aeration concentration along the bottom of the tunnel is higher than 3% at 140 m over the top of the dam. The aeration effect of this type is better, and it can provide effective long-distance protection for a drainage tunnel with high head and a mild bottom slope.

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Development of Bubble Characteristics on Chute Spillway Bottom

Cited by 4 publications

References 22 publications

Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

The Impact of Decreased Atmospheric Pressure on Forced Aeration of Discharged Flow

Study on the Shape of the Aerator of High-Head Discharge Tunnel with Mild Bottom Slope

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