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Bubble formation and scale dependence in free-surface air entrainment
Wangru Wei1, Weilin Xu1, Jun Deng2
1State Key Lab of Hydraulic and Mountain River Engineering, Sichuan University, Chengdu, 610065, China.
Scientific Reports
|July 31, 2019
Summary
Air bubble entrainment in water flows is crucial for gas transfer and preventing cavitation erosion. This study quanties bubble formation, revealing surface deformation power-law scaling drives bubble entrapment.
Area of Science:
- Fluid dynamics
- Multiphase flow
- Interface physics
Background:
- Air bubble entrainment and self-aeration in free-surface water flows are critical phenomena.
- Bubble size distribution impacts air-water gas flux, gas transfer, and cavitation erosion protection.
Purpose of the Study:
- To investigate the bubble-formation mechanism of free-surface air entrainment.
- To provide a quantitative description of bubble entrainment and microscopic bubble scale.
- To understand the relationship between free-surface deformation and bubble characteristics.
Main Methods:
- Laboratory investigation of free-surface air entrainment.
- Quantitative analysis of bubble formation and scale.
- Characterization of free-surface deformation using power-law scaling.
Main Results:
- Free-surface deformation follows a power-law scaling over time.
- Bubble entrainment occurs when the entrapped surface becomes enclosed during unstable movement.
- The size and shape of the entrapped free surface dictate the air bubble size distribution and skewness.
Conclusions:
- The instability of the local air-water interface is the primary driver of bubble entrainment.
- Further research is needed to define the interface instability criterion for multiphase flow.
- Understanding bubble formation enhances knowledge of multiphase flow generation and development.
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