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Environmental Fluid Mechanics

, Volume 19, Issue 6, pp 1455–1468 | Cite as

Experimental investigation of bubbly flow and air entrainment discharge downstream of chute aerators

  • Ruidi BaiEmail author
  • Shanjun Liu
  • Zhong Tian
  • Wei Wang
  • Faxing ZhangEmail author
Original Article
  • 222 Downloads

Abstract

In a chute aerator flow, a large air discharge that is introduced through an air supply duct is entrained into the flow and transported to the downstream zone. In this study, a series of experiments were conducted to quantify the two–phase flow properties, including air concentration, bubble frequency, and bubble diffusivity, and air entrainment flux for a wide range of Froude numbers (3.3 ≤ F0 ≤ 7.4) at relatively large Reynolds numbers (5 × 105 ≤ R ≤ 1.2 × 106). The distributions of air concentration and bubble frequency, which demonstrated two competitive turbulent processes, were presented. The air transport process of the chute aerator flow was quantitatively described based on the approach flow conditions and the aerator geometry. According to the characteristics of air discharge in the equilibrium zone, and based on the previous equation, qa = KV0L, the experimental results indicated that the dimensionless coefficient K was independent of the aerator structure and significantly increases with the flow Froude number.

Keywords

Chute aerator Air entrainment Air–water flows Physical modelling 

List of symbols

C

Air concentration

Cm

Bottom air concentration

Dt

The air diffusivity coefficient in the cavity zone

D#

The air diffusivity coefficient in the impact and equilibrium zones

f

Air bubble frequency

F0

Froude number

g

Acceleration of gravity

h0

Flow depth at the emergence

hs

Offset height

L

Cavity length

Lm

Distance between of x = 0 and the impact point of P = Pm

LD

Distance between of x = 0 and the intersection of the upper and the lower aeration regions

K

Dimensionless air discharge coefficient

P

Bottom pressure

Pm

Maximum bottom pressure

ΔP

Cavity subpressure

qa

Air dicharge

qw

Water discharge

R

Reynolds number

R2

Correlation coefficient

V0

Flow velocity at the emergence

W

Weber number

x

The stream–wise coordinate along the chute bottom

z

The perpendicular coordinate

z0

The location of C = 0

z50

The location of C = 0.50

z90

The location of C = 0.90

zCm

The location of maximum air concentration

zfm

The location of maximum air bubble frequency

α

Chute bottom angle

β

Air entrainment coefficient

θ0

Emergence angle

ρw

Density of water

σ

Surface tension of water

υ

Kinematic viscosity of water

Notes

Acknowledgements

This work was supported by the National Key Research and Development Program of China (2016YFC0401707), the National Natural Science Foundation of China (Grant Nos. 51709293 and 51679157), and the Fundamental Research Funds for the Central Universities (Grant No. 20826041A4305). Many thanks to Ning Sun and Mingcong Lv for helping in experiments.

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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.State Key Laboratory of Hydraulics and Mountain River EngineeringSichuan UniversityChengduChina

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