LABORATORY EXPERIMENTS OF BUBBLE FORMATIONS AND BEHAVIORS IN SURFACTANT SEAWATER

Takumi Nonaka(Hokkaido University), Yasunori Watanabe(Hokkaido University)

Introduction

Result① Needle Generated Bubbles

Result③ Residual Bubbles

Bubble Entrainment and Degassing Processes

Size Distributions

Pure Water (C=0µg/L)④Forming Residual Foams and Bursting②Bubbles Entrained③Bubbles Rising up

Atmosphere

Surfactant Water (C=400µg/L)

Pure Water (C=0µg/L)

Ocean(Watanabe et.al. 2005, Callaghan et al. 2013, Niida and Watanabe 2018,Lamarre and Melville 1991, Marmorino and Smith 2005)

Fine Bubbles(Log Normal Distribution)

RiverRichWater• Observation of Residual
Foams in Needle BubblingExperiment• Diameter, Population, andRate of Coalescence andCollapse Highly Depend on
Surfactant Concentration

Needle Generated Bubbles(Gaussian Distribution)

ExchangeHeat, Gas, Momentum etc.
via Bubbles Film

Ocean Surface Active

Surfactant Water (C=400µg/L)

Number of Bubbles

Bubbles Behavior
Depending on Surface EffectNumber of Bubbles①Wave Breaking

Surface active has Locality !

Potential of Surfactant as Characteristics Local Air-sea TransportThis StudyIdentify dynamics
of surfactant
bubbles and foams

Investigate surfactant effects ongeometric and kinematic features ofbubble plumes and residual foams.
Laboratory experiments
using high-resolution backlit
image measurements

Result② Jet Induced Bubbles
JET

JET

Concentration C (µg/L)• Fragmentation of Entrained Air→Bubbles
Surfactant• Frequently Fragmentation• Increasing Population of Bubbles• Small Mean Diameter• Size Distribution→Log Normal Distribution• Complexity Velocity

Fragmentation ofEntrained Air

Surfactant Water(C=400µg/L)

Population

Increase and Smaller

Mean DiameterConcentration C (µg/L)

Concentration C (µg/L)

Conclusion

Mean diameter

Population (#/cm2)

Pure Water(C=0µg/L)

Concentration C (µg/L)(mm)

Objective

Population (#/cm2)

Ocean• Needle Generated Bubbles → Gaussian Distribution• Fine Bubbles(Created by Breakup of Larger Ones) → Log Normal Distribution.
• Surfactant → Frequently Fragmentation

Rate of Collapse(Wurl et.al. 2011)

Surfactant Promotes Fragmentation

Rate of Coalescence

EutrophicandHigh Surface ActiveD/

Mean diameter

Produced by Biological Activity(e.g. ammonium, polysaccharide)D/(mm)

Surfactants in Ocean

Concentration C (µg/L)

Concentration C (µg/L)

Eutrophic(C=400㎍/L)

Artificial Seawater

Size Distributions• Surfactant promotes fragmentation of bubbles.
• Fine bubbles size follows log normal distribution.
• Bubbles kinetic feature in surfactant water have complexity.
• Foams behaviors highly depend on surfactant concentration.

Velocity

D/Fitting

References
In surfactant water

Relatively
Faster

Deceleration by Disproportionof Surface Active
Surfactant
Concentration

Contaminated Water
Pure Water(Clift et al. 1978)
Pure Water
Eutrophic Water
Artificial Seawater

Diameter D(mm)Air-sea Transport Varies with Local Oceanic Biological Activity.

FittingD/D/Velocity (mm/s)• Bubbled Detected by Level Set
Method (Watanabe and Ingram 2015)• Each Size of Bubbles Determined as
Equilibrium Diameter D.
• Bubbles Velocity Estimation by
Tracking their Centers Over
Sequential Images

Number of bubbles

Non-Fitting

When Many Bubbles Exist

Image Analysis
LevelSet
MethodPure Water(C=0㎍/L)

Number of bubbles

Number of bubbles

Estimated Log Normal Distribution

BubbleAdvection ofSurfactant• Watanabe, Y., Saeki, H., & Hosking, R. J. (2005). Three-dimensional vortex structures under breaking waves.
Journal of Fluid Mechanics, 545:291-328.
• Callaghan, A. H., Deane, G. B., & Stokes, M. D. (2013). Two regimes of laboratory whitecap foam decay:
Bubble-plume controlled and surfactant stabilized. Journal of physical oceanography, 43.6:1114-1126.
• Niida, Y., & Watanabe, Y. (2018). Oxygen transfer from bubble-plumes. Physics of fluids, 30.10:107104.
• Marmorino, G. O., & Smith, G. B. (2005). Bright and dark ocean whitecaps observed in the infrared. Geophysicalresearch letters, 32.11: L11604.
• Lamarre, E., & Melville, W. K. (1991). Air entrainment and dissipation in breaking waves. Nature, 351.6326:469472.
• Wurl, O., Wurl, E., Miller, L., Johnson, K., & Vagle, S. (2011). Formation and global distribution of sea-surface
microlayers. Biogeosciences, 8.1:121-135.
• Watanabe, Y., & Ingram, D. M. (2015). Transverse instabilities of ascending planar jets formed by wave impacts onvertical walls. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences,471.2182:20150397.