The ABS The ABS Acoustic Bubble Spectrometer Acoustic Bubble - - PowerPoint PPT Presentation

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The ABS The ABS Acoustic Bubble Spectrometer Acoustic Bubble - - PowerPoint PPT Presentation

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The ABS The ABS Acoustic Bubble Spectrometer Acoustic Bubble Spectrometer by G. L. Chahine D YNAFLOW , I NC . Jessup, MD www.dynaflow-inc.com Email: glchahine@dynaflow-inc.com www.dynaflow-inc.com Background Background Bubbles

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by

  • G. L. Chahine

DYNAFLOW, INC.

Jessup, MD www.dynaflow-inc.com Email: glchahine@dynaflow-inc.com

The ABS The ABS Acoustic Bubble Spectrometer Acoustic Bubble Spectrometer 

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Background Background

 Bubbles in a liquid are very sensitive to acoustic waves  Bubble acoustic cross section >10 times solid particle of the

same size

 Bubbles much more compressible than liquid  Bubbles act like a spring-mass oscillating system

 Mass from liquid inertia  Spring constant from permanent gas, …etc

 Possibility for strong resonance

 acoustic energy absorption, re-radiation

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Spherical Bubble Dynamic Spherical Bubble Dynamic Equation Equation

 Spherical Symmetry + Conservation of Mass:  Conservation of Momentum  Rayleigh Plesset Equation (when linear relationship stress-strain)

2 2 / u R R r r  

R(t)

ur

r

R  1

r r r

du dp u dt dr       3 3 2 2 4 2 k R R

  • RR

R P P P go v R R R                    

Pg Pv

3 3 k k g g

P R P R 

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Small scale oscillations Small scale oscillations

 Driving Pressure  Bubble Radius  RP Equation degenerates to:  

( ) R R a t   

 

0 1

cos P P t    

2

cos a a t      P

3 (3 1)2 / 1 kP k R R       ( , ) a f    3 1 kP R   ฀

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Resonance Resonance

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  • The ABS does not use the simple relationships showed

above.

  • It considers sound propagation in a bubble medium
  • Sound Speed Change/Dispersion
  • Attenuation/Damping

Dispersion Relation

Pure Liquid Sound Speed 2-Phase Medium Sound Speed Distance Between Hydrophones

Influence of Bubble Distribution Influence of Bubble Distribution

  • n Sound Propagation
  • n Sound Propagation
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Dispersion Relations Dispersion Relations

Resonance Radii

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The ABS The ABS

 The ABS Acoustic Bubble Spectrometer is an acoustics

based device that measures bubble size distributions in liquids.

 Very sensitive to bubbles  No need for transparent liquid or “container”  Easy to Use  Packaged User-Friendly System  Near Real-Time measurement  Could be part of:

 an on-line system  a distributive placement for large scale applications  a long-term continuous monitoring application  an off-line post-measurement analysis

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 Oceanography: Bubble Populations for Acoustic

Background Measurements, Aeration, Mixing,….

 Laboratory & Industrial Two-Phase Flows  Cavitation Susceptibility  Water/Cavitation Tunnels in which Underlying Nuclei

Population Should be Known/Controlled

 Biomedical Devices – Bubbles in Blood, etc.  Measurement of Effectiveness of Aeration Devices  Bubbles/voids and Gas/Air Content of “Engineered”

Specialty Fluids

 Bubble Clouds Used for Acoustic Signature Control  Boiling – High vapor content

POTENTIAL APPLICATIONS POTENTIAL APPLICATIONS

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PC

AMPLIFIER & FILTER OSCILLOSCOPE (if desired for checking)

Transmitting Hydrophone Receiving Hydrophone Tested Liquid with Bubbles Signal Generation Data Acquisition Signal Processing Inverse Method Bubble Model Algorithm USER INPUTS:

  • Properties
  • Frequencies
  • Amplitude
  • Sample Rate
  • Processing

Options

  • …………

Raw Signals u, v Bubble Size Distribution ABS OUTPUT Operation Control GUI

PC-BASED ABS SETUP

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User Input User Input -

  • I

I

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User Input User Input -

  • II

II

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User Input User Input -

  • III

III

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User Input User Input -

  • IV

IV

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RAW SIGNALS DISPLAY

SENT (EMITTED) RECEIVED

Output Output -

  • I

I

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Screen shot of the ABS graphical user interface showing the sound speed ratio, u, the attenuation ratio, v, and the resulting bubble size distribution

Output Output -

  • II

II

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www.dynaflow-inc.com Air Injection Microporous Tube Water shear Air/Water Mixing Tank Pump ABS Test Section High Speed Video Camera Transducers . Sketch of experimental setup

Photograph of the test section

Transducer

Transducers

Recent Validation Experiments

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Injector in operation Close up view

Bubble Injector

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ABS 80%waterFlow 30% Air

2 4 6 8 10 12 14 14 15 25 35 45 55 64 74 84 94 104 114 124 134 Bubble Radius, m N u m b e r p e r c m

3

Test 1 Test 2 Test 3 Test 4

ABS 80%waterFlow 30% Air

2 4 6 8 10 12 14 14 15 25 35 45 55 64 74 84 94 104 114 124 134 Bubble Radius, m N u m b e r p e r c m

3

Test 1 Test 2 Test 3 Test 4

ABS: one set of measurements each time Micro video photography: 55 frames per measurement

Illustration of the degree of variation in the bubble size distribution measurements

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1 2 3 4 5 6 7 14 25 45 64 84 104 124 144 163 Bubble Radius, m Number per cm 3 ABS Average 6 tests Photos Average 132 frames

Comparison between ABS measurements and micro video photography

VALIDATION VALIDATION

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  • ABS Acoustic Bubble Spectrometer
  • Near real time measurement of bubble size

distributions

  • Flexibility of measuring volume size
  • No need for optical transparency
  • ABS measurements in Newtonian fluids validated

in controlled experiments with microphotography

  • ABS and microphotography experiments found to

have comparable scatter and give very close results

CONCLUSIONS CONCLUSIONS