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

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 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 www.dynaflow-inc.com

Spherical Bubble Dynamic Spherical Bubble Dynamic Equation Equation u r  R r  Spherical Symmetry + Conservation of Mass: 2 2  R(t) r  P g u R R r / P v   Conservation of Momentum 3 k 3 k P R P R g g 0 0 du 1 dp      r u  r r dt dr  Rayleigh Plesset Equation (when linear relationship stress-strain) 3 k    R  3 R 2 2 o            RR R 4 P P P    go v 2 R R R   www.dynaflow-inc.com

Small scale oscillations Small scale oscillations       P P 0 1 cos t  Driving Pressure    R R a t ( )  Bubble Radius 0  RP Equation degenerates to:      2 P a a cos t 0    1 3 kP 1 3 kP (3 k 1)2 / R    ฀ 0 0 0  0  0 R R 0 0    f   a ( , ) 0 www.dynaflow-inc.com

Resonance Resonance www.dynaflow-inc.com

Influence of Bubble Distribution Influence of Bubble Distribution on Sound Propagation on Sound Propagation • The ABS does not use the simple relationships showed above. • It considers sound propagation in a bubble medium • Sound Speed Change/Dispersion Pure Liquid Dispersion Sound Speed Relation 2-Phase Medium Sound Speed • Attenuation/Damping Distance Between Hydrophones www.dynaflow-inc.com

Dispersion Relations Dispersion Relations Resonance Radii www.dynaflow-inc.com

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 www.dynaflow-inc.com

POTENTIAL APPLICATIONS POTENTIAL APPLICATIONS  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 www.dynaflow-inc.com

PC-BASED ABS  SETUP PC Tested Liquid with USER INPUTS: Bubbles Operation • Properties Control • Frequencies Signal • Amplitude Generation AMPLIFIER • Sample Rate & • Processing FILTER Options GUI Transmitting Receiving • ………… Hydrophone Hydrophone ABS OUTPUT Data Acquisition Raw Signals Signal u, v Processing Bubble Size Inverse Distribution Method OSCILLOSCOPE Bubble Model (if desired for Algorithm checking) www.dynaflow-inc.com

User Input - - I I User Input www.dynaflow-inc.com

User Input - - II II User Input www.dynaflow-inc.com

User Input - - III III User Input www.dynaflow-inc.com

User Input - - IV IV User Input www.dynaflow-inc.com

Output - -I I Output RAW SIGNALS DISPLAY SENT (EMITTED) RECEIVED www.dynaflow-inc.com

Output - -II II Output Screen shot of the ABS graphical user interface showing the sound speed ratio, u, the attenuation ratio, v, and the resulting bubble size distribution www.dynaflow-inc.com

Recent Validation Experiments Air/Water Mixing Tank Air Injection Transducers Microporous Tube Water shear Transducers Test High Section Transducer Speed ABS Video Pump Camera Photograph of the test section . Sketch of experimental setup www.dynaflow-inc.com

Bubble Injector Injector in operation Close up view www.dynaflow-inc.com

Illustration of the degree of variation in the bubble size distribution measurements ABS 80%waterFlow 30% Air ABS 80%waterFlow 30% Air 14 14 Test 1 Test 1 12 12 3 3 Test 2 Test 2 N u m b e r p e r c m 10 N u m b e r p e r c m 10 Test 3 Test 3 8 8 Test 4 Test 4 6 6 4 4 2 2 0 0 14 15 25 35 45 55 64 74 84 94 104 114 124 134 14 15 25 35 45 55 64 74 84 94 104 114 124 134 Bubble Radius, � m Bubble Radius, � m ABS: one set of Micro video photography: 55 measurements each time frames per measurement www.dynaflow-inc.com

VALIDATION VALIDATION 7 6 ABS Average 6 tests Number per cm 3 5 Photos Average 132 frames 4 3 2 1 0 14 25 45 64 84 104 124 144 163 Bubble Radius, � m Comparison between ABS measurements and micro video photography www.dynaflow-inc.com

CONCLUSIONS CONCLUSIONS • 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 www.dynaflow-inc.com