ABS Acoustic Bubble Spectrometer Brochure

®®AAAAAcousticcousticcousticcousticcousticBBBBBubbleubbleubbleubbleubbleSSSSSpectrometerpectrometerpectrometerpectrometerpectrometerMeasurement of Bubble Size, Bubble Number & Void FractionABSABSABSABSABS DYNAFLOW, INC. Research & Developmentin Applied SciencesDYNAFLOW, INC.ABSABSABSABSABS 2123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345123456789012345678901234567890121234567890123456789012345The ABS AdvantageThe ABS AdvantageThe ABS AdvantageThe ABS AdvantageThe ABS Advantage• Very sensitive to bubbles• Optically transparent liquid or containers are not required• Distinguishes bubbles from particles• Built on a PC Windows platform with a user-friendly graphical interface• Measurements are easily and rapidly conducted• Validated by comparison with microphotography• Near real-time measurement• Cost effective• User-friendly systemMaritime – hydrodynamics, propulsor performance, cavitation, power plants, turbomachinery, pumpsBiomedical – blood transfusions, artificial heart valve, bubbles in tissueand blood, decompression sicknessSpace – effects of microgravity on multiphase fluids, reduced pressureeffectsOceanography – atmosphere / ocean interface studies, air entrainment,oxygenation, sound transmission, background noiseMultiphase Flow – valves, pumps, propellers, fluid machinery,industrial & chemical processes, specialty fluids, measurement ofaeration bubbles, boilingEducation / Research – fluid dynamic & cavitation studies, bubble nucleiin water tunnelsEnvironmental – categorizing fish by size, monitoring sewage treatment,mixingApplicationsApplicationsApplicationsApplicationsApplications3 DYNAFLOW, INC.123456789012341234567890123412345678901234123456789012341234567890123412345678901234123456789012341234567890123412345678901234123456789012341234567890123412345678901234123456789012341234567890123412345678901234Cavitation is the formation of vaporous and gaseous filled bubbles or“cavities” in a liquid, typically due to a sudden change in pressure.This occurs, for example, along the flow path through a pump or overa propeller blade. Cavitation can have a dramatic effect on both theperformance and life of such devices. In particular, cavitationsignificantly affects the performance and operation of propellers,hydrofoils and pumps. The collapse of cavitation bubbles cause bothsubstantial physical damage and considerable noise. The distribution ofbubble nuclei strongly influences the propensity for cavitation. This isparticularly important if one wants to experimentally scale a devicesubject to cavitation since it is necessary to properly control and accountfor the existing bubble nuclei distribution in the liquid.Measuring bubble distribution, visually or optically, is painstaking orimpossible when dealing with a large system and a non transparentmedium. Moreover, it becomes increasingly difficult to distinguishsmall particulates from small bubbles. Bubbles, however, are moresensitive to acoustic waves than particulates, hence the ABS can readilypick out small bubbles in a liquid. The ABS also does not requireoptically transparent liquids or containing structures.BackgroundBackgroundBackgroundBackgroundBackgroundThe ABS Acoustic Bubble Spectrometer®© is an instrumentdeveloped by DYNAFLOW, INC. to measure bubble size distributionsand void fraction in gas/liquid mixtures and flows. Not only does theABS measure the total “void fraction” (volume fraction of the gasphase in the liquid ), it also measures the distribution of the sizes ofthe bubbles. This difficult-to-measure characteristic proves invaluablein numerous areas. For example the top ten meters of the sea containmany bubbles that greatly affect acoustic properties by scatteringsignals and creating noise. Knowledge of the bubble size distributionisalso important when modeling chemical or biological processes. TheABS is also useful in the development of processes that mix a gas in aliquid such as waste treatment and the design of aeration systems.Another application area where the ABS proves invaluable isengineered systems that might experience cavitation.AAAAAcousticcousticcousticcousticcoustic BBBBBubbleubbleubbleubbleubble SSSSSpectrometerpectrometerpectrometerpectrometerpectrometer®©ABSABSABSABSABS 4The ABS is built around a PC Windows platform and includes high-speedcards for signal generation and data acquisition. This high speed opera-tion is required because the signal bursts are very short in order to detectvery small bubbles. Additionally, since the system determines any changesin the speed of sound due to the presence of bubbles, truesimultaneous sampling is mandatory, especially when the distance betweenthe two hydrophones is small.The Raw Signals Display which shows the transmitted and received data.Two hydrophones or transducers are used, one to transmit and the otherto receive a series of short monochromatic bursts of varying frequencies.From these readings, the attenuation and phase speed in the bubbly liquidare determined as a function of the frequency. The data from thesesignals are processed and analyzed with the copyrighted software algorithmsdeveloped by DYNAFLOW. These algorithms employ specialized techniquesto solve the mathematically ill-posed inverse problems, and thus obtain thebubble size distribution and void fraction.How the ABS System WHow the ABS System WHow the ABS System WHow the ABS System WHow the ABS System WorksorksorksorksorksIn-line ABS MeasurementsSketch of the ABS Acoustic Bubble Spectrometer®© Operational System5 DYNAFLOW, INC.The ABS Acoustic Bubble Spectrometer®© exploits the fact that bubblesstrongly affect acoustic wave propagation. Bubble size distributionmeasurements are based on a dispersion relation for sound wavepropagation through a bubbly liquid. Bubbles in the liquid have an effect onthe strength of the signal that reaches the receiver, as well as on the speedat which the signal travels between the emitter and receiver. Bubbles of agiven size have a resonant frequency where effects are the strongest, butwill affect signals of all frequencies. For each burst, the system measuresthe changes in the speed of sound and the signal amplitude. With morebubbles, the speed of sound and the signal’s amplitude decrease further. The Principle of OperationThe Principle of OperationThe Principle of OperationThe Principle of OperationThe Principle of OperationA multiphase fluid model for sound propagation through bubbly liquidsis combined with a model for the bubble oscillations, including variousdamping modes. The combined model relates the attenuation and phasevelocity of a sound wave to the bubble population or size distribution.These relations produce two ill-posed Fredholm integral equations thatrequire special treatment for their solution, particularly in the presence ofnoise. Novel algorithms developed by DYNAFLOW are used to accuratelysolve these equations using a constrained optimization technique thatimposes a number of physical constraints on the solution.http://www.dynaflow-inc.com/Products/ABS/ABS.htmABSABSABSABSABS AAAAAcousticcousticcousticcousticcoustic BBBBBubbleubbleubbleubbleubble SSSSSpectrometerpectrometerpectrometerpectrometerpectrometer®©6ABSABSABSABSABSA “pure liquid” provides a background reference state. This “no bubble”reference state is used in calculating the bubble size distribution fromdata “with bubbles”. This reference state data set is obtained byconducting an experiment in the absence of bubbles under conditions andsettings otherwise identical to those which will be employed in determin-ing the desired bubble size distribution.The Dialog Box to Enter Physical Parameters The Dialog Box to enter Signal ParametersScreen shot of the ABS output graphical user interface showing the sound speed ratio u, theattenuation ratio v and the resulting bubble size distribution.Displayed ResultsDisplayed ResultsDisplayed ResultsDisplayed ResultsDisplayed ResultsResults from the analysis of the experimental data appear on the screenin easy to read displays in the form of plots.Sound Speed Ratio (u=c/co) versus frequencyAttenuation Ratio (v) versus frequencyBubble Size Distribution as the number of bubbles per cubic centimeter versus bubble radius in micronsVoid fraction contributions vs bubble sizeOperation of the ABSOperation of the ABSOperation of the ABSOperation of the ABSOperation of the ABSUser InputUser InputUser InputUser InputUser InputMeasurements are easily and rapidly conducted with the aid of a user-friendly Graphical User Interface. All physical, experimental, and ana-lytical parameters are input by the user via dialog boxes initially loadedwith default values. Both raw and processed experimental data can besaved to disk for future use. The signals and results are displayedgraphically by the interface in real time and can also be stored orprinted. The measurement can be started either by clicking on an icondisplayed on the screen or through use of an external trigger signal tosynchronize with a desired event.7 DYNAFLOW, INC.0123456714 25 45 64 84 104 124 144 163Bubble Radius, µmNumber per cm3ABS Average 6 testsPhotos Average 132 frames Comparison between ABS measurements and micro video photography-20246810120 20 40 60 80 100 120 140 160Bubblr Radius, µmNumber per cm3ABS 30% max airPhoto 30% max airABS 60% max airPhoto 60% max airSensitivity of the bubble size distribution measurements to the amount of injected airMain CharacteristicsMain CharacteristicsMain CharacteristicsMain CharacteristicsMain CharacteristicsData Acquisition 5 MS/s. , 10 MS/s.Transducers used :Size range 1cm 10 cmFrequency range 2 khz 300 khzTypical Bubble sizes 2µm 500 µmNote that the software and the principle of operation are not dependenton the ranges of instrument operation, which are controlled by the dataacquisition card and the hydrophones used. These can be upgradedwithout needing to modify the basic bubble size determination software.Total Void fraction of 2x10-3Comparison of the bubble density distribution between high speed video measurementsand ABS Acoustic Bubble Spectrometer®©VVVVValidationalidationalidationalidationalidationThe bubble distributions obtained from the ABS Acoustic BubbleSpectrometer® have been validated by comparison with microphotog-raphy. Bubble populations were generated using electrolysis and airinjection through porous tubes. The bubble population obtained usingthe ABS compared very favorably with the results of the micropho-tography.Air Injection Air/Water Mixing Tank Pump ABS Test SectionTransducers Bubbly Flow Bubble Size Distribution Display Microporous Tube Water Shear ABS Acoustic Bubble Spectrometer®©Generation IIGeneration II ABS Acoustic Bubble Spectrometer®© exploits new aquisition cards and PC hardwaredevelopments and significantly improves the ABS performance. It is built on a Windows XP basedPC (either a desktop or a laptop) with high-speed cards for signal generation and data acquisition. Itnow boasts a data acquisition speed up to 10 MS/s for each channel, provides stable signal outputover a wide frequency range, and is being developed to support more than one set of hydrophonesto improve bubble size measurement range.Base System Includes the following:• High-speed data aqusition card for signal generation and data acquisition (data samplingrate 5 MS/s per channel).• A desktop computer, cables and adapters.• First year support and upgrades of the D proprietary ABS Software to drive thetransducers/hydrophones, and to analyze the data.• Two 1/2in square transducers with 15 ft. cablesUpgrades for the system are as follows:• Laptop PC• Higher Data acquisition speed - 10 MS/s per channel• Different size transducers• Amplifier• Multi-set hydrophones supportYNAFLOWTotal Void fraction of 2x10Comparison of the bubble density distributionbetween high speed video measurements andABS Acoustic Bubble Spectrometer®©-3Generation II SpecsBase SystemUpgrade??Desktop Pentium IV (CPU Only), Windows XP5 MHz Data Acquisition Card?????1/2 inch Transducers (2)First Year Software Support and Upgrades10 MHz Data Acquisition CardNotebook PC w/Extension unit for PCI64 Bit Dual Core ProcessorD , IYNAFLOW NC.10621-J Iron Bridge Road, Jessup, MD 20794-9381 USAPhone: (301) 604-3688, Fax: (301) 604-3689E-mail: info@dynaflow-inc.com URL: http://www.dynaflow-inc.comRequirements Generation II Generation IGeneration IIAdvantagesSampling rate5 MS/s or 10 MS/s foreach channelUp to 2.2 MS/s sharedby two channelsMore accurate resultsespecially for highfrequency signalsResolution 12-bit 12-bit N/ASignal Generation-Voltage output20V peak-peak. Almostconstant voltage outputover the frequency range16V peak-peak, voltageoutput decreases withfrequencyBetter and almostconstant signal outputSignal Generation-Frequency limitCapable of emitting andreceiving signals up to450 kHzCapable of emitting andreceiving signals up to200 kHzHigher frequency signalsEnable detection ofsmaller bubblesRequirements Generation II Generation IGeneration IIAdvantagesComputerAny computer with onespare PCI slotsComputer must have 2spare ISA and 1 sparePCI slotsCan use virtually anyComputerOperating SystemWindows NT/XPcompatibleWindows NTCompatible with updatedWindows XPPortable SystemAny laptop computerwith a PCMCIA slotSpecial order lunch boxPC is requiredPortable system can usevirtually any laptopSide by Side Comparison of the Generation I and Generation II systemsDYNAFLOW, INC.10621-J Iron Bridge RoadJessup, MD 20794TEL: (301) 604-3688FAX: (301) 604-3689E-mail: info@dynaflow-inc.comURL: http://www.dynaflow-inc.comDYNAFLOW’s capabilities include :CavitationMultiphase FlowsAcousticsFlow VisualizationUnderwater ExplosionsComputational Fluid DynamicsSoftware DevelopmentWater Jet TechnologyComputed TomographyFluid-Structure InteractionLiquid & Air FiltrationMaterials ErosionOxidationDYNAFLOW, INC.