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About DYNAFLOW

DYNAFLOW, INC.® provides leading edge research and development services and products in fluid dynamics and material sciences. As a leader in the fields of multiphase flows, bubble dynamics, cavitation, fluid structure interactions and erosion dynamics, DYNAFLOW, offers services and products for the naval and marine, automotive, energy, chemical, environmental, healthcare and food and agriculture industries. DYNAFLOW pursues an interdisciplinary approach to problems and have strategic collaborations with federal agencies, commercial enterprises, and universities.

DYNAFLOW, INC.® provides leading edge research and development services and products in fluid dynamics and material sciences. As a leader in the fields of multiphase flows, bubble dynamics, cavitation, fluid structure interactions and erosion dynamics, DYNAFLOW, offers services and products for the naval and marine, automotive, energy, chemical, environmental, healthcare and food and agriculture industries. DYNAFLOW pursues an interdisciplinary approach to problems and have strategic collaborations with federal agencies, commercial enterprises, and universities.

Principle :

The device extracts the bubble population from acoustical measurements made at several frequencies. It consists of a set of two transducers/hydrophones connected to a computer. A data acquisition board controls the hydrophones' signal generation and acquisition. The PC is also used for analysis of the data and provides, using Dynaflows software, the sound speed and attenuation as a function of frequency.

The bubble population can be obtained from these measurements by a solution of two Fredholm Integral Equations of the first kind. These equations are ill-posed and are a challenge to solve - especially when the data has noise. In our research, we developed novel algorithms that are able to accurately solve these equations using a constrained optimization technique.

The instrument can provide the data in near real time, thus making it suitable for process applications. The bubble distributions from the ABS Acoustic Bubble Spectrometer®© have been validated by comparison with micro-photography.

 

Advantages:

Compared to optics based devices, ABS Acoustic Bubble Spectrometer ®© is easy to use. In addition, the acoustic technique is very sensitive to bubbles and is not fooled by the presence of particulate matter which are not readily distinguishable from optics.

Applications:

The device can be used in a wide variety of two-phase flow applications where knowledge of the bubble size distribution and the volume fraction and/or area of contact between the gas and the liquid is important. Major areas of application are in oceanography, controlled laboratory testing, and industrial flows. Possibilities for further application are in the field of bio-medical instrumentation.

Aeration:

Bubble counting has potential uses in monitoring aeration in areas such as sewage treatment. Another potential use is in the area of fish farming, where fish species can be categorized by the size of their swim bladders. Use of the present acoustic techniques would permit measurement of the numbers and size of fish in a given volume.

Oceanography:

Gas bubbles are generated in large numbers in the upper ocean layers, and have a significant effect on ocean acoustic properties. Bubbles strongly modify the sound speed and make the ocean acoustically dispersive. The modeling of the ambient sound-spectrum in the ocean requires the bubble size distribution as input. Knowledge of the amount and location of gas exchange is also required in ocean-atmospheric studies including the carbon-cycle, study of the balance of greenhouse-gases, the oxygenation of oceans and its role in the food-chain, etc.

Cavitation and Multiphase Flow:

Micro-bubbles act as nuclei for cavitation inception. Cavitation is a process in which cavities grow and implode violently in a liquid, occur in flows following a pressure drop, or in the presence of an acoustic field. Cavitation has a strong erosive effect on nearby boundaries such as valves, gates, pumps, propellers and fluid-machinery, and is a significant noise source. Knowledge of the sizes of bubbles in a medium along with knowledge of the flow/sound-field can be used to predict the likelihood of cavitation and provide important information for improving design. Naval architects now require information on bubble population under field conditions for the design of propellers so that conditions in the field can be related properly to conditions in the laboratory. Cavitation tunnels as well as turbine and power plant equipment users, which perform measurement of void-fraction/bubble population to determine optimal and safe operating conditions, should thus find use for the device.

 


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