Acoustic behavior of large encapsulated gas bubbles with resonance frequencies in the 50–100 Hz range.

2010 ◽  
Vol 127 (3) ◽  
pp. 2015-2015
Author(s):  
Mark S. Wochner ◽  
Kevin T. Hinojosa ◽  
Kevin M. Lee ◽  
Theodore F. Argo ◽  
Preston S. Wilson ◽  
...  
Keyword(s):  
Gas Bubbles ◽  
Acoustic Behavior ◽  
Resonance Frequencies

Acoustic behavior of large encapsulated gas bubbles with resonance frequencies in the 50 to 100 Hz range

2010 ◽  
Author(s):  
Mark S. Wochner ◽  
Kevin T. Hinojosa ◽  
Kevin Lee ◽  
Theodore F. Argo IV ◽  
Preston S. Wilson ◽  
...  
Keyword(s):  
Gas Bubbles ◽  
Acoustic Behavior ◽  
Resonance Frequencies

Sound propagation in water containing large tethered spherical encapsulated gas bubbles with resonance frequencies in the 50 Hz to 100 Hz range

2011 ◽  
Vol 130 (5) ◽  
pp. 3325-3332 ◽  
Author(s):  
Kevin M. Lee ◽  
Kevin T. Hinojosa ◽  
Mark S. Wochner ◽  
Theodore F. Argo ◽  
Preston S. Wilson ◽  
...  
Keyword(s):  
Sound Propagation ◽  
Gas Bubbles ◽  
Resonance Frequencies

Impedance Tuning of a Premixed Combustor Using Active Control

2007 ◽  
Author(s):  
Mirko R. Bothien ◽  
Jonas P. Moeck ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Combustion Chamber ◽  
Active Control ◽  
Combustion Process ◽  
Reacting Flow ◽  
Acoustic Behavior ◽  
Acoustic Boundary Conditions ◽  
Early Design ◽  
Resonance Frequencies ◽  
Arbitrary Frequency

In early design phases new burner concepts are mostly tested in single or multi burner test rigs. These test rigs generally exhibit a different acoustic behavior than the full scale engine. The acoustic behavior, however, is crucial to predict whether thermoacoustic instabilities are likely to occur. Tuning the test rig’s acoustic boundary conditions to that of the engine could overcome this issue. Through this, an effective assessment of new burners is possible even in early design phases. In this work a method is proposed, which uses an active control scheme to manipulate the acoustic boundary conditions. It is applied to an atmospheric combustor test rig with a swirl-stabilized burner. In a first step it is shown that the acoustic boundary conditions can be controlled in the cold flow case. Almost arbitrary frequency dependent impedances can be prescribed ranging from fully reflecting (both pressure and velocity node) to anechoic. In particular, an additional virtual length can be added to the combustor outlet by manipulation of the reflection coefficient’s phase. This introduces resonance frequencies different from those of the uncontrolled case. In a second step the impedance tuning concept is applied to the reacting flow. It is demonstrated that the concept is feasible despite the harsh environmental conditions in a combustion chamber. The effect of different levels of reflection at the combustion chamber outlet on the combustion process is investigated. In addition to that, a study of the influence of the simulated combustor length on the system’s resonance frequencies is conducted.

Microstreaming generated by two acoustically induced gas bubbles

2016 ◽  
Vol 796 ◽  
pp. 318-339 ◽  
Author(s):  
Alexander A. Doinikov ◽  
Ayache Bouakaz
Keyword(s):  
Numerical Simulations ◽  
Acoustic Field ◽  
Considerable Increase ◽  
Gas Bubbles ◽  
Stress Fields ◽  
Resonance Frequencies ◽  
Bubble Sizes

A theory is developed that describes microstreaming generated by two interacting gas bubbles in an acoustic field. The theory is used in numerical simulations to compare the characteristics of acoustic microstreaming at different frequencies, separation distances between the bubbles and bubble sizes. It is shown that the interaction of the bubbles leads to a considerable increase in the intensity of the velocity and stress fields of acoustic microstreaming if the bubbles are driven near the resonance frequencies that they have in the presence of each other. Patterns of streamlines for different situations are presented.

Fission Gas Bubbles in Fractured UO2

1968 ◽  
Vol 26 ◽  
pp. 286-287
Author(s):  
O. M. Katz
Keyword(s):  
Electron Microscopy ◽  
Thermal Gradient ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Thermal Gradients ◽  
Fission Gas ◽  
Beam Heating ◽  
Limited Application ◽  
Bubble Characteristics ◽  
Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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