Volume 126, Issue 5, November 2009
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
126(2009); http://dx.doi.org/10.1121/1.3183413View Description Hide Description
With a complete accounting of hydrodynamic forces on the translational-radial dynamics of a moving single-bubble sonoluminescence, temporal evolution of the bubble trajectory is investigated. In this paper, by using quasi-adiabatic evolution for the bubble interior, the bubble peak temperature at the bubble collapse is calculated. The peak temperature changes because of the bubble translational motion. The numerical results indicate that the strength of the bubble collapse is affected by its translational movement. At the bubble collapse, translational movement of the bubble is accelerated because of the increase in the added mass force on the bubble. It is shown that the magnitude of the added mass force rises by the increase in the amplitude of the driving pressure. Consequently, the increase in added mass force results in the longer trajectory path and duration.
126(2009); http://dx.doi.org/10.1121/1.3238156View Description Hide Description
An inverted pulse tube in which gravity-driven convection is suppressed by acoustic oscillations is analogous to an inverted pendulum that is stabilized by high-frequency vibration of its pivot point. Gravity acts on the gas density gradient arising from the end-to-end temperature gradient in the pulse tube, exerting a force proportional to that density gradient, tending to cause convection when the pulse tube is inverted. Meanwhile, a nonlinear effect exerts an opposing force proportional to the square of any part of the density gradient that is not parallel to the oscillation direction. Experiments show that convection is suppressed when the pulse-tube convection number is greater than 1 in slender tubes, where is the radian frequency of the oscillations, is their amplitude, is the end-to-end temperature difference, is the average absolute temperature, is the acceleration of gravity, is the length of the pulse tube and is its diameter, is about 1.5, and the tip angle ranges from 90° for a horizontal tube to 180° for an inverted tube. Theory suggests that the temperature dependence should be instead of .