Behavior Of Air Bubbles Research Articles

The response of microscopic bubbles to sudden changes in the ambient pressure

This paper focuses on the résponse of bubbles to sudden changes in the ambient pressure. Trains of bubbles with radii varying between 45 and 200 μm were exposed to various pressure steps, and their response was monitored by pulsed laser holography. The experiments were performed in a specially constructed chamber, allowing generation of pressure steps ranging from 0.1 to 20 times the initial value. Air, CO2, helium and hydrogen bubbles were selected, providing a range of mass, thermal diffusivities, solubilities in water and isentropic constants. The changes in the bubbles’ diameters were determined by reconstructing the holograms, magnifying the images and measuring the sizes of individual bubbles. Most of the experiments were performed with pressure changes at the rate of 20 KPa/ms, and most data were recorded in less than 20 ms. The results confirm that, within the present range of test conditions, the bubbles can respond instantaneously to changes in the ambient pressure. The experiments also demonstrate that the response of the bubbles at the present timescales can be assumed to be isothermal (polytropic constant of 1.0), irrespective of the bubble content or size. Repeated measurements with different pressure waveforms, but with the same final pressure resulted in identical results, demonstrating that bubbles can be used as pressure sensors. Variations in timescales up to a few hundred milliseconds still resulted in the same response, confirming the isothermal assumption. The dissolved gas content had a noticeable effect on the behaviour of the CO2 bubbles, the most soluble of the gases tested, and had no detectable effect on the behaviour of air bubbles. The paper also includes a detailed error evaluation of the present experiments and an estimate of the expected error when the bubbles are utilized as pressure sensors.

A Study of the Behavior of a Uniaxially Oriented Polyethymene Tape/Oil Insulating System Subjected to Electrical and Thermal Stresses

The occurrence of discharges in an insulation system consisting of lapped uniaxially oriented polyethylene tapes impregnated with dodecylbenzene oil and the behavior of air bubbles injected into the structure have been investigated. This insulation system should be suitable for use in power transmission cables because the tape is generally compatible with the oil and has suitable mechanical properties for cable manufacture in a conventional cable taping machine. The behavior of bubbles in the systems was monitored with a transparent electrode and a video system. An electronic protection system was used to remove the applied voltage just before breakdown so that the damage done by discharges to the tape structure could be measured. The discharge inception voltage was found to decrease with increasing butt gap depth and with increasing temperature. Bubbles were found to divide repeatedly and eventually to disperse at stresses above discharge inception. The rate of dispersal increased with increasing applied stress and temperature. Examination of the damage done to tapes showed a high level of correlation between the total energy of discharges in the insulation structure and the total surface area of visible damage. Measurement of the total discharge energy appears to be a promising diagnostic tool.

Rising behavior of air bubbles in superposed liquid layers

AbstractAn air bubble that passes through a horizontal interface from a lower layer of Freon‐113 to an upper layer of aqueous glycerol forms a two‐phase bubble in the upper layer as a result of entrainment of a certain volume of Freon‐113 from the lower layer. The volume of entrained Freon‐113 and the rise velocity of such a two‐phase bubble have been measured. The former increases with an increase of the bubble size irrespective of the viscosity of the upper liquid. The latter is somewhat lower than that of a normal air bubble of the same size.

Smaller salt particles in oceanic air and bubble behavior in the sea

Observations of the number and size of the smaller salt particles in the air over Hawaiian and Alaskan seas are presented. Differences in the mean curves representing particle distribution at the two locations are related to differences in the behavior of air bubbles of various sizes near and on a sea water surface. The relationships found suggest that a break in the curves among particles of ∼10−13–10−14 grams marks a zone of transition from a bubble jet to a bubble film source of droplets and that the Alaskan waters are a relatively poor source of particles of <∼10−14 grams.

Behavior of Air Bubbles in Dilute Aqueous Solutions

Behavior of Air Bubbles in Dilute Aqueous Solutions