Abstract: The relative contribution of jet and film drops from bursting bubbles to the sea-salt component of the marine aerosol is poorly understood. An analysis of the bubble and aerosol spectra produced by a laboratory model of a breaking wave or whitecap shows that film drops may play a much more important role than previously accorded. The model strongly suggests that most of the droplets smaller than 5–10 μm in diameter originate as film drops, derived from bubbles larger than 1 mm. The water-to-air flux of such droplets is adequate to account for the majority of maritime cloud condensation nuclei. The model also suggests that droplets larger than 20–25 μm originate as jet drops, derived from bubbles smaller than 1 mm. The model breaking wave produces an upwelling plume of bubbles whose concentration for all bubble sizes vastly exceeds the steady state or background bubble population observed at sea at depths greater than 1 m. Bubbles of up to 10 mm diameter were produced, and the bubble flux reached 200 cm−2 s−1. Whitecap bubble spectra, presently unavailable, are therefore essential in making more accurate assessments of marine aerosol production.

Abstract: This monograph is a highly technical analysis of the interaction of two phases in controlled experiments. By using a perforated plate and stirred tank, Dr Azbel has conducted experiments involving flow, mass bubbling, mass transfer during bubbling and in a liquid-solid system and the calculation of bubbling reactors for the two-phase oxidation reaction. The last chapter investigates the design of a reactor for microbiological processes. The behaviour of bubbles is a unifying theme of this book. From an explanation of the fundamentals of bubbles formation at a single orifice, Dr Azbel goes on to set up equations for bubble motion, bubble size, bubble-size distribution and pressure drop across a perforated plate. His treatment of bubbles is expanded in later chapters to include mass transfer in the dispersion of solid particles in a liquid and mass transfer accompanied by chemical reactions in a bubble dispersion system.

Abstract: We have considered the methods available for distinguishing between the rate-controlling mechanisms for gas bubble migration in metals at temperatures below 0.6 T m . We show that several combinations of mechanism, gas behaviour and rate-controlling process give rise to similar power laws describing the rate of growth of populations of bubbles by migration and coalescence. We have therefore extended the model developed by Gruber (1967) to take account of the condition of constant gas pressure in the bubbles, which is likely to obtain at low temperatures in the absence of continuous irradiation damage, and the additional possibility that the nucleation of a surface ledge can control the migration rate of faceted bubbles. The experimental growth rates of helium bubbles, which we have measured in niobium, niobium-zirconium alloys and vanadium, are shown to be consistent with bubble migration by a surface diffusion mechanism controlled by the surface diffusion coefficient for small bubbles but by ledge nucleation for larger bubbles. The bubble size above which the (slow) ledge nucleation process controls growth is sensitively affected by the ledge energy. We show that the addition of zirconium to niobium can alter the ledge energy by an order of magnitude by cleansing the bubble faces of oxygen. Subsequent segregation of Zr-O complexes to the bubbles further alters the ledge energy. The bubble growth rate, and hence the swelling and embrittlement behaviour of the material under these conditions, is therefore very sensitive to the material purity and to segregation effects either induced thermally or accelerated by transmutation and irradiation damage. We find that the ledge energy on the (100) face of pure niobium is ca . 11 x 10 -11 J/m, which is decreased to ca . 4 x 10 -11 J/m by the segregation of Zr-O to the surfaces. The ledge energy at a similar surface in niobium containing 400/10 6 oxygen is as low as 1.2 x 10 -11 J/m. In vanadium we find a ledge energy of 3.4 x 10 -11 J/m. These ledge energies result in the effective cessation of bubble growth at bubble sizes in the range 2-20 nm.

Abstract: We have derived an approximate expression for the threshold pressure for transient acoustic cavitation and have used this result with published expressions for the thresholds for gas bubble nucleation and for rectified diffusion in synthesizing cavitation prediction charts for water covering a frequency range from 10 kHz to 2.5 MHz, and for gas saturation percentages 10%, 50%, and 100%. This synthesis, which is applicable to other liquids, may provide guidance about the phenomena associated with acoustic cavitation to those who are either trying to minimize or to optimize its effects.

Abstract: A liquid droplet is formed by producing and eliminating a bubble in a liquid in such a way that the liquid flow in the liquid conduit is not intercepted even when the bubble reaches the maximum volume.

Abstract: The performance of a new type of bubble generating device, the rubber sheet sparger, is contrasted and compared with rigid spargers. Impulse response tests were analyzed using the weighted‐moments method to determine voidage and dispersion coefficients in counter‐current bubble columns of nominal diameters two, four, six and twelve inches. The flexible rubber sheet sparger produced more uniform emulsions, smaller bubbles and larger voidages than perforated plates, while dispersion coefficients were reduced for a range of superficial gas velocities. The dispersion data seem to fit the isotropic turbulence model, with slight modifications. It is demonstrated that the rubber sheet sparger is self‐regulating, with hole size increasing in direct proportion to pressure drop across the sparger.

Abstract: A theoretical and experimental study is carried out for the problem of the wall effect experienced by a fluid body moving with a constant speed along the axis of a vertical circular tube filled with a highly viscous liquid. In the theoretical study the body is limited to being either spherical or cylindrical and an optimization process with least squares is used to write the no-slip condition on the tube wall. Comparisons between the hydrodynamic and kinematic behaviour of a rigid, liquid and gaseous body are established. Furthermore, from an experimental investigation, based upon a fine visualization technique and rising-speed measurements, the respective limits of validity of the calculations have been found in the case of an air bubble. Information concerned especially with the shape of this bubble, and the hydrodynamic field that it generates, is given for the whole domain of the bubble and tube diameter ratio ranging from no wall influence to maximum wall influence.

Abstract: The influence of a plane solid or fluid surface on the thermocapillary migration of a gas bubble moving normal to it in a space laboratory is investigated in the quasi-static limit. Results are presented for a suitably defined “interaction” parameter Ω as a function of the scaled distance of the bubble from the plane surface, and compared with similar predictions for buoyant migration.

Abstract: The behaviour of silica sand particles with mean sizes 0.3, 0.45 and 0.6 mm fluidised by air under pressures from 0.1 to 0.8 MPa was observed in a transparent two-dimensional bed. Minimum fluidisation velocity, bed expansion and bed height fluctuation were measured by the usual methods, bubble characteristics such as the size, rising velocity and frequency by cine-photography. The minimum fluidisation velocity decreased with pressure, explainable by considering the increase of the turbulent flow contribution to bed pressure drop, and fairly well described by the Wen and Yu correlation. No virtual effect of pressure on bubble size was observed but bubble shape became flattened, which in turn accompanied a decrease in the bubble rise velocity. Based on these results, the increased bed expansion and the unchanged bed fluctuation could be consistently explained.

Abstract: A process and apparatus are disclosed for forming blown film of a low strain hardening polymer, such as a low pressure polymerized-low density ethylene copolymer, including an improved film bubble cooling technique which permits high production rates to be achieved with good film bubble stability. The disclosed process comprises cooling a molten film bubble by contacting the outside of the film bubble with separate annular streams of cooling fluid fed through at least two stacked annular cooling rings disposed around the film bubble, wherein all or substantially all of the cooling fluid exits the system through a common plane formed by the last cooling ring. The disclosed apparatus comprises means for forming a molten film bubble and means for cooling same including at least two separate annular cooling rings disposed around the bubble, each provided with means for feeding an annular cooling fluid stream against the bubble and further including means whereby all or substantially all of said cooling fluid exits the system through a common plane formed by the last cooling ring.

Abstract: Entrainment of solid particles (Glass beads, dp=300-600 μm, Umf=14 cm/s) from a gassolid fluidized bed was studied experimentally by following the rise of bubbles and measuring the velocity of particles leaving the bed surface. Photographs of the freeboard were taken continually to follow the particle movement in it. Based on analysis of these data, it was found that the particles in the wake for an isolated bubble scarcely contributed to entrainment but that bubble coalescence near the bed surface was the key factor in entrainment. Bubble bursting behavior was classified into four patterns:(I) Isolated bubble(II) Successively rising bubbles(III) Coalescent bubble(IV) Successively coalescent bubbles For the first two groups, the particle velocity leaving the bed surface was usually less than the bubble rising velocity and for the latter two, it exceeded the bubble rising velocity.

Abstract: Measurements of anisotropy in implanted bubble films indicate that in addition to straining the lattice, implantation also has the effect of suppressing the growth‐induced anisotropy. After annealing at 1000 °C, most of the as‐grown anisotropy is restored, which points to oxygen defects as the most likely mechanism for the effect. The Curie temperature has been found to be lowered by as much as 70 °C by implantation at a typical device dose, and the anisotropy of the implanted layer varies quite rapidly with temperature at elevated temperatures. The results indicate that with proper choice of material parameters and implantation conditions safisfactory bubble propagation can be obtained in high density small bubble diameter devices based on ion‐implanted propagation patterns over a wide temperature range.

Abstract: Drift lines produced after a single bubble passage were measured in a 0.19 m i.d. three-dimensional gas-fluidised bed of 0.163 mm glass beads which contains tiny but recognizable aggregates of jetsam particles or bulk particle tracers. Lateral distributions of the descending distance of jetsam relative to the bulk particles were obtained from the difference between the jetsam and the bulk drift lines, and were then reduced to the average descending distance over the bubble cross-sectional area. The segregation rate constants were calculated for four kinds of jetsam, fairly larger or denser than the bulk particles, and were applied to the estimation of jetsam concentration profiles based on an existing mathematical model. The results of comparison of the estimated concentration profiles with those observed by other investigators were quite satisfactory, indicating that the experimental results here obtained are reliable.

Abstract: The hydrogen attack of steel involves the formation of methane bubbles along the grain boundaries and their subsequent link-up to form fissures. This paper presents a detailed model for the kinetics of growth of such methane bubbles. The model considers two parallel processes which can control the growth—one involving the bubble growth by direct power-law creep and the other involving combinations of surface diffusion, grain boundary diffusion and matrix accommodation processes. The proposed model is more general and complete than the earlier ones and considers for the first time the possibility of bubble growth being controlled by surface diffusion and accommodation processes. The predictions of the model are shown to compare well with the experimental results obtained in our lab and with the literature data. The model also indicates the relative importance of lower carbon activity and increased creep stength of steel to its hydrogen attack resistance.

Abstract: One of the most persistent obstacles in the study of oxygen mass transfer in bubble columns is the technical difficulty of using large liquid and gas flow rates economically. This experimental limitation is reflected in the present, very incomplete, understanding of the mass transfer characteristics of these two-phase systems. In this work, a new experimental technique has been developed and used. The use of computer-calculated concentration contour diagrams permitted a detailed study of the mass transfer characteristics of the zone near the distributor. No similar study has been reported in the literature until now. The ability of the axial dispersion and two-zone models to describe the experimental data is analyzed. Finally, liquid side volumetric mass transfer coefficients have been calculated for both models. The results indicate that KLa increases, often linearly, with the superficial gas velocity. Furthermore, for the liquid-phase range [0, 10] cm/s, KLa had a minimum at Vl ∼ 7.5 cm/s. For larger liquid superficial velocities, an increase in KLa was found. These observations were valid for the axial dispersion (ADM), plug flow (PFM) and two-zone (T-ZM) models.

Abstract: Finite difference solutions of the mass transport equations governing the dissolution (growth) of a rising gas bubble, containing a single gas, in a glassmelt were obtained. These solutions were compared with those obtained from an approximate procedure for a range of the controlling parameters. Applications were made to describe various aspects of O2 and CO2 gas-bubble behavior in a soda-lime-silicate melt.