1. Invited Lecture at the Spring Meeting of Korean Society of Mechanical Engineers (KSME); April 24-25, 1998, Jinju (Kyung Sang University), Korea.
Bubble, bubble, toil and trouble:
Sonoluminescence Phenomena and Star Formation
The phenomenon og light emission from a oscillating gas bubble trapped in ultrasound field in water, SL, was discussed with spherical symmetry. Also the stability, spherical oscillation and gravitational collapse of Newtonian stars were stars were studied hydrodynamically.
2. Invited Lecture at the Research Workshop on Nucleation Theory and Applications; April 12-20, 1999,Dubna,Russia.
Cluster Models in the Theory of Bubble Formation and Related Problems
Using a new surface energy for the formation of the critical cluster, models for the gas bubble formation in gas-liquid solutions and for the vapor bubble formation within a liquid under tension are presented in this paper. The energy related to translational motion of molecule, which is lost during the dissolution process is considered as the surface energy needed for the gas bubble formation in solutions. Results from the model show good agreement with experiments for various gases dissolved in water solutions. On the other hand, the surface energy needed for the bubble formation is calculated from theLondon dispersion force between molecules. Also the vapor bubble formation model gives a very good prediction of tensile strength of simple liquids as well as the superheat limit of liquids. In another test of the vapor bubble formation model, the complete evaporation time of a butane droplet at its superheat limit is compared with experiments and found to be in good agreement. Transition from a critical cluster to a critical bubble where surface formation is needed in process is also discussed.
3. Plenary Speakers at the Fourth JSME-KSME Thermal Engineering Conference; Oct. 1-6, 2000,Kobe,Japan.
Bubble Dynamics/Sonoluminescence/Newtonian Stars
The sonoluminescence phenomenon which is the light emission associated with the catastrophic collapse of a gas bubble oscillating under ultrasound may be understood by the analytical solutions for the Navier-Stokes equations in spherical symmetry. Further the homologous solutions of the Euler equation with Newtonian gravity yield many fruitful results such as stellar stability, spherical oscillation and collapse of Newtonian stars. All these results came from an effort to understand the dynamics of a thin shelled sphere of gas, a tiny bubble.
4. Keynote Lecture at the Twelfth International Heat Transfer Conference, August 18-23, 2003,Grenoble,France.
Bubble Nucleation; A Microscopic Phenomenon
In this article, vaporous bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed based on clustering process of molecules (molecular cluster model for bubble nucleation). A puzzling phenomenon of carbon monoxide gas bubble formation in Fe-C-O melts was also discussed by the cluster model based on the interaction between solute gas and solvent molecules. For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due toLondon dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on micro heaters were also presented as one of the homogenous nucleation process with the molecular cluster model.