Takeo Takashima

Vapor film collapse around hot liquid drops when an external pressure wave is supplied

An external pressure wave generated by a magnetic hammer is applied to a single or multiple hot LiNO 3 drops which have been in stable film boiling in subcooled ethanol. The process of vapor film collapse triggered by the pressure wave is studied by photographic observations and pressure history measurements. The vapor film begins to destabilize about 0.1 ms after pressure wave arrival at the drop. About 1.0 to 1.5 ms later, the vapor film begins to collapse from the lower part. Collapse of the vapor film develops from a portion around the drop preceded by a complex destabilization process. The ripple waves generated from a portion in the initial stage are concluded to be due to a Rayleigh-Taylor instability. Generation of interface disturbance and that of tiny bubbles as well as that of hot liquid fragments are observed, though no penetration of cold liquid jets can be observed in these experimental conditions

Process of Vapor Film Collapse around Hot Liquid Drops Induced by an External Pressure Wave.

An external pressure wave generated by a magnetic hammer is applied as an explosion trigger to a single or multiple hot LiNO3 drops which have been in stable film boiling in subcooled ethanol and the process of vapor film collapse is studied by photographic observation and pressure history measurement. The vapor film begins to destabilize within about 0.1ms after the pressure wave arrival to the drop position. At about 1.0-1.5ms later, the vapor film begins to collapse from the lower part. The vapor film initiates to collapse at a portion around the drop after a complex destabilization process. The ripple waves generated near the central part of the drop at the initial stage are supposed to be due to the Rayleigh-Taylor instability because of the wave length. Generation of interface disturbance and that of tiny bubbles or hot liquid fragments are observed, though no penatration of cold liquid jets can not be observed in this experimental condition.