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This paper presents the results of detailed studies of the processes of droplet formation and its characteristics under conditions of artificially induction of a bag-breakup fragmentation event. A shadow imaging method was used in combination with the high-speed video filming of the side-view fragmentation process. Trajectories and ejection velocity characteristics of the formed droplets are determined by identifying particles in consecutive frames with combined use of Particle Imaging Velocimetry (PIV) and Particle Tracking Velocimetry (PTV). Based on the results of trajectory processing, the distributions of droplet velocities for the selected regions are obtained, and estimates of the ejection velocities at various heights are proposed. [ABSTRACT FROM AUTHOR]

This paper describes laboratory experiments (using a high-speed wind-wave flume) of the effects of water waves on heat and momentum exchange in the near-water atmospheric boundary layer at high wind speeds. Different from previous experiments of this type, the parameters of waves were controlled by a net stretched along the entire channel to effectively decrease the fetch. This helped to achieve dependency of the transfer coefficients on two independent parameters, namely, the wind speed and fetch (expressed via variations of the wavefield). Another key to the experiment was using a stable temperature stratification of the air flow, with the temperature of the air entering the flume 15-25° higher than the water. The experiments showed a sharp increase in the heat exchange coefficient at winds exceeding 33-35 m/s, similar to that observed earlier in the high-speed wind-wave flume of Kyoto University with conditions of unstable temperature stratification of the air flow. The joint analysis of the data obtained in the high-speed wind-wave flumes of IAP RAS and Kyoto University yields the universal dependency of the exchange coefficients and the temperature roughness on the peak wave number of surface wave spectra. This is independent of the type of temperature stratification of the atmospheric boundary layer, either stable or unstable. The sharp increase in the heat exchange coefficient is shown to be associated with increased whitecapping. [ABSTRACT FROM AUTHOR]

The processes of momentum and heat transfer between ocean and atmosphere in the boundary layer in case of foam present on the water surface were investigated within laboratory modeling for a wide range of wind speed and surface wave including hurricane conditions (U10 from 12 to 38 m/s). Experiments were carried out on the Hight Speed Wind-Wave Flume of the Large Thermostratified Tank of IAP RAS. A special underwater foam generator was used for continuous surface foam seeding. Theory of self-similarity of air flow parameters in the flume was used to calculate values aerodynamic and heat transfer coefficients from the velocity and temperature profiles measured by Pitot and hotwire gauges respectively. Simultaneous measurements of surface elevation with system of three wire wave gauges allow to obtain spectra and integral parameters of waves. Acknowledgments: The work was supported by RFBR grants (19-05-00249, 17-05-00703, 18-05-00265). Carrying out experiments themselves was supported by Russian Science Foundation (18-77-00074). [ABSTRACT FROM AUTHOR]