A SYSTEM OF ARTIFICIAL INITIATION OF THE BAG-BREAKUP FRAGMENTATION FOR INVESTIGATION OF THE SPRAY GENERATION PROCESSES DURING WIND-WAVE INTERACTION IN LABORATORY EXPERIMENTS

The paper presents an electronically controlled hydraulic system designed to induce a disturbance on the water surface for the artificial generation of bag-breakup type of spray formation phenomenon, which is the dominant mechanism of production of the sea aerosol. The system was used both in a test mode under conditions of a smooth water and for typical conditions of wavy surface under wind forcing on the Thermostratified Wind-Wave Tank (TSWiWaT) of the IAP RAS. For the last case a wave gauge was additionally included in the system to ensure the initiation of bag-breakups on the crests of waves, by analogy with conditions sporadically occurred. The system provided a high repeatability of the scales of the surface water elevation disturbance, which was a seed for the formation of a bag-breakup under the action of an airflow. High-speed video filming with the shadow imaging method demonstrated that it was possible to artificially reproduce all the main stages of this phenomenon, which are also observed for sporadically occurring ones: inflation of a thin membrane surrounded by a thicker rim, rupture of the membrane leading to the formation of small droplets, and fragmentation of the rim with the formation of large droplets. Special processing of the images allowed us to estimate typical lifetimes and sizes of membrane for artificial bag-breakup events which turned out to be close to the same parameters for sporadically occurring ones.