LAUSR

Abstract The issue of bubble sweep-down is of great importance within the field of marine research, as the phenomenon greatly affects the measurement accuracy of research vessels. To explore the characteristics of bubble sweep-down, an experimental study into this phenomenon in relation to research vessels was carried out. With the help of particle image velocimetry technology, the microbubble trajectory on the X-Y and X-Z planes was obtained by observing bubble sweep-down. It was found that the evolution trajectory of the X-Z plane had an approximately linear distribution in the experimental measurement range. By comparing the microbubble trajectory with the bow streamline obtained by the tuft method, it was found that the distribution of the streamline in the bow cannot be regarded as the trajectory of the microbubble, but the influence of bubble buoyancy and the tension of the water should be considered. Through further analysis, it was found that the thickness and width of the microbubble cloud cluster change greatly when the cluster is close to the bottom of the ship, and the change of the microbubble cloud cluster under high-speed conditions is much larger than that under low-speed conditions because is easier for the microbubble cloud to diverge and deform at high speed. The change in the microbubble cloud area under high-speed condition was lower than that under low-speed conditions, which was probably caused by the extrusion effect of flow fields around the bow on microbubble cloud clusters at high speed.