Experimental study on the transport characteristics of bubbles at the bow of research vessels

Bubble sweep-down represents a critical phenomenon adversely affecting the performance of acoustic equipment on research vessels. To investigate the transport characteristics of bow-entrained bubbles under the hull wake effect, we conducted model tests with a scale ratio of 1:40 in a towing tank. A micro-nano bubble generator was employed to produce an air-water mixture simulating bubble clouds. The motion trajectories of bubbles across multiple cross-sections were captured using high-speed photography combined with fluorescent tracer techniques. Through a self-developed image processing method, we systematically analyzed the morphological features and motion patterns of the bubble clouds. Results indicate that the width, height, and area of bubble clouds gradually increase along the flow direction, with their evolution significantly influenced by the vessel speed. At higher speeds, bubble clouds are more prone to sweep-down toward the vessel bottom and exhibit more pronounced shape variations. While the vertical motion of bubbles generally aligns with the flow streamlines, notable discrepancies are observed in the spanwise direction, reflecting the complex interaction between bubble dynamics and turbulent structures. This study provides experimental insights for optimizing the layout of acoustic equipment and developing effective strategies to mitigate bubble interference.