Dynamic and morphological analysis of oceanic vortex streets in the Yellow Sea using SDGSAT-1 imagery

The oceanic Kármán vortex street is a significant fluid dynamics phenomenon resulting from the unsteady separation of the boundary layer behind a bluff body. In this study, multispectral images from the Sustainable Development Goals Science Satellite 1 (SDGSAT-1) were utilized to observe oceanic vortex streets in the Yellow Sea from 2021 to 2024. A statistical analysis of 114 vortex streets was conducted from both dynamic and morphological perspectives. The relationship between vortex streets and ocean currents was explored from multiple perspectives, including single-factor statistical analysis, multi-factor statistical analysis, and case studies. Experimental results indicate that the formation of vortex streets in the Yellow Sea is primarily driven by interactions between tidal currents and islands. Furthermore, the spatiotemporal distribution and characteristic parameters of oceanic vortex streets were analysed using time-series SDGSAT-1 data. The observation frequency of oceanic vortex streets follows a general pattern of higher frequency in winter and lower frequency in summer, with most characteristic parameters being stronger in winter and weaker in summer. The seasonal characteristics of tidal currents have a significant impact on the vortex street characteristics. High-resolution satellite imagery reveals that the average aspect ratio of vortex streets is 2.75 and the Reynolds number is 403.56 in winter, compared to 1.92 and 185.86, respectively, in summer. This research presents the first temporal observations and systematic analysis of oceanic vortex streets across an entire marine area, offering practical significance for advancing and implementing multiple targets under SDG 14.