Dynamic Evolution Mechanisms and Lateral Spreading Prediction of Coral Sand Particle Clouds in Still Water

Coral sands are critical in the construction of islands and harbors in tropical regions. Studying their dispersal, specifically the movement of ‘sedimentary clouds’ during marine dumping/dredging operations, is essential for optimizing construction efficiency and mitigating impacts on marine ecosystems. This study investigates the evolutionary characteristics of coral sand particles in still water via controlled indoor experiments. By manipulating parameters such as particle size, mass, nozzle diameter, and air release height, this study evaluated the impact of aspect ratio, Stokes number, and initial particle momentum on the movement of coral sand clouds. The results indicate that variations in air release height modulated the cloud’s width and corresponding diffusion angle, but exerted a negligible impact on the cloud front’s velocity and position. Empirical formulas for traditional quartz sand have limitations in reflecting the complex hydrodynamic settling behavior of coral sand. To address this, this paper establishes a modified empirical equation. This equation effectively predicts the width of coral sand plumes across different air release heights and Stokes number ranges. Furthermore, rather than directly quantifying microscopic morphological features, this study interprets these macroscopic transport characteristics from a process-based hydrodynamic perspective. Ultimately, the resulting predictive data and empirical framework provide a practical reference for evaluating sediment dispersion in reef engineering projects.