Multifactorial and multi-indicator optimization of submerged jet-induced sandpit morphology via two-stage orthogonal design and solid–liquid two-phase flow simulation

This study employs an orthogonal test design method, integrating numerical simulation with experimental validation, to investigate the multifactor coupling effects of jetting time (tj), truncation time (t0), Reynolds number (Re), and impact distance (H/D) on the morphology of sandspits formed by submerged jet impingement on a sand bed. The depth (dep) and width (wid) of the sandspit serve as quantitative indicators for analyzing each parameter's main effects and interactions. Simulation reliability is affirmed through grid independence verification and comparison with the experimental data, showing a maximum error under 5%. Results reveal that the sandspit morphology is primarily influenced by Re, followed by tj, H/D, and t0. Interactions among these factors are negligible. For maximizing dep, the optimal parameters are Re = 39920, tj = 1.0 s, H/D = 2, and t0 = 0 s, which results in a 4% increase in dep relative to the original scheme. To maximize wid, the ideal combination is Re = 39920, tj = 1.0 s, H/D = 10, and t0 = 0 s, which results in a 25% increase in wid. Comparing both optimal combinations indicates that prioritizing wid is preferable; this choice leads to a 25% rise in wid and a corresponding 23% boost in dep compared to the initial scheme. The results offer theoretical foundation as well as a parameter optimization framework aimed at enhancing the scouring of submarine pipelines and cables in the context of marine engineering.