<p>In calculating pile–soil interactions, traditional methods treat fluid flow as an independent external load applied statically or quasi-statically to the structure via empirical or semi-empirical formulas (such as the Morison equation), while simplifying the foundation into a linear spring or fixed end. This approach overlooks real-time interactions between physical fields. This closed-loop feedback cycle—“structure motion → altered flow field → load update → structural response”—can trigger resonance or dynamic amplification under extreme conditions, phenomena that decoupling methods fail to capture. This study treats fluid, structure, and geotechnical components as a tightly interconnected dynamic system, aiming to establish mathematical models capable of describing their multiphysics coupling. Then, study about scour hole effect on offshore wind turbine pile foundations was carried out. It systematically analyzes the dynamic response of pile foundations within a scour hole depth range of 0<i>D</i> to 2<i>D</i> (<i>D</i> is the diameter of the pile). Results indicate that scour depth significantly alters the flow field characteristics and pile loading. When <i>S</i>_d &gt; 0.8<i>D</i>, resistance and lift fluctuations intensify, and vortex structures tend to fragment. Considering pile–soil coupling increases the pile drag force and reduces the vortex shedding frequency <i>St</i> by approximately 50%. Compared to traditional static methods, the two-way coupled simulation yields significantly higher pile displacement and stress responses, indicating that neglecting flow transient characteristics severely underestimates pile foundation dynamic risks. This research provides a theoretical basis for pile foundation safety assessment during scour disaster phases.&#xa0; </p>