This investigation is committed to resolving the challenges of Fluent’s accuracy in simulating cnoidal waves and the constraints of potential flow theory in real-world engineering contexts. By conducting secondary development on the Fluent platform, a numerical model grounded in viscous flow theory has been formulated. The study centers on the force analysis of small-scale structures subjected to varying wave parameters and, in alignment with practical engineering requirements, introduces a more refined numerical model and theoretical framework. This endeavor offers enhanced insights and solutions for the theoretical advancement and engineering application of hydrodynamic challenges. In the realm of nearshore and harbor engineering, wave characteristics undergo alterations due to the reduced water depth, leading to the emergence of shallow water waves. Nonlinear shallow water waves are conventionally characterized as cnoidal waves, which markedly diverge from Stokes waves. With the relentless progression of marine engineering, the demand for more precise nonlinear hydrodynamic analysis of marine structures has intensified. Accurately forecasting the wave forces exerted on small-scale members constitutes a pivotal concern in safety research. These issues are intricate, and the traditional potential flow theory falls short in delivering accurate analyses for such scenarios. Consequently, it is of paramount significance to investigate the wave action on small-scale members through the lens of viscous flow theory.