Enhanced Analytical Modeling of Lazy Wave Risers: Addressing Boundary-Layer Effects for Improved Configuration and Force Predictions

To address the challenge of boundary-layer effects in flexible lazy wave risers (LWRs) design, an improved model for analyzing the configuration and forces of LWRs is proposed. The boundary-layer effects are introduced by modifying the characterization functions of the vertical component force dV/ds in key segments. Firstly, an analytical model of the LWR, considering the boundary-layer effect is established, which requires multiple prior inclinations to achieve configurations and force calculations. Secondly, based on this analytical model, an improved model for LWRs is established. The riser configuration characteristics are classified into two forms under different hang-off angles, and the change rule of the boundary-layer effect is summarized. Then, riser segments are redivided, complex items in expressions are simplified and merged, and improved functions of dV/ ds are provided. Boundary conditions and solution methods are also given. Finally, to verify the accuracy and applicability of the proposed method, it is compared with the finite element method and the catenary method (without boundary-layer effect). Results show that the proposed model significantly reduces relative error (RE), root mean square error (RMSE), and mean absolute percentage error (MAPE) compared to the traditional catenary method. The improved model provides a more precise representation of the riser configuration and forces, making it a valuable tool for designing and optimizing LWR systems.