A Hybrid Coarse-Fine Mesh Generation Method for Hull Structures Based on Precise Geometric Models

Finite element analysis is essential for ship structural design because it enables accurate assessment of structural strength, fatigue, and vibration performance. However, mesh generation for large-scale hull structures remains challenging due to the trade-off between computational efficiency and local mesh resolution. This study proposes a semi-automatic hybrid coarse–fine mesh generation framework based on precise geometric models for local refinement. Users mark critical regions during geometric modeling; the framework then processes them automatically through a rule-driven strategy incorporating Common Structural Rules (CSR) requirements, while coarse meshes are retained in non-critical areas. A subdivision approach combining trisection with proportional and non-proportional transition patterns is developed to achieve smooth element-size variation between different mesh regions. For complex structural features, including stiffener-frame cut-outs and openings, an enhanced cross-field method is introduced to generate high-quality quadrilateral meshes while preserving geometric characteristics. A boundary simplification strategy is further developed to avoid mesh degradation near complex boundaries. Validation using representative transverse and bottom-side tank sections of a very large crude carrier (VLCC) with a deadweight tonnage (DWT) of 300,000 tonnes demonstrates the applicability of the proposed framework to local mesh refinement. The final refinement zones meet the specified mesh-density and geometric-quality criteria, whereas some transition-zone elements fall outside the adopted quality limits. Validation addresses local refinement results and geometric mesh quality rather than structural response. The proposed framework supports semi-automatic local mesh refinement of large-scale hull structures.