Numerical investigation of flow field characteristics around two different ship hull sections under various lightering arrangements

The investigation of flow field characteristics during lightering operations is crucial for maritime safety, but it is constrained by two main challenges: a limited understanding of flow field characteristic variations around two ships under different arrangements, and an absence of comparative analyses that systematically quantify the similarities and differences in the resulting flow fields. In response to these shortcomings, the present work investigates a range of relative arrangements between two fixed ship hull sections (KVLCC and Aframax) to evaluate their effects on the flow field. The modified Re-Normalization Group (RNG) k - ɛ model in OpenFOAM is validated against experimental data for two different ship hull sections at Reynolds numbers ( R e ) of 68,000 and 6800. Subsequently, a comparative analysis of eighteen arrangements for the two ship-to-ship configurations (KVLCC ∼ Aframax and Aframax ∼ KVLCC) at R e = 68 , 000 reveals that the global evolution trends of the flow fields remain similar under identical operation conditions, despite local flow discrepancies. Results show that the larger bilge radius on the upstream hull effectively suppresses bottom vortex formation, whereas the breadth and stern bilge of the downstream hull predominantly govern the wake flow. Moreover, increasing the inter-ship distance amplifies the inter-ship vortex for hulls with different drafts. Further analysis clarifies that under identical draft conditions, the flow field around the upstream hull is primarily governed by the draft, while the downstream hull flow is modulated by both draft and inter-ship distance. Furthermore, the free surface becomes the dominant factor at shallow draft, affecting the inter-ship vortex structure and thereby altering the adjacent flow field. • A modified RNG k - ɛ model enhances prediction accuracy in ship hull sections lightering simulations. • Inter-ship distance and draft affect vortex distribution and flow field variations. • Flow fields and interaction effects are compared for two ship configurations. • Bilge radius effects on bottom vortices and hull geometry effects on wake flows.