Geometric Design Optimization of an Energy-efficient Propeller Retrofit for Small-scale Shallow-water Maritime Transport

The small-scale shallow-water maritime transport in Southeast Asia heavily relies on traditional two-blade propellers, which frequently suffer from severe hydrodynamic degradation, ventilation, aeration and sheet cavitation under shallow immersion. To address these constraints, this study introduces an engineering design framework to develop an energy-efficient, three-blade retrofit propeller, designated as model B3-55. The blade geometry was optimized using a multi-subprogram algorithm incorporating regression analysis and response surface methodology to maximize open-water efficiency while minimizing cavitation risks. Hydrodynamic validations were executed utilizing Lattice Boltzmann method (LBM)-based CFD simulations via XFlow, coupled with water tunnel and field testing at 650-750 rpm. under a 50-cm immersion depth. Numerical and empirical results revealed that the optimized wide-chord tip geometry of model B3-55 achieved a remarkable open-water efficiency (η_o) of 0.830 at an advance coefficient (η_o) of 0.701. Crucially, the wide-chord configuration significantly suppressed tip vortex bursting and delayed destructive ventilation compared to the local baseline. This propulsion framework offers a scalable, socio-economically resilient solution that reduces fuel consumption and operational expenditures for rural fishing communities.