Thrust deduction analysis for wind-assisted ships

Paper in proceeding, 2026

Wind-assisted ship propulsion (WASP) presents a promising option for reducing emissions and decarbonizing the maritime industry. To better understand how wind sails influence ship performance, this study examines the effect of leeway angle on thrust deduction. The side forces and resistance components are also analyzed.
Computational Fluid Dynamics (CFD) simulations based on the Reynolds-Averaged Navier–Stokes (RANS) equations are conducted at model scale for the JoRes1 tanker at Froude number of 0.162. To minimize computational costs, a double-body approach is used, ignoring free-surface effects, and the propeller is modeled with a virtual disk approach. Resistance and self-propulsion simulations are performed across a range of leeway angles and sail thrust levels. The results indicate that the leeway angle affects resistance and side forces, with pressure resistance becoming more dominant at larger leeway angles. The traditional thrust deduction formula is shown to be inadequate for wind-assisted propulsion, as it produces values that differ from those of conventional vessels under high sail thrust. A modified thrust deduction formulation provides a more consistent representation of propulsion performance. The modified thrust deduction factor t∗ and the resistance increment coefficient r are more appropriate for analyzing
the effects of the leeway angle and sail thrust on ship resistance and propeller thrust.