Numerical investigation of multiple wingsails interaction under different apparent wind angles

• Investigated multiple wingsail interactions at varying apparent wind angles (AWAs) and angles of attack (AoAs). • At low AWAs, interactions are caused by downwash and upwash effects among wingsails. • At high AWAs, the pressure-field interaction between adjacent wingsails plays the dominant role. • High AoAs result in flow separation at the wingsail’s lower span due to the floor boundary layer flow. • Proper Orthogonal Decomposition (POD) analysis shows that interactions enhance force fluctuation at high AoAs. In the context of enhancing sustainability, wind propulsion using wingsails has emerged as a promising solution to reduce emissions in the maritime sector. This paper numerically studies a model-scale three-wingsail system to understand the interaction mechanism of multiple wingsails. Improved Delayed Detached Eddy Simulation (IDDES) is conducted with k − ω SST model and is validated by wind tunnel testing data. Two apparent wind angles (AWAs) of 30 ∘ and 90 ∘ , standing for representative wingsail-interaction scenarios are chosen and each AWA is studied with a low and high angle of attack (AoA). At AWA of 30 ∘ , the individual wingsail is subjected to the downwash or upwash effects generated by adjacent wingsails, leading to the variation of stagnation point location and performance change. At AWA of 90 ∘ where wingsails are located in the same streamwise position, adjacent wingsails interact through the pressure-field interaction, which impairs each other’s performance. At high AoA, the flow separation occurs at the low span of the wingsail due to the sluggish flow in the floor boundary layer. As compared to the single sail case, the interaction effect makes the flow separation more severe in the leading wingsail. In this regard, the vortical behavior is also amplified as indicated by proper orthogonal decomposition (POD) analysis, leading to an enhanced force fluctuation.