Wind Propulsion and Multi-Stage Performance Optimization of Flettner Rotors for a Cargo Vessel in the Concept Design Stage

Wind-assisted propulsion is a key solution for reducing maritime emissions, offering a cost-effective alternative to fully emission-free technologies. However, integrating wind propulsion into holistic ship design remains limited. This paper presents a parametric approach using Computational Fluid Dynamics (CFD) and topology modelling to optimize Flettner Rotor configurations on various ship types. An inviscid Eulerian flow method reduces computational costs while maintaining acceptable prediction accuracy for the considered early design stage. The study validates results against high-fidelity simulations and wind tunnel tests. Using HSVA's EcoLibrium tool, performance predictions and optimization loops enhance vessel's efficiency. The optimized design will undergo towing tank testing for further validation. INTRODUCTION The maritime industry faces increasing pressure to reduce greenhouse gas emissions and improve energy efficiency in line with international climate goals and evolving regulatory frameworks. Among various alternative propulsion technologies, Wind-Assisted Propulsion Systems (WAPS) have re-emerged as viable solutions for lowering fuel consumption and CO2 emissions. One promising approach is the integration of Flettner rotors—rotating vertical cylinders that harness the Magnus effect to generate lift that contribute to a vessel's propulsion. These systems can significantly improve overall energy efficiency, particularly on routes with favorable wind conditions. Whilst numerous installations (either by new building or retrofitting) of Flettner rotors promise significant gains in efficiency and emission reductions, full integration of wind propulsion solutions into an overall (holistic) ship design process remains sparse. This study focuses on the integration and performance optimization of Flettner rotors for a cargo vessel during the concept design phase. A multi-stage methodology combines Computational Fluid Dynamic (CFD) simulations and performance modeling tools to identify optimal rotor configurations and hull form adaptations. The workflow includes aerodynamic interaction analyses between multiple rotors, hydrodynamic hull optimization to preserve stability and minimize drag, and system-level assessments utilizing HSVA's in-house simulation platform, EcoLibrium. By evaluating rotor placement, operating conditions, and the impact of apparent wind angles, the study aims to maximize propulsion efficiency while maintaining operational robustness.