Ship behaviour under wind propulsion, proven in the tank

CMDC4 built the VME’s foundation: comprehensive ship behaviour modelling for wind propulsion, verified across full-scale CFD, model-scale CFD and physical experiment. A working coastal cargo vessel was digitally twinned. Its geometry was independently reconstructed, its powering validated against sea trial data, and its real route rebuilt from AIS movements and matched to 30 years of hindcast weather, with sensors on the vessel’s own bridge validating the weather models.

At the University of Southampton’s 138 m Boldrewood towing tank, a 1:32 scale model was run through 90+ self-propelled tests across speeds, leeway and rudder angles. Wind propulsion forces were applied by a steerable fan, so the hydrodynamic consequences of wind thrust could be isolated in a way sea trials never allow.

The campaign surfaced the physics that decides whether wind propulsion pays. Side force induces leeway, leeway demands rudder, and holding course can require up to 50% more power at large rudder angles, while sailing strategies that use the environment well showed power reductions of up to 20% in head waves. The interaction between propeller and rudder materially changes the ship’s balance, an effect standard simulation approaches miss entirely. Modelling this chain correctly is the difference between a device’s brochure figure and its net saving.

As part of the programme Spaera also designed, built and tank-tested its own wind propulsion device, taking a concept through aerodynamic CFD, generative structural design and physical test. The device programme proved the design capability; the methodology it validated is what every VME assessment now runs on.