How the geometry of a vessel's superstructure creates consistently faster wind than the ambient forecast -- and why that changes the economics of onboard generation.
Vessel wind data is almost always measured at a weather station. Vessel turbine performance depends on something different: the wind speed at the rotor, which is shaped by the vessel's own geometry. Understanding that difference is the foundation of accurate yield modelling for maritime installations.
When wind meets a solid obstruction -- a vessel's hull, bridge, or superstructure -- it does not stop. It accelerates around and over it. Where the geometry forces airflow through a narrowed channel, the acceleration is pronounced and consistent.
A vessel's superstructure creates exactly this condition on both beam and quartering wind angles. The bridge wings, funnel casings, and deck structure channel airflow across the working deck in a pattern that regularly produces wind speeds 15--30% above the free-stream ambient. For a wind turbine, that differential is not marginal: power output scales with the cube of wind speed. A 20% increase in effective wind speed produces roughly 73% more power output at that wind speed.
The venturi acceleration pattern on a given vessel class is not random. It is a function of the hull form, freeboard, and superstructure geometry. Vessels with a high bridge structure and clear working deck forward of the bridge -- which describes most bulk carriers, container feeders, and offshore support vessels -- produce a consistent acceleration corridor amidships and forward.
This predictability is what makes turbine placement an engineering problem rather than a speculative one. A site assessment for a maritime installation maps the acceleration corridors and identifies the mounting positions that capture the highest consistent wind speed. The result is a placement that outperforms a forecast-based model throughout the vessel's service life.
For a fleet operator, the venturi effect is compounding. Vessels with similar hull forms produce similar acceleration patterns -- which means a site assessment on one vessel type can be extrapolated across the class. Installation programmes across a fleet benefit from this consistency: commissioning data from the first vessel informs the yield models for all subsequent vessels of the same type.
Yield models for maritime turbine installations should use site-measured or CFD-modelled wind data at the rotor position, not ambient forecast data. Installations sized against ambient wind forecasts will underestimate actual yield in most cases -- the venturi effect is a consistent upward factor that the ambient model ignores.
HNordic's maritime site assessment process includes rotor-position wind modelling as standard. The output is a site-specific yield estimate that accounts for the actual wind environment at the turbine mounting point, not the forecast wind at open sea.
See also: How the venturi effect works · ROI for maritime wind · Full FAQ