HomeCalculatorsFlettner Rotor Wind Assist

Flettner Rotor Wind Assist

Rotating vertical cylinders generate thrust via the Magnus effect in crosswinds. Annual fuel saving depends on wind climate, ship route and rotor height - typical installed systems report 5–15 % main-engine fuel savings on wind-rich trades.

DesignWind assist

Rotor array

Number of rotors–Rotor heightmRotor diametermRotor drive power per unit (spin-up)kW

Wind climate

Average apparent-wind speedm/sFraction of voyage hours with useful cross wind%North Atlantic 50–70 %, Indian Ocean monsoon seasons 60–80 %, equatorial 20–30 %.

Displacement

ME SFOCg/kWhSea hours / yearhFuel

Effective thrust × speed power

0kW

Net fuel saved / year

0.0t

CO₂ avoided / year

0.0t

Formula, assumptions, and limits

Simplified Magnus-effect thrust. C_L for a rotating cylinder ≈ 5–8 at high spin ratios (3× ambient wind). A is rotor projected area. Real-world systems (Norsepower, Anemoi) publish route-integrated CFD + in-service data rather than spot calculations.