Flettner Rotor - Thrust Estimate
Lift-based thrust of a Flettner rotor given rotor size, rotation rate, and relative wind - the Magnus-effect calc used for sizing Rotorsail.
Spin ratio α
4.71 -
C_L
5.65 -
Rotor thrust along ship
52.0kN
Formula, assumptions, and limits
$$L = \tfrac{1}{2} \rho_a C_L A V^2 \sin \beta$$
$C_L$ peaks near α = 5. Magnus lift exceeds typical sail $C_L$ (1.2 max) by an order of magnitude. Requires power to spin rotor (~1 % of thrust converted to shaft power).
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\alpha$ | Spin ratio (tip speed / wind) | - | πDn/V |
| $C_L$ | Lift coefficient | - | Magnus coefficient curve |
| $A$ | Projected rotor area | m² | D × H |
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