Relative Rotative Efficiency (η_R)

Compare propeller torque or power between open-water and behind-ship conditions.

Method

Prop RPM

Advance ratio J

A) Torque / Power Route

Open-water Q₀ (kN·m)

Behind-ship Qᴴ (kN·m)

ηᴿ = Q₀ / Qᴴ = P_D,0 / P_D,H. If RPM entered → both delivered powers are displayed.

η_R: —

P_D,0: — kW

P_D,H: — kW

Ratio P₀/Pᴴ: —

ηᴿ compares propeller torque between open-water and behind-ship conditions.

Report: Relative Rotative Efficiency (η_R)

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Notes

ηᴿ > 1 means propeller performs slightly better in the ship’s wake (light loading); ηᴿ < 1 indicates heavier loading.

Typical range: 0.95–1.05.