Propeller Efficiency (η₀)

Open-water efficiency from KT–KQ–J or from thrust & torque. Optional Vₐ from Vₛ and wake fraction.

Method

Choose coefficients route or forces route.

Ship speed V_s (kn)

Wake fraction w

If Vₐ blank → Vₐ = Vₛ(1−w).

Advance speed V_a (kn)

Prop RPM (rev/min)

A) Open-Water Coefficients

K_T

K_Q

Advance ratio J

If blank, J = Vₐ/(nD) using Vₐ, RPM, D.

Diameter D (m)

Efficiency: η₀ = (J·K_T)/(2π·K_Q)

η₀ (open-water efficiency): —

Advance ratio J: —

V_a used: — kn

n (rev/s): —

Mode A: η₀ = J·K_T / (2π·K_Q). Mode B: η₀ = (T·V_a)/(2π·n·Q).

Report: Propeller Efficiency (η₀)

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Notes

Advance ratio \( J = \dfrac{V_a}{nD} \) (V in m/s, n in rev/s).

Open-water efficiency \( \eta_0 = \dfrac{J K_T}{2\pi K_Q} \) or \( \eta_0 = \dfrac{T V_a}{2\pi n Q} \).

If Vₐ is unknown, you can use Vₛ and w: \( V_a = V_s(1-w) \).