HomeCalculatorsWake Fraction & Thrust Deduction

Wake Fraction & Thrust Deduction

Hull-propeller interaction factors. Wake fraction w reduces the water arriving at the propeller disk vs the ship speed; thrust deduction t increases the thrust the propeller has to deliver vs bare-hull resistance. Both come from Harvald regression or model-basin tests.

DesignPropeller

Hull particulars

Block coefficient Cb–Length between perpendicularsmBeammConfiguration

Bare-hull input

Bare-hull resistance RTkNShip speedkn

Wake fraction w

0.360–

Thrust deduction t

0.226–

Hull efficiency η_H = (1−t)/(1−w)

1.209–

Advance velocity V_A

4.61m/s

Required thrust T

1,033.6kN

Formula, assumptions, and limits

Harvald 1983 closed-form fit - good enough for early design. Model-basin tests routinely produce lower w on modern stern shapes. η_H > 1 is the normal case for single-screw full hulls because the thrust gain from accelerated wake outweighs thrust deduction.