Wake-equalising duct

A Wake-equalising duct is a ship hull appendage mounted in the inflow region of a screw propeller intended to realign and adjust the velocity of the wake at the inflow to the propeller disc. Wake velocity may be straightened out, given contra-rotational swirl, accelerated, or a combination of these effects, all of which can improve propeller efficiency, giving either higher thrust or reducing power requirement for the same thrust.