The hub effect has been ignored in theoretical or numerical calculations of hydrodynamic characteristics of marine propellers so far. In this paper hub effects of some model propellers are investigated by the surface vortex lattice method (SVLM) for the hub and by the ordinary vortex lattice method (VLM) on the lifting surface for the blade. The surface, where the surface vortex lattices are distributed, is taken inside of the real surface of the hub in order to avoid the strong interference effect between the root vortex lattices of the blade and the surface vortex lattices of the hub.
It is found from the present investigation that the hub effect is noticeable on the pressure distribution on the blade surface near the root but the smaller on the outer blade surface toward the tip, but that the hydrodynamic forces of the propeller such as thrust and torque are scarcely affected by the existence of the hub of the normal size. The calculated pressure distributions on the blade including the hub effect show good or poor agreement with the measured results in case by case. The pressure distribution on the hub surface is calculated and assessed in this paper. Calculations also show that the hub effect is more significant for the larger hub diameter such as controllable pitch propellers (CPP), as expected.