Abstract
Numerical Analysis of Hub Effect on Hydrodynamic Performance of Propellers with Inclusion of PBCF to Equalize the Induced Velocity In this article the boundary element method (BEM) is applied to analyze the propeller hub as a non-lifting body and the blades in its vicinity as lifting bodies. In solver, the geometrical modeling of hub, blades are PBCF (Propeller Boss Cap Fin) constructed by quadrilateral elements. The velocity potential is determined on each element by discretized boundary integral equation. Iterative procedure is used to consider the adjacent body effect. In each step the body was independently analyzed with the influence of near body considered in inflow velocity. The induced velocity of propeller was calculated with and without PBCF in downstream. PBCF, an energy-saving device, reduces and uniforms the induced velocity of propeller in downstream. Numerical results of propeller hydrodynamic characteristics including hub effect, induced velocities, PBCF influence are presented.
Highlights
The propeller is located at the stern of a ship where the inflow current is non-uniform due to boundary layer and wake formation
One of the augmentation tools for increasing thrust is the use of propeller boss cap fins (PBCF) at the end of the hub, which causes to eliminate the hub vortex
The harmful effect of the hub vortex is twofold, firstly, it reduces the efficiency of the propeller and secondly, the rudder is exposed to corrosion because it is located downstream of the propeller where cavitation takes place
Summary
The propeller is located at the stern of a ship where the inflow current is non-uniform due to boundary layer and wake formation. According to the results obtained by Liu in 1995, in ordinary hubs of small diameter, which are mainly used in constant pitch propellers and surface ships, the effect of hub on hydrodynamic forces of the propeller such as thrust and torque, is not remarkable [6]. The SPD (Ship Propeller Design) software code has been prepared by Ghassemi (the first author) and employed to the various propulsors such as propeller-rudder system (PRS) [15], high-skewed propeller [16], contra-rotating propeller [17] and surface piercing propeller [18], underwater vehicle under surface and submerged conditions [19] In this code BEM is employed to perform the hydrodynamic analysis of marine propellers of all types.
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