Numerical Study on the Improvement of the Tip Cavitation Performance of a Twisted Rudder Using CFD

This paper presents the geometry modifications in rudder tip and the results of numerical simulations to improve the low speed cavitation inception performance of a twisted rudder developed by KRISO. First, to validate the RANS-based CFD method used to analyse rudder performances, the numerical results were compared with the experimental data for a flat rudder obtained from KRISO LCT tests. The present numerical results showed good agreement with the measured rudder forces, cavitation occurrence and rudder surface pressures. The KRISO twisted rudder was superior to the flat rudder in cavitation performance over the entire angle of attack at high speed condition. However, the cavitation inception angle at low speeds was lower than that of the conventional flat rudder. Two improved tip geometries were designed and the numerical analysis showed that the cavitation inception angle was improved for both modified rudders.