Numerical investigation of rake angle variations on the open-water characteristics of a toroidal propeller

In this study, a numerical investigation is conducted to examine the open-water characteristics and flow analysis around the toroidal propeller, with particular emphasis on the influence of positive rake angle. A toroidal propeller (denoted TP04) is constructed using effective geometrical parameters (roll, pitch, shift, vertical, lateral) for the rear, front and intermediate blades. Steady RANS simulations with the k−ω SST turbulence model are employed to evaluate the hydrodynamic performance of the baseline propeller, with detailed analyses carried out at advance coefficients J=1.0 and J=1.2, corresponding to operating conditions near peak propulsive efficiency. Sectional pressure coefficient distributions and blade-resolved hydrodynamic coefficients reveal distinct and asymmetric contributions of the front and rear blades across different operating conditions. The effects of positive rake angle are then examined through modified configurations with rake angles ranging from 0° to 25°, showing that increasing rake leads to a systematic reduction in thrust and torque coefficients, accompanied by a moderate decrease in efficiency. Wake characteristics assessed using turbulence intensity and swirl ratio, indicate reduced blade loading and a more stabilized, axially aligned flow at higher advance coefficients.