Numerical investigation on hydrodynamic performance of new canard-configuration tandem propellers

The complex flow field interference between the front and rear propellers will affect the efficiency of the tandem propeller. To reduce or utilize this kind of interference and improve efficiency, inspired by the excellent aerodynamic performance (lift-drag ratio) of the plane with canard-configuration wings, an exploratory numerical study has been carried out to investigate the hydrodynamic performance of new canard-configuration tandem propellers based on RANS method with SST k-omega turbulence model and moving reference frame using the STARCCM+ solver. The effect of diameter ratio, axial distance and angular displacement on the hydrodynamic performance of the tandem propeller has been widely investigated. In order to get a general conclusion, the new tandem propellers were designed based on two traditional tandem propellers, CLAU3-30-1-10-20-0 and CLB455-1-10-21-23.7. The numerical approach was applied to simulate the open water performance of the two traditional propellers first and the comparison of numerical results with the experimental data was in a good agreement. The study reveals that the efficiency of the tandem propeller can be improved by decreasing the diameter of the front propeller to a certain extent. Generally, the efficiency is also increasing with the increase of axial distance, but an extreme small axial distance with a specified angular displacement can improve the efficiency significantly, and the flow field interaction between the front and rear propeller blades was investigated to explain the efficiency improvement. The optimum angular displacement, which is important for a tandem propeller design, is related to the axial distance and the working condition (advance coefficient) of the propeller. Furthermore, the redistribution of the negative pressure on the front and rear propeller blades using the canard configuration may lead to a better cavitation performance than that of the traditional tandem propeller. Generally, this study presents a comprehensive study on the effect of three important geometrical parameters on the performance of the tandem propellers and demonstrates some advantages of the new canard-configuration tandem propellers over the tradition tandem propellers. The results have certain significance for the design and development of new tandem propellers.