Open water performance of B-Series marine propellers in tandem configurations

Abstract

The hydrodynamic performance of 4-bladed B-series tandem propellers with different design configurations in open water is numerically investigated using a RANS-based CFD solver. The integration of the co-rotating aft propeller increases the resultant thrust and torque coefficients in the entire range of propeller loading. The open water efficiency at moderate to high propeller loadings is reduced, but the range of positive thrust output is increased.Due to the induced velocities and flow acceleration caused by the forward propeller, a higher pitch ratio should be adopted for the aft propeller to generate the blade forces. While the forward propeller behaves very similar to a conventional single propeller, the thrust and torque coefficients of the aft propeller show minimal variations with advance coefficient due to high induced velocities. At higher advance coefficients and blade sections closer to the hub there is greater deviation of forces generated by the aft propeller blade as compared to a single propeller of similar design. Parametric investigations are presented, highlighting the influence of axial spacing, relative angular position, pitch difference, and diameter ratio between the forward and aft propellers on the open water performance. From the present study, a pitch ratio difference of 0.3 may be maintained between the two propellers for optimal open water performance.