Numerical design of contra-rotating azimuth propulsor using vortex theory coupled with panel method

A design procedure of contra-rotating azimuth propulsor (CRAP) is developed based on vortex theory coupled with low order potential-based panel method. The forward propeller (FP) and rear propeller (RP) are designed using the written computer code with the pod unit (PU) which includes the pod body and the strut being given first. The hydrodynamic interactions among FP, RP and PU are considered through induced velocities which are calculated using panel method. A conventional propeller (CP) supplying the same thrust with CRAP at the same inflow velocity is designed to analyze the energy saving performance of CRAP. The case study shows that, at design condition, CRAP has a decrease in delivered power by approximately 8% compared with CP. The tangential induced velocities in the slipstream indicate that CRAP recovers the rotational energy of slipstream effectively. The open water characteristics of CRAP are also analyzed systematically.