A chimera Reynolds-Averaged Navier-Stokes (RANS) method was coupled with a propeller analysis program to provide accurate resolution of the propeller-ship interactions. Calculations were performed for a Series-60 ship with the MAU propeller under various operating conditions. In the present interactive coupling approach, the propeller thrust and torque were represented by body-forces and added to the source functions of the RANS code to account for the propeller-induced effects. The propeller analysis program was then used to determine the new propeller blade loading distributions with the propeller inflow provided by the RANS solution. Several interactive coupling between the RANS and propeller analysis programs were performed to capture the propeller-ship interactions under various propeller operations including ahead, backing, crash-astern, and turning conditions.
The potential flow methods based on the assumptions of inviscid fluid and irrotational motion are widely used in propeller flow analysis (Kerwin and Lee, 1978; Greeley and Kerwin, 1982). However, some off-design propeller flow phenomena are dominated by viscous effects and cannot be accurately predicted by the potential flow methods. Off-design conditions include all four quadrants as defined by the ship velocity Vs and the propeller angular velocity ω. The four modes of propeller operation are defined as ahead or forward (+Vs, +ω), backing or astern (−Vs, −ω), crash-ahead or reverse breaking (−Vs, +ω) and crashback or crash-astern (−Vs, +ω). During crash-astern and crash-ahead operations, the reversal of propeller rotation creates a relatively large angle of attack, causing the flow to separate at the leading edge of the blade. Jiang et al. (1991) extended the inviscid- flow propeller design methods for the simulation of backing and crash-astern conditions. They adopted a simplified approach in propeller flow analysis program PSF (Propeller Steady Force) with three-dimensional correction factors to account for the leading-edge separation under crash-astern conditions.
