A coupled potential–viscous flow approach for the prediction of propeller effective wakes in oblique flow

Abstract

This paper presents a method for the estimation of propeller effective wakes in oblique flows. It extends to inclined flows an approach based on correction factors previously developed for the estimation of effective wakes in straight flow. The approach converts propeller-induced velocities approximately predicted via potential flow theory into viscous-induced velocities on the basis of a viscous flow RANS analysis. The correction factors are a function of both the radial and angular positions on the propeller disk. They are calculated for a reference advance number and work accurately in a neighboring continuous region of advance numbers. This procedure allows controlling one of the errors present in the calculation of effective wakes, namely the error derived from coupling a potential flow method for the representation of the propeller with a RANS solver. Consequently, it permits calculating the effective wake more precisely in off-design conditions, reducing the CPU time, and therefore, enlarging its range of applicability to situations like those resulting from ship maneuvering. The approach is tested for a podded propulsor unit in oblique flow.