A Coupled Viscous/Potential-Flow Method for the Prediction of Propulsor-Induced Maneuvering Forces

Abstract

A technique for the analysis of propulsor-induced maneuvering forces on the surface and underwater vehicles has been developed. The method is capable of modeling general propulsors but is especially suited to complex integrated propulsors and their highly contracting stern flows. Integrated propulsors exhibit strong interactions of the blade-rows, duct, and vehicle stern. The method described herein is a robust means to analyze propulsor-induced maneuvering forces, including those arising from complex propulsors. The heart of the maneuvering force prediction is a three-dimensional, unsteady lifting surface method for the calculation of blade forces on both rotors and stators. The lifting surface method includes features that are important for the modeling of complex propulsors. Temporally-varying forces are computed for a blade-row rotating in a spatially-varying flow field. The spatially-varying flowfield around a maneuvering vehicle is obtained by coupling the unsteady lifting-surface method with a three-dimensional, time-averaged Reynolds Averaged Navier-Stokes viscous flow solver. The coupled technique allows the designer to compute maneuvering forces while accounting for effective wake issues and propulsor-hull interactions. Issues important to the coupling of a potential-flow method and a three-dimensional viscous flow solver are discussed. Verification of the method has been performed on a variety of geometries and vehicles. Two examples are shown. Preliminary results show that the method is able to compute propulsor-induced maneuvering forces for such vehicles. The results suggest that this maneuvering force prediction method has great potential for the propulsor designer.