AN UNSTEADY INVISCID-FLOW MODEL TO STUDY PODDED PROPULSORS HYDRODYNAMICS

A theoretical and numerical methodology for the hydrodynamic analysis of podded propulsors is presented. This work is part of an extensive research program aiming to develop theoretical as well as experimental tools to investigate pod hydrodynamics and hydroacoustics. The proposed theoretical activity is addressed to the development of fast and accurate perfomance prediction tools. Specifically, the present formulation is based on a boundary integral equation method for the velocity potential that is valid for inviscid flows around multi-body configurations in arbitrary motion. A time-accurate approach is considered to describe the unsteady interactions among podded propulsors components. A wake alignement techinque and a vortex/wall impingement model are used to describe the propeller trailing wake and its interactions with the regions of the strut surface that are characterized by wake impacts in a pulling-type pod configuration. A domain decomposition techinque is introduced in order to limit the computational effort. As far as performance predictions are concerned, numerical results are presented to validate the trailing wake alignement procedure and the wake/wall impingement model. In addition, the application of the numerical code to determine the main geometrical parameters that influence the performance of a pulling-type pod is described. This analysis is intended to provide a preliminary guide for the experimental activity on pods to be performed at INSEAN.