An Examination of Axisymmetric Propeller-Hull Interaction Effects and Their Impact on the Design of Propeller-Vehicle Systems

It has been recognized for some time that the interaction between the flow past a vehicle hull with that through the vehicle's propulsor is significant in the sense that the loads experienced by the propulsor and the hull can be drastically alterred by the interaction. Traditionally these interactions have been taken into account empirically. More recently simple interaction models have begun to be used 10 obtain more accurate theoretical predictions of these effects. Herein is contained a program which advances the state-of-the-art by integrating currently available models to calculate these interaction effects directly. Separate numerical models presently exist for the calculation of the flow about an axisymmetric body and for the flow through a propeller. The present program, APHIPS (Axisymmetric Propeller-Hull Interaction Program System), employs a boundary-integral model for the axisymmetric potential flow about the vehicle hull, a finite-difference model for the axisymmetric boundary-layer flow along the hull and a full three-dimensional boundary-integral model for the calculation of the potential flow through the propeller. These three flow models interact and the solution of each modifies the solution of the other two. The final equilibrium achieved represents the flow solution about the hull-propeller system with all the interactions taken into account. The APHIPS program has been employed to predict the interaction of the hull and propeller flows about bodies of Navy interest for which experimental measurements exist. The results of the numerical calculation have been compared with the experimental findings for validation and the agreement has been found to be good. Preliminary investigations into the nature and magnitude of the flow interactions have also been performed. Examination of these results indicates that the interactions can be quite significant and can therefore have a large impact on the design of propeller-vehicle systems.