Evaluation of a Propeller Unsteady Force Computer Program to Predict Propeller Induced Unsteady Hull Pressures.

摘要

A potential flow computer program is used to predict the unsteady pressure field on a hullform caused by a rotating propeller. It was chosen over two other approaches and three programs. The program, PUF-3A, uses lifting surface theory and contains variables that are run in different combinations to ascertain their effects. The results are plots of sound pressure level (SPL) versus distance across the hullform and are compared to water tunnel model data. The baseline experimental configuration is a model of a single screw five blade propeller powered in the wake of a broad, relatively flat hull in a 48-in water tunnel. Another configuration tests an inflow altering device with the same hull and propeller geometry. The desired result is an identification of the program's strengths and weaknesses versus water tunnel data. Its strengths were in predicting the relative SPLs of the first blade rate harmonics in two different wake fields. In the case of a simple wake field, the overall relative SPLs of the second and third harmonics compare reasonably well with water tunnel data.