A Fast Quasi-Steady Procedure for Estimating the Unsteady Forces and Moments on a Marine Propeller Behind a Hull
Abstract
The development and implementation of a semi-empirical method to estimate the unsteady forces and moments on an open marine propeller mounted behind a hull are discussed. The method relies upon a quasi-steady approach that allows the code to rapidly estimate the forces and moments for a wide variety of propellers. Unlike most other quasi-steady methods that use a point velocity or a velocity integrated over a line, this method uses a technique to weight the chord-wise velocity distribution to obtain an equivalent velocity for each radius; then to integrate those velocities across the span of the blade. An empirical correction was also developed that allows this method to be used with propellers in inclined flow. It is this weighted integral that allows this method to perform as well as it does. In general, it works better than the Tsakonas method (1974) of Stevens Institute. However, it is not better than the Kerwin and Lee (1978) method of MIT when an expert runs the MIT program. The required input is easy to prepare and requires three types of normally available data: basic propeller geometry; propeller open water curve tabulation; and, wake survey results. The available unsteady experimental data is decomposed into a small subset used to develop the weighting, and the remainder used to validate the model. This represents a valuable departure from other empirical approaches that require most of the data for development. The results from this program, compared to experimental results and other prediction methods, are shown.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2011
- Accession Number
- ADA545303
Entities
People
- Robert F. Roddy
Organizations
- Naval Surface Warfare Center Carderock Division