A Practical Approach for Design of Marine Propellers with Systematic Propeller Series
Original scientific paper Although there have been important developments in marine propellers since their first use in 1850, the main concept has been conserved. Parallel to the developments in the computer technologies in the past 50 years, methods based on the circulation theory are often used for the design and analysis of propellers. Due to the ability to predict the propulsion performance with just a few design parameters, the use of systematic propeller series based on open water model experiments is still widespread. The design with standard propeller series is usually made with diagrams developed from model experiments. Reading errors during the use of these diagrams are inevitable. In the presented study a practical approach is developed for preventing reading errors and time loss during the design with standard propeller series. A practical approach based on empirical formulas for the design and performance prediction for four-bladed Wageningen B propeller series is presented, and design applications for three propellers with different loading conditions are realized. The results obtained from the presented method are compared with those of open water diagram data and a good agreement between the results is observed.
THE WAGENINGEN B-SCREW SERIES
The Wageningen B-screw series have been extended gradually to 21 screw series having blade numbers ranging from 2 to 7 and blade-area ratios between 0.30 and 1.05. Recently, the existing screw series were correlated with the new screw series with an up-to-date fairing technique. This correlation was made by means of a regression analysis. Further, the influence of the Reynolds number ( scale effect ) on the test results was taken into account. For ship maneuvering studies, it is necessary to know the propeller thrust and torque characteristics over a wider range of operating conditions. Therefore, open-water tests with B-series screws over the entire region of operation were carried out. In order to obtain systematic knowledge on the cavitation characteristics of the B-screw series in a uniform flow, tests have been conducted. The curves for cavitation inception were established and the influence of cavitation on propeller thrust and torque was determined.
COMPUTATIONAL ANALYSIS OF PROPELLER SHEET CAVITATION AND PROPELLER-SHIP INTERACTION
SUMMARY This paper describes a computational procedure which is being developed for the practical analysis of propeller sheet cavitation and propeller-ship interaction including hull pressure fluctuations. The computational procedure consists of three different, coupled methods: (i) a RANS method for the analysis of the viscous flow around the ship hull and the determination of the velocity field in the propeller plane, (ii) a boundary element method for incompressible potential flow developed for the analysis of propeller performance including sheet cavity extent and volume, and (iii) a boundary element method which solves the acoustic wave equation to compute the propeller radiated pressure fluctuations on the ship hull. The background to the three methods and the coupling procedures are briefly described followed by a discussion on validation work. The validation work concentrates on the ship wake field, the propeller sheet cavity extent and the hull pressure fluctuations for model scale as well as full scale. The differences found between model scale and full scale are used to discuss implications for model-scale testing.