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The problem of accurately predicting the performance of a sailing vessel has been researched since the turn of the century. Improvements in sail construction and materials have placed greater importance on optimizing sail aerodynamics. The goal of this research was to devise a testing method which would allow simple, inexpensive testing of sails to be conducted. This effort culminated in the design and construction of an outdoor sailing dynamometer which can measure all of the forces and moments produced by a sail. The apparatus is capable of testing full-size dinghy rigs or scaled-down offshore racers. It may be used both for rig selection and for the evaluation of different sail designs. High quality results may be achieved with a minimum expenditure of time and capital.

This paper describes the towing tank test procedure used for conducting propulsion tests of the Rolls-Royce Naval Marine (previously Bird-Johnson Co.) Advanced Waterjet 21 (AWJ-21™) propulsor. The tests were conducted on hull model 5565-1, an existing 22.5 scale model of a hull form representative of a future tumblehome naval destroyer. AII the test work described here took place at the Naval Surface Warfare Center, Carderock Divisions, David Taylor Model Basin. Design of the waterjet was carried out by Rolls-Royce Naval Marine in 1999 and the towing tank experiments were conducted in October 2000 and February 2001. The test procedure follow the guidelines for the "momentum flux" method as described in Appendix A of the 21st International Towing Tank Conference (ITTC) Waterjet Group Report (1996] and reproduced in the Quality Manual of the 22nd ITTC Special Committee on Waterjets Report [1999]. However, the ITTC procedure does not address the methods for obtaining the required data and does not provide guidance for scaling the model data to the full size ship. The paper deals with these issues and some of the measurement procedures that are specific to the AWJ-21™ test program. In particular, an accurate survey of the inflow and discharge velocity distribution is required to obtain the mass flow and head rise through the propulsor. In the present case, a Laser Doppler Velocimeter (LDV) is used to carry out these surveys. Because conducting LDV surveys is very time-consuming, it is not practical to determine the mass flow and head rise at every test speed by this method. In our case, the LDV surveys were conducted at only two speeds. · These data · are then used. to characterize the flow non-uniformity and to correlate with pitot-static probes located in the inlet and discharge of the jet system. With this correlation, the pitot-static probes are used to obtain the performance over the entire speed range. While a Laser Doppler Velocimeter provides a very accurate means of obtaining velocity, it does not provide the required static pressure in the flow. It was found that by locating the inlet and discharge survey planes properly, the variation in static pressure over the survey area is small compared to the dynamic pressure and can be neglected. This permits the single static tap on the pitot-static probe to provide the required mean pressure. This paper describes the procedure for using the LDV survey to obtain the waterjet performance.

A low speed retrofit bulbous bow that is capable of reducing resistance over a wide speed and displacement range has been designed for the T-AO 187 class ships. Preliminary model towing tests to simulate bulbs of different volumes and locations were performed with simple bodies of revolutions fitted to the stem of a T-AO 187 model. Data from these model towing tests aided in selecting the volume and location of the final bulb design. Resistance and propulsion model towing tests confirmed that a small volume bulb reduces resistance over a wide speed and displacement range in calm water. The bulbous bow designed for the T-AO 187 class ships reduces resistance across the entire speed range, 10 to 22 knots, at design displacement and provides for reduced fuel consumption.

The role of ship model tank testing in DoD ship construction programs has changed due to DoD policy and the advances made in hydronumeric modeling and simulation (M & S) computer codes. Performance improvements associated with innovative solutions need to be characterized in technical, schedule and cost areas in order to justify consideration. Computer simulations of system solutions performed early in the design cycle enable a wider range design space to be evaluated. Elements of steady flow and ship motions behavior have been successfully characterized with computer models. The validated range over which the performance of design concepts can be evaluated by computer models, however, is limited. The hydrodynamic performance risk associated with advanced hull forms developed for two surface ship programs has been handled using state of the art physical and computer modeling techniques. Hydronumeric computer codes using potential flow theory were used to develop the design concepts. The performance of the resulting concepts and the ability of the computer code to predict hydrodynamic behavior has been validated by physical model testing in this project. Water surface topological definition for the steady flow condition was obtained for ship models operating over a range of ship speeds. This data was obtained from towing tank experiments of candidate future surface-ship-hull forms conducted at the US Naval Academy and David Taylor Model Basin. These experiments included measurements of hull resistance, sinkage and trim, stern wave topology, and longitudinal and transverse wave cuts. The approach and results of the design process, the hydronumeric predictions used to develop the hydrodynamic designs, and ship model tests used to verify performance and increase the validated range of code predictions are presented. Details of the experimental procedures and data are provided. The test configuration, tank definition, model condition and other test conditions provide the code developers with an understanding of how the data was produced. Wave cut, free surface topology, model geometry, and test condition data will be provided on the DTMB Model 5415 web site when cleared for release.