Development of waterjet testing techniques

Thornhill, Eric (1999) Development of waterjet testing techniques. Masters thesis, Memorial University of Newfoundland.

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Abstract

In the last decade, waterjet propulsors have found increasing acceptance as an alternative to marine screws and other propeller types. Over the same interval, waterjets have evolved from relatively small, simple propulsors for small recreational craft, to sophisticated engineering systems appropriate for high speed and high power vessels. The continuing development of propulsors for such vessels is aided by research for improvement and evaluation of designs. The development of research capabilities in this field is in progress at the Institute for Marine Dynamics. It has been focusing on the ability to perform experiments of vessels and their propulsors at model scale in order to evaluate the performance of the integrated system. -- Model testing techniques for waterjet propelled craft are reviewed and discussed from various relevant works on the subject. Several types of waterjet propulsors as well as some of the common vessel types are identified with respect to the scope of the testing capabilities of the facility. Two phases of experiments were prepared for a model of a 12 metre recreational craft with simple model jets. The phases consisted of bare hull resistance tests and self-propulsion tests. The experiments were intended as trials for testing techniques and instrumentation since results could be compared with the full scale performance of the vessel. One conclusion drawn from the tests was that a model waterjet propulsor would have to be designed and instrumented specifically for such experiments. -- An experimental waterjet propulsor test platform was then developed to accommodate the requirements derived from the initial test phases. The platform housed a model which employed a modular design allowing variation of internal geometry of the waterjet design if required. The platform was fully instrumented to measure flow speeds and pressures in the nozzle and near the impeller. A transparent impeller region was designed to observe possible cavitation phenomena. Thrust, torque, shaft speed and volume flow rate were also measured. The design, instrumentation, test program and test results of the model waterjet and platform are presented and discussed.

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