ウォータージェット推進船の曳航能力

Abstract

The vessels with waterjet propulsion system increase with the rapid growth in numbers of high speed vessels. It has been increasing when waterjet vessels do towing work. However, the towing performance of waterjet vessels has not been researched clearly.The purpose of this study is to investigate the towing performance of waterjet vessels. Bollard pull test and 2 ways towing tests which are towing ahead and astern were carried out by using the patrol vessels with waterjet of Japan Coast Guard. In general, a standard tow force of propeller vessels is 1.0tf/100PS. However, it was found from the test results that tow force of waterjet vessels is almost half of propeller's one. The cause of drop of towing performance for waterjet is the flow separations at the inlet's lip part.Since the numbers of impeller rotations becomes high to the low ship speed during bollard pull and towing, and the inlet velocity ratio (IVR) which means the inlet velocity to the momentum velocity becomes 1.0 or more. Duct flow of flash type inlet on bollard pull and towing were computed by flow solver "SURF"developed by National Maritime Research Institute. On the basis of those computed results, the loss due to the waterjet duct and the head of propeller and waterjet were evaluated and were compared with the towing test data. Comparison of computed results with test data shows good agreement. The results indicate that towing performance of waterjet can be estimated by evaluating the loss due to the waterjet duct.