Inlet Velocity Distribution of a Full Scale Flush Inlet Waterjet,

摘要

Full scale experiments at sea were conducted to evaluate the performance of two waterjet impellers and to determine the velocity distribution in the inlet of a typical waterjet. Inlet velocity and nozzle velocity measurements were made concurrently with full scale performance evaluation of a waterjet powered planing craft. Two impellers were evaluated in the experiments; one stock impeller, standard with the waterjet and one newly designed and constructed at the David W. Taylor Naval Ship Research and Development Center (DTNSRDC). Evaluation of both impellers was conducted for bollard and underway conditions. Velocity distributions for the underway conditions varied from zero velocity at the top of the duct to approximately 175% of craft velocity at the bottom of the duct. Bollard conditions were markedly different with the highest flow velocity occurring at the center of the duct. Experimental results indicate a need to improve the inlet design before potential improvement can be made in impeller design. The inlet performance could be improved by lengthening and smoothing out the duct or by redirecting the inlet flow with the use of vanes. Results of the impeller evaluations have been reported under separate cover. (Author)