PROPELLER INDUCED HYDRODYNAMIC HULL FORCES ON A GREAT LAKES BULK CARRIER. RESULTS OF MODEL TESTS AND FULL SCALE MEASUREMENTS

Model tests have been performed in the deep water towing tank and large cavitation tunnel of the NSMB to study the propeller generated hydrodynamic hull forces of a Great Lakes bulk carrier, which suffered from severe vibrations. The investigation also comprised propulsion, wake, flow and cavitation tests. High speed movies were made to study in detail propeller-hull vortex cavitation and to investigate the correlation between this cavitation phenomenon and the pressure fluctuations on the hull. Further, pressure measurements on full scale were performed and a good agreement with the results from model tests was found. It is shown that a stern tunnel fitted to the hull above the propeller reduced the excitation forces more than a modified propeller design. Application of vertical fins, to avoid propeller-hull vortex cavitation, showed an increase of average excitation level.