Investigation of Hull Pressure Pulses, Making Use of Two Large Scale Cavitation Test Facilities

The well-known ship model basins MARIN of The Netherlands and HSVA of Germany have joint forces to investigate the problem of the occasional over-prediction of the propeller-induced hull pressure pulses when performing cavitation tests with complete ship models, i.e., with model propellers operating in a ship model wake field. For this investigation advantage was taken of the fact that both institutes can perform cavitation tests with the same ship and propeller model but with fundamentally different test set-ups. Among others, a full scale wake was modeled in both facilities using a so-called "Smart Dummy". The latter is a numerically determined slightly deformed version of the geometrical scale model, generating the expected full scale wake. It was found that the exaggeration of the flow deceleration due to the low Reynolds number at model scale is indeed one important reason for the over-prediction of hull pressure pulses. Other aspects, however, such as the gas content in the water also play an important role. The findings form a valuable basis for an investigation into future cavitation testing techniques that take this Reynolds number problem better into account.