Ship noise management and the ORCA class of ships

To support Transport Canada's projects to reduce underwater noise from shipping, Defence Research and Development Canada performed a series of experiments based on the Royal Canadian Navy's ORCA-Class training vessels. Sea trials measured onboard vibrations and underwater noise to support the development of a real-time prediction of propeller cavitation inception and underwater noise using only onboard sensors and to develop a database for assessing numerical predictions of underwater noise at the design stage. Based on these trials, it was noted that the noise impact of the vessel could be significantly reduced if the propeller cavitation inception speed could be increased. A series of numerical optimizations were conducted and a low-noise design was selected. Scale models of the ship and propellers were constructed and tested in a towing tank and cavitation tunnel. While the numerical predictions (done at full scale) were very promising, the model-scale tests did not bear them out.