NUMERICAL STUDY OF ACOUSTIC CHARACTERISTICS OF A DTMB 4119 PROPELLER DUE TO TIP RAKE

The impact of increased Underwater Radiated Noise (URN) over the past two decades on marine mammals has resulted in the pressing requirement to reduce it. Shipping contributes immensely to the URN. Propeller noise is a major source of URN. The reduction in Propeller noise can hence significantly help in the reduction of URN. With the sole objective of improving the hydrodynamic performance of propellers ways to prevent cavitation are being developed. However, the reduction of non cavitating noise produced by the propeller would still remain a challenge. The change in the propeller geometry can modify the acoustic characteristics. In this present study, effect of modifying the tip of DTMB4119 propeller on the acoustic and hydrodynamic characteristics is presented. The change in the flow pattern at the tip due to introduction of tip rake is also discussed. The SPL has been calculated by using the two-step Ffowcs William and Hawkings (FW-H) equations from the pressure distribution at various points around the propeller. SPL at various points in the downstream and propeller disk plane are numerically predicted and discussed.