Hydrodynamic and Hydro acoustic analysis of marine Propeller

Abstract

A detailed hydrodynamic and hydro acoustic analyses of a four bladed marine propeller INSEAN E-779A was carried out in this study. Unsteady RANS model k-ω SST was used to assess the hydrodynamics of propeller, while acoustic of propeller were studied by deploying Ffowcs William hawking acoustic analogy. Hydrodynamic and hydro acoustic characteristics were studied by changing advance ratio (J) from 0.6 to 0.9 along with change in flow incidence angle to the propeller (θ) from 0 – 40 degrees. Hydrodynamic Coefficients like thrust coefficient KT and torque coefficient KQ were determined along all directions for different values of J and θ. These coefficients were plotted to study their trends and how they effected the overall operational efficiency of the propeller. Efficiency decreased from 64% at 0 degrees to 28 % at 40 degrees for J=0.88 and from 51 % to 40% for J=0.6. Detailed directivity analysis was carried out for different sets of flow conditions to see how acoustic distribution around propeller changed. Acoustic pressure changed by 19%, 16.5% and 31% in XY, XZ and YZ planes respectively with change in advance ratio from 0.88 to 0.6 at 40 degrees. Moreover, FFT analysis of the acoustic signal was carried out to see which frequencies become dominant at different flow conditions and how acoustic signature changes at various distances in the wake of propeller. Peak SPL values were observed at 1xBPF and 2xBPF at various distances in the wake of the propeller to see how they are affected by the change in flow conditions. Near field and far field acoustic signature was also studied to see how the acoustic behavior changed with distance.