Numerical analysis of the effect of geometric pitch on the radiated noise level of high skew propeller

The purpose of this article is the numerical hydro acoustic analysis of non-cavitating radiated noise in different geometric pitches using the computational fluid dynamics method.The geometric pitch of the propeller is one of the most important influencing parameters in the design of marine propellers, Therefore, in this article, a sample of the standard underwater propeller series with different number of blades and different geometric pitches has been used and the data related to the vorticity field and the radiated noise level have been extracted and studied.In this numerical analysis, the DES turbulence model has been used, which has solutions with acceptable accuracy in the noise subject with an average grid number, compared to the large eddies method.In order to increase the accuracy of the numerical data, the grid generated around the propeller in the areas of the leading edge, trailing edge, tips of the blades and in the region of the downstream, has been produced with a higher grid density.According to the obtained results, by increasing the geometric pitch angle of the propeller blade, the static pressure on the pressure side of the blade increases, and the vortices caused by the boss and hub become longer, and the amount of change in the sound pressure level in the axial direction at low frequencies is less than 5 dB, but at high frequencies it is oscillating and the changes are more noticeable.The highest amount of change in the sound pressure level in terms of pitch is in the direction perpendicular to the flow direction and reaches up to about 40 db.