An investigation on hydro-acoustic characteristics of submerged bodies with different geometric parameters

Numerical analyses and acoustic experiments were performed to investigate the effects of geometric parameters on the hydro-acoustic characteristics of flow over cylinders with circular, square and rectangular cross sections, respectively. A hybrid method which combines RANS and FWH equations was applied for the numerical analyses. The hydro-acoustic characteristics were obtained for circular cylinders with diameters, D= 9.5 , 19.0, 38.0 and 65.0 mm, respectively, and aspect ratios, L/ D= 2.5 , 5.0 and 10.0. The effects of side-ratio, B/H, on the hydro-acoustic characteristics were investigated for cylinders with rectangular cross sections, for B/ H= 0.3 , 0.6, 1.0, 1.8 and 3.0, respectively. The range of Reynolds numbers considered for the numerical analyses and experiments is in the range of 2.25 × 10 ⁴ and 1.7 × 10 ⁵. It was observed that the hydro-acoustic characteristics are greatly affected by the shear layer separation, reattachment mechanism and intensity disturbances. The noise spectrum strongly depends on the cross-sectional geometry of cylinder. An increase in the side ratio causes the spectrum to be narrower, and the main peak frequency increases with reducing side ratio. At constant Reynolds numbers, the broadband noise level and maximum sound pressure level decrease with decreasing aspect ratio, L/D, for cylinders with circular cross section. Moreover, the main peak frequency decreases with increasing diameter, whereas aspect ratio has no effect. The increase in diameter results in a decrease in the broadband noise level and the maximum sound pressure level. The numerical predictions were compared with experimental measurements, and a good agreement was found between the results.