Analysis of hydrodynamic noise of podded propulsor based on DDES coupling FW-H method
To study the structure of the unsteady flow field and acoustic field of the podded propulsor,the DDES(delayed detached eddy simulation)method coupled with FW-H(Ffowcs Williams-Hawings)equation was used to carry out high-precision transient numerical simulations.The results show that the amplitude of the pressure pulsation in the area from propeller to the strut is increased,due to the rotor and stator interference induced by the strut.The vortex distribution of the podded pro-pulsor is complicated.Due to the turbulence effect of the cabin,in addition to the vortex generated by the propeller itself,the structure of the interference wake vortex is also appeared,and the main region of vortex is upward offset.By calculating the standard deviations of harmonic frequencies at various sound receivers on the disk surface,it is found that the sound field has no obvious sound directionality on the disk surface.The spatial distribution characteristics of the acoustic field of the podded propulsor are obtained by setting the spatial acoustic receiver arrays.It can be found that shaft frequency and blade passage frequency are always the main frequencies.There is no obvious directivity of the sound pressure pulsation near the propeller disk,but on the space surface,the distribution characteristics of shaft frequency and blade passage frequency are obvious,where there are high and low value areas with distinct shapes.Behind the podded propulsor,the sound pressure gradually attenuates,but the energy attenuation trend of the blade passage frequency is smaller than that of the shaft frequency.
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