Comparative study of tonal noise prediction methods for stator-rotor interaction

Tonal noise radiated from the periodic flow induced by stator-rotor interaction has attracted considerable attention as a primary noise component in pump-jet propulsors. This paper explores a multi-phase, multi-reference frame method (MMFM) for the fast prediction of the periodic flow in pump-jet propulsors. The method quickly extracts periodic features by simulating the steady flow at different relative circumferential positions between the rotor and the stator, thereby avoiding the computational inefficiency of the time-domain numerical method (TDNM). Using TDNM as a benchmark, a comparative analysis is conducted between MMFM and the nonlinear harmonic method (NLHM) to evaluate their computational accuracy and cost in predicting the periodic flow and associated tonal noise. The results show that NLHM outperforms MMFM in capturing the periodic flow. The maximum errors in predicting the sound pressure level of MMFM and NLHM are 2.2 dB and 3.6 dB, respectively, over 488 spherical observer points, with 20.5 % and 73.6 % of the points having errors within ±1 dB. Their computational times are 5.6 % and 4.7 % of TDNM, while their computational costs are 16.7 % and 1.2 % of TDNM, respectively. Both methods significantly reduce computational cost while maintaining acceptable accuracy, providing efficient tools for predicting the tonal noise of pump-jet propulsors. • Three methods compared to predict periodic flow inside pump-jet propulsor. • Both MMFM and NLHM reduce computational cost while maintaining computational accuracy. • Tonal noise mainly comes from the duct, followed by the rotor, with the stator contributing the least.