Study on the wall-pressure fluctuation characteristics of a pump-jet propulsor duct in turbulent boundary layer

Abstract

This study presents the distribution of excitation sources and pressure fluctuation characteristics on the duct wall of pump-jet propulsor. A modified submarine geometry based on the SUBOFF model is developed to provide a stern flow filed with turbulent characteristics for pump-jet. The Turbulent Boundary Layer (TBL) of outer wall is obtained by using Large Eddy Simulation (LES) numerical method to understand the velocity distributions. The characteristics of unsteady excitation force spectra are investigated respectively under different excitations excited by the internal and external flow field of duct. Besides, a spatial-temporal distribution of TBL pressure energy on duct wall excited by external flow field is emphatically revealed through the spectral analysis method. The results show that the force spectra excited by external flow field display an obvious broadband characteristic and discrete components appear at Blade Passing Frequency (BPF). While the force spectra excited by internal flow field present a remarkable discrete peak at BPF and its multiple. The BPF has a significant influence on the energy convergence range of excitation forces on outer wall of duct and a rapid decay trend starts to occur near BPF. The scale of vortices with most dominant energy contribution is determined by BPF and corresponding wavenumber, rather than the energetic wavenumber.