Research On Hydrodynamic Noise Of Duct Propeller And Its Control Technology

Propellers are the most common propulsion devices used in underwater navigation,but their operation generates significant noise,which greatly reduces their stealth capability.Flow noise control for propellers is a critical technology for underwater navigation,and has significant research and application value.In this article,a hydrodynamic noise flow control method is proposed,which applies a serrated structure to the duct of the NO.19A+Ka4-70 ducted propeller to reduce its hydrodynamic noise.Firstly,the hydrodynamic performance of the DTMB P4119 conventional propeller was calculated and compared with experimental results to verify the effectiveness of the simulation.The noise generation principle of the propeller was explained,and the flow noise and radiated noise of the propeller were calculated and analyzed.The radiated sound power curves under different advance speeds and rotational speeds were analyzed,and the main factors affecting the radiated sound power of the propeller were discussed.Secondly,the flow characteristics of the NO.19A+Ka4-70 ducted propeller were investigated,including the distribution of pressure,velocity,vorticity,and radiated sound power.The flow field distribution and pressure-velocity change laws of the ducted propeller under different tip clearances were discussed.Based on these laws,the effect of the serrated structure on the flow state of the ducted propeller and noise control mechanism were analyzed.Adding a serrated trailing edge effectively suppressed the boundary layer separation on the inner wall of the duct,and inhibited the large eddy structures in the wake of the propeller,disrupting the vortex distribution area at the tail of the model,and generating more small eddies.Adding a serrated leading edge changed the pressure distribution at the front end of the duct,reduced the pressure difference between the inside and outside of the duct,and reduced the adverse pressure gradient,thereby suppressing the boundary layer separation on the surface of the duct and reducing the size of the tip vortex structure generated by the propeller during motion.The noise control effect of different lengths and numbers of serrations was calculated and discussed,and the optimal ducted propeller with serrations was obtained.Finally,test models of the original ducted propeller and the serrated leading edge ducted propeller were designed and processed.Hydrodynamic noise was measured using the reverberation method and turbulent fluctuation pressure measurement method in a low-noise gravity water tunnel.The experiment showed that the serrated leading edge ducted propeller has good noise control performance under different advance coefficients and can effectively reduce the turbulent fluctuation pressure on the surface of the ducted propeller.