Research On Interference Noise Control Of Serial Cylinder Based On Bionic Square Wave Structure

With the rapid development of industrialization,noise pollution has become an important problem facing mankind,which seriously affects people’s physical and mental health.Aerodynamic noise generated by complex rods such as aircraft landing gear and high-speed train pantograph is an important noise source of aircraft body and high-speed train.These noise problems can be simplified to the interference noise of tandem double cylinders,which is one of the difficulties and hotspots in the field of aerodynamic noise control.This paper takes tandem double cylinders as the research object,explores the interference noise characteristics of double cylinders,and analyzes the noise generation mechanism.A series double cylinder interference noise suppression strategy based on bionic square wave structure is proposed.Combined with experimental measurement and numerical simulation,the interference flow field and sound field characteristics of square wave structure with different parameters are systematically studied,and the noise reduction effect and mechanism of square wave structure are analyzed.The main contents and conclusions of this paper are as follows:(1)Using the hybrid calculation method of large eddy simulation(LES)and acoustic boundary element method(BEM),the generation process of interference noise of tandem double cylinders is simulated,and the influence mechanism of flow field / sound field of bionic square wave structure is explored.The research shows that the square wave structure can reduce the single tone peak noise of series double cylinders by nearly 20 d B,and has a good noise reduction effect in all directions;The far-field noise radiation ability of tandem double cylinders in the direction of flow direction is weak,there is the largest radiation sound lobe perpendicular to the direction of flow direction,and the sound wave is strong;The square wave structure can effectively reduce the pressure fluctuation on the cylinder surface,the turbulence intensity on each section of the wake,the fluctuation of lift drag coefficient,the power spectral density,and reduce the area of the main sound source and the vibration amplitude of the sound source.(2)The experimental study of interference noise of tandem double cylinders was carried out in at 0.55 m×0.4 m acoustic wind tunnel,and the influence law of square wave structure with different parameters on interference noise and its noise reduction mechanism were explored.The results show that the pure tone frequency of reference tandem double cylinders increases linearly with the incoming flow condition;The bionic square wave structure can significantly weaken or even completely suppress the single tone peak noise,the maximum noise reduction is nearly 30 d B,and the maximum noise reduction of the total sound pressure level can reach 18.05 db;The noise suppression ability of different square wave structures changes with the change of working condition parameters.There are square wave parameters with good noise reduction effect in a wide range of working conditions.The noise reduction mechanism of the bionic square wave structure is that the square wave structure not only lengthens the low-speed region of the wake of the average velocity field,but also effectively reduces the peak intensity of turbulence fluctuation in the interference region.Compared with the reference cylinder,the square wave structure changes the characteristics of shedding vortices in the wake of bluff body turbulence from large-scale discrete "alternating vortices " to small-scale continuous "ribbon vortices".In conclusion,the bionic square wave structure can effectively improve the aerodynamic performance of the interference flow field of series cylinders and significantly reduce the farfield interference noise radiation.The size of the cylinder has little effect on the engineering strength of the square wave structure,and has a certain prospect of noise reduction.