Vibration And Noise Of Submarine Model Excited By TBL Fluctuating Pressure

The work environment of submarine is very complex, especially at the high-speed, the random fluctuating pressure of turbulent boundary layer will load on the surface of submarine, this pressure will cause the random vibration and sound radiation of structure. Submarine is very different from ordinary ships, once it was exposed, the consequences would be severe. So in the early stage of design, it must be considered how to reduce the noise effectively, there is a great significance to forecast the structural vibration and noise. This paper has analyzed the vibration and radiated noise of submarine model by using numerical methods, the full-text includes following contents:The CFD software FLUENT was used to calculate the dynamic pressure of submarine model TBL, the pressure information has been changed from time domain to frequency domain with the method of Fourier transform, So the power spectral density of dynamic pressure was got and input as the excitation of vibration.Since the spectral density of excitation was obtained, the pseudo-excitation method was used to calculate the random vibration of submarine model, the pseudo-excitation method changes the random process to harmonic process. By combing the pseudo-excitation method with the finite element method and the boundary element method, random vibration and acoustic radiation of the structure can be calculated quickly and efficiently.Based on finite element method and fluid-structure coupling theory, the vibration of a submarine model was calculated in water, the basic equations of finite element method and fluid-structure interaction equation of motion were introduced. Taking advantage of the finite element software ANSYS, this paper established finite element model of the submarine model and fluid around, the natural frequency and vibration of submarine model was analysed. Also, the vibration response of submarine model excited by TBL excitation was calculated.Based on boundary element method, the sound radiation of structure vibration was calculated. Based on the acoustic boundary integral equation, this paper calculated the radiation sound power of the structure and the sound pressure of any point in field with the boundary element software Virtual.Lab Acoustics. In order to prove the feasibility of this method, a cylind shell was studied in this paper, the thickness of the plate and motivating position were variable to research their influence on the vibration and acoustic radiation of shell, the results show that it is necessary to avoid resonance in order to reduce noise, sometimes, changing the parameters (such as increasing the thickness) can reduce the radiation noise.The results of numerical simulation fit the basic role of hydrodynamic noise, with the velocity doubled, the hydrodynamic noise increases18-21dB. It means the radiated sound power is proportional to the velocity to the sixth or seventh. Due to the fluctuating pressure of turbulent boundary layer is a broad spectrum force, it will arouse many order models of submarine. It can be observed that the vibration and sound radiation of submarine model excited by turbulent boundary layer can be calculated by the pseudo excitation method effectively.