Research On The Noise Characteristics And Reverberation Measurement Methods Of Underwater Jet

With the continuous improvement of the concealment performance of Marine underwater combat platforms,the jet noise produced by the self-propelled movement of underwater combat platforms such as torpedoes and underwater robots has gradually become one of the important factors affecting the concealment of underwater combat platforms..In order to reduce the exposure probability of underwater combat weapons and equipment due to jet noise generated by their own movement,it is necessary to master the characteristics of jet noise to apply targeted vibration and noise reduction measures.This paper studies the quantitative measurement method of underwater jet noise and its acoustic radiation characteristics.In this paper,a numerical calculation method of jet noise based on LES,finite element theory and Lighthill acoustic analogy theory is established.By using CAE simulation tool and ACTRAN acoustic simulation software,the underwater jet noise problem under free field condition and closed space condition is divided into fluid problem and acoustic problem.Through the calculation of underwater jet noise examples and comparison with references,the correctness of the numerical method established in this paper is verified.By using this method,the underwater jet noise in free field and closed space is simulated.The flow field characteristics and sound field characteristics of underwater jet in free field and closed space are summarized.The radiated sound power of underwater jet noise is proportional to the eighth square of jet velocity and its radiated characteristic is consistent with that of the quadrupole sound source.The flow field distribution and noise influence of underwater jet under different jet velocity,jet pipe inner diameter size and closed space size are further studied.For the problem of accurate measurement of underwater jet noise,this paper establishes a reverberation measurement method in the laboratory pool environment.The measurement method has good repeatability and accurate measurement results.The reverberation method is fast and efficient.It only needs to obtain the spatial average sound pressure level within the reverberation control area,and then calibrate the measurement results through the correction of reverberation.Then the radiated sound power of underwater jet noise under free field conditions can be obtained.The reverberation measurement method was used to carry out tests in the gravity water tunnel of the Underwater Acoustic Technology Laboratory of Harbin Engineering University.By comparing the test data of different jet velocities,it was found that the radiated sound power of jet noise measured in the gravity water tunnel was proportional to the eighth square of jet velocity,and the test measurement results matched the numerical simulation results.It is proved that the reverberation method is an accurate method to measure underwater jet noise,and the effectiveness of the numerical calculation method which combines LES,finite element method and Lighthill acoustic analogy theory for the simulation of underwater jet noise in closed space is verified.