Study On Correlative Technology Of Acoustic Jammer Of Underwater Continuous Explosion

With the development of torpedo technology,the torpedo threat to surface ship is increasing,thus,the research on anti-torpedo technology has become very urgent.The acoustic jammer based on underwater continuous explosion is a sort of effective soft-killing weapon.When detonated,it can produce sound signal which has relatively long duration,high power and wide bandwidth,effectively interfering the acoustic homing torpedo.Hence,in the far distance,it can be used as a false target for a relatively strong signal,and in close range,it can cause saturation and obstruction of the sonar array,so that the surface ship can gain time when it circumvent acoustic homing torpedo.This issue considers the technology of underwater acoustic countermeasure for anti-torpedo weapon as application background,and the acoustic jammer based on underwater continuous explosion as the research purpose.The structural shock response in spreading process of the acoustic jammer shrapnel and shock response of submunition entering the water are analyzed,the influence from shock wave and bubble pulsation of underwater explosion is studied,the tests of underwater explosion are carried out,the acoustic signals of underwater single and continuous explosion are processed and analyzed respectively,the acoustic characteristics of underwater single and continuous explosion sound signal are also analyzed,in addition,combining theory modeling and numerical method,the underwater continuous explosion simulation against acoustic homing torpedo is studied.The main researches include:(1)For the structural shock response analysis in spreading process of the acoustic jammer shrapnel,the piston dispersal Mechanisms with single and double combustion chambers are designed respectively.The dynamic dispersion pressures in the cabin are calculated based on Runge-Kutta method,and numerical simulation on shock strengths of the push plate,center pin,and baffle in spreading process are done using software LS-DYNA,so that the strength failure modes of different dispersion components under two pressure conditions can be studied;for the research on the shock response of the acoustic jammer submunition entering the water,the numerical simulation on the shock response of the six-prism submunition with flat head into the water is done using ALE method based on software LS-DYNA,and the rules of the phenomenon that the submunition entered the water,shock overload distribution,velocity attenuation and shock response on the shell are analyzed respectively.(2)In the research on stress wave with small-dose charge:the basic phenomena of underwater explosion and shock wave propagation law are analyzed.Combining underwater explosive shock wave empirical formula,the stress wave simulation of spherical bare charge is done.The super-spherical propagation regularity of underwater explosive shock wave is obtained,after analyzing the shock wave peak pressure changes in the close field.Then,the stress wave simulation of spherical charge with shell is calculated by setting the state equation of water.The relationship between shock wave peak pressure and shell thickness is analyzed,and the effects from different depth and thickness of the shell on bubble pulsation are discussed respectively.(3)In the research on underwater continuous explosion experiment:the experimental data is obtained through underwater explosion tests.The acoustic characteristics of underwater single and continuous explosion are studied respectively.The properties of underwater continuous explosion are studied such as shock wave attenuation,sound pressure level,acoustic duration,power spectrum and the relative energy distribution of acoustic signals.The sound signal of underwater continuous explosion has strong sound power,and the convex point of sound pressure level can be over 190 dB.The sound energy concentrates on the frequency band below 24 kHz,the sound energy below 10 kHz is particularly strong.The effective acoustic duration of underwater continuous explosion is the sum of time interval between explosive units.In all,underwater continuous explosion is a kind of acoustic source with high power,relatively long duration and wide bandwidth,and it can play an important role in underwater acoustic countermeasure.(4)In the acoustic signal processing and analysis of underwater continuous explosion:the wavelet transformation,Hilbert-Huang transformation and the improved HHT based on EEMD is applied.First,the acoustic signals of underwater single and continuous explosion are analyzed respectively,using spectrum estimation,energy distribution and time-frequency spectrum which are on the basis of wavelet transformation.Then,the acoustic signals of underwater single and continuous explosion are decomposed,reconstructed and spectrum analyzed using wavelet transformation,Hilbert-Huang transformation and the improved HHT based on EEMD.When analyzing the acoustic signal of underwater continuous explosion using Hilbert-Huang transformation,the signal is decomposed using EMD,so that IMF components are obtained,and then Hilbert transformation is done,for obtaining Hilbert energy spectrum.The results indicate that the energy distribution range of underwater continuous explosion is within 48 kHz.Comparing wavelet transform,Hilbert-Huang transform and the improved HHT based on EEMD together,it can be known that conclusion based on different methods is similar.(5)In the study on the acoustic jammer countermeasure of underwater continuous explosion:the theoretical modeling and numerical method on underwater explosion against acoustic homing torpedo are applied.In the acoustic utility analysis of underwater continuous explosion,models of active sonar and passive sonar are established according to the sonar equations.The underwater acoustic countermeasure effect is assessed based on evaluation standards,average reduction amount and average reduction rate of detection distance.In the research on underwater acoustic countermeasure strategy,the corresponding mathematical model is established,for solving the nonlinear programming problem and determining the optimal placement and circumvent angle of underwater continuous explosion.