Prediction Of The Target Strength Of Submarines With Anechoic Coatings At Low Frequency

Submarine is a very important type of naval equipment,and stealth is an extremely important performance of submarine.A submarine with good stealth is a huge threat to the enemy fleet.Target strength is an important parameter to describe the stealth of a submarine,the smaller the target strength,the better the stealth performance of the submarine.Currently,acoustic coatings are mainly applied on the surface of submarines to reduce the target strength of submarines,thereby improving the stealth performance of submarines.The planar element method is a commonly method for predicting the target strength of high-frequency of submarines in China,and the method can quickly and effectively predict the target strength of high-frequency of submarines.However,with the development of sonar detection technology,the detection frequency of active sonar shifts to medium and low frequencies.The low-frequency target strength of submarines is becoming more and more important.At present,the forecast of the low-frequency target strength of the submarines is not yet mature.In this paper,the parameter equivalent method and the finite element method predict the target strength of the low-frequency of submarines.First of all,the target strengths of rigid sphere,elastic sphere shell are calculated by the Virtual Lab Acoustic software.Then we compare the target strengths with their theoretical solutions.The effectiveness of Virtual Lab Acoustic to calculate the target strength of a simple target was verified.Then the paper has studied the parameter equivalent method.The anechoic coatings can be equivalent to homogeneous isotropic material by using the principle that the original reflection coefficients are equal to the reflection coefficients using the parameter equivalent method.The original reflection coefficients can be obtained by the impedance tube method,the reflection coefficients of homogeneous isotropic material can be obtained by the transfer matrix method.So the equivalent material parameters can be inverted by the genetic algorithm.Then the acoustic finite element method and automatic matching layer technology have been used to calculate the target strength of benchmark submarine.And the results are similar to the BASIS method.The physical parameters obtained by using the parameter equivalent method were substituted into Virtual Lab Acoustic to calculate the target strength of the submarine with acoustic coatings.Then the target strengths of submarines with different grazing angles and different subdivision angles are calculated.Then,Some rules have been obtained.