Influence Analysis of Internal Solitary Wave on Towed Line Array Shape and Compensation Strategy

Abstract

Due to the flexibility of the towed line array, shear currents caused by an internal solitary wave (ISW) distort the array shape. This will lead to a mismatch between the conventional target detection algorithm and the array shape, resulting in a significant decline in the performance of the towed line array gain, azimuth resolution, etc. Based on the improved motion model of towed cable constructed by Ablow and Schechter (Ocean Eng, 10: 443-457, 1983), we propose a motion model of the towed line array under an ISW according to the Korteweg-De Vries (KdV) equation and solve the model by finite difference method combined with the Newton iteration method. In addition, the DFT beamforming theory is used to detect the target signal after the array shape distortion compensation to verify the validity of the model. The data analysis shows that the array shape distortion caused by the ISW is mainly affected by the relative position between the array and the ISW, the amplitude of the ISW, the fluid layer density, the fluid layer depth, the towing velocity, the tangential/normal drag coefficient, the elastic modulus, and the towed cable density. The influence of elastic modulus and the towed cable density on array shape distortion can be ignored. The detection results show that the output signal power is about 6 dB higher than the output noise power, and the array gain and azimuth resolution are improved after array shape distortion compensation.

All-fiber acoustic-posture integrated towed linear array based on fiber laser hydrophone

“…At present, for the ultra-fine towed linear array without attitude sensor, only the shape of the tow cable is estimated [7] . Odom J L [8] et al propose to combine the two estimations using adaptive weights to obtain improved shape estimation during maneuvering; Yue-Hui T [9] et al proposed a method to a shape deformation estimation method for towed array sonar has been proposed based on parabolic model and exponential model; Maofa W [10] et al pointed out that a motion model of the towed linear array under an ISW according to the Korteweg-De Vries (KdV) equation and solve the model by finite method combined with the Newton iteration method. There is currently no all fiber towed linear array that can integrate distributed attitude measurement and point type sound measurement.…”