Graphical acoustic computing method incorporated with the shooting and bouncing ray: application to target strength prediction of concave objects with second-order reflection effects

Abstract

The acoustic backscattering prediction of underwater targets has been drawing concerns from underwater vehicle designers. A graphical acoustic computing method combined with the shooting bouncing ray method (GRACO-SBR) is introduced to solve the acoustic target strength of complex underwater target with concave surfaces. The graphical acoustic computing (GRACO) is an asymptotic method based on physical acoustics. Aided with OpenGL 3D graphical rendering pipeline, this method can process the acoustic integration parallelly and efficiently. Since the traditional GRACO only considers the first-order scattering, the shooting and bouncing ray (SBR) is compounded with the GRACO to cope with the higher-order scattering of concave structures. The target strength of an impedance sphere is solved with several different methods including the GRACO. The results show that the GRACO has an outstanding advantage of the efficiency over the finite element method (FEM) and the traditional Kirchhoff approximation at minor cost of the accuracy in high frequency range. Besides, the prediction of the backscattering of a dihedral corner reflector tells that the GRACO-SBR which considers the second-order scattering can acquire much more accurate solutions than the traditional GRACO method. Further, a stern with cross rudders is considered by both GRACO and GRACO-SBR, and the solutions show that the second-order scattering cannot be overlook when predicting the backscattering of concave structures.