Technical Papers and Presentations

This paper presents a finite element (FE) model of the scattering studies of cylindrical pressure housings made of different metallic alloys such as aluminium, stainless steel 316L and titanium. Understanding the acoustic scattering behavior of underwater objects helps in improving target detection and classification algorithms. This also helps to select the optimum enclosures for underwater acoustical research activities. The model has been made using pressure acoustics-asymptotic scattering (paas) physics of COMSOL Multiphysics software, which models the scattering problems at higher frequencies using the Kirchhoff–Helmholtz integral formulation. The scattering object was chosen to be the underwater cylindrical pressure housings of three materials. The backscattering was measured as a function of rotation angle about an axis perpendicular to the surface for frequencies from 2 to 30 kHz. The corresponding ka value has been calculated for each model where, ‘k’ is the wave number of the incident sound in water, and ‘a’ is the cylinder radius. The scattered acoustic pressure with respect to ka value for different models has been given in figure 1.The evaluated scattered pressure and the known incident pressure signal value helped to compute the target strength (TS) for all the solutions for the orientation 0° to 90° as given in figure 2. Though, all three housings are geometrically similar, variation in scattered pressure is observed due to the different material composition and reflection capabilities i.e. the reflection coefficient and absorption coefficient of the materials. It has been identified that the cylindrical housing made up of SS 316L material recorded more scattered pressure compared with aluminium and titanium pressure housing.