开式呼吸蛙人专用氧气瓶声散射特性

Sound Scattering Characteristics of Oxygen Cylinder for Open Breathing Diver

解决开式呼吸蛙人所携带的氧气瓶目标强度对目标全体散射的贡献问题,为掌握蛙人的精确特性预报和识别奠定基础.构建非轴对称激励下三维目标的二维有限元轴对称模型,运用声固耦合-频域多物理场接口计算不同方位声波照射目标散射远场的频率特性数值解,解释频率响应共振频率亮条纹产生的原因和估计公式.在线性声学的假设下,将有限元数值解作为系统函数,同带宽线性调频信号为系统输入信号,根据时域卷积定理得到时域回波仿真结果,结合亮点模型和弹性环绕波理论给出距离-角度时域回波的精确预报模型.结果表明:影响氧气瓶回波强度的主要因素为目标的镜反射和角反射,气瓶阀门和球冠等精细结构产生的附加亮点和环绕波对不同方位散射频率响应特性的影响不可忽略.通过收发合置的湖试实验,验证回波机理和散射指向分布共振频率特性预报的正确性.

This paper aims to solve the problem of the oxygen cylinder contribution to the overall scattering intensity of the open breathing diver,which is the basis for mastering the accurate prediction and identification of the diver.A two-dimensional finite element axisymmetric model of 3D-object with non-axisymmetric excitation is constructed.The numerical solution to the far-field frequency characteristics of the acoustic scattering by the object with different azimuths is obtained by using the acoustic-solid coupling multi-physical interface in frequency domain.The reason and the estimation formula of the bright fringe at the resonance frequency are given.Under the assumption of the linear acoustics,the numerical solution to finite element method(FEM)is taken as the system function,and the linear frequency modulation signal with the same bandwidth is taken as the input signal of the system.The echo simulation in time domain can be obtained based on the convolution theorem.Combining the bright spot model and the elastic circumferential wave theory,the precise prediction model of the distance-angle echo in time domain is proposed.The results show that the main factors that affect the strength of the echo include the mirror reflection and the angular reflection.The additional bright spots and circumferential waves generated by the fine structures such as valves and spherical cap have a non-negligible influence on the frequency response characteristics in different azimuths.The validity of the echo prediction and resonance frequency characteristics is verified by the lake experiment in monostatic mode.