一种基于流固耦合问题的低频散射声场预报方法

A method for low frequency scattering sound field prediction based on fluid-structure interaction

提出了一种流固耦合作用下的低频散射声场预报方法。从边界积分方程出发,推导弹性散射中流固耦合方程,通过引入附加质量、附加阻尼、附加压力概念实现解耦。将弹性散射表述为纯刚性散射项与二次辐射项的叠加,建立了刚性散射与弹性散射的联系。与辐射问题不同,散射中流体对结构的作用不仅表现为附加质量和附加阻尼,还存在一个与结构响应无关的压力项,且该压力项是二次辐射项的激励源。采用Fortran编写了边界元算法程序,用DMAP语言实现与Nastran的对接,形成了完整的散射声场预报方法,通过与理论结果对比,验证了预报方法的正确性。圆柱壳散射的计算结果表明:低频散射时弹性不可忽略;圆柱壳厚度对弹性散射强度和指向性有明显影响;肋骨对柱壳散射的影响与振动形式有关,环肋骨对以弯曲模态为主的弹性散射影响很小。

Here,a low frequency scattering sound field prediction method under fluid-structure interaction was proposed.Based on boundary integral equation,the fluid-structure interaction equation in elastic scattering was derived.Additional mass,additional damping and additional pressure were introduced to realize decoupling.The elastic scattering is expressed as the superposition of pure rigid scattering term and secondary radiation term,and the relation between rigid scattering and elastic scattering was established.Being different from radiation problems,the action of fluid on structure in scattering not only was manifested as additional mass and additional damping,but also has a pressure term being independent of structural response,and this pressure term was excitation source of secondary radiation term.A boundary element algorithm program was coded using Fortran language and docked with Nastran using DMAP language to form a complete scattering sound field prediction method.The correctness of this prediction method was verified by comparing it with theoretical results.The calculation results of cylindrical shell scattering showed that elasticity can’t be ignored in low-frequency scattering;the thickness of cylindrical shell obviously affects intensity and directivity of elastic scattering;effects of ribs on scattering of cylindrical shell is related to vibration form,and effects of ring ribs on elastic scattering dominated by bending modes are very small.