Vibro-acoustic behavior of finite-length fluid-loaded periodic structures using local-global homogenization
Local-Global Homogenization (LGH) is a method to predict directly the smooth global response of periodic fluid-loaded structures in a self-contained manner. Many fluid-loaded structures, such as fuselages and hulls, have periodically spaced braces, ribs, or attachments. Structural motion, acoustic radiation, and the interior sound field are of interest. Calculating the motion of such fluid-loaded structures is difficult because of their complexity and the disparity of length scales. Periodic discontinuities cause the structural response to occur in a broad spectrum of spatial wavenumbers, and to exhibit stop-band and pass-band behavior. The broad spatial wavenumber spectrum contains both radiating and non-radiating components. The global low-wavenumber part of the response is most efficiently coupled to the acoustic field, since low wavenumbers correspond to supersonic phase speeds. In the LGH reformulation, an infinite order operator that embodies both the structural modes and the evanescent component of the fluid loading governs the equivalent smooth global problem. Numerical implementation is demonstrated for the structural response and acoustic radiation from a finite-length fluid-loaded plate with periodic impedance discontinuities. Fluid radiation and loading is calculated used a boundary element method. Calculations show good agreement with the exact solution and substantially improved computational efficiency.
