Modeling the Vibroacoustic Behavior of Submerged Stiffened Cylindrical Shells Coupled to Non-axisymmetric Internal Structures and Excited by a Turbulent Boundary Layer

Abstract

Modeling the vibroacoustic behavior of structures excited by random pressure fields, such as turbulent boundary layers (TBL), is of interest for naval applications. Most works in the literature address the problem by considering periodically stiffened plates or shells. These studies have highlighted the role of Bloch–Floquet waves in increasing radiated pressure in certain frequency bands. However, in industrial applications, the stiffened structure excited by the TBL is generally coupled with internal structures such as bulkheads, floor partitions and engine foundations. To understand how these internal structures can modify the propagation of Bloch–Floquet waves and, consequently, the pressure radiated in the far field, it is necessary to have an efficient simulation tool. We propose developing a dedicated numerical process to estimate the radiated pressure from a cylindrical shell stiffened by axisymmetric/non-axisymmetric internal frames and excited by a homogeneous TBL. The process is based on the wavenumber-point reciprocity principle, which states that the sensitivity functions at a given point M correspond to the spectral responses of the system when excited by a monopole located at M. The condensed transfer functions approach is employed to derive these responses, thereby partitioning the problem: The immersed cylindrical shell is represented by an analytical model, whereas the internal frames are described using finite element models. Numerical results highlight a significant influence of the internal structure on the acoustic radiation of the stiffened shell in far field, induced by the coupling of the circumferential modes.