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Acoustic Transmission Loss through Periodic Elastic Structures

Model Database 1974

Background and Motivation

• In this model, two fluid domains are separated by a solid elastic structure. An acoustic pressure wave impacts the structure resulting in a reflected wave and a wave transmitted with a loss through the structure. This model investigates the transmission loss through the structure. The effects of incident angle, frequency, and damping are studied.

• Important features used: Acoustic-structure multiphysics interaction with arbitrary incident angle, scattered field formulation, the perfectly matched layer (PML), and periodic Floquet boundary conditions.

• Reference: S. Dey and J. J. Sirron, Proceedings of IMECE 2006, ASME 2006 Internal Mechanical Engineering Congress & Exposition, Chicago, USA

k

Geometry and Operating Conditions

k

Lx

water

solid

water

dL

• Incident plane wave at angle , with wave vector k.

• Infinite periodic structure

• Infinite water domain

x

y

Modeled infinite periodic domain

Floquet periodic condition

Model Setup • The model is solved using the Acoustic-Solid Interaction, Frequency

Domain multiphysic interface of the Acoustics Module.

• The interface provides pre-defined multiphysics couplings between solids and acoustic domain as well as periodic Floquet conditions.

• Add two integration operators to determine the average pressure at the top and bottom side of the solid. At the top both the incident (background) acpr.p_b and the reflected (scattered) acpr.p_s pressures are defined (because of the addition of the background pressure field option). On the bottom only the transmitted total field exists as acpr.p_b=0.

• Also add variables that define the incident, reflected and transmitted pressures along with the transmission loss TL:

T𝐿 = 20log(|𝑝𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡/𝑝𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑|)

Results: Reflected and transmitted pressure

The curves match the theoretical curves in the reference: S. Dey and J. J. Sirron, Proceedings of IMECE 2006, ASME 2006 Internal Mechanical Engineering Congress & Exposition, Chicago, USA

Results: Transmission loss

Results Incident (background) pressure for an angle of incidence of 11 deg.

Results Scattered (above) and transmitted (below) pressure for an angle of incidence of 11 deg.

Results Total pressure field for an angle of incidence of 11 deg.

Results Total pressure and deformation amplitude for an angle of incidence of 40 deg.