1. Example: Vibration of a Disk Backed by an Air-Filled Cylinder

2. Vibration of disk backed by an air-filled cylinder Constants: The thin disk: E=210 Gpa nu=0.3 rho=7800 kg/m 3 t_disk=0.38 mm Air: density: 1.2 kg/m3 speed of sound: 343 m/s Extended Multiphysics model : Coupled system using DRM plate for the thin disk and a 3D PDE application mode for the acoustic equations in the air. 38 mm Thin disk Air within perfectly rigid walls Clamped edges 255 mm Heavy slab

3. Vibration of disk backed by an air-filled cylinder The first eigenmode, a tightly coupled structural and acoustic mode at 637 Hz Results

4. Vibration of disk backed by an air-filled cylinder The second eigenmode, a phase shifted tightly coupled structural and acoustic mode at 707 Hz Results