The Estimation of Trapped Modes in a Cavity-Duct Waveguide Based on the Coupling of Acoustic and Flow Fields

Trapped modes that exist in the waveguide have different engineering applications. Excited acoustic modes are due to the interaction between acoustic and flow fields. To further study the influence of nonpotential flow on trapped modes for a two-dimensional cavity-duct system, a numerical simulation method that combines the finite-element method (FEM) associated with a mixed formulation of the Galbrun equation and computational fluid dynamics (CFD) is proposed. The calculation model is composed of a two-dimensional waveguide with cavities and perfectly matched layers (PMLs) to limit the computational domain. The effects of the Mach number and different cavity lengths on the resonance modes are investigated.