Sub-Component Lumping in Acoustics Using the Impedance Boundary Condition

Application ID: 33371

This application illustrates a modeling approach for deriving physically consistent simplified models in the Acoustics Module. The approach consists of converting complex sub-components to an impedance boundary condition and otherwise using simple acoustics throughout the COMSOL model. As a consequence, significant computational speed-up can be achieved.

The example treated here consists of a simplified muffler-like system consisting of a main duct and a Helmholtz resonator (the sub-component). The acoustics in the resonator are modeled with thermoviscous acoustics because viscous and thermal boundary-layer losses are important. The aim is to lump the thermoviscous acoustic domain with an impedance model.

The application gives step-by-step illustrations of how to derive impedance boundary conditions in a complex acoustics model as well as how to call this impedance in a new, simple model. In addition, the model also details how to use the Optimization Module to fit the derived impedance to an RCL model. It is discussed how this second approach can be used to derive additional insight about the modeled system.

This model example illustrates applications of this type that would nominally be built using the following products: