A Numerically Efficient Damping Model for Acoustic Resonances in Microfluidic Cavities

Acoustofluidic damping is a crucial factor that limits the attainable acoustic amplitudes and therefore the effectiveness of acoustofluidic devices. It can be traced back to viscous and thermal dissipation in the bulk and in the boundary layers at cavity walls or suspended particles. However, numerical 3D simulations that include all relevant physics are prohibitively expensive since the acoustic boundary layers need to be resolved. We present a way to incorporate the dissipation effects into a synthetic acoustofluidic loss factor for the use in 3D device simulations. It comes at minimum numerical cost since boundary layers are resolved analytically. Our results and the validity of the physical assumptions we make in the derivation have been verified by analytical and numerical reference solutions. The acoustofluidic loss factor is easily incorporated in device models for a numerically feasible and quantitatively accurate prediction of acoustic amplitudes. In this sense, our work represents the missing link that allows to make not only qualitative but also quantitative predictions of acoustofluidic forces in realistic 3D devices.