Lagrangian Velocity Field
When modeling acoustic streaming with the multiphysics couplings the flow field in the Laminar Flow interface represents the Eulerian velocity field. When modeling the drag force on a particle the Lagrangian velocity field should be used instead of the Eulerian velocity field. The Lagrangian velocity field is defined as,
(10-1)
where the last term is the so-called Stokes drift. The Acoustic Streaming Domain Coupling defines variables for the Lagrangian velocity field (asdc1.u_lagx, asdc1.u_lagy, asdc1.u_lagz) and a variable for the magnitude of the Lagrangian velocity field (asdc1.U_lag). The variables are announced and can easily be selected in the Drag Force feature in the Particle Tracing for Fluid Flow physics interface.
The Lagrangian velocity differs from the Eulerian velocity inside the viscous boundary layer and in the case of evanescent, rotating, or traveling acoustic fields.
Acoustic Streaming in a Microchannel Cross Section. Application Library path Acoustics_Module/Nonlinear_Acoustics/acoustic_streaming_microchannel_cross_section