The multiphysics interfaces Acoustic Streaming from Thermoviscous Acoustics and Acoustic Streaming from Pressure Acoustics, couples a frequency domain acoustic study to an either stationary or time-dependent fluid flow. If the flow is time-dependent, the coupling is only valid if the time-scale of the acoustic field is a lot shorter than the characteristic time-scale of the fluid flow. This requirement is fulfilled in microfluidic devices ran at typical frequencies used in microfluidic (MHz to GHz).

The simplest study configuration is to have two study steps. First a Frequency Domain study step that includes the acoustic fields, and secondly a Stationary study step that includes the fluid flow interface and the multiphysics coupling. The Stationary study step needs to use the solution from the Frequency Domain study step for Values for variables not solved for. This is a one-way coupling from the acoustic field to the fluid flow.

For studying the transient behavior of acoustic streaming there are two possibilities. First if the acoustic pressure field is constant, the solver can be setup as the previous stationary study. First a Frequency Domain study step that includes the acoustic fields, and then a Time-dependent study step that includes the fluid flow interface and the multiphysics couplings. The Time-dependent study step needs to use the solution from the Frequency Domain study step for the Values for variables not solved for. If the acoustic pressure field changes with time, due to changes in actuation or changes in material properties due to heating, then the Frequency-Transient study step can be used. It is important to note that all changes in the acoustic fields has to be on a time-scale a lot longer than the acoustic time-scale. The Frequency-Transient study solves for the acoustic fields in each time step of the transient solver.