The Acoustic Streaming Boundary Coupling () is a multiphysics coupling from an acoustic interface to a fluid flow (CFD) model, used to add the boundary source contributions necessary to model an acoustic streaming flow. The multiphysics coupling should be used in combination with the Acoustic Streaming Domain Coupling to ensure that all sources are modeled.

The coupling is between either the Thermoviscous Acoustics, Frequency Domain or the Pressure Acoustics, Frequency Domain and a fluid flow interface. When Pressure Acoustics, Frequency Domain is used as the acoustic source interface, the Fluid model should be set to the Thermally conducting and viscous option (see Thermally Conducting and/or Viscous Fluid Model) and the Thermoviscous Boundary Layer Impedance condition is best used to include boundary layer losses. In situations with highly curved or sharp edges, when the boundary layer impedance formulation is not valid, the acoustic interface should be changed to thermoviscous acoustics instead of pressure acoustics.

See Settings for further details about Label and Name.

The default Name (for the first multiphysics coupling feature in the model) is asbc1.

This section defines the physics involved in the multiphysics coupling. The multiphysics interface couples a Source acoustic interface to a Destination single-phase fluid flow interface. The acoustic interface can be either Pressure Acoustics, Frequency Domain or Thermoviscous Acoustics, Frequency Domain. In the Pressure Acoustics, Frequency Domain interface it cannot couple to a Poroacoustics, Narrow Region Acoustics, or Anisotropic Acoustics domain. The fluid flow interface can be a Single-Phase Flow interface, but it cannot couple to a Porous Medium domain. The interface can couple to a turbulent flow interface, but it is advised to take caution since the derivation of the source terms does not take turbulent flow into consideration. For a mathematically consistent formulation, the coupling is typically to the Creeping Flow or the Laminar Flow interface.

These settings are shown when the Advanced Physics Options is selected. It controls how the constraint that adds the boundary slip velocity contributions is handled in the Fluid Flow interface. For the Constraints select either Default (the default), Use DG constraints, or Use pointwise constraints. The Default option results in the Use DG constraints option and should in general be used. The Use pointwise constraints option is really only applicable on flat boundaries; as soon as the boundary is curved, so-called numerical locking effects can occur for this option.