COMSOL 6.2 - Acoustic Streaming Domain Coupling

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

See Settings for further details about and .

The default (for the first multiphysics coupling feature in the model) is asdc1.

This section defines the physics involved in the multiphysics coupling. The multiphysics interface couples a acoustic interface to a single-phase fluid flow interface. The acoustic interface can be either or . In the interface it cannot couple to a , , or domain. The fluid flow interface should be a interface, but it cannot couple to a domain. The interface can couple to a turbulent flow interface but it is advised to take extra 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 or the interface.

Choose to select the options (selected per default) to subtract the Lagrangian energy density from the momentum flux tensor. The Lagrangian energy density does not induce streaming flow u2 since it results in a pure gradient force; however, it does induce a gradient in the streaming (time averaged) pressure field p2. Subtracting the Lagrangian energy density can make the simulation converge more easily on a coarser numerical mesh. The Lagrangian energy density has a large numerical value compared to the other terms even though it does not induce streaming. Note that because the Lagrangian energy density is subtracted, the resulting pressure calculated in the flow module is not the correct physical pressure, but the velocity field is correct. The Lagrangian energy variable asdc1.Lac can be added to the pressure p2 in postprocessing to get the correct pressure.

Choose to select the option to include linear perturbation contributions to the viscosity in the governing equations. When selected choose the to be either (the default) or .

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When is selected it is important that the viscosity in the material (under the node) is both has a pressure and temperature dependent, if not the specific contribution will evaluate to zero.

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For enter the derivative of the dynamic viscosity with respect to temperature and pressure (evaluated at T0 and p0). This can, for example, be a constant value, an analytical expression, or data from an interpolation function.