Sources of Acoustic Streaming
Acoustic streaming can be induced by different physical mechanisms that are included either in the Acoustic Streaming Domain Coupling or Acoustic Streaming Boundary Coupling, so to understand which multiphysics couplings are important to include, it is necessary to understand the underlying mechanisms. The five main types of acoustic streaming are:
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Rayleigh streaming induced by stresses in the viscous boundary layers. Rayleigh streaming is well known and is often dominant in microfluidic systems with a standing pressure field.
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Eckart streaming induced from viscous damping in the domain of the fluid. Eckart streaming is often important for traveling acoustic fields.
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Streaming due to a vibrating boundary, known as Stokes slip. This is typically important when the wall velocity is comparable to the acoustic velocity in the fluid, which is often the case for systems working off resonance.
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Thermoacoustic streaming (baroclinic streaming) induced when there are gradients in the density and/or compressibility of the fluid. These gradients can be due to either a solvent or temperature gradient (in the background temperature).
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Streaming from sharp edges. Sharp edges are geometry features with a length scale smaller than or similar to the viscous boundary length. This effect can only be modeled when using the Acoustic Streaming from Thermoviscous Acoustics interface.