Outer streaming within a two-dimensional channel

Acoustic streaming is the net time-averaged flow that results from the nonlinearities in an oscillating flow. Extensive research has sought to identify different physical mechanisms and types of acoustic streaming in systems of various geometries. While streaming in a channel maintains one of the simplest geometries, dimensional analysis of the governing equations reveals that multiple regimes of streaming may occur within a channel. In this study, a framework is developed for investigating and understanding the physical streaming regimes in a two-dimensional channel. By taking different limits of the dimensionless number ratios found within the framework, streaming models derived in previous works are recovered to demonstrate the different streaming regimes within a channel. The onset of fast streaming is then analyzed with the framework and nonlinear Reynolds numbers, which indicate whether the streaming is slow or fast, are found for the different physical streaming regimes. As a result, the framework provides a base for analyzing fast streaming in a channel and streaming in multi-scale systems while organizing previous streaming models into a physical spectrum for a channel geometry.