  We analyze acoustic streaming flows using an ALE perspective. The formulation
stems from an explicit separation of time-scales resulting in two subproblems:
a first-order problem, formulated in terms of the fluid displacement at the
fast scale, and a second-order problem formulated in terms of the Lagrangian
flow velocity at the slow time scale. Following a rigorous time-averaging
procedure, the second-order problem is shown to be intrinsically steady, and
with exact boundary conditions at the oscillating walls. Also, as the
second-order problem is solved directly for the Lagrangian velocity, the
formulation does not need to employ the notion of Stokes drift, or any
associated post-processing, thus facilitating a direct comparison with
experiments. Because the first-order problem is formulated in terms of the
displacement field, our formulation is directly applicable to more complex
fluid-structure interaction problems in microacosutofluidic devices. After the
formulation's exposition, we present numerical results that illustrate the
advantages of the formulation with respect to current approaches.
