Two-dimensional streaming flows driven by sessile semicylindrical microbubbles

Steady streaming flow from oscillating sessile bubbles at walls is the centrepiece of many microstreaming experiments. A complete asymptotic theory of the flow is developed, requiring only the oscillatory driving frequency and material parameters as input, and properly accounting for bubble and wall boundary conditions. It is shown that mixed-mode streaming of neighbouring bubble oscillation modes is responsible for the robustness of the generic 'fountain' vortex pair flow pattern, and that the pattern reverses for high frequencies when wall-induced streaming becomes dominant. The far-field flow and its dependence on control parameters are in agreement with experimental data and can be understood considering just a few asymptotic coefficients.