Numerical simulation and coupling mechanism study of acoustic-inertial micromixer

Acoustic-inertial micromixers exhibit a wider operating range and higher mixing efficiency than conventional mixers. We have carried out experimental studies and numerical simulations of acoustic-inertial micromixers. It is found that the acoustic streaming will be changed in morphology and intensity by the background flow, and the coupling mechanism between them is obtained. Specifically, we developed the numerical model of acoustic inertial micromixer by using perturbation theory and the Generalized Lagrangian Mean (GLM) theory. By dividing the flow variables into zero-order, first-order and second-order variables, we obtained the control equations representing background flow, acoustic response and time-averaged streaming flow. Then realized the decoupling analysis of the acoustic-inertial coupling phenomenon. It is found that in terms of acoustic streaming flow, the intensity extreme of it increases as the background flow rate increases. The flow velocity at 5Vpp can reach 0.46 m/s under 500 mu L/min, which is 30 times for the same condition under 10 mu L/min. However, the streaming morphology no longer behaves as a symmetric vortex distributed on both sides of the sharp edge, which is stretched and twisted by the background flow and structure at a high flow rate. The percentage of acoustic contribution at different working conditions is also investigated quantitatively, and the acoustic contribution index (ACI) will generally decrease to less than 0.5 after the background flow dominates the flow field. The results of the study can provide a reference for the design of acoustic-inertial micromixers with larger flow ranges and higher efficiencies.