Performance evaluation of laminar micromixer based on two-degree-of-freedom flow-induced vibration

Solution mixing in microfluidic devices is very common in chemical, biological, medical and other fields, and it is challenging to achieve rapid mixing in laminar flow. In this paper, flow-induced vibration is introduced to promote laminar mixing and the influence of two-degree-of-freedom vibration of bluff body on the mixing performance of solutions are studied numerically. The vibration response of body, mixing concentration, vorticity, and mixing index under different blocking ratios are analyzed, and the motion trajectory under the optimal blocking ratio is presented. It is found that the blocking ratio directly affects the vibration of cylinder, and then has a significant impact on the mixing performance. When the blocking ratio & beta;=1/4, although the mixing index is not the maximum of all the blocking ratios considered, the kinetic energy loss of the fluid is lower than that at larger blocking ratio, resulting in excellent comprehensive mixing performance. When the reduced velocity U*=4 for & beta;=1/4, the best mixing performance is achieved with a mixing index of 0.55, and the pressure drop of the fluid during the mixing process is very small. Besides, the motion trajectory of the cylinder presents a typical shape of "8 & DPRIME;. The strong vibration in the y direction and the shedding vortex at the downstream position of the cylinder can effectively promote fluid mixing.