A numerical study on the performance of micro-vibrating flow pumps using the immersed boundary method

Abstract

A micro-vibrating flow pump (micro-VFP) drives the fluid by the vibration of an elastic cantilever-like structure in the pump, which is actuated by a sinusoidal magnetic field. In the present study, we clarify the pumping mechanism of the micro-VFP through a numerical simulation. A two-dimensional simulation code based on the immersed boundary method was developed to obtain the flow field in the micro-VFP together with the vibration of the cantilever. The motion of the cantilever, which was imitated by the immersed body, was expressed as an external forcing term of the Navier–Stokes equations. Here, the magnetic force required to actuate the cantilever was calculated based on a two-dimensional magnetic model, and an integral approach was used to calculate the large deflection of the cantilever. The working conditions and length of the cantilever were numerically studied to determine their effects on the pumping performance. It was shown through the numerical simulations that the pumping mechanism could be explained as a result of elongation of the cantilever in the effective stroke induced by the actuating magnetic field. The pumping performance, which was characterized by the volumetric flow rate and the shut-off pressure, was enhanced by increasing the actuation frequency of the cantilever as has been found in previous experiments. It was also found that the cantilever has an optimum length to give the maximum flow rate. The mechanism was explained with respect to the kinetic energy transferred to the fluid by the vibrating cantilever and the choking level, which is determined by the clearance between the ceiling of the microchannel and the tip of the cantilever.