Unsteady characteristics of the diffusion/nozzle tube for valveless piezoelectric micropumps at a lower frequency

Abstract

In this study, transient flow performance of the diffusion/nozzle tube with diffusion angle of 10° under different Wo numbers was studied using ANSYS CFX software. The purpose of this work is to obtain the factors which influence the flow characteristics of the diffusion/nozzle tube for valveless piezoelectric micropumps under unsteady conditions. A time-dependent sinusoidal pressure is exerted for the entrance as the boundary condition, and the pressure amplitudes P0 are 50Pa, 100Pa, 500Pa, 1000Pa and 5000Pa. The simulation results show that the change of flow lags behind the variation of pressure under unsteady flow conditions. The greater the Wo numbers, the smaller the pressure amplitude P0 , and the greater the phase difference. Both the loss coefficient of pressure in the diffusion ξd , and the nozzle ξn increase with increasing Wo numbers, and decrease with increasing P0 . The vortex has a great influence on the flow characteristics of the valveless piezoelectric micropumps.