This paper presents a millimeter scaled device which can generate a closed flow with magnitude velocity of order of m/s. The device consisting of a piezoelectric pump connecting to a closed network channel through a specific nozzle is investigated by using computational fluid dynamics (CFD). With this device, numbers of laminar jet-flow are produced depending on the structure of the channel. In this study, four laminar jet-flows are demonstrated. If the amplitude of the vibration of PZT membrane is large enough, in a jet flow, the self-similar of the axial velocity (along jet direction) to the half-widths of the jet is observed. The two remains components of the flow are small compared with the axial component. Moreover, each jet flow can vibrate almost freely in three dimensions. Therefore, this device promises a rich application into the sensors based on a flow.
