Affiliations: Department of Energy and Refrigerating
Air-Conditioning Engineering, National Taipei University of Technology, Taipei
106, Taiwan. E-mail: [email protected] | Department of Mechanical and Automation Engineering,
Da-Yeh University, Changhua 51505, Taiwan. E-mail: [email protected]
Abstract: The purpose of this paper is to investigate the compressible
turbulent synthetic jet flow characteristics of a dual diaphragm piezoelectric
actuator. Experimentally, a flow visualization system was established to obtain
the particle streak images scattered from 10-μm red fluorescent
spheres for observing the synthetic jet flowfield produced by a dual diaphragm
piezo actuator. The centerline velocity of the synthetic jet was also measured
by using a hot-wire anemometry system. In the analysis, the computational
approach adopted the transient three-dimensional conservation equations of mass
and momentum with the moving boundary specified to represent the piezo
diaphragm motion. The standard k-ε two-equation turbulent model
was employed for turbulence closure. For the actuator operating at the
frequency of 648 Hz, the particle streakline images in the cross-sectional
plane visualized a turbulent jet flow pattern in the far-field area. The
hot-wire anemometry data indicated that the measured centerline velocity of
synthetic jets reached 3.8 m/s at y/d = 50. The predictions were compared with
the visualized particle streak images and centerline velocity of the synthetic
jet in order to validate the computer code. The numerical simulation revealed
the time-periodic formation and advection of discrete vortex pairs. Caused by
the outward movement of the piezo diaphragms, air near the orifice was
entrained into the actuator cavity when the vortex pairs were sufficiently
distant from the orifice.
Keywords: Synthetic jet flow, Piezoelectric actuators, Flow visualization system