The Effects of the Synthetic Jet on the Mixing Promotion in Low Reynolds Number

Abstract

The present paper describes a synthetic jet interaction with the cross flow in low Reynolds number condition by flow visualization and the wall static pressure measurements. The primary focus of the current study is to examine the possibility on the interaction of the synthetic jet with the cross flow in low Reynolds number viscous dominant flow. The low bulk velocity of the cross flow is set in a small scale of the wind tunnel with a high aspect ratio. A wide range of Reynolds number based on the tunnel height and the bulk velocity is covered. The flow visualization at Reynolds number of 1,000 is conducted in X-Y and Y-Z planes to clarify the development of the interaction process in the downstream. Both the time averaged and phase averaged wall static pressure were obtained downstream of the jet injection. The synthetic jet has a diameter of 0.5 mm and a frequency of 100 to 400 Hz. The penetration of the jet in the cross flow depends on the jet velocity ratio, and the deepest penetration occurs at the phase of π/2 at the highest jet velocity ratio. The counter rotating longitudinal vortex pair is generated even in low Reynolds number and can be observed at 100d downstream from the injection. The vortex pair shows the up-wash motion at the center of the jet core and the down-wash motion at the outsides of the jet. For the synthetic jet in cross flow, the fluctuated wall static pressure is increased, and the wall static pressure has similar frequency to the synthetic jet.