Study on flow characteristics of a synthetic jet by using a vortex method

Abstract

A synthetic jet is generated by an oscillating flow that a time-averaged mass flow is zero, unlike continuous jets. Synthetic jets have been used for various applications such as mixing enhancement and active controls. The present study investigated flow characteristics of a synthetic jet by using the vortex method. Continuous and synthetic jets were simulated by distributed sources on a slot and vortex pairs discharged from slot lips and their images. The wall boundary was simulated by the images of vortices. The onset condition of the synthetic jet by the vortex method agrees well with the Holman's result. The mean velocity distribution on the x axis by the vortex method reasonably agrees with the experimental one. For the dimensionless stroke lengths larger than 3.14, vortices remain in the flow field after the period of the suction. The induced velocity of the vortex remaining in the flow field generates the synthetic jet. During the suction, the largest velocity is located near a pair of the vortex groups. The 2nd local maximum in the mean velocity distribution corresponds to that in the frequency distribution of the maximum velocity. The 2nd local maximum is caused by a pair of the vortex groups flowing between x=15 and x=25 slowly.